/
\ 
HUMAN  PHYSIOLOGY;
ILLUSTRATED BY
NUMEROUS ENGRAVINGS.
BY
           ROBLEY  DUNGLISON, M. D.

rROFESSOR OF PHYSIOLOGY, PATHOLOGY, &C  IK THE UNIVERSITY OF VIRGINIA,
         MEMBER OF THE AMERICAN PHILOSOPHICAL SOCIETY, &.C.
" Vastissimi studii primas quasi lineas circumscripsi."—Haller,
VOL. I.
r>;j
   PHILADELPHIA:
CAREY &  L.EA
1833. 
QT
v.  I
  [Entered according to the Act of Congress, in the year one thousand eight
hundred and thirty-two, by Robley Dunglison, M. D. in the clerk's office of the
District Court of the Eastern District of Pennsylvania.]
£KERRETT--NINTH STREET,

     PHILADELPHIA. 
                              TO

           JAMES   MADISON,  ESQ.

EX-PRESIDENT  OF THE UNITED STATES, RECTOR OF THE UNIVERSITY
                      OF VIRGINIA, &C &C

            ALIKE  DISTINGUISHED AS AN ILLUSTRIOUS

                BENEFACTOR TO HIS COUNTRY;

   A ZEALOUS  PROMOTER  OF SCIENCE  AND  LITERATURE, AND  THE
                      FRIEND OF MANKIND?

                   THIS   WORK,

INTENDED TO ILLUSTRATE  THE  FUNCTIONS EXECUTED BY THAT BEING,
    WHOSE  MORAL AND POLITICAL CONDITION HAS BEEN WITH
        HIM AN OBJECT OF ARDENT AND SUCCESSFUL STUDY,
              IS, WITH HIS  PERMISSION, INSCRIBED,

                IN TESTIMONY OF THE UNFEIGNED

                          RESPECT

    ENTERTAINED FOR HIS TALENTS  AND PHILANTHROPY, AND  OF

                        GRATITUDE

            FOR NUMEROUS  EVIDENCES OF FRIENDSHIP,

                   BY HIS OBEDIENT  AND OBLIGED  SERVANT,

                                             THE AUTHOR.
University of Virginia,
   July 3d, 1832. 
%.*
■J 
PREFACE.
  The present work  was undertaken chiefly for the purpose of
forming a text-book for the author's students in the University
of Virginia, in which a full course  of lectures on Physiology is
made to precede the investigation of Pathology, or "diseased Phy-
siology," as it has been, not inappropriately, termed.
  Of late, the study of Physiology has  become  much more com-
mon both with  the professional and  unprofessional inquirer.  The
necessity for studying man physically, as well as morally, has been
strongly inculcated by some of the best writers on morals and legisla-
tion ; and, in France, M. Bourdon has compiled a series of dialogues
for the young female student,—such topics being suppressed, as
were regarded by him to be unsuitable, but enough being retained
to preclude their admission into the library of the American lady.
  In preparing the present work, the author  has availed  himself
freely of the labours of his predecessors.  His object has  been to
oner a view of the existing state of the science rather than to strike
out into  new, and perhaps devious, paths. To the labours of Ade-
lon and Chaussier,—especially of  the former,—of Blumenbach,
Richerand,Magendie, RuDOLPHi,BROussAis,SirCharles Bell
and others, who have had the chief agency in raising Physiology to
its present elevated condition, he has been indebted for essential aid;
and many of the illustrations have been taken from  the admirable gra-
phic delineations of the last mentioned distinguished  physiologist.
Some of these sketches, owing to the distance of the author from
the press, are not so uniform in regard to size, or so unexceptiona-
ble in certain other respects, as is desirable; but  their general  exe-
cution reflects credit upon Mr. Drayton, under whose  superin-
tendence they were engraved.
   The author has to regret his not having seen a copy of the "Prin-
ciples of Medicine,"  recently published by Dr. Samuel Jackson;
especially as he is satisfied, from the reputation  of the author, as
well as  from a notice of the work in the nineteenth number of
 The American Journal of the Medical Sciences, from the pen of
 an able  professor in the University of Maryland, that he would
 have met with many valuable remarks and suggestions.   He has
 likewise to regret that the useful notes, appended  to the third
American edition  of the translation of Broussais' Physiology
 applied  to Pathology, by Drs.  Bell  and La  Roche,—did n0t
reach him in time to  be available. 
 
CONTENTS  OF VOL.  I.
                                                                Page.
Preliminary Observations.........1
Of Natural Bodies...........ib.
      Difference between Inorganic and Organized Bodies   -    -    -    2
      Difference between Animals and Vegetables -----    7
General Physiology of Man........12
On the Material Composition of Man      .......ib.
      I. Organic Elements that contain Azote.....15
      II. Organic Elements that do not contain Azote                    18
      Of the Solid parts of the Human Body  ------   21
      Of the Fluids of the Human Body......26
      Of the Elementary Structure of Animal Substances                 29
      Physical Properties of the Tissues.......33
Of the  Functions of man........-37
      Table of the Functions.........38

                               CLASS I.
Animal Functions, or Functions  of  Relation.....41
Of Sensibility, or the Function of the Sensations.....ib.
      Of the Nervous System.........ib.
Physiology of Sensibility -........-64
      Of the Sensations..........ib.
External Sensations..........70
Sect. I.—Sense of Tact or Touch........73
      Anatomy of the Skin, Hair, Nails, &c.       .....ib.
      Physiology of Tact and Touch.....-    -   79
Sect. H.—Sense of Taste or Gustation......-   87
      Anatomy of the Organs of Taste.......88
      Of Savours...........89
      Physiology of Taste.....-    -    -    -   92
Sect. III.—Of the Sense of Smell, or Olfaction.....97
      Anatomy of the Organ of Smell.......ib.
      Of Odours    -    -.........lul
      Physiology of Olfaction.........106
Sect. IV.—Of the Sense of Hearing or Audition.....113
      Anatomy of the Organ of Hearing.....-   ib.
      Of Sound     -    -.........120
      Physiology of Audition.........125
Sect. V.—Of the Sense  of Sight, or Vision......140
      Of Light     .--........141
      Anatomy of the Organ of Vision.......150
      Accessory Organs..........160
      Physiology of Vision.......*    -  165
      Phenomena of Vision........,   -  182
Internal Sensations.........'      *^8
Of the Mental Faculties, &c.   -    -    -    -    -    -    -    -    -  j30
      Physiology of the Intellectual and Moral Faculties -    -    -    -  24,7
Of Muscular Motion, especially of Locomotility or Voluntary Motion,    -  282
      Anatomy of the Motory Apparatus.......*»•
      Of the Muscles    --------       ib.
      Of the Bones  -----------  j™
      Physiology of Muscular Motion.....-    -  ^4 
viii                          contents.

                                                                 Page.
                                                                   340
Of the Attitudes..........       ^
Of the Movements........              '  „. g
Locomotive Movements  --....."         '.,
      Walking........"         '  *S2
      Leaping.....;-                         353
      Running      .......    -    -    -    -     -  ^

                                         ".-----  357
Swimming
Of the Function of Expression or of Language.....^
Of the Voice.......-----  Jbt)
      Anatomy of the Vocal Apparatus  -        .....«<>.
      Physiology of the Voice......' -     -  ^63
      Timbre, or Quality of the Voice.......«*78
      Of Natural or Inarticulate Language    -    -     -,   -    -     -  384
      Of Artificial or Articulate Language.....•   -  386
      Of Singing  -    -    -........398
Of the Gestures    -..........399

                               CLASS n.
Nutritive Functions..........414
Of Digestion        ...........*»•
      Anatomy of the Digestive Organs.......«»•
      OftheFoodof Man.........438
      Physiology of Digestion......-     -  460
      I. Digestion of Solid Food........461
      II. Digestion of Liquids........514
Of Eructation, Regurgitation, Vomiting, &c.  -    -     -    -    -     -  517 
HUMAN   PHYSIOLOGY.
         PRELIMINARY  OBSERVATIONS.

                     OP NATURAL  BODIES.

  The extensive domain of Nature is divisible into three great
classes:—Minerals,  Vegetables, and Animals. This division was
universally adopted  by the ancients, and still prevails, especially
amongst the unscientific.  When, however, we carefully examine
their characteristics, we discover that the animal and the vegetable
resemble each  other in many essential particulars.   This resem-
blance has given occasion to  the partition of all bodies into  two
classes:—the Inorganic, or those not possessing organs or instru-
ments adapted for the performance of particular actions or functions,
and the Organized, or such as do possess this arrangement.
  In all ages, philosophers have attempted to point out, as the poet
Milton expresses it, a

            " Vast chain of being, which from God began,
             Natures ethereal, human, angel, man,
             Beast, bird, fish, insect, what no eye can see,
             No glass can reach"—

the links of which chain they have considered to be constituted of
all natural bodies;  passing by insensible gradations, through the in-
organic and organized, and forming  a rigid and unbroken series.
  Crystallization-has been considered by them as the highest link
of the inorganic kingdom; the lichen, which encrusts the stone, as
but one link higher than  the stone itself; the mushroom and the
coral, as the connecting links between the vegetable and the animal;
and the  immense space, which separates man, the highest of the
mammalia, from his Maker, they have conceived to be occupied, in
succession, by beings of gradually increasing intelligences.
  If, however,  we investigate the matter  minutely,  we discover
that many links of the chain  appear widely separated from each
other; and that, in the existing state  of our knowledge, the catena-
tion cannot be esteemed rigidly  maintained.
  Let us inquire into the great characteristics of the different king-
doms, and endeavour to describe the chief points in which living
bodies differ from those that have never possessed vitality, and into
the distinctions between organized bodies themselves.
  Vol.  I.                     1 
2
NATURAL  BODIES.
     Difference between Inorganic and Organized Bodies.

  Inorganic bodies possess the common properties of matter.  Their
elements are fixed and uncontrolled under ordinary circumstances.
Their study constitutes Physics, in its enlarged sense, or Natural
Science.   Organized bodies have properties  in common with the
inorganic, but they have likewise others superadded, which control
the first in a singular  manner.  They are beings, whose elements
are undergoing constant mutation, and the sciences treating of their
structure and functions are Anatomy and Physiology.
  1. Origin.—They differ,  in  the first place, from each other in
their origin. Inorganic bodies are not born; they do not arise from a
parent; they spring from the general forces of matter, the particles
being merely in a state of aggregation,  and their  motions are regu-
lated by certain fixed  and invariable laws.  The  animal  and the
vegetable, on the other hand, are the products of generation; they
must spring from a being similar to themselves, and they possess
the principle of life, which controls the ordinary forces  of matter.
Yet it has been supposed that they are  capable of creating life; in
other words, that a particular organization presupposes life.
  This is not the place for entering into the question of generation.
It will be sufficient at present to remark, that in  the  upper classes
of animals, the necessity of a parent cannot be contested; the only
difficulty,  that can possibly arise,  regards the very lowest classes,
and analogy warrants, in their case, the conclusion, that every living
being must spring from an egg or a seed.
  2. Shape.—Again,  the shape of  inorganic bodies is not  fixed in
any determinate manner.   It is true that, by proper  management,
every mineral can be reduced to a primitive nucleus, which  is the
same  in all  minerals  of  like composition; still  the shape of the
mineral, as it presents itself  to us, differs.   Carbonate of lime, for
example, although it may always be reduced to the same primitive
nucleus, assumes various appearances; sometimes  being rhomboidal,
at others, in regular  hexaedral prisms;  in solids, terminated by
twelve scalene triangles, or in  dodecaedrons, whose surfaces are
pentagons.
  In organized bodies, on the contrary, the shape is constant.  Each
animal and vegetable has the one that  characterizes its  species, so
that no possible mistake can be indulged; and this  applies not only
to the whole body, but to every one of its parts,  numerous as they
are.
  3. Size.—The size  of an  inorganic  body is by no means  fixed.
It may be great or small, according to the quantity present  of the
particles that  have to form it.  A crystal, for  example, may be
minute or the contrary, according to the number of saline particles
in  the solution; whilst organized  bodies attain  a  certain  size,—at
times by a slow, at others by a more rapid growth; but in all cases
the due proportion is preserved between the various parts, between 
INORGANIC  AND ORGANIZED.
3
the stem and the root, the limb and the trunk. Each vegetable and
each animal has its own size, by which it is known; and although
we occasionally meet with dwarf or gigantic varieties, these are in-
frequent and mere exceptions,  confirming the position.
   4.  Chemical character.—Great difference exists between  inor-
ganic and organized bodies in this respect.
   In the mineral kingdom are  found all the elementary substances,
or those which chemistry, at present, considers simple, amounting
to upwards of fifty, and comprising oxygen, hydrogen, boron, car-
bon, phosphorus, sulphur, selenium, iodine, fluorine, chlorine, bro-
mine, azote,  silicium, zirconium,  aluminium, yttrium, glucynum,
magnesium, calcium, strontium, barium, sodium, potassium, lithium,
manganese, zinc,iron, tin, arsenic, molybdena, tungsten,columbium,
chromium, antimony, uranium, cerium, cobalt, titanium, bismuth,
cadmium, copper, tellurium, lead, mercury, nickel, osmium, silver,
gold, platinum, palladium, and iridium.  In the organized, a few only
of these elements of matter are met with, viz. oxygen,  hydrogen,
azote, carbon, sulphur, phosphorus, &c.
   In  the inorganic body, the composition is more simple;  several
consist of but one element, and when composed of more, the  com-
bination is rarely higher than ternary.  The organized body, on the
other hand, is never simple nor even binary.   It is always at least
ternary or quaternary.   The simplest vegetable consists of a union
of oxygen, carbon, and hydrogen; the  simplest animal, of  oxygen,
hydrogen, carbon, and azote.
   The composition of the mineral again is constant.   Its elements
have entirely satisfied their affinities, and  all  remains at rest.  In
the organized kingdom, however, the affinities are not satisfied;
compounds are formed to be again decomposed, and this  happens
from  the earliest period of fcetal formation till the cessation of life;
all is  in commotion, and  the chemical character  of the corporeal
fabric is incessantly undergoing modification.
   In  chemical nomenclature, the term  element has a  different ac-
ceptation, according as it is applied  to inorganic or organic che-
mistry.   In the former, it means a substance, which, in the pre-
sent state of  the science, does not admit of  decomposition.   We
say in the present state of the science,  for many of the  bodies,
now  esteemed compound, were not  many years  ago   classed
amongst the  simple or elementary.   It is not more than  twenty-
five years since the alkalies were found to  be  composed  of two
elements.  Previously, they were considered simple.   In  the ani-
mal and the vegetable, we find  substances, also called elements, but
with the epithet organic, because only found in organic or living
bodies, and therefore the exclusive products of organization and life.
For example, in both animals and vegetables, we meet with  oxy-
gen, hydrogen, carbon, azote, and  different metallic  substances;
these  are  chemical or inorganic  elements, and we further meet
with  albumen, gelatine,  fibrine,  osmazome, &c. substances which 
4
NATURAL BODIES.
constitute the various organs, and which,  therefore,  have been
termed organic elements or compounds of organization;  yet
they are capable of decomposition, and in one sense, therefore, not
elementary.
   In the inorganic body, all the elements, that  constitute it, are
formed by the agency of general chemieal affinities; but in the or-
ganized, the formation is produced by the force, that presides over
the formation of the organic elements themselves—the force of life.
Hence the cause why the chemist is able to decompose and restore
many of the inorganic bodies, whilst  the products of organization
and of life place his art at defiance.
   The different parts of an inorganic body enjoy an existence inde-
pendent of each other; whilst those of the organized are materially
dependent.  No part can, indeed, be injured without the mass and
the separated portion being more or less affected.
   If we take a piece of marble, composed of carbonic acid and of
lime, and break it into a thousand fragments, each portion will  be
found to consist of carbonic acid  and of lime.   The mass will be
destroyed, but no piece will suffer from the disjunction. They will
continue as fixed and unmodified as at first.  Not so with an or-
ganized body.   If we break the branch from a tree,  the stem itself
participates more or less in the injury; the detached branch speedi-
ly undergoes  striking  changes; it withers; becomes  shrivelled,
and in  the case of the succulent vegetable, undergoes decomposition;
a portion of its constituents, no longer held in control by the vital
agency, enter into new combinations, are given off in the  form of
gas, and the remainder sinks to earth.
   Changes, no less impressive, occur in the animal, when a limb is
separated from the body.  The parent trunk suffers; the system re-
coils at the first infliction  of the injury, but subsequently arouses
itself to a reparatory effort, at times with such energy as to destroy
its own vitality.   The separated limb, like the branch, is given up,
uncontrolled, to  new affinities; and putrefaction soon  reduces  the
mass to a state in which its previously admirable organization is no
longer  perceptible.
   Some of  the  lower  classes of  animals may indeed  be divided
with impunity, and with no other effect than  that of multiplying
the animal in proportion to the number of sections, but these  are
exceptions;  and we may  consider the  destructive process,  es-
tablished when parts of organized bodies are separated, as one of the
best media  of distinction  between the inorganic and organized
classes.
   5. Texture.—In this respect the inorganic and  organized differ
considerably, a difference which has given  rise to  their respective
appellations.   To one of these only can the term texture be with
propriety applied.
   If we examine a vegetable or animal substance with attention
we shall find, that it has a regular and determinate arrangement or 
                  INORGANIC AND ORGANIZED.                5

structure; and we readily discover, that it consists of various parts.
In the vegetable, of wood, bark, leaves, roots, flowers, &c.; and in
the animal, of muscles, nerves, vessels, &c; all of which appear to
be instruments or organs for specific purposes  in the  economy of
the being.  Hence the body is said to be organized, and the result,
as well as the process, is called organization.
   The particles of  matter  in  an organized body, so far as we can
detect them, constitute fibres, which in-
terlace and intersect each other in all         Fig.  1.
directions, and form a spongy areolar tex-
ture or tissue. (Fig. 1.) Of these tissues the
various organs of the body are composed.
In the inorganic substance, the mass is
homogeneous;  the smallest particle of
marble, as we have seen, consists of car-
bonic acid and lime; and all the particles
concur alike to the formation and pre-
servation of the body.
   Lastly,  whilst an inorganic  body, of a determinate species, has
always a fixed composition, the living  being, although constituting
a particular species, may present individual differences, giving rise,
in the animal, to various temperaments, constitutions, &c.
   6. Mode of preservation.—Preservation of the species is, in the
 animal, the effect of reproduction.  As  regards individual preserva-
 tion,  that of the  mineral is  dependent upon the same actions that
 effected its formation;—on the persistence of the affinities of cohesion
 and combination, which united its  various particles.  The animal
 and the vegetable, on the  other hand, are maintained  by a mecha-
 nism peculiar to them.  From  the  bodies surrounding them, they
 lay hold of  nutritious matter, which, by a process of elaboration,
 they assimilate to their own composition; at the same time, they
 are constantly absorbing or taking up particles of their  own struc-
 ture, and  throwing them out.  The actions of composition and de-
 composition are constant,  whilst life exists, although subject to par-
 ticular modifications, at different periods  of existence,  and  under
 different circumstances.   This  process is called nutrition.
   The inorganic and organized are alike subject to changes during
 their existence; but the  character of these changes, in the two
 classes, differs essentially.
   The mineral retains its form, unless acted upon by some mecha-
 nical or chemical force. Within, all the particles are at rest, and no
 internal force exists which can  subject them to modification.  There
 is no succession of conditions  which  can be  termed  ages.   How
 different is the case with  organized bodies! Internally there is no
 rest; from birth to death all is in a state of activity.  The plant and
 the animal are subject to incessant  changes.  Each runs through a
 succession of conditions or ages.   We see it successively develope
 its structure and functions, attain maturity, and finally decay.
 
6                      NATURAL BODIES.
   Characteristic differences exist in  the nature  of the  exterior of
 the two divisions, as well as in their mode of increase.   Inorganic
 bodies have no covering to defend them, no exterior envelope to
 preserve their form.   A stone is the same at its centre as at its cir-
 cumference, whilst organized bodies are protected by an elastic and
 extensible covering, differing from  the parts beneath, and  inser-
 vient to valuable purposes in the organized economy.
   Every change, to which an inorganic body is liable,  must occur
 at its surface.   It is there that the particles are added or abstracted
 when it experiences increase or diminution of size.  This increase,
 for growth it  can scarcely be termed, takes place by accretion or
juxtaposition, i. e. by the successive application of fresh particles
 upon those that form the primitive nucleus; and diminution in bulk
 is produced by the removal of the external layers or particles.   In
 organized substances, increase or growth is caused by particles de-
 posited internally,  and  diminution  by particles  subtracted from
 within.  We  see them,  likewise, under two conditions, to which
 there is nothing similar in the mineral kingdom,—health and disease.
 In the former, the functions are executed with freedom and energy;
 in the latter, with oppression and restraint.
   7.  Termination—Every  body,  inorganic or  organized,  may
 cease to exist, but  the mode of  cessation varies greatly in the two
 great divisions of natural bodies.
   The mineral is broken down by mechanical violence,  or it ceases
 to exist in consequence of modifications in the affinities, which held
 it concrete. It has  no  fixed duration, but its  existence may be ter-
 minated at any moment,  when the circumstances, that retained it in
 aggregation, are destroyed.
   The vegetable and the animal, on the other hand, can carry on
 their functions for a period only, which is fixed and determinate for
 each species.  For  a time, new particles are deposited  internally.
 Its bulk is augmented, and its external envelope distended, until
 maturity or full development is attained; but, after this,  decay com-
 mences ; the functions are exerted with gradually diminishing en-
 ergy ;  the fluids decrease in quantity;  and the solids become more
 rigid—the precursors to  the total cessation of vitality.  This term
 of duration is  very  different in different species.  Whilst many of
 the lower classes of animals and  vegetables have but an ephemeral
 existence, some of the more elevated individuals of the two king-
 doms will outlive a century.
   8. Motive forces.—Lastly, observation has satisfactorily proved,
 that there are  certain forces which affect matter in general, the in-
 organic as well as the organized; but that in addition to these, the
 organized possess a peculiar force or forces, which modify them in
 the most remarkable manner.  Hence, we have general forces and
 special or vital; the first acting upon all matter, the dead and the
 living, and including the forces of gravitation, cohesion, chemical
 affinity, &c. the latter being exclusive to living  beings. 
ANIMALS AND VEGETABLES.
7
  Such are the chief  distinctions to be  drawn between the two
great divisions  of natural  bodies, the inorganic and the organized.
By the comparison which  has been instituted, the great objects of
physiology, the phenomena of life, have been indicated.   To in-
quire into  the  mode in which a living being is born, nourished,
reproduced and dies, is the legitimate object of this science.
  We have, however,  entered into a comparison only of the inor-
ganic with  the organized.  The two divisions constituting this latter
class differ  also materially  from each other.  Into these differences
we shall now inquire.

         Difference between Animals and Vegetables.

  The distinctions between these divisions of organized bodies are
not so rigidly fixed or  so readily appreciated, as those we have con-
sidered.
  There are certain functions possessed  by each, and hence called
vegetative  or  organic; nutrition and reproduction for example.
But vegetables  are endowed with these only. All organized bodies
must necessarily have the  power of assimilating foreign matters to
their own  substance, and that of producing a living being similar
to themselves,  otherwise  all species, having  a limited duration,
would perish.
  In addition to these common  functions, animals have two others,
sensation and voluntary  motion, by the possession of which they
are said to  be animated.  Hence they are termed animals, and the
condition is called animality.  This division of the functions into
animal and organic has been adopted with more or less modifica-
tion  by the generality of physiologists.
  Between the animals and  vegetables,  that are situated high in
their respective classes, no error can possibly be indulged.  The
characters are obvious at sight.  No one can confound the horse and
the oak, the butterfly and  the potatoe.  It is on the lower confines
of the two kingdoms that we are liable to be deceived.  Many of
the zoophytes have alternately been considered vegetable and ani-
mal; and it is not until of  modern date, that the sponge has  been
universally elevated  to that kingdom to which it is entitled.  Nor
is this to be wondered  at.   In its attachment to the rock,  it is as
immoveable as  the lichen  is to  the  slate, and almost  equally defi-
cient in the usual characteristics of animality. In general, however,
we are able to  classify any doubtful substance with accuracy, and
the following are the principal points of difference.
   1. Composition.—The essential  elements, of organized  matter
are, carbon, oxygen, hydrogen and azote, with alkaline and earthy
salts, variously  combined.   Vegetables consist of the  three first of
these elements, carbon, oxygen, and hydrogen.  Azote is possessed
in addition by the animal; yet  there  are many animal substances,
as we shall see, that contain none.   Plants contain scarcely any; 
8
NATURAL  BODIES.
and, generally,  when  it is met with, it will  be found in some
part,—scarcely ever distributed through the whole.  In the fungi,
traces of a vegeto-animal matter have been detected by the che-
mist,  but they have only  been traces.  In consequence of this
difference of  composition, animal  substances  are easily known
from vegetable by burning; a fact which, as Dr. Fleming has re-
marked, is interesting to the young naturalist, when he may be
uncertain to which kingdom to refer any  substance met with in his
researches. The smell of a burnt sponge, coral, and other zoophy-
tic animal, is so peculiar, that it can scarcely be mistaken for that
of a vegetable body in combustion.
  2. Texture.—In this respect,  important differences are observa-
ble.  Both animals and vegetables consist of solid and fluid parts.
In the  former, however, the fluids bear a large  proportion; in the
latter the solids.  This  is the cause why decomposition occurs so
much more rapidly in the animal than in  the vegetable,  and in the
succulent than in the dry vegetable.
  If we analyze the structure of the vegetable, we cannot succeed in
detecting more than one elementary tissue, which is vesicular, or
arranged in areolae or vessels, and appears to form every organ of
the body, whilst in the animal, we discover at least three of these
anatomical elements, the cellular, analogous to that of the vegeta-
ble, the muscular and the nervous.
  The vegetable has  no great splanchnic cavities containing the
chief organs of the body.   It has a  smaller number of organs, and
none that are destined for sensation or volition;  in other words,  no
brain, no nerves, no muscular system; whilst the organs, of which
it consists, are simple and readily convertible into each other, which
is not the case with the animal.
  But  these differences  in  organization,  striking  as they may ap-
pear, are not sufficient for rigid discrimination, as they are applica-
ble only to the upper classes of each kingdom.  In many vegetables,
the fluids appear to preponderate over the solids.  Numerous animals
are devoid of muscular and nervous tissues, of splanchnic cavities,
and apparently of vessels and distinct organs; and Messrs. Dutro-
chet, Brachet, and others, admit  the existence of a rudimental
nervous system, even in vegetables.
  3. Sensation and voluntary motion.—One manifest distinction
exists  between animals and vegetables;  whilst the latter receive
their nutrition from the objects situated around them, irresistibly
and without volition, or the participation  of mind; and whilst the
function of reproduction is effected without the  union of the sexes;
volition and sensation are both necessary for the nutrition of the
former, and for the acts requisite for the reproduction of the species.
Hence, the necessity of two faculties or  functions in the animal,
which  are wanting in the vegetable, viz. sensibility, or the faculty
of consciousness and feeling; and motility, or the power of moving
the whole of the body or any of its parts at the will of the being 
ANIMALS AND VEGETABLES.
9
Vegetables are possessed of spontaneous, but not of voluntary mo-
tion.   Of the former we have numerous examples in the direction
of the branches and upper surfaces of the leaves, although repeatedly
disturbed, to the light; and in the unfolding and closing of flowers,
at stated periods of the day.  This, however, is quite distinct from
the sensibility and motility that characterize the animal.
   By sensibility he  feels his own existence, becomes acquainted
with the universe, appreciates the bodies  that compose it, and ex-
periences all the desires and inward feelings that solicit him to the
performance of those external actions, which are  requisite for his
preservation, as  an individual and as  a species.   By  motility he
executes those external  actions which  his sensibility may suggest
to be necessary.
   By  some naturalists it has been maintained, that those  plants
which are borne about on the waves, and fructify in that situation,
exhibit to us examples of the locomotility which is described as
characteristic of the animal.  One of the most interesting novelties,
in the  monotonous occurrences of  a voyage across the Atlantic to
the Gulf of Florida, is the almost interminable quantity of the Flo-
rida weed, or Gulph weed, with which the surface of the ocean is
covered.  But how different  is this motion from the locomotility
of animals ! It is a subtlety to conceive them identical.   The weed
is passively and  unconsciously borne whithersoever the winds and
the waves may urge it, whilst  locomotion requires the  direct
agency of volition, of a nervous  system  that  can excite, and of
muscles that can act  under such excitement.
   The spontaneity and perceptivity of plants, as they have been
termed, must also be explained in  a different manner from the ele-
vated  function of sensibility, on which we shall have to dwell.
These properties must be referred to the fact of certain vegetables
being possessed of the faculty of contracting on the application of
a stimulus, independently of sensation  or consciousness.
   If we touch the leaf of the sensitive  plant, the Mimosa pudica,
the various leaflets collapse in rapid succession.  In the barberry
bush, Berberis vulgaris, we have another example of  the  posses-
sion of this faculty.   In the flower, the six stamens, spreading mo-
derately, are sheltered  under the concave tips of the petals, till
some extraneous body, as the feet or trunk of an insect in search of
honey, touches the inner part of  each  filament near the bottom.
The susceptibility of this part is such, that the filament immediately
contracts, and strikes its anther, full of pollen, against  the  stigma.
Any other part of the filament may be touched  without this result,
provided no concussion be given to the whole.  After a while, the
filament retires gradually, and may be  again stimulated, and when
each petal, with its annexed filament, has fallen to the  ground, the
latter, on being touched, shows as much sensibility as ever.
   These singular effects  are  produced  by the  power of contrac-
   Vol. I.                     2 
10
NATURAL  BODIES.
tility or irritability, the nature of which will fall under consider-
ation hereafter.  It is possessed equally by animals and vegetables,
and is essentially organic and vital. This power, we shall see, needs
not the  intervention  of volition: it is constantly exerted in the ani-
mal without consciousness, and therefore  necessarily without voli-
tion.  It is exerted in the heart, in the muscular tunic of the intes-
tines, in every muscle, indeed, of involuntary, as well as of volun-
tary motion.  Its existence" in the vegetable does not, consequently,
demonstrate that it is possessed of consciousness; and we can hence
understand how certain spontaneous motions may persist without
the presence of any thing  like consciousness or volition.
  4. Nutrition.—A great difference exists between plants and ani-
mals in this  respect  The plant, being fixed  to the  soil,  cannot
search after food.  It must be entirely passive, and obtain  its sup-
plies from the materials around, and in contact with it, and the ab-
sorbing vessels of nutrition must necessarily open on its exterior.
In the animal, on the other hand, the aliment is scarcely ever found
in a state fit for absorption; it is crude, and in general requires to
be received into a central  organ, the stomach, for the  purpose of
undergoing changes  by a process termed digestion, which adapts it
for the nutrition of the individual. The absorbing vessels of nutri-
tion arise, in this case, from the internal or lining membrane of the
alimentary tube. The analogy, however, that exists between these
two kinds of absorption is great, and had  not escaped the attention
of the ancients:—" Quemadmodum terra arboribus, ita anima-
libus ventriculus, ventriculus sicut humus," was an aphoristic
expression of universal reception.  With similar feelings  Boer-
haave asserts, that animals have their roots of nutrition in their
intestines;  and Dr. Alston  has fancifully termed a plant  an  in-
verted animal.
  Again, in both plants and animals the residue of the matters ab-
sorbed is ejected from  the body; but the form and character of
the rejected portion varies in the two kingdoms.  In the plant,  the
superfluous quantity is thrown off in  gaseous, hydrogenated, or
aqueous exhalations:  in the animal, the useless portion is excreted,
or rejected as excrement,  of which azote is a constituent.
  After all, the most essential difference consists in the steps that
are preliminary to the reception of food.   These, in the animal, are
voluntary, requiring prehension, often locomotion, and always con-
sciousness.
  5. Reproduction.—In this function we find a striking analogy
between animals and vegetables; but differences exist, which must be
referred to the same causes, that have produced many  of the  dis-
tinctions already pointed out—the possession, by the animal, of sen-
sibility and locomotility. For example, every part of the generative
act is, in the vegetable, without the perception  or volition  of  the
being—the union  of the  sexes, fecundation,  and the birth of  the
new individual, are alike automatic.  In  the animal, on the other 
ANIMALS AND VEGETABLES.
11
hand, the approximation of the sexes is always voluntary, and ef-
fected consciously—the birth of the new individual being not only
perceived,  but somewhat aided by  volition.   Fecundation alone
is involuntary and irresistible.
  Again, in the vegetable the sexual organs do not exist at an early
period, and are not developed until the period when reproduction
is practicable. They are capable of acting for once only, and perish
after fecundation; and if the plant be vivacious, they fall  off after
each reproduction, and are annually renewed.  In the animal, on
the contrary, they exist from the earliest period of foetal develop-
ment, survive repeated fecundations, and continue during the life
of the individual.
  Lastly,  the  possession of sensibility and locomotility  lead to
other characteristics of animated beings.  These functions  are inca-
pable of constant, unremitted exertion.  Sleep, therefore, becomes
necessary.   The animal is also capable of  expression or  of  lan-
guage, in  a degree proportionate to the extent of his sensibility,
and of his  power over the beings that surround him.
   But these differences in  function are not  such  striking  cha-
racteristics as they  at  first appear.   There  are many  animals
which are  as irresistibly attached to the soil as the vegetables them-
selves.   Like  the latter, they must, of necessity, be compelled to
absorb their food in the state in which it is presented to them.  Sen-
sibility and locomotility appear, in  the zoophyte, to be  no more
necessary  than in the vegetable.   No nervous, no muscular system
is required;  and, accordingly, none  can be traced in them; whilst
many of those spontaneous  motions of the  vegetable, which  have
been described, have been considered by some to indicate the first
rudiments of sensibility and locomotility:  and  Linnjeus has re-
garded the closure of the flowers towards  night as the sleep, and
the movements of vegetables, for the approximation of the sexual
organs, as  the marriage of plants. 
12
MATERIAL COMPOSITION OF MAN.
       GENERAL  PHYSIOLOGY  OF  MAN.

  The observations, that have been made on the difference between
animals and vegetables, have anticipated many topics, which would
require consideration under this head.  Those general  properties
that he possesses, along with other animals, have been referred to
in a cursory manner. They will now demand a more special inves-
tigation.

           ON THE MATERIAL COMPOSITION OF MAN.

  The detailed study of human organization is the province of the
anatomist; of its intimate composition, that of the chemist.  In ex-
plaining the functions executed by the various organs, the physio-
logist will frequently have occasion to trench  upon both of these
departments.
  The bones, in the aggregate, form the skeleton.  The base of this
skeleton is a series of vertebrae, with the skull as a capital—itself
considered a vertebra by De Blainville. This basis is situated on
the median line through the whole trunk, and  contains a  cavity, in
which are lodged the brain and spinal marrow.   On  each side of
this, other bones are arranged  in  pairs, which by some have  been
called appendices. Upon the skeleton are placed muscles, for mov-
ing the different parts of the body, and for changing its situation
with regard to the soil. The body is again divided into trunk and
limbs.  The trunk, which is the principal portion, is composed of
three splanchnic cavities, situated one above the other—the abdo-
men, thorax, and head. These contain the most important organs
of the body—those that effect the functions of sensibility, digestion,
respiration, circulation, &c.  The head comprises the face, which
contains the organs of four of the senses—those of sight, hearing,
smell, and taste; and the cranium, which lodges the brain,—the or-
gan of the mental manifestations, and the most elevated part of the
nervous system. The thorax or chest contains the lungs, organs of
respiration, and the heart, the great organ of the circulation.   The
abdomen, the principal organs of  digestion, and, (if we include in
it the pelvis,) those of the urinary secretion and of generation.  Of
the limbs, the upper, suspended on each side of the thorax, are in-
struments of prehension, and are terminated by the hand, the great
organ of touch.  The lower are situated beneath the trunk, and are
agents for supporting the body, and for locomotion.  Vessels, ema-
nating from the heart,  are distributed to every part; conveying to
them the blood necessary for their vitality and nutrition: these are
the arteries.  Other vessels communicate with these, and convey 
INORGANIC ELEMENTS.
13
the blood back to the heart—the veins: whilst a third set commu-
nicate also with the arteries, and convey into the circulation, by a
particular channel, a fluid  called lymph—whence they derive the
name lymphatics.  Nerves, communicating with the great central
masses of the nervous  system, are  distributed to  every part to
complete their vitality; and lastly, a membrane or layer, possessed
of acute sensibility—the skin, serves  as an  outer envelope to the
whole body.
   It has been already remarked, that the animal body  consists, es-
sentially, of four ultimate elements—oxygen, hydrogen, carbon,
and azote.  This is correct as a general principle; but organic che-
mistry has shown us, that some of the constituents afford little or
no traces of azote.   It was likewise observed that two kinds of ele-
ments enter into the composition of the body—the chemical or in-
organic, and the organic, which are compound, and formed only
under the principle of life.
   The chemical  or inorganic elements met with, are—oxygen,
hydrogen, carbon, azote,phosphorus, calcium; and, in smaller quan-
tity, sulphur, iron, manganese, silicium, chlorine; also sodium, mag-
nesium, &c.
   1. Oxygen.—This is widely distributed in the solids and fluids,
and a constant supply of it from the atmosphere is indispensable to
animal life. It is almost always found  combined with other bodies,
often in the form of carbonic  acid, i. e. united with  carbon.  In a
separate state it is met with in the  air-bag of fishes, in which it  is
found varying in quantity, according to the species and the depth
at which the fish have been caught. Carbonic acid has  been detect-
ed by Proust in  an uncombined state in urine, and by Vogel in
the blood.  Carbonic acid gas likewise exists in the intestines of
animals; but it is chiefly met with in animal bodies, in  combination
with the alkalies or earths; and it is emitted by all animals in the
act of respiration.
   2. Hydrogen.—This gas occurs universally in the animal  king-
dom. It is a constituent of all the fluids, and of many of the solids;
and is generally in a state of combination with carbon.  In the hu-
man intestines it  has been found pure, as well as combined with
carbon and sulphur.
   3.  Carbon.—This substance is met with, under various forms,
in both fluids and solids. It is most frequently found under that of
carbonic acid.
   4. Azote.—This gas is likewise widely distributed  as a compo-
nent part of animal substances. Indeed, so generally does it prevail,
that it often affords, as we have seen, a distinctive mark by which
they may be known from vegetables.  It likewise occurs, in an un-
combined state, in the swim-bladder of certain fishes.
   5. Phosphorus is found united with oxygen—in the state triphos-
phoric acid—in many of the solids and fluids. This is the acid that
is combined with the earthy matter of bones, and with potassa, soda, 
14
MATERIAL  COMPOSITION OF MAN.
ammonia, and magnesia, in other parts. It is supposed to give rise
to the luminousness of certain animals, as to the fire-fly, Pyrosoma
atlanticum, &c.; but nothing precise is known on this subject.
   6.  Calcium.—This metal is found only  in the state of oxide in
the animal economy; and it is generally united with the phosphoric
or carbonic acid. It is the earth, of which the hard parts of animals
are constituted.
   7.  Sulphur is not met with extensively in the animal solids or
fluids: nor is it ever found free, but always, in combination with
oxygen, united to soda, potassa, or lime. It seems to be an invaria-
ble concomitant of albumen, and is found in the lower part of the
intestines in the form of sulphuretted hydrogen gas; and as an ema-
nation from  fetid ulcers.  Brugmans indeed maintains, but on fal-
lacious grounds, that this gas is the bearer of the contagious princi-
ple in hospital gangrene.
   8. Iron.—This metal has been detected  in the colouring matter
of the blood, in bile,  and  in milk.  For a long time it was consider-
ed to be in the first of these fluids in the state of phosphate or sub-
phosphate. Berzelius, however, showed that this was not the case;
that the ashes of the colouring matter always yielded oxide of iron
in the proportion of l-200th of the original mass.  That distinguish-
ed chemist was, however, unable to detect the condition in which
the metal exists in the blood,  and could not discover its presence
by any of the liquid tests. More recently, Engelhart,  a German
chemist, has  shown that the fibrine and albumen of the blood, when
carefully separated from colouring particles, do not contain a trace
of iron, whilst he could procure it from the red globules by incinera-
tion.  He also succeeded in proving its existence in the red globules
by liquid tests, and his experiments  have been repeated with the
same results by Rose of Berlin.  In milk,  iron seems to be in the
state of phosphate.
  9. Manganese has been found in  the state of oxide, along with
iron, in the ashes of the hair.
   10. Silicium.—Silica is found in the hair, urine, and in urinary
calculi.
   11. Chlorine.—In combination  with hydrogen, and forming
muriatic acid, chlorine is met with in most of the  animal fluids.
It is generally united with soda.  Free muriatic acid has also been
found by Prout in the stomach of the rabbit, hare, horse, calf, and
dog; and he  has discovered the same acid in the sour matter ejected
from the stomachs of those labouring under indigestion. Mr. Chil-
dren and Messrs. Tiedemann and Gmelin have made similar ob-
servations.
   12. Sodium.—The oxide of sodium, soda, forms a part of all
the fluids. It has never been discovered in a free state, but is united,
(without an  acid,) to albumen.   Most  frequently it is combined
with the muriatic and phosphoric acids; less so with the lactic, car-
bonic, and sulphuric acids. 
                     ORGANIC ELEMENTS.                   15

^ 13. Potassium.—The oxide, potassa, is found in  many animal
fluids, but always united with acids—the sulphuric, muriatic, phos-
phoric, &c.  It is much more common in the vegetable kingdom,
and hence one of its names—vegetable alkali.
  14. Magnesium.—The  Oxide, magnesia, exists  sparingly in
bones, and in some other parts, but always in combination with the
phosphoric acid.

  The organic elements, proximate principles, or compounds
of organization, are the primary combination of two or more ele-
mentary substances in definite  proportions.   Formerly four  only
were admitted—gelatine, f brine, albumen, and oil.  Of late years,
however, organic chemistry has pointed out numerous  others, which
are divided into two classes—1st, those that contain azote, as albu-
men, gelatine, fibrine, osmazome, mucus, caseine, urea,  uric  acid,
the red colouring principle of the blood, the yellow colouring prin-
ciple of the bile, &c;  and 2d, those  that do  not contain azote, as
oleine, stearine, the fatty matter of the brain and nerves, the acetic,
oxalic, benzoic, and lactic acids, the sugar of milk, that of diabetes,
picromel, the colouring principle of the  bile, and that of other so-
lids and liquids.

           I.  Organic Elements that contain Azote.

  1. Albumen.—This is one of the most common organic consti-
tuents, and appears under two forms—liquid and concrete. In its
purest state the former is met with in the white of  egg—whence
its name;  in the serum of the blood, the lymph  of the absorbents,
the serous fluid of the great splanchnic cavities and of the cellular
membrane, and in the synovial secretion. It is colourless and trans-
parent, without smell  or taste, and is  coagulated by acids, alcohol,
ether, metallic solutions, and infusion of galls, and by a temperature
of 165° Fahrenheit.
  Concrete, coagulated, or solid albumen, is white, tasteless, and
elastic; insoluble in water, alcohol, or oil, but readily  soluble in al-
kalies.
  Albumen is always combined with soda.  It  consists of carbon,
52.883; oxygen, 23.872; hydrogen, .7.540; and azote, 15.705.
  In both forms it exists, in abundance, in different parts of the ani-
mal  body. Hair, nails, and horn consist of it.  It is the great consti-
tuent of tumours in some form or other.
  2. Gelatine.—This is the chief constituent of the cellular tissue,
skin, tendons,  ligaments, and  cartilages.  The  membranes  and
bones also contain a large quantity of it.  It is obtained by boiling
these substances, for some time, in water; clarifying the  concen-
trated solution, allowing it to cool, and drying the substance,  thus
obtained, in the air. In this state it is called glue; in a more liquid
form, jelly.  Gelatine dissolves readily in hot water;  it  is soluble 
16
MATERIAL  COMPOSITION OF MAN.
in acids and alkalies; insoluble in alcohol, ether, and in the fixed
and volatile oils. Alcohol precipitates it from its solution in water.
It consists of carbon, 47.881; hydrogen, 7.914; oxygen, 27.207;
and azote, 16.998.
  Gelatine occurs,  nearly in a pure  state, forming  the  air-bag of
different kinds of fishes, and is well known under the name of isin-
glass.  It is used also extensively in the arts, under the form of glue
and size, on account of its adhesive quality.   What is called port-
able soup, is dried jelly seasoned with various spices.
  3. Fibrine.—This proximate principle exists in  the chyle; en-
ters into the composition of the blood; forms the chief part of mus-
cular flesh, and may be looked upon  as the most abundant animal
substance.  It is obtained by beating the blood as  it issues from
a vein  with a rod.   The fibrine attaches itself to each twig  in the
form of red filaments, which may be deprived of their colour by
repeated washing with cold  water.   Fibrine is solid, white, flexi-
ble, slightly  elastic, insipid, inodorous, and heavier than water.
It is neither soluble in water, alcohol, nor acids; but dissolves in
liquid  potassa or soda,  in  the cold, without much change; but,
when warm, becomes decomposed.
  Fibrine consists of carbon, 53.360; oxygen, 19.685; hydrogen,
7.021; azote, 19.934.  It constitutes the huffy coat of blood;  and is
thrown out from the blood-vessels, as a secretion, in many cases of
inflammation, becoming subsequently organized or  penetrated by
blood-vessels and nerves.
  4. Osmazome.—This  is  the matiere extractive  du bouillon,
extractive,  and saponaceous extract of meat.—When  flesh,
cut into  small fragments, is macerated in successive portions of
cold water, the albumen, osmazome,  and salts are dissolved, and,
on boiling the solution, the albumen is coagulated. From the liquid
remaining, the osmazome may be procured in a  separate state, by
evaporating to  the  consistence of an extract, and treating with
cold alcohol.  This substance is of a reddish-brown colour,  and is
distinguished from  the  other  animal principles by solubility in
water and alcohol,—whether cold or at the botling point,—and by
not forming a jelly when its solution is  concentrated by evapora-
tion.
  Osmazome exists in  the  muscles of animals, in the  blood, and
in the  brain.  It gives the peculiar flavour of meat to soups; and,
according to Fourcroy, the brown crust of roast meat consists
of it.
  5. Mucus.—This term has been applied  to various  substances;
and hence the discordant characters ascribed to it.  Applying it to
the fluid secreted by mucous surfaces, it varies  somewhat accord-
ing to  the source whence it is derived. Its leading characters may
be exemplified in that derived from the nostrils, which has the fol-
lowing properties:—It is insoluble in alcohol and water, but im-
bibes a little of the latter, and becomes transparent.   It  is neither 
ORGANIC ELEMENTS.
17
coagulated by  heat,  nor rendered  horny; but  is coagulated by
tannin.
  Mucus, in a liquid  state, serves as a protecting covering to differ-
ent parts. Hence it differs somewhat in its characters, according to
the office it has to fulfil.  When inspissated, it forms, according to
some, the minute scales that are detached from the surface of the
body by friction; the corns and the thick layers on the soles of the
feet, the nails, and horny parts; and it is contained in considerable
quantity in the hair, in wool, feathers, scales of fishes, &c.
  6. Caseum or  Caseine, or Caseous matter.—This substance
exists only in milk, and is the basis of cheese.   To obtain it, milk
must be left at rest, at the ordinary temperature, until  it is coagu-
lated ; the cream that collects on the surface must be taken off; the
clot well washed with water, drained upon a filter, and dried. The
residuum is pure caseum.  It is  a  white, insipid, inodorous sub-
stance, insoluble in water, but readily soluble in the alkalies, espe-
cially in ammonia.  It possesses considerable analogy with albu-
men.  Proust ascribes the characteristic  flavour of cheese to the
presence of the caseate of ammonia.
  Caseine  consists of carbon, 59.781; oxygen, 11.409; hydrogen,
7.429; azote, 21.381.
  7.  Urea.—This proximate principle exists in the urine of the
mammalia when in a state of health.  In  human urine it is  less
abundant after a meal, and nearly disappears in diabetes, and in af-
fections of the liver.  It is obtained by evaporating  urine to the
consistence of syrup.  It is then treated with  four parts of alcohol,
which are  afterwards volatilized by heating the  alcoholic extract.
The mass, that remains,  is dissolved in water,  or rather in alcohol,
and crystallized.
  The purest urea, that has been obtained, assumes the shape of acicu-
lar prisms, similar to those of the muriate of strontian. It is colour-
less, devoid of smell, or of action on blue vegetable colours, trans-
parent, and somewhat hard. Its taste is cool, slightly sharp, and its
specific gravity greater than that of water.  According to Berard,
it consists  of oxygen, 26.40; azote, 43.40; carbon, 19.40; and hy-
drogen, 10.80.
   8.  Uric or lithic acid.—This acid is found in the urine of man,
birds, serpents, tortoises, crocodiles, lizards, and silk-worms;  and
very frequently in urinary calculi. It is obtained by dissolving any
urinary calculus which contains it, or the sediment of human urine,
in warm liquid potassa, and precipitating the uric acid by the mu-
riatic.  Pure uric acid is white, tasteless, and inodorous.  It is inso-
luble in alcohol, and is dissolved very sparingly by cold or  hot
water, requiring about 10,000 times its weight of that fluid, at 60°
of Fahrenheit, for solution.  It consists of carbon, 36; hydrogen,
2;  oxygen, 24;  nitrogen, 28; in ninety parts.   The xanthic acid,
found by Marcet in urinary calculi, seems to have been this acid.
   9. Red  colouring  principle of the blood.—It has been already
   Vol. I.                      '3 
18
MATERIAL  COMPOSITION OF MAN.
observed, that Engelhart and Rose, German  chemists, had de-
tected iron in the red globules of the blood, and had  not found  it
in the other principles of that fluid.  It is probable, therefore, that
it has something to do with the colour. Engelhart's experiments
have not, however, determined the manner in which it acts, nor in
what state it exists in the blood.  The sulpho-cyanic acid, which is
found in the saliva, forms, with the peroxide of iron, a colour exactly
like that of venous blood; and it is not improbable but that the co-
louring matter may be found to  be  a sulpho-cyanate of iron.
  To obtain the red colouring matter, allow the crassamentum or
clot, cut into  thin pieces, to drain as much as possible  on bibulous
paper, triturating it with water, and then evaporating the solution
at a temperature not exceeding 122° of Fahrenheit.  When thus
prepared,  the colouring particles are no longer of a bright red co-
lour, and  their nature  is  somewhat  modified; in consequence  of
which they are insoluble in water.   When half  dried  they form a
brownish-red, granular, friable mass; and, when completely dried,
at a temperature between  167°  and 190°, the mass is tough, hard,
and brilliant.
  10.  Yellow colouring principle of the Bile.—This substance is
present in the bile of nearly all  animals.  It enters into the compo-
sition of almost all gall-stones, and  is deposited in that organ under
the form of magma.  It is solid, pulverulent when dry, insipid, in-
odorous, and heavier than water.  When decomposed by heat, it
yields carbonate of ammonia, charcoal, &c. It is insoluble in water,
in alcohol, and the oils, but is soluble in the alkalies.

       II.  Organic Elements that do not contain Azote.

  1. Oleine and Stearine.—Fixed oils  and fats are not pure proxi-
mate principles, as was at one time supposed. They consist of two
substances, one of which is solid at the ordinary temperature of the
atmosphere, and the other fluid;  the former of these is called Stea-
rine, from erectp, suet, the latter Elaine, or  Oleine, from  «a«<«»,
oil.  Stearine is the chief ingredient of vegetable and animal  suet,
of fat and butter, and is found, although in small  quantity, in the
fixed oils.  In the suety bodies, it is the cause of their solidity.
Elaine and stearine may be separated from each other by exposing
fixed oil to a low temperature, and  pressing it, when  congealed,
between folds of bibulous paper.   The stearine  is thus obtained in
a separate form, and by pressing the bibulous paper  under water,
an  oily matter is procured, which is elaine in a state of purity. The
stearine of mutton fat consists of carbon, 78.776; hydrogen, 11.770;
and oxygen, 9.454.  The  oleine of hog's lard, of carbon, 79.030;
hydrogen, 11.422; and oxygen, 9.548.
   2.  Fatty matter of the Brain and Nerves.—Vauquelin found
two varieties of fatty matter  in the brain, the one white, the  other
red, the properties of which have not been fully investigated.  Both 
organic elements.
19
possess the singular property of giving rise to phosphoric acid by
calcination, without there being any evidence of an acid or a phos-
phate in their composition.  They may be obtained by repeatedly
boiling the cerebral  substance in alcohol, filtering  at each time,
adding the various liquors, and suffering them to cool; alamellated
substance is deposited, which is the white fatty matter.   By then
evaporating the alcohol, which still contains  the red  fatty matter
and osmazome, to the consistence of bouillie, and  exposing this,
when cold, to the action of alcohol, the osmazome is entirely dis-
solved, whilst the alcohol takes up scarcely any of  the red fatty
matter.
   3. Acetic  acid.—This acid exists in a very sensible manner in
the sweat, urine, and in  milk,—even when entirely sweet.  It is
formed in the stomach in  indigestion, and is  one of the constant
products of the putrid fermentation of animal or  vegetable sub-
stances.  It consists, according to Gay Lussac and Thenard, of
carbon, 50.224; oxygen, 44.147;  and hydrogen, 5.629.   It is the
most prevalent of the vegetable acids, and the most easily formed
artificially.
   4.  Oxalic acid.—This acid,—which exists extensively in the
vegetable kingdom,  but always united with lime, potassa, soda, or
oxide of iron,—is only found as an animal  constituent in certain
urinary calculi, combined with lime.   It is formed  of carbon  one
part, oxygen two parts.
   5.  Benzoic acid.—This acid, found in many individuals of the
vegetable kingdom, is likewise met with in the urine of the horse,
cow, camel, rhinoceros;  and sometimes in that of man, especially
of children.  It consists of carbon, 74.71;  oxygen, 20.02; hydro-
gen, 5.27.
   6.  Lactic acid.—The acid of milk is met with in the blood,
 urine, milk, marrow, and also in  muscular  flesh.   Sometimes it is
 in a free state, but usually united with alkalies.  However much it
 may be concentrated, it does not crystallize, but remains under the
 form of syrup or extract.  When  cold it is tasteless, but when
 heated has a sharp acid  taste.  It is proper to  observe, that this
 acid, although described by Berzelius, has  not  been universally
 admitted by chemists.  Berzelius himself, indeed, now considers
 it to be acetic acid, disguised by animal matter;  and Tiedemann
 and Gmelin are of the same opinion.
   7. Sugar of milk.—This substance is so called, because it has a
 saccharine taste, and exists only in the milk.   It differs from sugar
 in not fermenting.  It is obtained  by evaporating whey, formed
 during the making of cheese, to the consistence of honey; allowing
 the mass to  cool, dissolving it, clarifying, and crystallizing. It com-
 monly crystallizes in regular parallelipipedons, terminated by pyra-
 mids with four faces.   It  is white,  semi-transparent, hard, and of
 a slightly saccharine taste, and is formed of carbon, 38.825; oxygen,
 53.834; and hydrogen,  7.341. 
20
MATERIAL  COMPOSITION OF  MAN.
   8. Sugar of diabetes.—-In the disease, called diabetes mellitus,
 the urine, which is passed in enormous quantity, contains, at the
 expense of the economy, a large quantity of a peculiar saccharine
 matter, which, when properly purified,  appears identical, both in
 properties and composition, with vegetable sugar, approaching nearer
 to the sugar of grapes than to that of the cane. It is obtained in an
 irregularly crystalline  mass, by  evaporating diabetic urine to the
 consistence  of syrup, and keeping it in a warm  place  for  several
 days.  It is  purified  by washing in cold, or at  the most, gently
 heated alcohol, till the liquor comes off colourless, and then dissolv-
 ing it in hot alcohol. By repeated crystallization it is thus rendered
 pure. (Prout.)  In the notes of two cases of diabetes mellitus now
 before us, we find that sixteen ounces of the urine of one of the pa-
 tients, of the specific gravity 1.034, afforded a straw-coloured ex-
 tract, which, when cold and consolidated,  weighed one ounce  and
 five drachms.  The same quantity of the urine of the other patient,
 specific gravity 1.040, yielded one  ounce  and seven drachms.
 Neither extract appeared to contain urea when nitric acid  was
 added, but when a portion was dissolved in water and subjected to
 a temperature of 212°, traces of ammonia were manifested on the
 vapour being presented to the fumes of muriatic acid.  From this,
 a conclusion was drawn that urea was present, as it is the only
 known animal matter which is decomposed by the heat of  boiling
 water. During a little more than one month that the subject of the
 latter case was under care, he passed about four hundred and eighty
 pints of urine, or about seventy-five pounds troy of diabetic sugar!
 much of this being derived from the system itself.  According to
 the analysis of Gay Lussac  and Thenard, this  sugar  consists of
hydrogen, 7.341; carbon, 38.S25; oxygen, 53.S34.
  9. Picromel.—Thenard discovered this principle in the bile of the
 ox, sheep, dog,cat, and of several birds; Chevallier, in that of man.
 To obtain it, the acetate of lead of commerce must be added to bile
 until there is no longer  any precipitate.  By this means, the  yellow
 matter of the bile and the whole of the fatty matter are thrown down,
 united with the oxide of lead; the phosphoric acid, of the phosphate
of soda, and the sulphuric acid, of the sulphate of soda, are likewise
precipitated.   The picromel may then  be thrown down from  the
fiUered liquor by the sub-acetate of lead.  The precipitate, which is
 a combination of picromel with oxide of lead, must now be washed
 and dissolved in acetic  acid.   Through this  solution, sulphuretted
 hydrogen is passed to separate the lead; filter and then drive  off
 the acetic acid by evaporation.
  Pure picromel is devoid of colour, and has the  same  appearance
 and consistence as thick turpentine.   Its taste is at first acrid and
 bitter, but afterwards sweet.   Its smell is nauseous, and its specific
gravity greater than that of water.  When digested with the resin
of the bile, a portion of the  latter is dissolved, and a solution  ob-
 tained, which has both a bitter and sweet  taste, and yields  a pre- 
solid parts.            .           21
tiipitate with the subacetate of lead and the stronger acids.  This is
the compound that causes the peculiar taste of the bile.  According
to Thomson, Picromel is  composed of carbon, 54.53; oxygen,
43.65;  and hydrogen, 1.82.
   10.  Colouring principle of the bile.—Of the nature of this prin-
ciple, which  exists in the bile of different animals, we have no defi-
nite ideas. It is generally precipitated along with the fatty matter;
and, by means of  ether, which dissolves it, may be obtained pure.
   The colouring principles of other parts of animals are not suffi-
ciently known to  admit of classification.
   These inorganic and organic elements, variously combined and
modified by  the vital principle, constitute the different parts of the
animal fabric. Chemistry, in its present improved condition, enables
us to separate these substances, and to investigate their  properties;
but all the information we derive from this source relates to bodies
that have been influenced by the vital principle, but are no longer
so; and in the constant mutations, that are occurring in the system,
whilst life exists,  and under its controlling  agency, the same tex-
tures might  exhibit very  different  chemical characteristics could
our researches  be directed  to them  under  those circumstances.
Whenever, therefore, the physiologist has to apply chemical eluci-
dations to operations of the living machine, he must recollect that
all his analogies are drawn from  dead matter—a state so widely
 differing  from the living, as to suggest to him  the necessity of a
 wise and discriminating caution.
   The components of the animal body are invariably found under two
forms—solids and fluids. Both of these are met with in every animal,
the former being  derived from the latter, for from the blood every
part of the body is separated; yet  they are mutually dependent, for
 every liquid is contained in a solid.   The blood itself circulates in
 a solid vessel;  both, too, possess an analogous composition, are in
 constant motion, and are incessantly converted  from  one  into the
 other.  Every animal consists of a union of the two, and this union
 is indispensable to life.  Yet certain  vague notions, with regard to
 their relative preponderance in the economy, and to their agency
 in the production of disease, have led to very discordant  doctrines
 of pathology—the solidists believing that the cause of most affec-
 tions is resident in the solids; the humorists, that we are to look
 for it in the fluids.  In this, as in similar cases, the mean will lead
 to the most rational result.   The causes of disease ought not to be
 sought in the one or the other exclusively.

             Of the Solid parts of the Human Body.

   A solid is a body whose particles  adhere  to  each  other, so  that
 they will not separate by their own weight, but require the agency
of some extraneous  force to effect the separation.  Anatomists  re- 
22
.  MATERIAL COMPOSITION OF MAN.
 duce all the solids of the human body to twelve varieties:—bone,
 cartilage,  muscle,  ligament,  vessel, nerve, ganglion, follicle,
 gland, membrane, cellular membrane,  and viscus.
   1. Bone is the hardest of the solids.   It forms the skeleton—the
 levers for the various muscles to act upon, and serves for the pro-
 tection of important organs.
   2. Cartilage is of a white colour, formed of very elastic  tissue,
 covering the articular extremities of bones to facilitate their move-
 ments;  sometimes added to bones to prolong them, as in the case
 of the ribs; at others placed within the articulations, to act as elastic
 cushions; and in the foetus, forming a substitute for bone; hence
 cartilages are divided into articular or  incrusting, cartilages of
prolongation, inter articular cartilages, and cartilages of ossifi-
 cation.
   3. The muscles constitute the flesh of animals.  They consist of
 fasciculi of red  and contractile fibres, extending from one bone to
 another, and are the agents of all movements.
   4. The ligaments are very tough, difficult to tear, and, under the
 form of cords or membranes, serve to connect  different  parts with
 each other, particularly the bones and  muscles; hence their di-
 vision, by some anatomists, into ligaments of the bones, as the li-
 gaments of the joints, and into  ligaments of muscles, as the ten-
 dons and aponeuroses.
   5. The vessels are solids, having the form of canals, in which the
 fluids circulate.   They are called, according to the fluid they con-
 vey, sanguineous, (arterial and venous,J chyliferous, lympha-
 tic or secretory vessels.
   6. The nerves are solid  cords, consisting of numerous fasciculi.
 These are connected with the  brain,  spinal  marrow, or great
 sympathetic; and are the  organs by which impressions are con-
 veyed to the nervous centres, and by which each part is endowed
 with vitality.   There are three great divisions of the nerves, those
 of motion, sensation, and expression.
   7. A ganglion is a solid knot, situated in the course of a nerve,
 and seeming to be formed by  an inextricable interlacing  of the
 nervous filaments. The term is likewise applied, by many modern
 anatomists, to a similar  interlacing  of the  ramifications of a lym-
 phatic vessel.  Ganglions may, consequently, either be nervous or
 vascular; and the latter again may be divided into chyliferous or
 lymphatic, according to the kind of vessel in which they may appear.
 Professor Chaussier, of Paris, a distinguished anatomist and  phy-
 siologist, whose recent loss science  has  to  deplore, has  given the
 name glandiform ganglions to certain organs, whose nature and
 functions are unknown to us, but which  he considers to  be  organs
 for the admixture and elaboration of fluids,—as the thymus eland.
 the thyroid gland, &c.                                   &    '
   S. "The follicle or crypt is a secretory  organ, shaped like a mem- 
SOLID PARTS.
23
branous ampulla or vesicle, and  always seated in the substance of
one of the outer membranes  of  the body, the skin or the mucous
surfaces, and secreting a fluid intended to lubricate them. They are
often divided into the simple or isolated, the conglomerate, and
the compound, according to their size or the number in which they
are grouped and united together.
  9. The gland is also  a secretory organ, but differing from  the
last. The fluid secreted by it is of greater or less importance.  Its
organization is more complex than that of the follicle; and the fluid,
after secretion, is poured out by means of one or  more excretory
ducts.
   10. Membrane.—This is one of the most extensive and important
of the substances formed by the cellular tissue.   It is spread out in
the shape of a web, and  in man serves to line the cavities and reser-
voirs, and to form, support, and envelope all the organs.
  Bichat divides membranes into two kinds, the simple and com-
pound, according as they are formed of one or more layers.
  The simple membranes are of three kinds, the serous, mucous,
and fibrous.
   1st. The serous membranes  or those that constitute all the sacs
or shut cavities of the  body, those of the chest and abdomen, for
example.
   2dly. The mucous, or those that line all the outlets of the body;
the air passages, alimentary canal, urinary and genital organs, &c.
   3dly. Fibrous membranes, or those which compose tendon, apo-
neurosis, ligament, &c.
   The compound membranes are formed by the union of the sim-
ple, and are divided into sero-fibrous, as the pericardium; sero-
mucous, as the gall-bladder, at its lower part; and fibro-mucous,
as the ureters.
   11.  The cellular or laminated tissue, to be described presently,
is a sort of spongy or  areolar  structure, which forms the  frame-
work of all the solids, fills up the spaces between them, and serves
 at the same time as a bond of union and of separation.
   12.  The viscus is the most complex solid  of the body, not only
 as regards intimate organization, but use.  This name is  given  to
 organs contained in the splanchnic cavities,—brain, thorax, and ab-
 domen ;—and hence called cerebral, thoracic, or abdominal.
   Every animal solid is either amorphous or fibrous; that is, it is
 either without apparent arrangement, like jelly, or it is disposed in
 minute threads, which are called fibres.  The disposition of these
 threads in  different structures is various.  Sometimes they retain
 the form of threads; at others they have that of laminae, lamellae,
 or plates. Accordingly, when we examine any animal solid, where
 the organization is perceptible, it is found to be either amorphous,
 or fibrous and laminated.
    This circumstance led the ancients to endeavour to discover an 
24
MATERIAL COMPOSITION OF  MAN.
elementary fibre, or filament, from which all the various organs
might be formed.  Haller embraced the idea, and endeavoured
to unravel every texture to this ultimate element; asserting, that it
is to the physiologist  what the line is to the geometer; and that, as
all figures can be constructed  from the  line, so  every tissue and
organ of the body may be built up from the filament.  Haller,
however, admits, that his elementary fibre is not capable of demon-
stration, and that it is visible only to the "mind's eye," ilinvisibilis
est eafibra, sold mentis acie distinguimus."  It must be regard-
ed, indeed, as a pure abstraction; for as different animal substances
have different proportions of carbon, hydrogen, oxygen and azote,
it is fair to conclude, that the elementary fibre must differ also in
the different structures.
   The ancients believed, that the  first product of the  elementary
fibre was cellular tissue, and that this tissue formed every organ of
the body;—the difference in the appearance of these organs arising
from the different degrees of condensation of its laminae.
   Anatomists, however, have been unable to  reduce all the animal
solids to cellular tissue solely.
   In the upper classes of animals, three primary fibres or tissues,
or anatopiical elements, are usually admitted, the cellular or lami-
nated, the muscular, and the nervous, pulpy, or  medullary.
   1. The cellular or  laminated fibre or tissue.—This is the most
simple and abundant of the animal solids.   It exists in every orga-
nized being, and is an element of every other solid.  In  the enamel
of the teeth only it has not been detected.  It is formed of an as-
semblage of thin laminae of delicate, whitish,  extensible filaments,
interlacing and leaving between each other areolae or cells.   (See
Fig. 1.) These plates or filaments are neither sensible nor irritable,
and are composed of concrete gelatine.  The  great bulk of animal
solids consists of cellular tissue, arranged in the form of membrane.
  2. Muscular fibre  or tissue.—This is a substance of a peculiar
            nature, arranged in fibres of extreme delicacy.   The
   Fig. 2.   fibres are linear, soft, grayish or reddish, (see Fig. 2.)
            and possessed of irritability; that is,  they  move very
            perceptibly under the influence of mechanical or che-
            mical  stimuli.   They  are composed,  essentially, of
            fibrine.  Prochascha,  a distinguished anatomist of
            Vienna,  maintains, that the ultimate  fibre  or filament
            of muscular tissue is discernible, and that it is, in every
            part,  of  the same magnitude,  about  TVtn  part of the
            diameter of the red globule of the  blood, or about
            To-oVo-oth Paft  °f an mch m diameter.  It is probable,
            however, that were our means of examining minute
             objects still further improved, we should  be able to
             detect a  filament even more delicate than this.
              The muscular fibres, which are arranged  in the form
 
PRIMARY AND COMPOUND TISSUES.            25
of membranous expansions or muscular coats, differ from proper
muscles chiefly in the mechanical ar-
rangement of their fibres. (Fig. 3,afy           Fig. 3.
b.) The physical and chemical charac-
ters of both  are identical. The fibres,
instead of being collected  into fasci- <x
culi, are in layers, and instead of be-
ing parallel,  interlace.   This tissue
does not exist in the zoophytes.
  3. Nervous, pulpy, or medullary
fibre or tissue.—This tissue is much
less distributed than the preceding.
It is of a pulpy consistence, is com-
posed essentially of albumen, united
to a fatty matter, and is the organ of
sensibility, or for receiving and trans-
mitting impressions to the mind.  Of it, the brain, cerebellum, me-
dulla spinalis, nerves and their ganglia are composed.  The ultimate
nervous filament is, by Fontana, Reil, and others, considered to be
about twelve times larger  than the ultimate muscular filament. The
same remarks, however, may be made here concerning our limited
means of observation, that were made on the elementary muscular
fibre.
  Professor Chaussier has added another primary fibre or tissue,
the albugineous. It is white, satiny, very resisting, of a gelatinous
nature, neither sensible  nor irritable, and constitutes the  tendons
and tendinous structures.   Chaussier is, perhaps, the only anato-
mist that admits this tissue.  Others regard it as a very condensed
variety of the cellular.
  These various fibres or tissues, by uniting differently, constitute
the first order of solids; and these again, by union,  give rise to
compound solids, from which  the different organs, bones, glands,
&c. are formed.   A bone, for example, is a compound of various
tissues, osseous in its body, medullary in its interior, fibrous ex-
ternally, and cartilaginous at its extremities.
  Bichat was the  first anatomist who possessed any clear views
regarding the constituent tissues of the animal frame; and whatever
merit may accrue to after  anatomists and physiologists, he  is en-
titled to  the credit of having pointed out the path, and facilitated
the labours of the anatomical  analyst.  The following table exhibits
the compound tissues generally admitted.
             1.  Cellular.
                                       C Arterial.
             2. Vascular                -< Venous.
Systems. <l                              ( Lymphatic.
                                        C Cerebral.
                                        I Ganglionic.
               Osseous.
  Vol. I. ~                   4
3. Nervous
4. 
26
material composition of man.
5.  Fibrous
6.  Muscular -
Systems. «j
 7.
 8.
 9.

10.
Erectile.
Mucous.
Serous.
C Fibrous.
3 Fibrocartilaginous.
£ Dermoid.
C Voluntary.
i Involuntary.
C Pileous.
I Epidermoid.
 Glandular.
               Corneous or Epidermic

           11. Parenchymatous.
  In combining to form the different structures, the solids are ar-
ranged in a variety of ways.  Of these, the chief are into filaments
or elementary fibres, tissues, organs, apparatuses, and systems.
  The filament, we have seen, is the elementary solid.  A fibre
consists of a  number of filaments united together.   Occasionally,
this is called a tissue.
  The term tissue usually, however, means a particular  arrange-
ment of fibres.  An organ is a compound of several tissues.  An
apparatus is an assemblage of organs, concurring to the same end.
The digestive apparatus consists of the organs of mastication, in-
salivation, and deglutition, of the stomach, duodenum,pancreas, liver,
chyliferous vessels, &c.  These organs  may  be, and are of very
dissimilar character, both  as regards their structure and functions;
but if they concur  in the same  object, they form an apparatus.
  A system, on the other hand, is an assemblage of organs,  all of
which possess the same or an analogous structure.   Thus, all the
muscles of the body have a common structure and function, and
they constitute, in the aggregate, the muscular system.   All the
vessels of the body, and all the nerves, for like reasons, constitute
respectively the vascular and nervous systems.

              Of the Fluids of the Human Body.

  The positive quantity or proportion of the  fluids in the human
body does not admit of easy appreciation, as  it must obviously vary
at different periods, and under different circumstances.  The younger
the animal, the greater is the preponderance of the fluids.  When
we first see the embryo, it appears to be almost entirely fluid.  As
it becomes gradually developed, the  solid parts are increased in
their relative proportion, until the adult age;  after which this pro-
portion  becomes less  and  less as the individual advances in life.
During the whole of  existence, too,  the  quantity of fluids in the
body fluctuates.  At  times there  is plethora or unusual fulness of
vessels; at others, the blood is less in quantity.  Experiments have
been made for the purpose of ascertaining the relative proportion
of the  fluids to the  solids. Richerand says, that they are in
the ratio of six to one; Chaussier, of nine to one. The  latter 
FLUIDS.
27
professor  put a dead body,  weighing one  hundred and  twenty
pounds, into a heated oven, and dried it.  After desiccation, it was
found to be reduced to twelve pounds.  It is  probable, however,
that some of  the  more solid portions were driven  off by the heat
employed, and hence that the evaluation of the proportion of the
fluids is too high. In the Egyptian mummies, which are completely
deprived of fluid, we find the solids extremely light, not weighing
more than seven pounds;  but, as we are ignorant of the original
weight of the body, we cannot arrive at any comparative approxi-
mation. The dead bodies, found in the arid sands of Arabia, afford
additional instances of this reduction by desiccation, as well as the
dried preparations of the anatomical theatre.  To a less extent, we
have the same thing exhibited in the excessive diminution in weight,
which  occurs in disease,  and  occasionally in those  who are appa-
rently in  health.   Not many years ago, an anatomie vivante was
exhibited  in London, to the gaze of the curious and scientific, whose
weight was not more than eighty pounds.  Yet the ordinary func-
tions were carried on, apparently unmodified.  In the year 1S30, a
still more wonderful phenomenon was exhibited in New York, who
was called the "living skeleton."   This extraordinary being was
forty-two  years old, five feet two inches high, and weighed but
sixty pounds.   His weight was formerly one hundred and thirty-
five pounds.  For sixteen years previously, he had  been gradually
losing flesh, without any apparent disease, having enjoyed perfect
health and appetite, eating, drinking, and sleeping  as well as any
one. We have it also on the authority of Captain Riley, that, after
protracted sufferings in Africa,  he was reduced from two hundred
and forty pounds to below ninety !
  The fluids  are variously contained;  sometimes in vessels, as the
blood and lymph; at others, in cavities, as the fluids secreted by the
pleura, peritoneum, arachnoid coat of the brain, &c.; others are in
minute areolae, as the fluid of the cellular membrane; whilst others
again are intimately combined with the solids.
  They differ likewise in density,  some existing  in the  state of
halitus or vapour; others are very thin and aqueous, as the fluid of the
serous membranes; others of more consistence, as the secretion of
the mucous membranes, the animal oils, &c.
  The physical and chemical  properties of the fluids will engage
our attention  when they fall individually under consideration, and
we shall find  that one of them at least, the blood, exhibits certain
phenomena analogous to those of the living solid.
  The fluids  have been differently classed, according to the  parti-
cular views that have from time to  time prevailed in the schools.
The ancients  referred them all to four—blood,  bile, phlegm  or pi-
tuita, and atrabilis; and each of these was found to  abound in one
of the four ages, seasons, climates, or  temperaments.  The  blood
predominated in youth, in the spring, in cold mountainous regions, 
28
material composition of man.
and in the sanguine or inflammatory temperament. The pituita, or
phlegm, had the mastery in old age, in winter, in low  and moist
countries, and in the lymphatic temperament.  The bile predomi-
nated in mature age, in summer, in hot climates, and in  the bilious
temperament; and lastly, the atrabilis was the characteristic of mid-
dle age, of autumn, of equatorial  climes, and of the melancholic
temperament.   This was their grand humoral system,  which has
vanished before a better observation of facts and improved methods
of physical and  metaphysical  investigation.   The atrabilis was a
creature of the imagination; the pituitous condition is unintelligible
to us; and the doctrine of the influence of the humours on the ages,
temperaments, &c. irrational.
   Subsequently, the humours were classed according to their phy-
sical and chemical properties; for instance, they  were divided into
liquids, vapours, and gases;  into acid, alkaline  and neutral; into
thick and thin;  into  aqueous, mucilaginous, gelatinous, and  oily;
into saline,oily, saponaceous, mucous, albuminous, and fibrinous, &c.
In more modern times, endeavours have  been made to class them,
according to their uses in the economy, into l,recrementitial fluids,
or those intended to be again absorbed; 2, excremential, those
that have to be expelled from the body;  and  3, those which parti-
cipate in both uses,and arehencetermed excremento-recrementitial.
Blumenbach divided them into crude humours, blood, and secreted
humours, a division which has been partly adopted by Adelon; and
lastly, Professor  Chaussier, whose anatomical arrangements and
nomenclature have rendered  him justly  celebrated,  reckons five
classes:—1, those produced by the act of digestion, the chyme,and
the chyle; 2, the circulating fluids, the lymph and the  blood; 3, the
perspired fluids;  4, the follicular; and 5, the  glandular.  This  ar-
rangement has been adopted by Magendie, and is  as satisfactory
as any that has been proposed.
   The following is an enumeration of the different fluids or hu-
mours of the body, all of which will have to engage attention here-
after.
   1. The chyme and the chyle.
   2. The blood and the lymph.
   3. The perspired or exhaled fluids, including the serous fluids,
the synovia, the fat, the medulla, the coloring matter of the skin, the
colouring matters of the uvea and choroid of the  eye, the  three
humours of the eye,the liquor of CoTUGNO,the cephalo-spinal fluid,
the fluid of the lymphatic and glandiform ganglions, the humour
exhaled from the interior of vessels, the liquor amnii, the water of
the chorion and that of  the umbilical vesicle, the cutaneous trans-
piration,  the  pulmonary transpiration, the perspired humours of
the digestive apparatus, and  those  of  the  urinary and  genital
organs.  In  the female, during the time she  is capable  of  fe-
cundation, a  monthly exhalation  takes  place, called the catame- 
                  ELEMENTARY  STRUCTURE.                29

nia, or menses; and after delivery, a similar secretion occurs, called
the lochia.
  4. The follicular fluids—the sebaceous humour of the skin, the
cerumen, the humour of Meibomius, that of the caruncula lachry-
malis, the humour secreted at the base  of the  glands in the male,
and within  the vulva of the female, the humour of the mucous fol-
licles of the respiratory, digestive,  urinary, and genital apparatuses,
including that of  the  tonsils, cardiac  glands, prostate, Covvper's
glands, &c.
  5. The glandular fluids—the  tears, saliva, pancreatic juice,
bile, urine,  sperm,  and  milk.

     Of the Elementary Structure of Animal Substances.

  Anatomists have not  been content with endeavoring  to  reduce
the different organized textures to primary fibres and filaments, but,
by the aid of the microscope, they have attempted to discover the
particular arrangement of the constituent corpuscles. The discovery
of that valuable  instrument gave  the impulse, and very soon the
scientific world was presented with the results obtained by numerous
observers.  These observations have been, from time to  time, con-
tinued  until the present day.  It is, however, to be regretted, that
our information, derived from this source, has  not been as accurate
as it would appear to admit of.  From different quarters we  have
had the most discordant statements, so  as to exhibit clearly, either
that the  narrators  have employed instruments of very different
powers, or  that they have been blinded, or had the vision depraved
by preconceived theories or hypotheses. One of the very first ef-
fects of the discovery of the microscope was the detection of a glo-
bular structure of  the  primitive tissues of the body, by Leeuen-
hoek, an announcement that gave  rise to much controversy, which
has coutinued indeed till the present time, and has  engaged  the at-
tention particularly of Prochaska, Fontana, Sir Everard Home,
Mr. Bauer, the  brothers Wenzel, Dr. Milne Edwards, MM.
Prevost and Dumas, Dutrochet, Hodgkin,  and  others.
   The observations and experiments,  of Dr.  Edwards  especially,
have recently occasioned much interesting speculation and inquiry.
They may  perhaps be taken as the foundation on  which the be-
lievers in the globular structure now rest their  opinions.  The views
of Dr. Edwards were first published in 1823,  in a communication,
entitled " Mimoire sur la structure e'tementaire des principaux
tissus organiques des Animaux;" and in a second  article in the
Annates des  Sciences Naturelles, for December, 1826, entitled,
" Recherches microscopiques sur  la structure in time  des tissus
organiques des Animaux." He examined all the principal textures
of the  body, the cellular tissue, the membranes, tendons, muscular
fibre, nervous tissue, the skin, the coats of the  blood-vessels, &c.
   When the cellular tissue was viewed by a powerful lens, it seemed 
SO             MATERIAL composition of man.
Fig. 4.
Fig. 5.
 to consist of cylinders; but by using still higher magnifying powers,
                    these cylinders  were found to be formed  of
                    rows of globules, all of the same size, that is,
                    about the YTVntn or ttVii^ °^ an *ncn m ^*
                    ameter; (Fig. 4.) separated  from  each other,
                    and lying in various directions; crossing and
                    interlacing, some of the rows straight, others
                    bent,  and some twisted,  forming irregular
                    layers, united by a kind of net-work.
                      The membranes, which  consist of  cellular
                    tissue, were found to present exactly the same
                    kind of arrangement.
                      The muscular fibre, when examined in the
                    like manner, was found to consist of globules
 also -gVoirth 0I> an mcn m diameter.   Here, however, the rows of
             globules are always  parallel.  The fibres never in-
             tersect each other like those of the cellular tissue,
             and this is the only discernible difference; the form
             and size of the globules being alike.   The size of the
             globules and the linear arrrangement they  assume,
             seem to be the same in all animals  that possess a
             muscular structure.   (Fig. 5.)
               The  nervous structure  has, by  almost  all ob-
             servers, been esteemed globular.  The examination
             of Dr. Edwards yielded similar results.   It seemed
             to be composed of lines of globules of the same  size
             with those  that form the cellular membrane  and the
             muscles; but holding an intermediate place as to the
             regularity of their arrangement, and having  a fatty
matter interposed between the rows.
                     In regard to the size of the  globules, how-
                  ever, Dr. Edwards differs materially from an
                  accurate and experienced microscopic observer,
                  Mr. Bauer, who asserts that the cerebral glo-
                  bules are of various sizes. (Fig. 6.)
                     From the result of his diversified observa-
                  tions, Dr. Edwards  concludes, that  "sphe-
                  rical corpuscles, of the diameter of ?£7th of a
                  millimeter,  constitute,  by their aggregation,
                  all the organic textures, whatever may be the
                  properties, in  other  respects, of those  parts,
                  and the functions for which  they are des-
                  tined."
  The beautiful harmony and simplicity, that would thus seem to
reign through the structures of the  animal body,  have attracted
great attention  to  the  labours of Dr. Edwards.   The vegetable
kingdom was subjected to equal scrutiny; and, what seemed still
more astounding, it was affirmed, that the microscope proved it also
Fig. 6.
 
elementary structure.
31
to be constituted of globules exactly like those of the animal, and of
the same magnitude, TtV^tn °f an mc^ m diameter; hence it  was
assumed, that all organized bodies possess the same elementary
structure, and of necessity, that the animal and the vegetable  are
readily convertible into each other under favourable circumstances,
and that they differ only in the greater or less complexity of their
organization.  Independently of all other objections, however, the
animal differs, as we have  seen,from the vegetable in composition;
and,this difference must exist not only in the whole but in its parts;
so that even were it demonstrated, that the globules of the beings of
the two kingdoms are alike, it would by no means follow that they
are identical in intimate composition.
  The discordance, that we have deplored, is strikingly  applicable
to the case before us.  The appearance of the memoir of Dr. Ed-
wards excited the attention of Dutrochet, and in the  following
year his " Researches" on the  same  subject were published, in
which  he asserts,  that the globules which compose the different
structures of the invertebrated animals are considerably larger than
those of the vertebrated;  that the former appear to consist of cells,
containing other globules still smaller; and hence he infers that the
globules of vertebrated animals are likewise cellular, and  contain se-
ries of still smaller globules.
   Dr.  Edwards, in  his experiments, found that the globules of the
nervous tissue, whether examined in  the brain, in the spinal cord,
in the  ganglia, or in  the nerves,  have  the same shape and  diame-
ter, and that no difference can be distinguished in them from what-
ever animal the tissue be taken.   Dutrochet,  on the other hand,
considers, with Sir  Everard Home and the  brothers Wenzel,
that the globules of  the brain are cellules of extreme minuteness,
containing a medullary or  nervous substance, which is  capable of
becoming concrete by the action of heat and of acids.  This struc-
ture, he remarks, is strikingly evidenced in  certain
molluscous animals; and he instances  the small pulpy  Fig. 7.
nucleus, forming the cerebral hemisphere of the Umax
rufus, and the heMx pomatia,  composed of globular,
agglomerated cellules, on the parietes of which a con-
 siderable number  of globular or ovoid corpuscles are
perceptible.   (Fig. 7.)
'  M.  Dutrochet, again, has not found the structure of the nerves
to correspond with that of the brain.   He asserts that the elemen-
tary fibres, which enter into their composition, do not consist simply
 of rows of globules, according to the opinion of Edwards and
 others, but that they are cylinders of a  diaphanous substance, the
surface of which  is  studded with  globular corpuscles, and  that as
these cover the whole surface of the cylinder, we are led to believe
that they are situa'ted  internally. After detailing this  difference of
structure  between  the brain and nerves,  the former  consisting
chiefly of nervous corpuscles, the latter chiefly of cylinders or fibres,
 
33
MATERIAL COMPOSITION OF MAN.
Dutrochet announces the hypothesis which exhibits  too  many
indications of having been formed prior to his microscopic investi-
gations, that these cerebral corpuscles are destined for the produc-
tion of the nervous power, and that the nervous fibres are tubes,
filled with a peculiar fluid, by  the agency of which nervi-motion is
effected.   For further  developments  of the analysis of Dutro-
chet, the reader is referred to the work itself, which exhibits  all
the author's  ingenuity and enthusiasm, but  can  scarcely  be  consi-
dered historical.
  The beautiful superstructure of Dr. Edwards, and the ingenuity
of Dutrochet have, however, been most fatally assailed  by subse-
quent experiments, with a microscope of unusual power, by Dr.
Hodgkin.   The globular structure of the animal tissues, so often
developed, and apparently so  clearly and satisfactorily established
by Dr. M. Edwards, is, we are told  by Dr. Hodgkin, a mere de-
ception; and we have again to refer the most minute parts of the
cellular membrane, muscles, and  nerves to the striated  or fibrous
arrangement. A part of the discrepancy, between Messrs. Edwards
and Dutrochet, may be explained by the fact of the former using
an instrument of greater  magnifying power  than  the latter, who
employed the simple microscope only.  It has been observed, that
when Dr. Edwards used an ordinary lens, the  arrangement of a
tissue appeared cylindrical, which, with the compound microscope,
was distinctly globular.  The discordance  between  Messrs. Ed-
wards and Hodgkin is reconcileable with more difficulty.  On the
whole, our minds on this subject must be kept in a state of doubt,
and we must wait until the point is fully ascertained, if  it is ever
destined to be so.  In our uncertainty regarding the existence of
the globules themselves, it is  hardly  necessary to inquire into the
opinion professed by Messrs. Prevost  and Dumas, and by Dr.
Edwards, that  all the  proximate  principles,  albumen, fibrine,
gelatine, &c. assume a globular form,  whenever they pass from the
fluid to the solid state, whatever may be the cause producing such
conversion.
  Lastly, J.  F. Meckel, from his observations, infers, that all the
solids and fluids of the human body are formed  of two elementary
substances:  1, of an  amorphous matter, which  is concrete in the
former and fluid  in the latter; and 2, of globules.   Of  these two
substances, the former may exist alone, and constitute some of the
textures;—for instance, the cellular tissue,the bones, cartilages, &c.
The globules, on the contrary, are always  united with  the  amor-
phous substance, which in the solids serves as a bond, and in which
the globules are immersed in  the fluids.  This  anatomist believes
that the globules differ in shape, size, and number, in different ani-
mals, and in different parts of the same animal, and even in the
same part, according to age. 
PHYSICAL PROPERTIES OF TISSUES.
33
              Physical Properties of the Tissues.

   The tissues of the body possess the physical properties of matter
in general.  They are  found to vary in consistence, some  being
hard, and others soft, as well as in colour, transparency, &c.  We
find also certain physical properties, analogous, indeed, to what are
met with in several inorganic substances, but generally superior in
degree.  These are flexibility, extensibility, and elasticity, which
are variously combined and modified in the different forms of ani-
mal  matter, but exist to a greater or less  extent  in  every organ.
Elasticity is only exerted under particular circumstances.   When
the part, for example, in which it is seated, is put upon the stretch
or is compressed, the force of elasticity restores it to  its primitive
state, as soon as the distending or compressing cause  is removed.
The tissues, in which elasticity is adherent, are so disposed through
the body, as to be kept  in a state of distention by the mechanical
circumstances of situation; but as soon as these circumstances are
deranged, elasticity comes into play and  produces shrinking of the
substance.  It is easy to see, that these circumstances, owing to the
constant alteration in the relative situation of parts, must be ever
varying.  Elasticity is, therefore, constantly called into action, and
in many cases acts upon the tissues as a new power.   The  carti-
lages of the ribs, joints, &c. in this manner, are valuable agents in
particular functions. We have other examples of the mode in which
elasticity exhibits itself under similar circumstances, when the con-
tents of hollow parts are withdrawn, and whenever muscles are di-
vided transversely.  The gaping wound, produced by a cut across
a shoulder of mutton, is familiar to all.   Previous to the division,
the force of elasticity is kept neutralized by the mechanical circum-
stances of situation,—or by the continuity of the parts; but as soon as
this continuity is disturbed, or in other words, as soon as the me-
chanical circumstances are altered, the force of elasticity is exerted
and  produces recession of the edges.  This property has been de-
scribed under various names.  It has been  called tone, or tonicity,
contractility de tissu, contractility par  dS-faut d'extension, fyc.
   The other properties of flexibility and extensibility vary greatly
according to the structure of the parts.   The tendons, which are
composed of the cellular tissue, exhibit very little extensibility, and
this for wise purposes.  They are the conductors of the force de-
veloped by the  muscle, and were they to yield, it would be at the
expense of the muscular effort; but they possess great flexibility.
The articular ligaments are very flexible, and  somewhat more ex-
tensible.  On the other hand, the fibrous or ligamentous structures,
which are employed to support weights, or which  are antagonists
to muscular action,—such as the ligamentum nuchas, or the strong
ligament, which passes from the spine to the head of quadrupeds,—
are very extensible and elastic.
;   Another physical property, possessed  by animal substances, is a
   Vol.  I.    '                   5 
34
MATERIAL COMPOSITION OF MAN.
   kind of contractility, accompanied with sudden corrugation  and
   curling.  This effect, which Bichat terms mcornissement, is pro-
   duced  by heat and by chemical agents, especially by the strong
   mineral acids.  The property is exhibited by leather when thrown
   into the fire.
     An effect,  in some measure resembling this, is  caused by the
   evaporation of  the water which is united to  animal substances.
   This constitutes what Dr. Roget calls the hygrometric property
   of animal membranes.  It is characteristic of dry,  membranous
   structures, all of which are found to contract, more  or less, by the
   evaporation of moisture, and to expand again by its re-absorption;
   hence the employment of such  substances as hygrometers.   Ac-
   cording to Chevreul, many of the tissues are indebted  for their
   physical properties to  the water they contain, or with which they
   are  imbibed.  When deprived of this fluid, they become  unfit for
   the  purposes for which they are destined in life, and resume them,
   as soon as they have again recovered the fluid.
     A most important property, possessed by the tissues of organized
   bodies, is that of imbibition; a property to which attention has been
   chiefly directed of late. If a liquid be put in contact with any organ or
   tissue, in process of time the liquid will be found to have passed into
   the areolae of the organ or tissue, as it would enter the cells of a sponge.
   The length of time, occupied in this imbibition, will depend upon
   the  nature of the liquid and the kind of tissue.   Some parts of the
   body, as the serous membranes and small vessels, act as true sponges,
   absorbing with  great promptitude; others resist imbibition for a
   considerable time,—as the epidermis.
     Liquids penetrate equally from without to within; the process is
   then called transudation, but it does not differ from imbibition.
     Within the last few years some singular facts have been observed
   regarding the  imbibition of fluids and gases.  On filling membra-
   nous expansions, as the intestine of a chicken, with  milk  or some
   dense  fluid, and immersing it in  water, Dutrochet observed that
   the  milk left the intestine, while the water entered  it; and hence
   he concluded, that whenever an organized cavity, containing a fluid,
   is immersed in another fluid, less dense than that which is in  the
   cavity, there is a tendency in the cavity to expel the denser and
   absorb  the  rarer fluid.  This Dutrochet terms endosmose, or
'   " inward impulsion;" and he conceives  it  to be a  new power—a
   " physico-organic or vital action." Subsequent experiments showed
   that a reverse  operation could likewise have place.   If the  internal
   fluid was rarer than the external, the transmission occurred in  the
   opposite direction.   To this reverse process Dutrochet gives
   the  name exosmose, or " outward impulsion."
     Soon after  the appearance of Dutrochet's essay, similar  ex-
   periments were repeated, with some modifications, by Dr. Togno, of
   Philadelphia, and with like results. The fact of this imbibition and
   transudation was singular and impressive; and with so enthusiastic 
PHYSICAL  PROPERTIES  OF TISSUES.
35
an individual as Dutrochet, could not fail to give birth to nu-
merous and novel conceptions.  The energy of the action of both
endosmose and exosmose is in proportion, he asserts, to the differ-
ence between the specific gravities of the two fluids;  and also, inde-
pendently of their gravity, their chemical nature affects their power
of transmission.  These  effects—Dutrochet  at once decided—
must be owing to electricity.  The cavities in  which the changes
take place he conceives to be like Leyden jars, having their two
surfaces charged with opposite electricities, the ultimate effect or
direction of the current being determined by the excess of the one
over the other.
  In  an  interesting  and  valuable communication  by Dr. J.  K.
Mitchell, of Philadelphia, " on the penetrativeness of fluids,"
many of the visionary speculations of Dutrochet are sensibly ani-
madverted upon.  It is there shown,  that Dutrochet has asserted,
in the teeth of some of his most striking facts, that the current was
from a less dense to a more dense  fluid; that it was from positive to
negative, dependent not on an inherent power of filtration, a power
always the same when the same membrane is concerned, but modi-
fied at pleasure by supposed electrical agencies.
  The facts and arguments, adduced by Dr. Mitchell, clearly ex-
hibit that imbibition and transudation are dependent upon the pene-
trativeness of the liquid  and the penetrability  of the membrane;
that if two liquids, of different rates of penetrativeness, be placed on
opposite sides of an animal membrane, " they will in time present
the greater accumulation on the side of the  less penetrant liquid,
whether more or less dense; but will finally, thoroughly, and uni-
formly mix on both sides; and at length, if any pressure exist on
either side, yield to that and pass to  the other side."
  A portion of the communication of Dr. Mitchell relates to an
analogous subject, to which, as M. Magendie has observed, little
or no  attention has been paid  by physiologists—the permeability
of membranes by gases.  " The laminae," Magendie remarks, " of
which membranes are constituted, are so arranged, that the gases can
penetrate them, as it were, without obstacle.  If we take a bladder, and
fill it with pure hydrogen gas, and afterwards leave it in contact
with atmospheric air, in a very short time the hydrogen will have
lost its purity, and will be mixed  with  the atmospheric air which
has penetrated the bladder.  This phenomenon is the more rapid
in proportion as the membrane is thinner and less dense.  It pre-
sides over one of the most important acts of  life—respiration,  and
it continues after death."
  Dr. Mitchell is the first individual who  directed his observa-
tion to the relative penetrativeness of different gases.   This he was
enabled to discriminate by the following satisfactory experiment,
which we give in his own words.  " Having constructed a syphon
of glass, with one limb three inches  long, and the other ten or
twelve inches, the open end  of the short leg was enlarged  and 
36
MATERIAL COMPOSITION OF MAN.
formed into the shape of a  funnel, over  which finally was firmly
tied a  piece of thin  gum elastic.  By inverting this syphon, and
pouring into its longer limb some clean mercury, a portion of com-
mon air was shut up  in  the short  leg, and was in communication
with the membrane.   Over this end, in the mercurial trough, was
placed the vessel containing the gas to be tried, and its velocity of
penetration measured by the time occupied in elevating to a given
degree the  mercurial column in the other limb. Having thus com-
pared the gases with common air, and subsequently, by the same in-
strument, and in bottles, with each other, I was able to arrange the
following gases according to their relative  facility  of transmission,
beginning  with the  most powerful.  Ammonia, sulphuretted hy-
drogen, cyanogen, carbonic acid, nitrous oxide, arsenuretted hydro-
gen, olefiant gas, hydrogen, oxygen, carbonic oxide, and nitrogen."
  He found that ammonia transmitted in one minute as much  in
volume as sulphuretted hydrogen, in two minutes and a half; cya-
nogen in three minutes and a quarter; carbonic acid, five minutes
and a half;  nitrous oxide, six minutes and a half; arsenuretted hy-
drogen, twenty-seven minutes  and a half; olefiant gas, twenty-
eight  minutes; hydrogen, thirty-seven minutes and a half; oxygen,
one hour and fifty-three minutes;  carbonic oxide, two hours and
forty minutes.
  It was found too, that up to  a pressure of sixty-three inches of
mercury,* equal to more  than the weight of two atmospheres, the
penetrative action was capable of conveying the gases,—the subjects
of the experiment,—into the short leg through the gum elastic mem-
brane.  Hence the degree of force exerted in the penetration is con-
siderable.
  The experiments were all repeated with animal membranes, such
as dried bladder and goldbeater's skin, moistened so as to resemble
the  natural  state.  The same results, and  in the same order, follow-
ed as with the gum elastic.  The  more  fresh  the membrane, the
more speedy and extensive was the effect; and in living animals the
transmission was very rapid.
  To these experiments we shall have frequent occasion to refer in
the  course of this work.
  All these different  properties of animal solids are independent of
the  vital properties.  They continue for  some  time after the total
extinction  of life, in all its functions; and appear to  be connected
either  with the physical arrangement of molecules, the chemical
composition of the substance in which they reside, or with peculiar
properties in the body that is made io act on the tissue.  They do
not, indeed, seem to be affected, until the progress of decomposition
has  become sensible.   Hence many of these  agencies have  been
termed collectively, by Haller, the vismortua. 
FUNCTIONS OF MAN.                   37
         OF  THE FUNCTIONS OF MAN.

  Having described the intimate structure of the tissues, we pass
to the consideration of the functions, the character  of each of
which is,—that it fulfils a special and distinct office in the economy,
for which it has an organ or instrument or an evident apparatus of
organs.
  Physiologists have not,  however, agreed on the number of dis-
tinct offices that are so performed;  and hence the difference in the
number and classification of the functions that prevails  amongst
them.
  The oldest division is into the vital, natural, and animal; the
vital functions comprising those of such importance as not to ad-
mit of interruption,  such as circulation, respiration, and the func-
tions of the brain and spinal marrow; the natural functions in-
cluding  those that effect nutrition, as digestion, absorption,  secre-
tion; and the animal, those possessed exclusively by animals, as
sensation, locomotion, and voice.   This classification  is the basis
of that which generally prevails at the present day.
  The character of this work will  not admit of  a detail of every
classification that has been proposed by the physiologist; that of
Bichat, however, has occupied so large a space in the public eye,
that it cannot well be passed over.   It is the one followed by M.
Richerand, and by many modern  writers.
  Bichat includes all the functions under two heads, according as
they work to one or other of two ends,—functions of nutrition or
life of the individual, and functions of reproduction or life of
the species.  Nutrition requires that the being shall  establish rela-
tions  around him  to obtain the materials of which he may stand in
need; and  in animals, the  functions, that establish such relations,
are under the volition and  perception of the being.   Hence they
are divided into two sorts; those that commence or precede nu-
trition,  consist  of external relations, are dependant upon the will,
and  executed with  consciousness;  and those that are carried on
within the body, spontaneously and without consciousness. Bichat
adopted this basis, and to the first aggregate of functions he applied
the term animal  life, because it  comprised the functions  that
characterize animality; the latter he  called  organic life, because
the functions comprised under it are common to every organized
body.  Animal life includes sensation, motion and expression; or-
ganic life, digestion, absorption, respiration, circulation, nutrition,
secretion, &c.
  In animal life, Bichat recognised two series of actions, opposed
to each  other, the one proceeding from without and terminating in 
38
FUNCTIONS OF MAN.
the brain, or passing from centre to circumference, and comprising
the external senses; the other, commencing in the brain and acting
on external bodies, or proceeding from centre to circumference,
and including the internal senses, locomotion and voice. The brain,
in which one series of actions terminates and the other begins, he
considered the centre of animal life.
  In organic life he likewise recognised two series of actions; the
one proceeding from without to within, and effecting composition;
the other passing from within to without, and effecting decomposi-
tion.  In the former, he included  digestion, absorption, respiration,
by which  the blood is formed; the circulation, by which the blood
is conveyed to different parts, and the functions of nutrition and
calorification.   In  the latter, that absorption which takes up parts
from the body; the circulation, which conducts those parts or mate-
rials to the secretory or  depuratory organs;  and the secretions,
which separate them from the economy.
  In this kind of life, the  circulation is common to the two move-
ments of composition and decomposition;  and  as  the  heart is the
great organ of the circulation, he considered it the centre of organic
life; and, lastly, as the lungs  are  united both with animal  life, in
the reception of air, and with organic life, as the organ of sanguifi-
cation, Bichat regarded those organs as the bond of union between
the two lives.   Generation constituted the life of the species.
  The classification, adopted in this work, wjll be that embraced by
Magendie; and after him, by Adelon, who has written one of the
best systems of human physiology that we possess.
  The first class, or functions  of relation or animal functions,
includes those that establish  our  connexion with the bodies  sur-
rounding us; the sensations, voluntary motions, and expressions.
The second class, or functions of nutrition, comprises digestion,
absorption, respiration,  circulation, nutrition, calorification,
and secretion, and the third class, the functions of reproduc-
tion,—generation.
Table of the Functions.
Functions. <
I. Animal or of Relation. <
II. Nutritive.
..III. Reproductive.
 1. Sensibility.
 2. Muscular motion.
 3. Expressions or lan-
      guage.
 4. Digestion.
 5. Absorption.
 6. Respiration.
 7. Circulation.
 8. Nutrition.
 9. Calorification.
10. Secretion.
11. Generation. 
FUNCTIONS OF MAN.
39
  In studying each of these functions, we shall first of all describe
the organ or apparatus concerned in its production; but, so far only
as is necessary in a physiological point of view,—the further deve-
lopment and the application of such development to other depart-
ments of medical science, not immediately concerning the physio-
logist,—and shall next detail what has been called the mechanism
of the function, or the mode in which it is effected.
  In many cases it will happen, that  some external  agent  is con-
cerned  in its production,  as light in vision; sound in audition;
odours in olfaction; tastes in gustation, &c.
  The properties of these will, in all instances, be detailed in a brief
manner, but so far only as is necessary for our immediate purpose.
  The difficulty of observing actions, that are carried on by the very
molecules of which the organs are composed, has given rise to
many hypothetical speculations, some of which are sufficiently in-
genious, others too  fanciful to be indulged, by the reflecting, for a
moment; and, as might be expected, the number of these phantasies
generally bears a direct proportion to the difficulty and obscurity
of the subject.  It will not be proper to pass over the most promi-
nent of these, but they will not be dwelt upon, whilst the results of
direct observation and experiment will be fully detailed; and where
differences prevail amongst observers, such differences will be at-
tempted to be reconciled where practicable.
   The functions, executed by different organs of the body, can be
deduced from direct observation, although the minute and molecu-
lar action, by which they are accomplished in the very tissue of the
organ, may  not admit  of detection.   We  see, for example, blood
proceeding to the liver, the vessels, that convey it, ramifying in the
texture  of that viscus, and becoming so minute as to escape vision,
even  when aided by a powerful microscope. We find, again, other
vessels  becoming  perceptible,  gradually augmenting in  size, and
ultimately terminating in a larger duct, that  opens into the small
intestine.   If we examine each of these orders of vessels in their
most  minute, appreciable ramifications, we discover, in the  one,
always blood, and, in the other, always a very different fluid,—the
bile.  We are hence led to the conclusion,  that in the intimate
tissue of the liver, and in some part, communicating directly or in-
directly with both these orders of vessels, bile is separated  from
the blood; in other words, that the liver is the organ of the biliary
secretion.  On the other hand, functions  exist which cannot be so
demonstratively referred to an organ.   We have every reason for
believing that the  brain is  the exclusive organ of the mental and
moral manifestations;  but  as few  opportunities occur for seeing it
in action, and as the operation is too molecular to  admit of direct
observation, when we do see it, we are compelled to connect the
organ and function  by a process of reasoning only; yet we shall
find thqt the results, at which we arrive in this manner, are by no
means the least satisfactory. 
40                   FUNCTIONS OF MAN.
  The forces, that preside over the various  functions, are  either
general,—that is, physical or chemical; or special,—that is, organic
or vital.   Some of the organs afford us examples of purely physical
instruments.  We have, for instance, in the eye, an eye-glass, if we
may so call it, of admirable construction; in the organ of voice, an
instrument of music; in the ear, one  of acoustics.   The circulation
is carried on through an ingenious hydraulic apparatus, whilst sta-
tion and  progression involve various  laws of mechanics.  In many
of the functions, again, we  have examples  of chemical agency,
whilst all those, in which innervation  is concerned, we are incapable
of explaining on any physical or chemical principle, and are  neces-
sarily constrained to esteem vital. 
ANIMAL FUNCTIONS.
41
                         CLASS  I.

ANIMAL FUNCTIONS, OR FUNCTIONS OF RELATION.

  The functions of relation consist, 1st, of sensibility, and 2dly, of
muscular motion, including expression or language.  All these ac-
tions are subject to intermission, constituting sleep; a condition which
has, consequently, by many physiologists, been investigated under
this head; but as  the functions of reproduction are also influenced
by the same condition,  the consideration of sleep will be deferred
until the third class of functions has engaged attention.

     OF SENSIBILITY, OR THE FUNCTION OF THE SENSATIONS.

  Sensibility is the function  by which an animal experiences feel-
ing, or has the perception of an impression.   In  its general accep-
tation, it means the property possessed by living parts of receiving
impressions, whether the  being exercising the property has con-
sciousness of it or not. To the former of these cases,—in which there
is consciousness,—Bichat gave the epithet animal; to the second,
organic; the latter being  common to animals and vegetables, and
presiding over the organic functions of nutrition, absorption,  ex-
halation, secretion,  &c.;  the latter, existing  only in animals, and
presiding over the sensations, internal as well as external.
  It is to animal sensibility, that our attention will have to be di-
rected.
  Pursuing  the plan, already laid down, we shall commence  the
study of  this interesting and elevated function, by pointing out, as
far as may be necessary, the apparatus that  effects it, comprising
the whole of the nervous system.

                    Of the Nervous System.

  Under the name nervous  system, anatomists  include all those
organs, that are composed of the nervous or pulpy tissue.  In man,
it is constituted of three portions;  1st, of  what has  recently been
called the cerebrospinal axis, a central part having the form of a
long cord, expanded at  its superior extremity,  and contained^ within
the cavities of the cranium and spine; 2dly, of cords, called nerves,
in number thirty-nine pairs, according to some,—forty-two accord-
ing to others; passing off, laterally, from the cerebro-spinal axis to
every part of the body; and, lastly, of a nervous cord, situated on each
side of the spine, from the head to the pelvis, forming ganglia oppo-
site each vertebral foramen, and called the great sympathetic nerve.
  1. Of the encephalon.—Under this term are  included the con-
tents of the cranium, viz. the cerebrum or brain proper; the cere-
  Vol. I.                      6 
42
SENSIBILITY.
bellum, or little brain; and the medulla oblongata. These various
parts have been included by some under the name brain.  When
we look at a section of the encephalon, and at the three organs, in
their natural position, we find that there are many  distinct  parts,
and appearances  of  numerous  and separate organs.  So  various,
indeed, are the prominences and depressions met with, on the dis-
section of  the brain, that it is generally esteemed one of the most
difficult subjects  of anatomy.  Yet,  owing to the attention that has
been paid to it in all ages, it is now one of the structures best un-
derstood by the anatomist.
  This complicated organ affords us a  striking illustration of the
truth, that the most accurate anatomical knowledge will not neces-
sarily teach the function.
  The elevated actions which the encephalon has to execute  have
likewise attracted a large share of the attention of the physiologist,
too often,  however, without any satisfactory result; yet it may, we
think, be safely asserted, that we have become better instructed re-
garding the uses of particular parts of the brain within the last few
years, than during the whole of the  century preceding.
  The encephalon being of extremely delicate organization, and its
functions easily derangeable, it was  necessary that it should be se-
curely lodged and protected from injuries.  Accordingly, it is placed
in a sound, bony case, and by an admirable mechanism, is defended
against damage from surrounding bodies.
  Amongst these guardian agents, or tutamina cerebri, must be
reckoned;—the hair of the head, the skin, muscles, pericranium,
bones of the skull, the diploe separating the two tables of which the
bones are composed, and the dura mater.
  It is not an  easy matter to assign  probable uses to  the hair on va-
rious parts of the body.   On the  head, its function  seems more
readily appropriable.  It deadens the concussion, that the brain would
experience from  the infliction  of  heavy blows, and prevents the
skin of the scalp from being injured by the attrition  of bodies.  In
military service, the  former of these uses has been taken advan-
tage of, and an arrangement somewhat similar to that which  exists
on the head, has been adopted with  regard to the helmet. The me-
tallic substance, of which the ancient and modern helmets are formed,
is readily thrown into vibration; which vibration, being communi-
cated to the brain, might, on the receipt of heavy blows, derange its
functions more even than a wound inflicted by a sharp instrument.
To obviate this, in some measure, the helmet has been covered with
horse hair.  This arrangement prevailed in the helmet worn by the
Roman soldier.
  There can be no doubt, likewise, that being bad conductors of ca-
loric and forming a kind of felt, which intercepts the air, the hairs
may tend  to preserve  the  head of a more uniform temperature.
They are, moreover, covered with  an oily matter, which prevents
them from imbibing moisture, and  causes them to dry speedily.
Another use, ascribed to them  by Magendie, is somewhat more 
NERVOUS SYSTEM.
43
hypothetical;—that being bad conductors of electricity, they may
put the head in a state of insulation, so that the brain may be  less
affected by the electric fluid!
  It is unnecessary to explain in what manner the different layers,
of which the scalp is composed, the cellular membrane beneath, the
panniculus carnosus or occipito-frontalis muscle, and the pericra-
nium covering the bone, act the parts of tutamina.  The most im-
portant of these  protectors is the bony case itself.  In the short
treatise on Animal Mechanics, contained in the Library of Useful
Knowledge, and written by one of the most distinguished physiolo-
gists of the present day, Sir Charles Bell, we have some beautiful
illustrations of the wisdom of God, as displayed in the mechanism
of man, and in that of the skull in particular; and although some of
his  remarks may  be liable to  the censures, that  have been  passed
upon  them by Dr. Arnott, the greater part are admirably adapted
to the contemplated  object.   It is  impossible indeed for the unin-
itiated to rise from the perusal of Mr. Bell's interesting essay, with-
out being ready  to exclaim with the poet,  " how wonderful, how
complicate is man!  how passing wonder  He that made him  such."
  Mr. Bell attempts to prove that the best illustration of the form
of the head is  the dome; whilst Dr. Arnott considers it to be "the
arch of a cask or  barrel, egg-shell, or  cocoa-nut, &c. in which the
tenacity of the material is many times greater than necessary to re-
sist the influence of gravity, and  comes in aid, therefore,  of the
curve, to resist forces of other kinds approaching in all directions,
as  in falls, blows, unequal pressures," &c.  The remarks  of Dr.
Arnott on this subject are just; and it is owing to this form of the
cranium, that any blow received upon one part of the skull is rapidly
distributed to  every other;  and that a heavy blow inflicted on the
forehead or vertex, may cause a fracture, not in the parts struck,
but in the occipital or sphenoidal bones.
  The skull does not consist  of one bone, but of many.   These are
joined together by sutures,—seeming as if they were stitched to-
gether.  Each bone consists like-
wise  of two tables; an external,             Fig. 8.
fibrous and tough, and an internal,
of  a  harder character  and more
brittle, hence called tabula vitrea.
These two tables are separated
from each other by a cellular  or
cancellated structure,  called di-
ploid.  On examining the mode in
which these tables form a junction
with each other respectively at the
sutures,  we have additional evi-          A. rhf.parUtal bone<
dences of design  exhibited.   The          £ ^^g^J"^
edges of the outer table are ser-          »■ The temporal bone.
  P ,     ,            1   j  1           E. The sphenoid bone.
rated, and  so arranged as to be
accurately dove-tailed  into each other; the tough fibrous  texture of
 
44
SENSIBILITY.
the external plate being well adapted for such a junction.   On the
other hand, the tabula vitrea, which, on account of its greater hard-
ness,  would be liable to fracture, to chip off, is merely united with
its fellow at the sgture, by what is called harmony: the two tabulae
are, in other words, merely placed in contact.
  The precise object of these sutures is not apparent.  In the mode
in which ossification takes place in the bones of the skull, the radii
from  different ossific points must necessarily meet in the progress
of ossification. This has, by  many, been esteemed the cause of the
sutures, but the explanation  is insufficient.  However it may be, the
kind of junction affords an example of beautiful adaptation.  During
the foetal state, the sutures do not exist.   They are  fully formed in
youth, persist in the adult age, but, in after periods of life, become
entirely obliterated, the bone then forming a solid spheroid. It does
not seem, however, that after the sutures are established, any dis-
placement of the bones can take place; and observation has  shown,
that they do not possess much if any  effect in putting a limit  to
fractures.  In all  cases of severe blows, the skull appears to resist
as if it were constituted of but one piece.
   But the separation of the skull into distinct bones, having a mem-
branous union, is of striking advantage to the foetus, in parturition.
It enables the bones to overlap each other ; and in  this way, to oc-
cupy a much smaller space than if ossification had united them, as in
after life.  It has, indeed, been imagined by  some, that there is an
advantage in this pressure upon the brain by  the investing  bones—
that the foetus does not  suffer from the  violent efforts made  to
extrude  the child ; but that, during the passage through the pel-
vis, it is in a state  of fortunate insensibility.   That pressure sud-
denly exerted upon the brain is attended with  these effects,  is
well known to the pathologist. It is, indeed, the great principle to
be borne in mind in the management of apoplexy, fracture of the
skull, &c.
   The uses of the diploe, which separates the  two tables of the
skull, are not equivocal. Composed of a cancellated structure, it is
well adapted to deaden the force of blows,  as will be shown here-
after; and  as it forms,  at the same time, a bond of union and of se-
paration, a fracture  might be inflicted  upon the  outer table of the
skull and yet be prevented from extending to the tabula vitrea. Such
cases have occurred, but they are rare; as it will generally  happen,
that a blow, intended to cause serious bodily  injury, will be suffi-
cient to break through  both  tables or neither.
   Lastly, the dura mater, which has been reckoned as one of the
tutamina cerebri,  lines  the skull and constitutes a kind of  internal
periosteum to it.  It may also be inservient to useful purposes, by
deadening the vibrations, into which the head may be thrown by sud-
den concussions; as the vibrations of a bell  are arrested by lining it
with  some soft material. It is chiefly,  however, to protect the brain
against itself, that we have the arrangement which  prevails in the
dura mater. 
NERVOUS SYSTEM.
45
  The cerebrum, as well as the cerebellum, consists of two hemis-
pheres; and its posterior part is situated immediately above the
cerebellum.  It is obvious, then, that  without  some protection,
the hemisphere of one side would press upon  its fellow, when
the head is inclined to the opposite side; and that the posterior
lobes of the brain  would weigh upon the cerebellum in  the  erect
attitude.

                           Fig.  9.
   Fig. 9, is a posterior view of the cerebrum and cerebellum:  the
cranium  and dura mater being removed. A A are the hemispheres,
separated from each other by the falx cerebri, in the upper mar-
gin of which is the superior longitudinal sinus, d d.  The falx
passes between the hemispheres in the mode exhibited at a a, Fig.
10.  c c, Fig. 9, is the situation of the tentorium cerebello super-
extensum, which passes horizontally forwards, so as to support  the
posterior lobes of the brain, and prevent them from  pressing inju-
riously on the cerebellum, B B.  A process of the dura mater passes
also between the hemispheres of the  cerebellum, B B.  Indepen-
dently of the protection afforded  to the encephalon, the dura mater
lodges the great sinuses into  which the veins discharge their blood.
These different sinuses empty themselves into the torcular Hero-
phili or confluence of the sinuses at d, (Fig. 9 & 10,) and ultimately
proceed in  the direction cc, constituting the lateral sinuses, which
pass through the temporal bone and form the  internal jugular
veins, one of which is represented at e, Fig.  10. 
46                        SENSIBILITY.

                            Fig. 10.
a a. The falx cerebri.
 d. The torcular herophili.
c c. The lateral sinuses.
 e. The internal jugular vein.
  The tutamina are not confined to  the  contents  of the cranium.
The spine appears to be, if possible,  still better protected.   In the
skull, we see a firm, bony case; in the spine, a structure admitting
considerable motion  of the parts, without risk of pressure to the
spinal marrow.  Accordingly, the spine consists of  numerous dis-
tinct bones or vertebrae, with fibro-cartilaginous,—technically called
intervertebral substances, placed between each, so that, although
the extent of  motion, between  any two of these bones, may be
small,  the  amount, when  all are concerned,  is  extensive.   The
great use of this intervertebral  substance is to prevent the jar, that
would necessarily be communicated to the delicate parts within the
cavities of the spine and cranium, were the spine composed entirely
of one bone.   In falls from a height, upon the feet or breech, these
elastic cushions are forcibly compressed;  but they immediately re-
turn to their former condition,  and deaden the force of the  shock.
In this they are aided by the curvatures of the spine, which  give it
the shape of the Italic f, and enable  it to resist, in the same manner
as a steel spring, any force acting upon it in a longitudinal direc-
tion.   So well is the medulla spinalis protected by the strong bony
processes, jutting out in various directions from the spine, that it is
extremely rare to meet with lesions of the part; and it is compara-
tively of late years,  that any ex-professo treatises have appeared on
the subject.
   Besides the protection  afforded  by the bony structure  to the
delicate  medulla, Magendie  has  pointed  out another,  which 
NERVOUS SYSTEM.
47
he was the first to detect.   The canal, formed by the dura  mater
around the spinal cord, is much larger than is necessary to contain
that organ; but, during life, the whole of the intermediate space is
filled  with a serous fluid, which strongly distends the membrane, so
that it will frequently spirt out to a distance of several inches, when
a puncture is made in the membrane.  To this fluid, he has  given
the epithet cephalo-spinal; and he conceives, that it may act as one
of the tutamina of the marrow, (which is,  as it were suspended in
the fluid,) and exert upon it the pressure necessary for the healthy
performance of its functions.
   Beneath the dura mater is situate'd a very delicate membrane,—
the arachnoid, belonging to the class of serous membranes. It sur-
rounds the encephalon in every part, but is best seen at the base of
the brain.  Its chief use is to secrete a thin fluid, to lubricate the
brain. This membrane enters into all the cavities of the organ, and
in them, fulfils a like function.  When the fluid accumulates to a
great  extent, it constitutes the disease called hydrocephalus chro-
nicus.
   Anatomists  usually  describe a  third tunic of  the  brain—the
pia mater.  As a distinct membrane, this is not demonstrable. It
is generally conceived to consist of the minute terminations of the
cerebral arteries, and those of the corresponding veins, forming, at
the surface of the brain, a vascular net-work, which passes into the
cavities; and, in the ventricles, forms the plexus choroides and tela
choroidea.  The dura and  pia mater were so called by the older
anatomists, because they were conceived to  be the origin of all the
other membranes of the body.
   The cerebrum or brain proper has the form  of  an  oval, larger
behind.  On its  outer surface are various undulating eminences,
called convolutions, because they have been thought  to  resemble
the folds of the intestines—separated from each  other by depres-
sions, called anfractuosities.  (See Fig.  12.)  In the brain of man,
these convolutions are larger than in animals and the anfractuosities
deeper.  In different brains, the number, size, and arrangement of
these vary. They are not the same, indeed, in the same individual;
those of the right hemisphere being disposed differently from those
of the left.
   The hemispheres, we have seen, are separated above, by the falx
cerebri:  below, they are united by a white medullary commissure,
the corpus callosum, mesolobe, or great commissure.   If we ex-
amine the brain at its base, we find that  each hemisphere is divided
into three lobes: an anterior, which rests on the vault or roof of
the orbit—a rniddle or temporal, filling the middle and lateral parts
of the base of the cranium, and separated from the former by a con-
siderable depression, called the fissure of Sylvius: and a posterior,
which rests on  the  tentorium cerebelli.   This part of  the  cere-
brum is divided into two very distinct portions by the medulla ob-
longata. Anterior to it are the crura cerebri or cerebral peduncles; 
48
SENSIBILITY.
by most anatomists considered to be a continuation of the anterior
fasciculi forming the spinal marrow and medulla oblongata, and pro-
ceeding to form the hemispheres of the brain.  Between the ante-
rior extremities  of the  peduncles, are two hemispherical projec-
tions,  called  eminentiae  mamillares,  which are  possessed  by
man exclusively, have the shape of a  pea, and are formed of the
white nervous tissue externally, of the gray within.  Anterior to
these again is the infundibulum, and a little farther forwards the
chiasma of the optic nerves, or the part at which these  nerves de-
cussate.
   Laterally, and at the inferior surface of the anterior  lobes, is a
groove or furrow, running from behind to before, and from without
to within, in which the olfactory nerve is lodged.  At the extremity
of this furrow is a tubercle, which  is trifling in man, but in certain
animals is equal to the rest of the brain in bulk.  From  this the ol-
factory  nerve  arises.  It is called the olfactory tubercle or lobe.

                            Fig.  11.
Base of the Brain.
  A A. Anterior lobes of the brain—B B. Middle lobes—C C. Posterior lobes—D D. Cerebellum—a. Me-
dulla oblongata—6. Pons Varolii—c. Chiasm of the optic nerves—d. Olfactory nerves—e. Crun^cerebri—
/. Crus cerebelli.

   When we examine the interior of the brain,  we find a numberof
parts to which the anatomist assigns distinct names.   Of these, the
following chiefly concern the physiologist.   It has been already re-
marked, that the corpus callosum forms, at once, the bond of union
and  separation between the two hemispheres.  It is distinctly per-
ceived, on separating these parts from each other, in the form of  a 
NERVOUS SYSTEM.
49
long and broad white band.   Beneath the corpus callosum is the
septum lucidum, or median septum, which passes perpendicularly
downwards, and separates from each other the two largest cavities
of the brain—the lateral ventricles.  It is formed of two laminae,
which leave a cavity between them, called the fifth ventricle. The
fornix is placed horizontally below the last.  It is of a triangular
shape, and constitutes the upper paries of another cavity—the third
ventricle.  Beneath the fornix, and behind it, is the pineal gland,
respecting which so much has been said by Descartes and others,
as the seat of the soul.  Within it, is a small  cavity; and after six
or seven years of age, it always contains some concretions.  Again,
anterior  to the  pineal gland, and immediately below the fornix,
is another cavity—the third ventricle.  Its  bottom is very near
the base of the brain, and is formed  by the  nervous layer, which
unites the peduncles  of the brain with the  eminentiae mamil-
lares. (Fig. 11.)  At the sides it has the  thalami nervorum  opti-
corum.
   In  the lateral ventricles, situated on each side of the corpus cal-
losum, some parts exist which demand attention.  In  the upper or
anterior half, commonly called the anterior cornu, and in the ante-
rior part of this, two pyriform eminences  are seen, of a brownish-
gray  colour;  and which, owing to their being formed of an assem-
blage of alternate layers of white and gray substance, are called the
corpora striata.  Behind these, are two whitish medullary bodies,
called thalami nervorum opticorum, which are situated before the
corpora quadrigemina, and envelope the anterior extremities of the
crura cerebri.
   The cerebellum occupies the lower occipital  fossae, or the whole
of the cavity of the cranium which*is beneath the tentorium cerebelli.
   The size and weight of the cerebellum, like  those of the brain,
differ according to the individual, and the  age of the subject under
examination.  We  do not observe convolutions in it.   It appears
rather to consist of laminae  in  superposition, separated from each
other by a furrow.  We shall  see hereafter, that the number of
cerebral convolutions has  been  found, in some  respects, to accord
with  the intellect of the  individual; and Malacarne asserts, that
he has observed a similar  correspondence, as regards the number of
the laminae composing the cerebellum; that  he found only  three
hundred and twenty-four in the  cerebellum of an insane individual,
whilst in others he  had counted upwards of eight hundred.
   From the medullary part of the cerebellum, two large white cords
pass to the pons varolii, having  the same  disposition  as the  crura
cerebri.  They are the crura cerebelli.
   Owing to the peculiar arrangement of the white and gray cerebral
substances, when one of the hemispheres  of the cerebellum  is di-
vided vertically, an arborescent appearance is presented; the trunks
of the arborizations being white, the  surrounding substance  gray.
This appearance is called  arbor vitas.  The part where  all  these
  Vol. I.                      7 
50                         SENSIHILITY.

arborizations meet, near the centre of the cerebellum, is called cor-
pus denticulatum vel rhomboidale.   Gall is of opinion, that this
body has great agency in the production of the cerebellum.  Lastly,
the cerebellum covers the posterior part of the medulla oblongata,
and forms with it a cavity, called the fourth ventricle.

                              Fig. 12.
 11. Section of the corpus callosum—2 2. Lateral ventricle: the septum being removed—3 3. The fur-
nix—4. Third ventiicle—5. Pins al gland—6. Tubercula quadrigeniina—7. Fourth ventricle—8. Iter a
tertio ad quavtum ventriculum—9 9. Internal carotid artery—10 10. Artery of the corpus callosum—
11111111. Superior longitudinal sinus—1212. Fourth sinus—A A. Cerebrum—B. Cerebellum— C. Pom
varolii—E E. Medulla spinalis—F. Medulla oblongata.
  The medulla oblongata is so called, because it is the continua-
tion of the medulla spinalis in the cavity  of the cranium. It is like-
wise termed mesocephale, from its being continuous with the spinal
marrow in one direction, and sending, towards the brain, the strong
prolongations—the crura  cerebri; and to  the  cerebellum  similar
prolongations—the crura cerebelli; so that  it appears to be the bond
of union between these various parts.   In  its lower portion,  (Fig.
11, a.)  it appears to be merely a continuation of  the medulla spi-
nalis, except that it is more expanded superiorly where it joins the
pons varolii, b.  This  portion of the  medulla  oblongata is called, 
NERVOUS SYSTEM.                     51
by some, the tail of the medulla oblongata; by others, the rachi-
dian bulb; and by others again it is made to embrace the whole me-
dulla oblongata.   Its lower surface, seen in the figure, rests on the
basilary gutter of the occipital bone, and exhibits the groove, which
divides the spinal cord into two portions.  On each side of this fur-
row are two oblong eminences, the innermost of which is called
corpuspyramidale, the outermost, corpus oKvare, (Fig. 11.) which
arise from the anterior column of the medulla spinalis, or are a con-
tinuation and subdivision of this  column.  On the posterior surface
of the medulla oblongata, the posterior fasciculi separate to form the
fourth ventricle; (Fig. 12, 7.)  at the sides of this ventricle are the
corpora resliformia, or inferior peduncles of the cerebellum, so
called, because they seem to aid in the formation of that part of the
encephalon; and on the inner side of each corpus restiforme, is the
small  body—the posterior pyramid.   Again,  in addition to the
corpora pyramidalia and olivaria, which derive their origin from,or
are continuous with, the anterior fasciculi of the spinal cord, and are
destined, according to some, to  form the brain, and  the corpora
restiformia, which are continuations of the posterior  fasciculi, and
are destined to form the cerebellum, there exist, according to  some
anatomists, other fasciculi in the  rachidian bulb.  All these are in-
teresting points of general anatomy, but are  not yet  of much im-
portance physiologically; if we except, perhaps, the views promul-
gated by Sir Charles Bell.  He considers that  a  column exists
between  the corpora olivaria and  corpora restiformia, which extends
below, through the whole spine,  but above, does not proceed farther
than the point where the rachidian bulb joins the tuber  annulare,
and that this column gives origin to a particular order of nerves—
those inservient to respiration.
  The anterior and upper half of the medulla oblongata bears the
name pons varolii, tuber annulare, and nodus cerebri; and to this
are attached, superiorly, the corpora or tubercula quadrigemina.
In the very centre of  the pons, the crura cerebri bury themselves;
and  are, by many, considered  to decussate; by others, to be pro-
longations of the anterior column of the  spine. Sir C. Bell thinks,
that the pons varolii stands in the same relation to the  lateral por-
tions of the cerebellum that the corpus callosum does to the  cere-
brum: that it is the great commissure of the cerebellum, uniting its
lateral parts and associating the two organs.
  2. The spinal marrow extends, in the vertebral canal, from the
foramen magnum of the occipital bone, above, to the cauda equina,
below. It is chiefly composed of medullary matter, but not entirely
so.   Within, the cineritious substance is ranged irregularly, but has
a crucial form  when a section is made  of it.  From  the calamus
scriptorius in the fourth ventricle, and the rima, formed by the cor-
pora pyramidalia before, two fissures extend downwards, which di-
vide the spinal marrow into lateral portions.   The two lateral por-
tions are divided into an anterior and posterior, so that the cord has 
52
SENSIRILITY.
four distinct portions.  By some, indeed, it is conceived to consist
of three columns—an anterior, posterior, and middle.
   The vertebral canal is connected by a strong ligamentous sheath,
running down its whole length.   The dura mater likewise enve-
lopes the medulla at the occipital foramen, being firmly united to
the ligaments, but farther down  constituting a separate tube.  The
tunica  arachnoidea from  the brain adheres loosely  to the  cord,
having the cephalo-spinal fluid within it, and the pia mater closely
embraces it.
   3. Nerves.—The nerves are cords of the same  nervous sub-
stance  as that which composes the encephalon and spinal marrow,
extending  from these parts, and being  distributed to the various
organs of the body, many of them interlacing in their course, and
forming plexuses; others having knots  or ganglions upon them;
and almost all vanishing in the parts to which they are distributed.
The generality of  English anatomists  reckon thirty-nine pairs
of nerves;  the  French, with  more propriety,  forty-two.   Of
these,  nine, according to the English;  twelve, according to the
French, draw their  origin from, or are connected with, the ence-
phalon, and are hence called encephalic nerves;  thirty from the
medulla spinalis,  and hence termed spinal. The encephalic nerves
emerge from the  cranium by means of foramina at its base.  They
are, proceeding from before to behind, the first pair or olfactory,
distributed to the organ of smell; the second pair  or optic, the
expansion of which forms  the  retina; the third pair, motores
oculorum or common oculo-muscular,  which send filaments to
most of the muscles of the eye ; the fourth pair, trochleares, pa-
thetic, or internal oculo-muscular,  distributed to the greater ob-
lique muscle of the eye;  the fifth pair, trifacial, trigemini, or
symmetrical nerve of the head, (Bell,) which sends its branches
to the  eye, nose, and tongue; the sixth pair, abducentes or exter-
nal oculo-muscular, which is  distributed to the abductor or rec-
tus externus oculi; the facial nerve, portio dura of the seventh
pair, nervus communicans faciei,  or respiratory nerve of the
face, distributed  to the muscles of the face; the acoustic nerve,
auditory nerve, or portio mollis of the seventh pair, which passes
to the  organ of hearing; the eighth pair, pneumogaslric, or par
vagum, or middle sympathetic, which  is dispersed particularly
to the  larynx, lungs, heart, and stomach ; the glossopharyngeal,
often considered assart of the  last, and whose name indicates its
distribution to the tongue and pharynx; the great hypoglossus,
ninth pair, or lingual nerve, distributed to the tongue;  and the
spinal accessory of Willis, which arises from the spinal cord in
the cervical region, ascends into the cranium, and issues by one of
the foramina, to be distributed to the muscles  of the neck.   All
these proceed from the medulla oblongata, the brain and cerebellum
not furnishing one.
   The spinal  nerves are thirty in  number on  each  side.   They 
NERVOUS SYSTEM.
53
make their exit by the intervertebral foramina, and are divided into
eight cervical, twelve dorsal, five lumbar, and five or six sacral.
  The encephalic nerves are irregular in their formation, and with
the exception of the fifth pair,  originate from one root.   Each of
the spinal  nerves arises from two  fasciculi, the one anterior and
the other posterior; these are  separated from  each other by the
ligamentum denticulare;  but  they unite  beyond this ligament,
and, near the intervertebral foramina, present one of those knots,
known under the name  of ganglions, in the formation of which
the posterior root is alone concerned.
  When the nerves have made their exit from the cranium and
spine, they proceed  to the organs, to which  they have to be distri-
buted, ramifying more  and more, until  they  are ultimately lost
sight of,  even when vision  is aided by a powerful microscope.  Of
the encephalic nerves, the olfactory, auditory, and acoustic, which
are nerves of special sensibility, pass on to their destination, with-
out communicating with any other nerve.   The  spinal nerves,
at their exit from  the  intervertebral foramina, divide  into two
branches, an anterior and a posterior, one  being sent to each aspect
of the body.  The  anterior branches of the four superior cervical
pairs form the cervical plexus, from which all  the  nerves of the
neck arise;  the  four last cervical pairs, and the first dorsal,  form
the brachial plexus, whence proceed the nerves of the upper ex-
tremities, whilst the branches of  the five lumbar nerves  and the
five sacral form the lumbar and sciatic plexuses, the former of
which gives rise to the nerves distributed  to the parts within the
pelvis, and the second to those of the lower limbs.  The anterior
branches, moreover, at a little distance from the exit of the nerve
from  the vertebral  canal,  communicate  with an important and
unique portion of the nervous system, the great sympathetic.
  Each nerve consists of numerous  fasciculi, surrounded by cellu-
lar  membrane;  and, according to  Reil, of  an  external envelope,
called neurilema, which, in the opinion of most anatomists, is no-
thing more than a  cellular envelope,  similar to that which sur-
rounds the vessels and muscular fibres.
  Until of late years, the nerves were universally divided, accord-
ing to their origin, into encephalic and spinal; but, more recently,
an anatomical division has been proposed, formed  upon the uses
they appear to fulfil in  the  economy.   For one of the most  beau-
tiful arrangements of this kind we are indebted to Sir Charles
Bell. We have already seen, that the encephalic nerves are con-
nected with the encephalon  by only one root, whilst the  spinal
nerves arise from two; the  one connected with the anterior part of
the spinal marrow,  the other with the posterior. If these different
roots  be  experimented on, we meet with results varying consider-
ably from each other. If we divide, for example, the anterior root,
the  part to which the nerve is distributed  is deprived of the power
of motion, whilst if the posterior root be cut, the part is deprived of 
54
SENSIBILITY.
sensibility. We conclude, therefore, that each of the spinal nerves
consists of filaments destined for both motion and sensibility; that
the encephalic nerves, which have but one root, are destined to one
of these exclusively, and that they are either nerves of motion or
of sensation, according as their  roots arise  from the anterior or
posterior column of the medulla oblongata.

                           Fig. 13.
A. The spinal marrow, viewed in front.
B. A spinal nerve.
C. Anterior root of a spinal nerve.
D. Ganglion on the posterior root.
   It has already been remarked, that the medulla oblongata is, ac-
cording to some anatomists, composed of three fasciculi or columns
on each side;  an anterior, middle, and posterior; and it has been
affirmed by Sir Charles Bell, that whilst the anterior  column
gives origin to nerves of motion, and the posterior to nerves of sen-
sibility, the middle gives rise to a third species, having the function
of presiding over the respiratory  movements, and to which  Sir
Charles accordingly assigns the name of respiratory nerves.  To
this third order of nerves belong the  accessory nerve of Willis,
or superior respiratory, the vagus, the glossopharyngeal,  the
facial, called  by  him the respiratory nerve of the face, the phre-
nic nerve, and another, having the  same  origin  as the  last, the
external respiratory.  Sir  Charles  Bell's  experiments lead,
consequently, to  the belief,  that there are at least  three sets of
nerves, those  destined for sensation,  motion, and for a particular
kind  of motion—the respiratory; and that  every nerve of motion
communicates to the muscles, to which  it is distributed, the power
of aiding or taking part, in motions of one kind or another, so that
a  muscle may be paralyzed, as regards certain  movements, by the
section of a nerve, and yet may be capable  of others of a different
kind, by  means of the nerves that  are uninjured.
   The accompanying plate exhibits a view  of the system of respi-
ratory nerves, as given by Mr. Shaw, the son-in-law of Sir Charles
Bell, who, within the last few years has been prematurely snatched
from existence, after having made numerous useful contributions to
medical and surgical science. 
nervous system.
55
  In it, A is the cerebrum, B, the cerebellum, C C C, the spinal
marrow, D, the tongue, E,the larynx, F, the lungs, G, the heart, H,
the stomach, I, the diaphragm.
  111. The par vagum, arising by a single set of roots, and passing
to the larynx, lungs, heart, and stomach.
  2. Superior laryngeal branches of the par vagum.
  3. Recurrent or inferior laryngeal of the par  vagum.
  4. Pulmonic plexus of the par vagum.
  5. Cardiac plexus of the par vagum.
  6. Gastric plexus of the par vagum.
  7. Respiratory nerve or portio dura to the muscles of the face,
arising by a series of single roots.
  8. Branches of the glossopharyngeal.
  9. Lingualis, sending branches to the tongue and to the muscles
on the fore part of the larynx.
  10. Origins of the superior external respiratory or spinal ac-
cessory.
  11. Branches of the last nerve to the muscles of the shoulder.
  12 12 12. Internal respiratory or phrenic to the diaphragm.
  The origins  of this nerve are seen to pass much higher up than
they are generally described.
  13. Inferior external respiratory, to the muscles on the side of
the chest.
  To Sir C. Bell we are indebted for a further arrangement of the
nerves, infinitely more natural and philosophical than the unmean-
ing numeration of the nerves, according to the system of Willis,
and better adapted to facilitate the comprehension of this intricate
portion of anatomy. It is, indeed, to the labours of Bell, Magen-
die, Meckel, and one or two others, that we owe the  great im-
provements in  our knowledge of the structure  and functions of the
nervous system.
  According to Sir C. Bell's arrangement, all the nerves of the
body may be referred  to two great classes—the original, primitive
or symmetrical, and the irregular or superadded.
  It has been already remarked, that  a division of the spinal cord
corresponds to the cerebrum  and cerebellum.  Now, every regular
nerve has two roots, one from the  anterior of these columns, and
another from the posterior.   Such are the fifth pair, the sub-occipi-
tal, the seven cervical, the  twelve dorsal, the  five lumbar, and the
six sacral—i. e. thirty-two perfect, regular, or double nerves, includ-
ing, to express it more briefly, all the spinal nerves, and  one ence-
phalic—the fifth pair.   This fifth pair is found to arise from the en-
cephalon, by two roots, and to have a ganglion upon the posterior
root.  It is, accordingly, classed with the spinal  nerves, and  like
them, conveys both motion and sensibility to the  parts to which it
is distributed.
  These regular nerves are common  to all animals, from the zoo-
phyte to man.   They  run out laterally; or in other words, in a di- 
56                       SENSIBILITY.
 rection, perpendicular to the longitudinal division of the body, and
 never take a course parallel to it.
   The other class of nerves is called irregular or superadded. The
 different nervous cords proceeding from it, are distinguished by  a
 simple fasciculus or single root.  All  these nerves  are simple  in
 their origins, irregular in  their distribution, and deficient in that
 symmetry, which characterizes the first class. They are superadded
 to the original class, and correspond to the number  and  complica-
 tion of the superadded organs. Of these, there are the third, fourth,
 and sixth, distributed to the eye; the seventh to the face; the ninth
 to the tongue; the glosso-pharyngeal to the pharynx; the vagus
 to the larynx, heart, lungs, and  stomach; the phrenic to the dia-
 phragm; the spinal accessory to the muscles of the shoulder; and
 the external respiratory to the outside of the chest.
   The reason of the seeming confusion, in this latter class, is to be
 looked for in  the complication of the superadded apparatus of res-
 piration, and in the variety of offices it  has to perform, in the higher
 classes of animals.  The plate exhibits, in one view, the nerves
 destined to move  the muscles  in all  the varieties of respiration,
 speech, and facial expression.
   In the plate of regular or symmetrical nerves, A is the cerebrum,
 B, cerebellum, C C, crura cerebri, D D, crura cerebelli, E E E, spinal
 marrow.
   1  1. Branches of the fifth pair, arising from the union of the crura
 cerebri and crura cerebelli, and having a  ganglion at the root.   2 2.
 Branches of the  sub-occipital nerves, which have double origins and
 a ganglion.   3 3. Branches of the four inferior cervical nerves, and
 of the first dorsal, forming the axillary plexus.  The origins of these
 nerves are  similar to those of the  fifth  and of the sub-occipital.
 4 4 4 4. Branches of the dorsal nerves, which also arise in the same
 manner.   5 5. The lumbar nerves.   6 6. The sacral nerves.
   The fact of the fifth pair of encephalic nerves having two roots,
 and essentially resembling the spinal nerves in arrangement and
 function, has drawn the attention of anatomists to the other ence-
 phalic nerves.  The brain and cerebellum having been considered
 expansions of the anterior and posterior columns of the spinal mar-
 row, and the cranium itself having, by  some, been esteemed the
 uppermost vertebra of the body, differing from the others only in
 disposition, attempts have been made to reduce all the encephalic
 to the same nature as the spinal nerves, and to show that the great
difference, in the case of the former, consists in the  two roots not
 being united into a single trunk, and in each forming,  consequently,
 a distinct pair of nerves.   This is the opinion  of Meckel, who
accounts for the  separation of the roots into distinct  nerves by the
large development of the central mass of the nervous system within
the cranium;  and 2dly, by the existence, within the cranium, of
particular organs for  the  senses, which  keep the roots separate
from each other. 
 
Rtae 55.
SYSTF.M  OF KKSP.I R ATOKY  NKIU'ES.
 
REGULAR, OR  SYMMETRICAL NERVES.
Tac/t 56
\ If'
^>^;^  \,/' - If. - - ^^^
 
 
NERVOUS SYSTEM.
57
  The facts and reasoning, adduced by this distinguished anatomist
on this subject, are, however, scarcely entitled to the epithet " in-
genious," and are too indicative of the spirit of system and inno-
vation to be accepted, were they even devoid of the weighty ob-
jections, that might be urged against them by the anatomist.
  So much  for the anatomy of the two great parts of the  nervous
system.  We have still to consider a third, and by no means the
least interesting.
  4. Great sympathetic—-This nerve, called also the trisplanch-
nic, ganglionic, and great intercostal, is constituted  of a series
of ganglions, joined to each other by a nervous trunk, and extend-
ing down the side of the spine,  from the  base  of the cranium to
the os coccygis or lowest bone of the spine. It communicates with
each of the  spinal nerves and with several of the encephalic;  and
from the ganglions, formed by  such  communication, it sends off
nerves, which accompany the arteries, and are distributed particu-
larly to the  organs of involuntary functions.  At its upper part,
it is situated in the carotid canal, where it appears under the form
of a ganglionic plexus, two filaments of which proceed to join the
sixth pair of encephalic nerves, and another to  meet the vidian
twig of the fifth pair.  By means of the fifth pair, it communicates
also with the ophthalmic ganglion, which Bichat considered to be-
long to it.   On issuing  from the carotid canal, the nerve passes
downwards, along the side of the spine, to the sacrum, presenting
a series of ganglions;—three  in the  neck, the superior, middle,
and inferior cervical; twelve in the back, the thoracic ganglions;
five in the loins, the lumbar; and three or  four in the  sacrum,
the sacral.   When it reaches the coccyx, it terminates by a small
ganglion, called coccygeal,  or by uniting with the great  sympa-
thetic of the opposite side.
  The ganglions are of an irregular, but generally roundish, shape.
They consist of nervous filaments, surrounded by a reddish-gray,
pulpy, albuminous, or gelatinous substance, which differs from the
gray matter of the brain. Authors have differed considerably with
regard to their uses.  Willis, Haller, Vieussens, and others,
regarded them to be small  brains for  the secretion of the nervous
fluid or animal spirits;  an opinion which  has been embraced by
Richerand and Cuvier, the latter of whom remarks, that the gan-
glia are larger and more numerous when the brain is deficient in
size. Lancisi and Vicq d'Azyr regarded them as a kind  of heart
for  the propulsion of these spirits, or as reservoirs for keeping them
in deposit.   Scarpa treats of them as synonymous with plexuses,
being, according to  him, plexuses with the filaments in close ap-
proximation, and the plexuses ganglions, whose filaments are more
separated.   He consequently believes, with many physiologists,
that their office is to mix and unite various nervous filaments with
each other.  Dr. Wilson Philip believes, that they are secondary
sources of nervous influence, the specific office of which is to re-
  Vol. I.                     8 
58
SENSIBILITY.
ceive supplies of it from all parts of the brain and spinal marrow,
and to transmit their united influence to the organs to which the
nerves are distributed.
  The most probable view, in our uncertainty, is that of John-
stone and Bichat, that their use is  to render the organs  which
derive their nerves from them independent of the will. The sym-
pathetic is, indeed, the great system of involuntary nerves; and
although connected with the brain by the branches of the fifth and
sixth pairs of encephalic nerves, and  with the spinal cord, by the
spinal nerves, it does not  appear to be directly influenced  by
either; as the functions of  the parts to which the  ramifications of
the great sympathetic are distributed, can continue for some time
after both brain and spinal marrow have been separated; nay, as in
the case of the heart  and intestines, after they have been removed
from  the body.   Yet many discussions have been indulged, re-
garding the origin of this important part of the nervous  system;
some assigning it to the brain, others to the spinal marrow,  whilst
others again, with more justice, esteem it a distinct nerve, commu-
nicating with the brain and spinal cord, but not originating from
either; receiving, according to Broussais, by the cerebral nerves,
the stimulant influence, and applying it to movements which are
independent of the centre of perception.  In like manner, he  af-
firms, when irritation predominates in the viscera, it is conveyed
by the ganglionic to the cerebral nerves, which transmit it  to the
brain. The point is still sub lite. Reil and Bichat, esteeming this
nerve to be the great nervous centre of involuntary functions, have
termed it the organic  nervous system, in contradistinction to
the animal nervous system, which presides over the animal func-
tions.
  The great sympathetic is esteemed to be the visceral nerve, par
excellence; or in  other words, the nerve that supplies the different
viscera with  their nervous influence; a part of its  office  as the
nervous system  of involuntary functions, for  different  offices of
the viscera are carried on/Independently of volition.   On examin-
ing the course of the grqat sympathetic, we find many filaments
proceeding from the  cervical  and  thoracic ganglions, interlacing
and forming the  cardiac plexus, from which the nerves of the heart
and great vessels arise.   The same thoracic ganglions furnish a
branch to each intercostal artery.  A nerve of the  great sympa-
thetic, called  the great splanchnic or  visceral, proceeding from
some of the  thoracic ganglions, passes through the pillars  of the
diaphragm into the abdomen and terminates in a large plexus or
ganglion, called the semi-lunar, and this, by uniting.with its fel-
low of the opposite side, constitutes the still more extensive inter-
lacing, the solar plexus.  From this,  numerous filaments proceed,
which, by accompanying the coronaria ventriculi, hepatic, splenic,
spermatic, renal, superior and inferior mesenteric, and hypogastric
arteries, are distributed to the parts that are supplied with blood by 
                       NERVOUS SYSTEM.                    59

these arteries, as the stomach, liver, spleen, testes, kidneys, intes-
tines, &c.
  Weber, however, a German anatomist of distinction, who ex-
amined the great sympathetic in  different animals, has afforded
reason for believing that the splanchnic may not be the sole visce-
ral nerve, but that the eighth pair, or par vagum may share in the
function.
  According to him, the great sympathetic is less developed, the
lower the animal; whilst  the par  vagum is more and more deve-
loped as we descend in the scale, and at length is the only visceral
nerve in some of the mollusca.  But we shall have to refer to the
subject of innervation hereafter.
  All the parts that we have  described as constituting the nervous
system, brain, cerebellum, medulla  spinalis, and nerves, are formed
of the primary nervous fibre,  the nature of which has been already
described.  The substance of which  they are constituted is soft
and pulpy, but the consistence varies in different portions, and in
the whole,  at different ages.  In the foetus it  is almost  fluid; in
youth, of greater firmness; and of still greater in the adult.  This
softness of structure in the encephalon of the foetus is by no means
inutile.   It admits of the pressure which takes place more or less
in all cases of parturition, whilst the  head is passing through the
pelvis, without the child sustaining any injury.
  In examining the  consistence of different brains, however, it is
necessary to inquire into  the period that has elapsed  since the
death of the  individual, as the brain  loses its firmness by being
kept, and ultimately becomes semi-fluid.   It is likewise rendered
fluid by disease, constituting the ramollissement du cerveau, or
mollescence of the brain, to which the attention  of pathologists
has been directed of late, but without much important advantage
to science.
  When the encephalon is fresh, it  has  a  faint, spermatic, and
somewhat tenacious smell.   This, according  to  Chaussier, has
persisted for several years in brains that have been dried.
  The  substance, of which the  nervous system is composed, has
been subjected to analysis by Vauquelin, and found to contain, wa-
ter,  80.00; white fatty  matter, 4.53; red fatty matter, called cere-
brine, 0.70; osmazome, 1.12; albumen, 7.00; phosphorus, 1.50;
sulphur, acid phosphates of potass, lime, and magnesia, 5.15.   In
the spinal  cord, there  is more fatty matter, and  less osmazome,
albumen and water.   In the nerves, the albumen predominates,
-and  the fatty matters are in less quantity.  Recent researches, by
Lassaigne, show, that water constitutes -/^ths °f the nerves, and
■^ths of the brain; whilst the proportion of albumen, in the for-
mer, is  T2^ths; in the latter, T£oths.
  Neither the chemical analysis  nor the inquiry into its minute
structure, by the aid of the microscope, has thrown light upon the
wonderful functions executed by this elevated part of the economy. 
60
SENSIBILITY.
  To the naked  eye, the nervous  substance appears under two
forms, the one of a gray colour and softer consistence, the other of
a white colour and more compact.   The former is called the cor-
tical or cineritious substance; the latter the white or medullary.
The gray substance is not always, however, at the exterior, nor
the medullary in  the interior.  In the medulla spinalis, their situa-
tion is the reverse of what it is in the brain. Ruysch considered,
that the cineritious  portion  owes its colour to the blood-vessels
which enter it; and, in the opinion,Haller and Adelon concur;
but this is not probable, and it has by no means been demonstrated.
The medullary portion has the appearance of being fibrous.  Mal-
pighi believed the gray cortical  substance to be an assemblage of
small follicles, intended to secrete the nervous fluid, and the white
medullary substance to be  composed of the excretory vessels of
these glands.
  Gall and Spurzheim, on the other hand, conjecture, that the
use of the cineritious is to form the medullary part. The facts, on
which they support their view, are, that the nerves appear to be
enlarged when they pass through a mass of cineritious matter, and
that masses of this substance are  deposited in all parts of the spinal
cord where it sends out nerves;  but Tiedemann  has  remarked,
that in the foetus  the medullary  is developed  before the cortical
portion, and he conceives  the use of the  latter to be  to convey
arterial blood, which may be needed by the medullary portion for
the due execution of its functions.
  Sir Charles Bell affirms, that he has found, at different times,
all the internal  parts of the brain diseased without loss of sense,
but that he has never seen disease general  on the  surfaces of the
hemispheres, without derangement or oppression of mind, during
the patient's life;  and hence he concludes, that the cineritious mat-
ter  of the brain is the seat of intellect, and the medullary  of the
subservient parts.
  This view would  afford considerable support to the opinions of
Gall, Spurzheim,  and others,  who consider the organs of the
cerebral faculties to  be constituted of expansions of the columns of
the spinal marrow and medulla  oblongata, and to terminate  by
radiating fibres on the periphery of the  brain ; and of  Desmoulins
and those who regard the convolutions as the seat  of  mind.  We
have, however, cases  on record, which signally conflict with this
view of the subject; cases in which the  cortical substance has been
destroyed; and yet the moral and intellectual manifestations have
been little,  if at  all injured.  Some years ago we dissected the
brain of an individual of rank in the British army of  India, the
exterior lobes of which were in such a state that neither medullary
nor cortical portion could be distinguished, both one and the other
appearing broken down into a semi-purulent amorphous fluid; yet
the intellectual faculties had been nearly unimpaired,  although the
morbid process had been of considerable duration. 
NERVOUS SYSTEM.
61
  The encephalon affords us many striking instances of the differ-
ent effects produced by sudden and by gradual interference with
its functions. Whilst a depressed portion of bone or an extravasa-
tion of blood may suddenly give rise to the abolition of the facul-
ties ; the gradual compression produced by a tumour may scarcely
interfere with any of its manifestations.
  The circulation of blood in the encephalon requires mention.
The arteries are four in number,—the two internal carotids and
the two vertebrals; to these may be added the spinal artery, or
middle artery of the dura mater,—the arteria meningaea media.
The carotid arteries enter  the head  through the carotid canals,
which open on each  side  of the sella turcica, or of the chiasma
of the  optic nerves.  The  vertebral  arteries  enter the  head
through  the foramen  magnum  of the  occipital  bone, unite on
the medulla oblongata to form the basilary artery, which passes
forward along the middle of the pons varolii, and at the anterior
part of the pons gives off lateral branches, that inosculate with
corresponding branches of  the carotids, and form a kind of circle
at the base of the brain,  which has been called the circulus  arte-
riosus of Willis.
  The passage  of the blood-vessels is extremely tortuous, so that
the blood does  not enter  the head with great impetus; and the ves-
sels become capillary before they penetrate the organ, an arrange-
ment of essential importance, when we regard the large amount of
blood sent  to the encephalon.  This has been estimated as high as
one-eighth of  the whole fluid distributed  from the heart.   The
amount does not admit of accurate appreciation, but it is consider-
able.  It must of course vary according to circumstances. In hyper-
trophy of the heart, the quantity sent is sometimes increased; and
in ordinary cases of what are called determinations of blood to
the head.  Here, too large a quantity is sent by the arterial vessels;
but an equal accumulation  may occur, if the return of the blood
from the head,  by means of the veins, be in any manner impeded,
as when we stoop, or compress the veins of the neck by a tight
cravat, or by keeping the head turned for a length of time, &c-
  The cerebral, like other  arteries, are accompanied by branches
of the great sympathetic.
  The encephalic veins are disposed as already mentioned, termi-
nating in sinuses formed by the dura mater, and conveying  their
blood to the heart by means of the  lateral sinuses and  internal
jugulars. (See  Fig. 10.)
  No lymphatic vessels have been detected in the encephalon; yet,
that absorbents  exist there  is proved by the dissection of apoplec-
tic and paralytic individuals.  In these cases,  blood is sometimes
effused within the brain,  the red particles are gradually taken up,
and a portion of the fibrinous part of the blood, leaving a cavity
called an apoplectic cell,  which is, at the same time, the evidence
of previous extravasation and of subsequent absorption. 
62
SENSIBILITY.
  When the skull of the new-born infant, which at the fontanelles,
consists of membrane only, or the head of one who has received
an injury, that exposes the brain, is examined, two distinct move-
ments are perceptible.   The  one,  which is generally obscure, is
synchronous with the pulsation of the heart and arteries; the other,
much more apparent,  is connected  with respiration, the organ
seeming to sink down at the time of inspiration, and to rise during
expiration.  This phenomenon is  not confined to the brain, but
exists likewise in the cerebellum and spinal marrow.
  The motion of the  encephalon, synchronous with  that of the
heart, admits, we think, of easy explanation.   It is owing to the
pulsation  of the circle of arteries at the base of the brain ele-
vating the organ  at each systole of the heart.  The other move-
ment is  not so readily intelligible.   It  has been attributed to the
resistance experienced  by the blood in its  passage through the
lungs during expiration.  An accumulation of blood consequently
takes place in the right side of the  heart; this extends to the veins
and to the cerebral sinuses, and an augmentation of bulk  is thus
occasioned.  We shall see hereafter that one of the forces, con-
ceived to propel  the  blood along the vessels, is atmospheric pres-
sure.  According to that view, also,  the sinking down of the
brain during inspiration is explicable.  During inspiration, the
blood is rapidly drawn to the  heart; the veins are consequently
emptied, and the sinking down of the brain succeeds.
  On dissection, we find that the encephalon fills the cavity of the
cranium;  during life, therefore, it must be pressed upon, more or
less, by the blood in  the vessels, and by the serous fluid exhaled
by the arachnoid.
  The spinal marrow does not, as we have seen, fill the vertebral
canal, but the cephalo-spinal fluid exerts upon it the necessary de-
gree of  pressure; added to which,  the  pia mater seems to press
more upon this organ than upon the rest of the cerebro-spinal sys-
tem.  A  certain degree of pressure appears, indeed, necessary for
the due performance of its functions,  and if this be either suddenly
and considerably augmented or diminished, derangement of func-
tion is the result. Magendie, however, asserts that he has known
animals, from which this fluid has  been removed, survive  without
any sensible derangement of the nervous functions.   It  is this,
which is  drawn off by the surgeon when he evacuates the fluid of
spina bifida.
   When  the brain is examined in the living body, it exhibits pro-
perties, which some years ago  it would  have been esteemed the
height of hardihood and ignorance to ascribe to it.   The  opinion
has universally prevailed, that all nerves are exquisitely sensible.
We have seen how far this universal sentiment is  founded upon
fact; but we are now prepared  to assert, that even the encephalon
itself,—the organ or organs in which perception takes place,—is in-
sensible,  in the common acceptation  of the termj that is, we may 
                       NERVOUS  SYSTEM.                    63
                         «

prick, lacerate, cut, and even cauterize it, yet no painful impres-
sion will be produced.  Experiment leaves no doubt regarding the
truth of this, and we find the fact frequently confirmed in patholo-
gical cases.
  Portions of brain may be discharged from a wound in the skull,
and yet  no pain be evidenced;  and,  in  the  last edition  of his
"Anatomy and Physiology," Sir C. Bell remarks, that he can-
not resist stating, that on the morning he was writing,.he had had
his finger deep in the anterior lobes of the brain, when the patient,
being at the time acutely sensible, and capable of expressing him-
self, complained only of the integument.  A pistol ball had passed
through  the head, and  having ascertained that it had penetrated
the dura mater by forcing his finger into the wound, Sir Charles
trepanned on  the opposite  side  of the head and extracted the
ball.
  By the experiments, instituted  by Magendie and others, it has
been shown, that an animal may live several days, and even weeks,
after the whole of the hemispheres has  been removed; nay, that in
certain animals, as reptiles, no change  is  produced in their habi-
tudes by such abstraction.  They move about as if unhurt.
  Injuries of the surface of  the cerebellum exhibit, that it also is
not sensible to that kind of irritation; but deeper wounds, and
especially those that interest the peduncles, have singular results,
to be explained hereafter.
   The spinal cord is not exactly circumstanced in the same man-
ner.  Its sensibility is  very exquisite on the posterior surface;
much less on the anterior, and almost null at the centre.   These
columns are, as we have seen, respectively the origins of the nerves
of sensibility, motion, and respiration.
  Considerable sensibility is also found within, and at the sides of,
the fourth ventricle; but this diminishes as we proceed towards
the anterior part of  the medulla oblongata, and  is very feeble in
the tubercula quadrigemina of the mammalia.
  It has been shown that the spinal nerves, by means of their pos-
terior roots, convey general  sensibility to  the parts to which they
are distributed.  But there are other nerves which, like the brain,
are themselves entirely devoid of general sensibility.  This has
given occasion to a distinction of nerves into those of general and
of special sensibility.   The nerves, that must be considered as in-
sensible or devoid of general sensibility,  are the optic, olfactory,
and auditory.   Each of these has, however, a special sensibility,
and although they may exhibit no pain when irritated, they are
capable of being impressed by appropriate stimuli, as by light, in
the case of  the optic nerve; by odours, in that of the olfactory;
and by sound, in that of the auditory.   Yet we  shall find, that
each of these nerves of special sensibility requires the influence of
a nerve of  general sensibility, the fifth pair.   Many other nerves
appear also devoid  of sensibility, as the third, fourth, and  fifth- 
64
SENSIBILITY.
pairs; the portio dura of the seventh; the ninth pair of encephalic
nerves; and, as has been shown, all the anterior roots of the spinal
nerves.
  The parts of the encephalon, concerned in muscular motion, will
fall under consideration hereafter.

                 physiology op sensttut.tty.

  Sensibility we have defined to be the function by which an ani-
mal experiences feeling, or has the perception of an  impression.
It includes two great sets of phenomena, the sensations, properly
so called, and the intellectual and moral manifestations. These
we shall consider in succession.

                     Of the Sensations.

  A sensation is the perception of  an impression made on some
organ;  or, in the language of Gall, it is the perception of any
irritation whatever.
  By the sensations we receive a knowledge of what  is passing
within or without the body; and, in this way, our notions or ideas
of them are obtained.  When these  ideas are reflected upon and
compared with each other, we exert thought and judgment; and
they can be recalled, with more or less vividness  and accuracy,
by the exercise of memory.
  The sensations are very numerous, but they may be all com-
prised in two divisions,  the external and the internal.   Vision
and audition afford us examples of the  former, in which the im-
pression made upon the organ is  external to the part impressed.
Hunger and thirst are instances of the second, the cause here be-
ing internal, necessary, and depending upon influences seated in
the economy  itself.   Let us endeavour  to  discover in what they
resemble each other.
  In the first place, every sensation, whatever may be its nature,
external or internal, requires  the intervention of the encephalon.
The distant organ, as the eye  or ear, may receive the impression,
but it is not until this impression has been communicated to  the
encephalon that sensation is effected.  The proofs of this are easy
and satisfactory.  If we cut the  nerve proceeding to any sensible
part, if we put a ligature around it, or compress it in any manner,
it matters not that the body, which ordinarily excites a sensible
impression, be applied to the part; no sensation is experienced.
Again, if the brain, the organ  of  perception, be  prevented in any
way from acting, it matters not  that the part impressed, and the
nerve communicating with it, be in a condition necessary for the
due performance of the function, sensation is not effected. We see
this in numerous instances. In pressure on the  brain,  occasioned
by fracture of the skull,  or in apoplexy, a disease essentially de- 
SENSATIONS.
65
pendant upon pressure, we find all sensation, all mental manifesta-
tion lost;  and they are not  regained until  the compressing cause
has been removed. The same thing occurs if the brain be stupefied
by opium or any other narcotic, and to a less degree in sleep, or
when the brain is engaged in intellectual meditations.   Who has
not found, that in a state of reverie  or brown study, he has suc-
ceeded in threading his way through a crowded street, carefully
avoiding every obstacle, yet  so little impressed by the objects
around him  as not to retain the slightest recollection of them ? On
the other hand, how vivid are the sensations when the attention
is directed to them!
  Again,  we have numerous cases in which the brain itself en-
genders the  sensation, as in dreams, and in  insanity.
  In the former we see, hear,  speak, make use of every one of
our senses apparently, yet there has been no impression from with-
out. Although we may behold  in our dreams the figure of a friend
long since deceased, there can  obviously be no  impression made
on the retina from without.  The whole history of spectral illu-
sions, of morbid hallucinations, and maniacal phantasies, is to be
accounted for in this manner.  Whether, in such cases, the brain
reacts upon  the nerves of sense and produces an impression upon
them from within, similar to what they experience from without,
during the production of a sensation, will form the subject of future
inquiry.
  Pathology also affords several  instances where the brain engen-
ders the sensation, most of which are precursory signs of cerebral
derangement.   The appearance of spots flying before the eyes, of
spangles, depravations of vision,  of hearing, &c.  as well as a sense
of numbness in the extremities, are referable to the same cause.
  These, facts prove that  every sensation, although referred to
some organ, must  be  perfected in the brain. The impression is
made upon the nerve of the  part, but the appreciation takes place
in the common sensorium.
  There are but few organs  of the body which could be regarded
as insensible, provided we were aware of the precise circumstances
under which their sensibility is elicited. The old doctrine,—as old
indeed as Hippocrates—was, that the tendons and other membra-
nous parts are among the most sensible organs of the body.  This
opinion was implicitly credited by Boerhaave, and his follower
Van Swieten; and in many cases had a decided influence on sur-
gical practice especially.   As the bladder consists  principally of
membrane, it was agreed for ages by all thelithotomists,that it would
be improper to cut or  divide any part of it;  and therefore, in order
to extract the stone, dilating instruments were used, which caused
the most painful lacerations of the parts implicated in the operation.
  Haller considered  the tendons, ligaments, periosteum, bones,
meninges of the brain, different  serous membranes, arteries, and
veins, entirely insensible;  yet  we know that these parts are ex-
  Vol. I.                   9 
66
SENSIBILITY.
quisitely sensible when attacked with inflammation.   One of the
most painful affections to which man is liable, is the variety of
whitlow that implicates the periosteum; and in  all affections of
the bone, which inflame or press forcibly upon that membrane, we
have excessive sensibility exhibited.
  Many parts, too, are affected by special irritants; and after they
have appeared insensible to a multitude  of agents, will show great
sensibility when a particular irritant is applied.  Bichat, for ex-
ample, endeavoured to elicit the sensibility of ligaments in a thou-
sand ways, and without success;  but when he subjected them to
distention or twisting, they immediately gave evidence of it.  It is
obvious then, that before we determine  that a part  is  insensible,
we must have submitted it  to  every kind of  irritation.   Adelon
affirms that there is no part but what may become painful by dis-
ease.   From this assertion the cuticle might  safely be excepted.
It is, so far as we know, totally devoid of blood-vessels and nerves,
—the elements of sensibility,—and appears to be extra-organic. If
we are right, indeed,  in our view of its origin and uses, as de-
scribed hereafter, sensibility would be of no advantage to it, but the
contrary.  In the present state, then, of our knowledge, we are jus-
tified in asserting, that bones, cartilages, and membranes are not
sensible to ordinary external irritation, when  in a state of health,
or in other words, that we are not aware of the irritants which
are adapted to exhibit their sensibility.
  That sensibility is due to the nerves distributed to a part is so
generally admitted as  not to require comment. It is true, however,
that such sensibility is by no  means in proportion to the number
of nerves it receives.  Nay, some parts are  acutely sensible in
disease  into which nerves cannot be traced.  To  explain these
cases Reil supposed,  that each  nerve is  surrounded at its termina-
tion by a nervous atmosphere, by which its action is extended be-
yond the part in which it is seated.  This opinion is a mere crea-
tion of the imagination. We have no evidence of any  such atmos-
phere,  and it is more  philosophical in us to presume, that the rea-
son we do not discover nerves in these parts may be owing to the
imperfection of our vision.
  We may conclude,  then, that the action of impression occurs in
the nerves of the part to which the sensation  is referred.
  The facts, already mentioned, show that the action of perception
takes place in the  brain, and  that the nerve  is merely the  con-
ductor of the impression between the part impressed and that or-
gan.  If a ligature be put around a nerve, sensation is  lost below
the ligature, but is uninjured above it.   If two ligatures be placed,
sensibility is lost in the portion included  between  the ligatures,
but is restored if the upper ligature be removed.'  The spinal mar-
row is sensible along the whole of its posterior column, but it also
acts only as a conductor of the impression.  Flourens destroyed
gradually the spinal cord from below, by slicing it away, and he 
SENSATIONS.
67
found that sensibility was gradually extinguished in the parts cor-
responding to the destroyed medulla, but  that the parts  situated
above evidently continued to feel.   Perception therefore occurs in
the encephalon; and not in the whole but in some of its  parts.
Many physiologists, amongst whom may be  mentioned Haller,
Lorry, Rolando, and Flourens, have sliced away the brain, and
found that the sensations continued  until  the  knife  reached  the
level of the corpora quadrigemina; and again  it has been  found
that if the spinal cord  be sliced away from below upwards, the
sensations persist until we reach the medulla oblongata. It is then
in the medulla oblongata that we must place  the cerebral organs of
the senses, and it is with this part of the cephalo-spinal axis that
the nerves of the senses communicate.
  If we divide the posterior roots of the spinal nerves and the fifth
pair, all general sensibility is lost; but if we divide the nerves of
the senses, we destroy  only their functions.  We can thus under-
stand why,  after decapitation, sensibility may still remain for a
time in the head.  It is instantly destroyed in the trunk, owing to
the removal of all communication with the encephalon, but the fifth
pair remains entire in the head, as well as the nerves of the organs
of the senses. Death must of course follow almost instantaneously
from loss of blood,  but there may be an appreciable space, during
which the head may continue to feel, or  in other words, during
which the external senses may act.
  It has  been remarked that the  cerebral hemispheres  may  be
sliced away without abolishing the senses.  The experiments of
Rolando and Flourens, which have been repeated by Magen-
die, show however that the sight is an exception; that it is lost by
the removal of the hemispheres.  If the right hemisphere be sliced
away,  the sight of the  left eye is lost, and  vice versa; one of the
facts proving the decussation  of the optic nerves. The experiments
of these gentlemen show that vision, more than the other senses,
requires a connexion with the organ of the intellectual faculties—
the cerebral hemispheres; and this, as Magendie has judiciously
remarked, because vision rarely consists in  a  simple impression
made by the light, but is connected with an intellectual  process,
by which we judge of the distance, size, shape, &c. of bodies.
  Having arrived at a  knowledge of the part  of the encephalon
in which perception occurs, our acquaintance with this mysterious
process is suddenly arrested.   We know  not,  and we probably
never can know, the action of the brain in  accomplishing it. This
is certainly not allied to any physical phenomenon, and if ever we
are justified in referring a function to the class of organic and
vital, it would be those that belong to the  elevated phenomena
which we have to consider under the head of the animal functions.
We know them but by their results.   We  are but little better ac-
quainted,  however, with many topics of physical inquiry;—with
the phenomena of the electrical or magnetic fluids, for example. 
68
SENSIBILITY.
  The organs, then, that form the media  of communication  be-
tween the parts impressed and the brain, are the nerves and spinal
marrow. Broussais, indeed, affirms, that every stimulation capa-
ble of causing perception in the brain, runs through the whole of
the nervous system of  relation;  that it is repeated in the mucous
membranes, whence it is again returned to the centre  of  percep-
tion,  "which judges of it  according to the view of the viscus to
which the mucous membrane belongs, and adapts its action accord-
ing as it perceives pleasure or pain."
  As we are totally unacquainted with the material character of
the fluid which  passes with the rapidity of lightning along these
cords, it is as impossible for us to describe  its  mode of transmis-
sion as it is to depict that of the electric fluid along a conducting
wire.  As in this last case, we are aware of such transmission only
by the result.   Still, hypotheses,  as in  every obscure matter of
inquiry, have not been wanting.   Of  these, three are  chiefly  de-
serving of notice. The first, of greatest antiquity, is, that the brain
secretes a subtile fluid which circulates through the nerves, called
animal spirits, and which is the medium  of communication  be-
tween the different parts of the nervous system; the second regards
the nerves as cords, and the transmission as effected by means of
the vibrations or oscillations of these  cords;  whilst the  third
ascribes it to the operation of electricity.
  The hypothesis of the animal spirits has prevailed most exten-
sively.   It was the doctrine of Hippocrates, of Galen, of  the
Arabians, and of most of the physicians of the last centuries.  Des-
cartes adopted  it energetically, and was  the  cause of its more
extensive diffusion. The great grounds assigned for  this  belief
were, 1st, that as the brain receives so much more blood than is
necessary for its own nutrition, it must be an organ of secretion;
2dly, that the nerves seem to be a continuation  of the medullary
matter of the brain; and it has already been remarked, that Mal-
pighi considered the cortieal part of the brain to be follicular,  and
the medullary to be secretory tubes.   It was not unnatural, there-
fore,  to regard the  nerves as vessels for the transmission of these
spirits.  As, however,  the animal spirits  had never been met with
in a tangible shape, ingenuity was largely invoked in the surmises
regarding their nature; and  generally opinions  settled down into
the belief that the fluid was of an ethereal character.  For the va-
rious opinions that  have  been held upon the subject, the reader is
referred to the Elementa Physiologiae of Haller, who was him-
self an ardent believer in the existence  of the animal spirits,  and
has wasted much time and  space in  an unprofitable inquiry into
their nature.
   The  truth is, that we have not the slightest evidence, direct or
indirect, of the existence of any nervous fluid of the kind described;
the nerves do not seem to consist of tubes, nor  have we  any  rea-
son for considering the brain the organ  of any  ponderable  secre- 
SENSATIONS.
69
tson.  Yet the term animal spirits, although their existence is not
now believed in, adheres to us in popular language.  We speak of
a man who has a great flow of animal spirits,  but without regard-
ing the  hypotheses whence the expression originated.
   The expression nervous fluid is still constantly used by physio-
logists.  By this, however, they simply mean the medium of com-
munication or of conveyance, by which  the nervous influence is
carried  with the rapidity of lightning, from one part of the system
to another, but without committing themselves as to its character;
so that after all the idea is in  part retained, although the term, as
applied  to the nervous fluid, is exploded.
   Good directly admits their existence, under the more modern
title; and it is not easy to conceive that the brain does not possess
the function of  elaborating some fluid, galvanoid  or other, which
is  the great agent in the  nervous function.
   The hypotheses of vibrations is ancient, but  has by  no means
been as generally received as the last.  Among the moderns it has
received the support of Condillac, Hartley, Blumenbach,
and others; some supposing that the nervous matter itself is thrown
into vibrations; others,  that  an invisible  and  subtile ether is dif-
fused through it which acts the sole or chief part. As the latter is
conceived by many to be  the mode in which electricity is trans-
mitted along conducting wires, it is not  liable to the same objec-
tions as the former.  Simple inspection of a nerve at once exhibits,
that it  is incapable  of  being thrown  into vibrations.   It is soft,
never tense, always pressed upon in its course; and as it consists
of filaments destined for very different functions, sensation, voli-
tion, respiratory motion, &c.  we cannot conceive  how one of these
filaments can be thrown into vibration without the effect being ex-
tended  to others, and great confusion being induced.
   The last hypothesis is of later  date, subsequent to the discove-
ries made in animal electricity. The rapidity, with which sensa-
tion and volition  are communicated along the nerves,  could not
fail to suggest a resemblance  to the mode in which the electric and
galvanic fluids fly along conducting wires.  Yet  the great support
of the opinion was in the  experiments instituted by Dr. Wilson
Philip and others, from which it appeared, that  if the nerve pro-
ceeding to a part be  disordered, and the secretion which  ordinarily
takes place in  the part be thus arrested, it  may be  restored by
causing the galvanic fluid to  pass from one divided extremity of
the nerve to the other.
   The  experiments  connected with secretion will be noticed more
at length hereafter.   It will  likewise be shown,  that in the effect
of galvanism upon the muscles, there is the same  analogy; that the
muscle  may be made to contract for a length of time after the
death of the animal,  even when a limb has been removed from the
body, on the application of the galvanic stimulus; and comparative
anatomy exhibits to  us great  development of nervous structure in 
70
sensibility.
those electrical animals, which surprise us by the intensity of the
shocks they are capable of communicating.
  Physiologists  of the present day generally, we think, accord
with the electrical hypothesis.  The late Dr. Young, so celebrated
for his knowledge in numerous departments of science, adopted it
prior to the interesting experiments of Dr. Philip; and Mr. Aber-
nethy, whilst he is strongly opposing the doctrines of materialism,
goes so far as to  consider some subtile fluid not merely as the agent
of nervous transmission, but as forming the essence of life itself.
  Dr. Bostock,  however, has remarked, that before the electric
hypothesis can be considered proved, two points must be demon-
strated ; 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.
This is true, as concerns the belief in the identity of the  nervous
and electrical fluids;  but we have, even now, evidence sufficient
to show their similarity,  and that we are justified in considering
the nervous fluid as electroid or galvanoid in its nature, emanating
from the brain by some action unknown to us, and  distributed to
the different parts of the system to supply the expenditure which
must be constantly going on.
  Reil and Prochaska  are of opinion,  that the nervous agency
is generated through all the nervous system,  and that every part
derives sensation and motion from its own nerves.  Such likewise
is the opinion  of Broussais. We have satisfactorily shown, how-
ever, that  a communication with the brain is absolutely necessary
in all cases, and  that we  can immediately cut off sensation in the
portion of a nerve included between two ligatures, and as instantly
restore  it  by removing the upper ligature and renewing the  com-
munication with the  brain.

                 •  EXTERNAL SENSATIONS.

  The external sensations are all those perceptions occasioned by
the impressions of bodies external to  the part impressed.  They
are not confined  to impressions made  by objects  external to us.
The hand  applied to  any part  of the body,  any  two of its  parts
brought into contact, the presence of its own secretions or excre-
tions, may equally excite them. Adelon has divided the  external
sensations into two orders—1st, the senses, properly so called, by
the aid of which the mind acquires its notion of external bodies and
of their different  qualities; and 2dly,  those  sensations which are
still  caused by the contact of  some body, and yet  afford no in-
formation  to- the mind.
^ It is by the agency of the organs of the external senses, that we
become acquainted with  the bodies that  surround us.  They are
the instruments by which the brain receives its knowledge of the
universe; but they are only instruments, and  cannot be considered 
                   EXTERNAL SENSATIONS.                  71

as the sole regulators of the intellectual sphere of the individual.
This we shall see is dependant upon another and still higher ner-
vous organ,—the brain.
  The external senses are generally considered to be five in num-
ber; for, although others  have been proposed, they may perhaps
be reduced to some modification  of these five,—tact  or  touch,
taste, smell, hearing,  and vision. All these have some properties
in common.  They are all situated at the surface of the  body, so
as to be capable of acting with due facility on  external bodies.
They all consist of two parts; the one, physical, which modifies
the action of the body, that causes the impression ; the other, ner-
vous or vital, which receives  the impression, and conveys it to
the brain. In the eye and the  ear,  we have better exemplifications
of this distinction than in  the other senses.  The physical portion
of the eye is a  true optical instrument, which modifies  the light,
before it impinges upon the retina.  A similar modification is pro-
duced by the physical portion of the  ear on the sonorous vibra-
tions, before they reach the auditory nerve,  whilst, in the other
senses, the physical portion forms part of the common integument
in which the nervous portion is situated, and  cannot  therefore be
as easily distinguished.
   Some of them, again, are symmetrical; that is,  composed of two
separate and similar halves, united by a median line,  as the skin,
tongue, and nose.  The others, the eye and the  ear,  are in pairs;
and this, partly perhaps, to enable us to judge of the distances of
external objects.   We shall find,  at least, that there are certain
cases, in which both the organs are necessary for accurate appre-
ciation.
  Two of the senses,—vision  and audition,—have, respectively, a
nerve of special sensibility; and until of late years the smell has
been believed to be similarly situated.  In the present state of our
knowledge, we cannot decide  upon the precise nerve  of taste,  al-
though it  will be seen that a plausible opinion may be indulged on
the subject.  The general sense of touch is seated in the nervesof
general sensibility. All, however, seem intimately connected with
one of the nerves of general sensibility,—the fifth encephalic pair,—
and, in the case of those senses, more particularly, which possess
nerves  of special  sensibility,  it is found, that they are under the
presidency of this nerve of general sensibility; for if it be cut, the
function is abolished, although the nerve of special sensibility may
remain entire.
   Constituting instruments by which  the mind becomes acquaint-
ed with external bodies, it is  manifestly  of importance, that the
senses should be influenced by volition.  Most of them are so. The
touch has  the pliable upper extremity, admirably adapted for the
purpose. The tongue is moveable in almost every direction.  The
eye can be turned towards objects, in almost all  positions, by its 
72
sensibility.
 own immediate muscles.  The ear and the nose possess the least
 individual motion; but the last four, being seated in  the head, are
 capable of being assisted by the muscles, adapted for its movement.
   All the senses may  be exercised passively or actively.  By
 directing the attention,  we can render the impression much more
 vivid; and hence the difference between simply seeing, or passive
 vision, and looking attentively; between hearing and listening;
 smelling  and  snuffing;  touching  and  attentively feeling.  It is
 to  this active  exercise of the senses, that we are indebted for
 many of the pleasures and comforts of social  existence.  Yet, to
 preserve the senses in  the vigour and delicacy, which they  are
 capable of acquiring by  attention, the impressions must not be too
 constantly or too strongly made.   The occasional use of the sense
 of smell, under the guidance of volition, may be the test on which
 the chemist, or the perfumer,  or the wine-merchant,  may rely in
 the discrimination of the numerous  odorous characteristics of  bo-
 dies; but, if the olfactory nerves be constantly or too frequently
 stimulated by excitants  of this or any other kind, dependance  can
 no  longer be placed upon  that means of discrimination.  The
 maxim, that " habit blunts feeling," is true only in such cases as
 the last.   Education can indeed render it extremely acute.
  Volition, on the other hand, enables us to deaden the force of
 sensations.  By corrugating the eyebrows and approximating the
 eyelids, we can diminish the quantity of light when too powerful.
 We can breathe through the mouth,  when a disagreeable odour is
 exhaled around us;  or we can  completely shut off the  passage by
 the nostrils, with the aid of the upper extremity^  Over the hear-
 ing we have less command, as regards  its individual action;  the
 upper extremity is here always called into service, when we  de-
 sire to diminish the intensity of any sonorous impression.
  Lastly. It is  a common observation, that the loss of  one  sense
 occasions greater vividness in the others.  This is only true as re-
 gards the senses which administer chiefly to the intellect,—those of
touch,  audition, and vision, for example.  Those of smell and taste
may be destroyed, and yet the intellectual senses may be  uninflu-
enced in their action.
  The cause of the superiority of the remaining intellectual senses,
when one or more has been lost, is not owing  to any  superior  or-
ganization in these senses, but  is another example of the influence
of education.   The remaining senses  are attentively  exerted to
compensate for  the privation, and become surprisingly delicate.
  We proceed to the consideration of the  separate senses, begin-
 ning with that of tact or touch, because it is the most generally
distributed, and may be  regarded as that from which all the others
are derived.  They are  all, indeed, modifications of the sense of
touchy In the taste, the sapid body; in the smell, the odorous par-
ticle ; in the hearing, the sonorous vibration; and in the sight, the 
SENSE  OF TOUCH.
73
particle of light, must impinge upon or touch the nervous part of
the organ, before sensation can, in any of the cases, be effected.

             Sect. I.—sense op  tact  or touch.

   The sense of tact or touch is the general feeling or  sensibility,
possessed  by the skin especially; and which instructs us regarding
the temperature and  the  general  qualities of bodies.   By some,
touch is confined to the sense of resistance alone; and hence they
have conceived it necessary to raise into a distinct sense one of the
attributes  of tact or touch.   Dr. Fleming,  for example, has sepa-
rated  the  "sense of heat"  from tact,  but we think on  insufficient
grounds.   It properly belongs to the sense we are considering, in
the acceptation here given to it, and  adopted by  all the French
physiologists.   According to them, tact is spread generally in the
organs; and especially on the cutaneous and mucous surfaces.   It
exists in all animals, whilst touch is exercised only by  parts evi-
dently destined for that purpose.   It  does  not exist in every ani-
mal, and is nothing more than tact, joined to muscular  contrac-
tion and directed by volition. So  that, in the exercise of tact, we
may be regarded passive; in that of touch active.
   The organs, concerned in touch, execute other functions besides;
and in this respect it differs from the other senses. Its chief organ,
however, is the skin; and hence it is necessary to inquire into its
structure, so far as is necessary for our purpose.

           Anatomy of the Skin, Hair, Nails, Sec.

   The upper  classes of animals agree in  possessing an outer enve-
lope or skin, through which the insensible perspiration passes;  a
slight degree  of absorption takes place; the parts beneath are pro-
tected ; and the sense of touch is accomplished.
   In  man, the skin consists of four parts,—the cuticle, rete muco-
sum,  corpus papillare, and corium.
   1.  The epidermis or  cuticle is  the outermost layer.  It is a dry,
membranous structure, devoid of vessels and nerves, and decidedly
the most  inorganic part of the body.   It is, so far  as  we know,
entirely insensible, and takes no  part in the  functions  of the true
skin, or in its diseases.  It resists putrefaction for a long time, and
may be easily obtained,  in  a separate state from the other layers,
by maceration in water.   It is the thin pellicle raised by a blis-
ter.
   The cuticle is probably a  secretion  from the true skin, which
coagulates on the surface, becomes dried, and affords  an efficient
protection to  the corpus  papillare  beneath. It is composed, accord-
ing to some, of concrete albumen; according to others, of mucus.
   The epidermis is described as pierced by  oblique pores  for
   Vol. I.                  10 
74                       sensibility.
 the passage of hairs, and for the orifices of exhalent and  absor-
 bent vessels.  Humboldt, however, asserts, that he has never seen
 these  pores,  even with a microscope  which  magnified 312,400
 times.   It is probable,  indeed,  that this inorganic substance is
 placed at the surface of the body, not simply to protect the corpus
 papillare, but to prevent the constant imbibition  and transudation
 that might take place did no such envelope exist.  The cuticle  ex-
 foliates,  in the form of scales, from our heads; and, in large pieces,
 from every part of the body, after certain cutaneous diseases.
   2.  The corpus  or rete mucosum, rete Malpighii  or mucous
 web, is the next layer.  It was considered by Malpighi  as mucus,
 secreted by the papillae, and  spread on  the surface of the corpus
 papillare, to preserve it in the state of suppleness necessary for  the
 performance of its functions.  In this rete mucosum, the  colouring
 matter of the races seems to exist.  It is white in the European,
 and those of European descent; black in the African, or rather in
 the Ethiopian;  and copper-coloured in  the mulatto.  Gaultier
 considers the rete  mucosum to be composed of four layers, but this
 notion is not universally admitted, and scarcely concerns the pre-
 sent inquiry.
   3. The corpus  papillare  is seated  next below the rete muco-
 sum.   It consists of a collection of small papillae, formed by the
 extremities of nerves and vessels, which, after  having passed
 through  the corium beneath,  are grouped in small pencils or villi
 in a spongy, erectile  tissue.   These pencils are disposed in pairs,
 and, when not in action, are  relaxed, but become erect when em-
 ployed in the  sense of touch.   They are very readily seen, when
 the cutis vera is exposed by the action of a blister, and are always
 evident at the palmar surface of the  hand, and  especially at the
 tips of the fingers, where they have a concentric arrangement.
 These villi are sometimes called the papillae of  the skin.
  4. The corium,cutis vera,derma,or true skin,is the innermost
 of the layers of the skin.   It consists of a collection of dense fibres,
 intersecting each other in various directions, and leaving between
 them, holes for the passage of vessels and nerves.   It forms a firm
 stratum,  giving the whole skin the necessary  solidity for accom-
 plishing its various ends.
  The true skin consists chiefly of gelatine.  Hence it is used  in
 the manufacture of glue.   Gelatine, when united with tannin, forms
 a substance which  is insoluble in water;  and it is to this  combina-
tion, that leather owes the properties it possesses.   The hide is first
macerated in lime-water to remove the cuticle and hairs, and leave
the corium  or gelatine.  This is then placed in an infusion of oak
bark, which contains the tannin.   The tannin and  the skin unite,
and leather is the product. 
SENSE OF TOUCH.
75
Fig. 14.
l. Cuticle.
2. Rete mucosum.
3. Corpus papillare.
4. Cutis vera.
5. Cellular membrane.
6. Panniculus carnosus.
   These four strata con-
stitute the skin, as it is
commonly  called; yet
all are comprised in the
thickness  of  two  or
three lines.  The cutis
vera is  united to the
structures below by cel-
lular membrane ; and
this, with the layers ex-
ternal to it, forms the
common integument.  In certain parts of the body, and in animals
more particularly, the cutis vera is adherent to muscular fibres; in-
serted more or less obliquely, as at 6, Fig. 14.  These form the
muscular  web, or panniculus carnosus.   The  layer is well seen
in the hedge-hog and porcupine, in which it rolls up the body and
erects the spines; and in birds,  raises the feathers.   In man, it can
hardly be said to exist.  Some muscles, however, execute a similar
function.   By  the occipito-frontalis,  for instance,  many persons
can move the hairy scalp:  by the dartos, the  skin of the  scrotum
can be  corrugated.  These two parts, therefore,  act  as panniculi
carnosi.
   In the skin,  are situated numerous sebaceous follicles or crypts,
which separate an oily fluid from the blood, and  pour it  over the
surface  to  lubricate and defend it from the  action of moisture.
They are most abundant where there are folds of the skin, or hairs,
or where the surface is exposed to friction.  We can generally see
them on the pavilion of the ear, and their situation is often indicated
by small dark spots on the surface, which, when pressed  between
the fingers, may be forced out along with the  sebaceous secretion,
in the form of small worms.  By the vulgar, indeed, these are con-
sidered  to be worms.  The follicular secretions will engage us
hereafter.  At  present, it is sufficient to remark, that they differ
materially according to the part of the body where they exist;—the
characters of the  fluid, secreted in the axillae, groins, feet, &c. vary-
ing considerably.
   The consideration  of the  hair belongs naturally to that of the
skin.  The roots of  the hair  are in  the form  of bulbs, taking
their origin in  the  cellular membrane.  Each  bulb consists of
two parts, an  outer, which is vascular, and from which  the hair
obtains its nourishment, and  an inner, which  is  membranous, and
forms a tube or sheath to the hair, during its passage through the
layers of the skin.  The hair itself consists of  a horny, external co-
vering, and a central part, called the medulla  or pith.  When we
take hold of a hair by the base, with the fingers, and draw it through
them from the root towards the point it feels smooth  to the touch;
but if we draw  it through,  from the point to the  root, we feel  the
surface rough, and that it offers considerable resistance. It is, there- 
76
SENSIBILITY.
 fore, concluded, that the hair  is bristled or consists of eminences
 pointing towards its outer extremity; and it is upon this structure,
 that the operation of felting is dependant;—the hairs being mechani-
 cally entangled together and retained in this state, by the inequali-
 ties on their surface. Observers have, however, failed frequently in
 detecting this striated appearance, by the aid of the microscope; and
 Dr. Bostock affirms, that  he  had an opportunity of viewing the
 human hair and the hair of various kinds of  animals in the excellent
 microscope of Mr. Bauer, but without  being able'to  detect  it.
 Still, Bichat,  and  more recently, Dr. Goring, have assigned this
 as their structure;  the fact being exhibited by the microscope, and,
 in their minds, admitting of no doubt.
   The colour of the hair is singularly different in different races and
 individuals.  By some, this is considered to depend  upon the fluids
 contained in the pith.   Vauquelin analyzed the hair most atten-
 tively, and found that it consists chiefly of an animal matter, united
 to a portion of  oil, which appears to contribute to its flexibility and
 cohesion.  Besides this, there is another substance, of an oily na-
 ture, from which he considers the colour of  the hair to be derived.
 The animal matter, according to that chemist, is a species of mucus,
 but other chemists  believe it to be chiefly albumen.  Vauquelin
 found  that the colouring matter of the hair  is destroyed by acids ;
 and he suggests, that when it has suddenly changed colour and be-
 come gray, in consequence of any great mental agitation, this may not
 be owing to the production  of an  acid  in the  system, which acts
 upon the colouring matter.  The explanation is purely hypotheti-
 cal, and is considered and characterized as such by  Dr. Bostock;
 but the same objection must be admitted to apply to the view he has
 substituted.   He conceives it " more  probable, that  the effect de-
 pends upon the sudden stagnation of the vessels, which secrete the
 colouring matter, while the absorbents continue to act and remove
 that which already  exists."   There is no  more real evidence  of
 " stagnation of  vessels" than there is of the  formation of an  acid.
 Our knowledge is limited to the fact, that there is a sudden  and de-
 cided change in the whole pileous system after great or prolonged
 mental agitation.   But a similar,  though more gradual change, is
 produced by age.   We find persons  entirely gray at a very  early
 period of life; and in old age, the change happens  universally.   It
 is not then  difficult  to suppose, that some alteration in the nutrition
 of the  hair  may be induced, resembling that which occurs under
 these circumstances.  Dr. Bostock doubts the fact of such  sudden
 conversions;  but the instances are too numerous for us to consider
 them entirely fabulous. Besides, as we have seen, the cases are not
 so preternatural as they might at first sight appear. The change in-
duced is identical with that which occurs naturally to every indivi-
 dual, sooner or  later.
  According to other  physiologists, the seat of colour  is in the
horny covering  of the hair; and, in the largest hairs or spines of the 
SENSE OF  TOUCH.
77
porcupine, this seems to be the case, the pith being manifestly white,
and the horny covering coloured.
  The exact relations between the cuticle and rete  mucosum and
the hair are not known.   It is not determined whether the layers
are simply perforated by  the hair in its passage outwards, or whe-
ther they furnish it coats  as it proceeds along.  There is often, how-
ever, an intimate relationship observed between the colour of the
hair and that of the rete mucosum.  The fair complexion is accom-
panied  with light hair,  the swarthy with dark; and we see the
connexion still more signally displayed  in those  animals that are
spotted, the colour of the  hair being variegated like that of the skin.
  Hairs differ very materially,  according to  the  part of the body
on which  they appear. In some parts they are extremely short, as
in the armpits, whilst on the head it is not easy to say what would
be the precise  limit to the growth, were they left  entirely to na-
ture.  In the Malays, it  is by  no means uncommon to see them
touch the  ground.
  The hair has various names assigned  to it, according to  the part
on which  it appears, as  beard, whiskers, mustachios, eyebrows,
eyelashes, &c.
   In many animals it is long and straight; in others crisped, when
it is called wool.  If stiff,  it is termed a bristle; if inflexible, a spine.
   The hairs are entirely  insensible, and, excepting in their bulbous
portion, are not liable to  disease.  Dr. Bostock affirms, that 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 sensibility of the hair,  under any
known  circumstance, may, however, be doubted. It appears to be
almost  inorganic, except at its root; and, like  the cuticle, resists
putrefaction for  a great  length  of time.  Bichat and Gaultier
were of the opinion  of Dr. Bostock; misled, apparently, by erro-
neous reports concerning the plica polonica; but Baron Larrey has
satisfactorily shown, that the affection is confined to the bulbs, and
that the hairs themselves continue totally devoid of sensibility.
   It is difficult to assign  a plausible  use for the  hair.  That of the
head has already engaged our attention; but the hair, which appears
on certain parts at the age of puberty, and not till then, and that on
the chin and upper lip of the male sex only, sets our ingenuity at
defiance.   In this respect, however, the hair  is not unique.  Who
can venture to suggest a  probable use for the nipple on the  male
breast?  Many of the French physiologists regard certain parts, that
exist in one animal, apparently without  function, but which an-
swer useful purposes in  another, as vestiges, to  indicate  the har-
mony which reigns through nature's works. The useless nipple on
the breast of one sex  might  be regarded  in this light; but the tufts
of hair  on  various parts  cannot in any way,  be  assimilated to the
hairy coating, which envelopes the bodies of animals, and is in
them manifestly  intended as a protection against  cold. 
78
sensibility.
   There  is another class of bodies, connected with the skin, and
 analogous in nature to the last described,—the nails. These serve a
 useful purpose in touch, and consequently require notice here.
   In the system of M. De Blainville,  they constitute a  subdivi-
 sion  of the hairs, which he distinguishes  into simple and com-
pound—simple, when each bulb is  separated, and has a  distinct
 hair—compound,  when  several pileous  bulbs  are agglomerated,
 so that the different hairs, as they are secreted, are cemented toge-
 ther to form one solid body of greater or less size—a  nail, scale,
 horn, &c.
   In man, the nail alone exists, the chief and obvious use of which
is to support the pulp of the finger, whilst it is exercising touch.
   Animals are provided with  horns,  beaks, hoofs, nails, spurs,
scales, &c.  All these,  like the hair,  grow from roots,  and are
considered to be analogous in  their  physical  and vital  proper-
ties.   Meckel and De Blainville  are,  indeed,  of opinion, that
the teeth are of the same class,  and that they belong, originally, to
the skin of the mouth.   The latter zoologist, who has been distin-
guished for his labours in natural science, considers the hair to be
the rudiment of every constituent of the  skin, and even of every
organ of sense; the eye and the ear being, in his view, bulbs analo-
gous to those of the hair, but considerably modified, so  as to adapt
them to the extremely delicate functions they have to execute!
  Physiologically, the above description is enough, and more than
enough.   A few words  will be necessary regarding the  mucous
membranes, which resemble the skin  so much in  their properties
as to be, with propriety, termed dermoid.  If we trace the skin into
the various outlets, we find, that a continuous, soft, velvety mem-
brane exists through their whole extent;  and if the channel  have
two outlets, as in the case of the alimentary canal, this membrane,
at each outlet, commingles with the skin,  and appears to differ but
slightly from  it.   So much,  indeed, do they seem to form part of
the same organ, that physiologists have described the  absorption,
which takes place from the intestinal  mucous membrane, as exter-
nal.   They cannot, however, in the higher order of animals, be
considered completely identical; nor  is the  same  membrane alike
in its whole extent. They have all been referred to two great sur-
faces—the gastro-pulmonary, comprising the membranes of the
outer surface of the eye,  of the ductus ad nasum, of the nose, of the
mouth, and of the respiratory and digestive passages; and  the genito-
urinary, which line the whole of the genital and urinary  appara-
tuses. In addition to these, a membrane of similar character lines the
meatus auditorius externus and the excretory ducts of the mammae.
  In the mucous membranes, especially at their extremities, which
appear to be alone concerned in the sense of touch, the same super-
position of strata exists as in the skin—viz. epidermis, rete mucosum,
corpus papillare, and cutis vera.  They have likewise similar follicles,
called mucous, but nothing analogous to the hairs, unless we regard 
SENSE OF TOUCH.
79
the teeth to be so, in correspondence with the phantasies of Meckel
and De Blainville.

               Physiology of Tact and Touch.

  In describing the physiology of the sense of touch it will be con-
venient to revert to the distinction already made between the sense
when passively and when  actively exerted, or between tact and
touch.  The mode, however, in which the impression  is made on
each is alike and equally simple.  It is merely necessary, that the
substance, which has to cause it, should be brought in contact with
the physical part of the organ—the cuticle; the nervous  part is
seated in the corpus papillare, for if the nerves proceeding  to this
layer of the  skin be cut, the sense becomes destroyed.  In the exer-
cise of touch, each of the layers seems to have its appropriate office;
the corium, which forms the innermost layer, the base on which the
others rest, offers the necessary resistance when bodies are applied
to the surface; the rete mucosum is either unconcerned in the func-
tion, or keeps the corpus papillare in the necessary state of supple-
ness.  The erectile tissue, on which the papillae are grouped, probably
aids them in their appreciation of bodies; and the epidermis modi-
fies the tactile  impression, which might become too  intense or be
painful did this envelope not exist. The degree of perfection of the
sense is, indeed, greatly  influenced by  the state of  the cuticle.
Where it is thin,  as upon the lips, glans penis, clitoris, &c. the
sense is very acute; but where thick and hard, it is very obtuse;
and where removed, as by blistering, the contact of bodies gives
pain,  but does  not occasion the appropriate impressions of touch.
  It has been supposed, that some of the instances of  great resist-
ance to heat have been caused by unusual thickness and compact-
ness of cuticle, together with a certain degree of insensibility of the
skin.   The latter may be an important element in the explanation,
but some of the feats, executed by persons of the  character alluded
to, could hardly have been  influenced by the former, as the resist-
ance seemed almost equally great in the  delicately organized mu-
cous membranes.  A Madame Girandelli, who exhibited in Great
Britain many years ago, was not only in the habit of drawing a box
with a dozen lighted candles along her  arm, and of  putting her
naked foot upon melted lead, butof dropping melted sealing-wax upon
her tongue and impressing it with a seal, without appearing to expe-
rience the slightest uneasiness; and at this very time, (1832,) a man
by the name of Chabert, is exciting, in this country,  the surprise
which followed his exhibitions in London a year or two ago, and
which gained him the appellation of the " Fire King." In addition
to the experiments performed by Madame  Girandelli, he swal-
lows forty grains of phosphorus,  washes his fingers in melted lead,
and drinks boiling Florence oil with perfect impunity.  In the case
of the phosphorus he professes to take an antidote, and doubtless 
80
sensibility.
does so. It is probable, also, that agents are used by him to deaden
the painful  impressions ordinarily produced by hot bodies, when
applied to the surface.  A solution of borax or alum, spread upon the
skin is said to exert a powerful effect of this kind; but in addition to
Ijie use of such agents, there must be a degree of insensibility about
the corpus papillare, otherwise it is difficult to understand why these
hot substances do not injure the coats of the stomach. We see, daily,
striking differences in the sensibility of the mucous membrane of
the mouth and gullet, and  are frequently surprised at the facility
with which certain persons swallow fluids at a temperature which
would excite the most  uneasy sensations  in others.  In this, habit
has unquestionably much to do.
   In the mucous membranes, tact is effected precisely in the same
way as in the skin.  The layers, of which it is constituted, partici-
pate in like manner; but the sense is more exercised at the extremi-
ties of the membrane than  internally.  The food received into the
mouth is felt there, but after it has passed into the gullet it excites
hardly any tactile  impression; and it  is not until it  reaches the
lower  part of the membrane, in the shape of excrement, that its pre-
sence is again indicated by the sense of tact.
   Pathologically, we have some striking instances  of this difference
in the different parts of a mucous membrane. If an irritation exists
within the intestinal canal, the only notice we may have of it is by
itching of the nose, in other words, at one of the extremities of the
membrane.  In  like manner, a calculus in the bladder is indicated
by itching of the glans penis.  A similar exemplification  is offered
during the passage of a gall-stone  through the ductus communis
choledochus;—the duct formed  by the union of a  canal proceeding
from the liver with another from the gall-bladder, and which opens
into the small intestine.   Calculi occasionally form  in  the biliary
passages,  and after a time enter the common duct in their way to
the intestine.  On their first entrance, the pain experienced  is of
the most  violent character; but  this after a time subsides, as soon,
indeed, as the calculus has got fairly into the canal; but violent irri-
tation is again experienced, when it is about to clear  the duct and
enter  the intestine.
   One of the great purposes of the sense of tact is to enable  us to
judge of  the temperature of bodies.   This office  it executes alone.
No other sense  participates in it.  It requires no previous exercise;
is felt equally by  the infant and the adult, and requires  only the
proper development of its organs.
   The relative  temperature of  bodies is accurately designated by
 the instrument  called the thermometer;  very  inaccurately by our
 own sensations, and the reason of this inaccuracy  is sufficiently in-
 telligible.  In both cases the effect is produced by the disengage-
 ment of a subtle fluid, called caloric or the matter  of heat, which
 pervades all bodies, and is contained in  them to  a  greater or less
 extent   This caloric  is constantly passing and repassing between 
SENSE of  touch.
81
bodies either by radiation or by positive  contact, until  they attain
the like temperature, or until there is an equilibrium of  caloric, and
all have the same  temperature  as indicated by  the thermometer.
Hence objects in the same apartment will, casteris paribus, exhibit
the  same temperature by this test.   From this  law, however, the
animal body must be excepted.   The power which it possesses of
generating its own heat and of counteracting the external influences
of temperature, preserves it constantly at  the same point.   This
power will fall under consideration in another place.
   Although, however, all objects may exhibit the same tempera-
ture, in the same apartment, when the  thermometer is applied to
them, the sensations communicated to the body may be very differ-
ent.  Hence the difficulty that the uninstructed have in believing
that they are actually of identical temperature: that a hearth-stone,
for instance, is of the same degree of heat as the carpet in the cham-
ber.  The cause of the different sensations, experienced in the two
cases is, that the hearth-stone is a much better  conductor of the
matter of heat than the carpet.  The consequence is, that caloric is
more rapidly abstracted by it from the part of the body that comes
in contact with it, than it is by the carpet; and  the stone appears
to be the colder of the two.  For the same reason;  when these two
substances are raised in temperature above that of the human body,
the hearth-stone will appear the hotter of the two;  because, again,
it conducts caloric and communicates it more rapidly to the body
than the carpet.
   When the temperature of the surrounding air is higher than 98°,
we receive heat from the atmosphere, and experience the sensation
of heat.  The human body is capable of being  penetrated by the
caloric of substances  exterior to it, precisely like those substances
themselves; but within certain limits  it possesses  the faculty of con-
suming the heat and retaining the same temperature.
   When the temperature of the atmosphere is the same as our own
—an elevation  which it not unfrequently attains  in many  parts of
the  United States, we still experience  the sensation  of unusual
warmth: yet no caloric is communicated to us.   The cause of this
feeling is, that we are accustomed to live  in a medium of a less ele-
vated temperature and consequently to give off caloric habitually to
the atmosphere.
  Lastly, in an atmosphere of a temperature much lower than that
of the body, heat is incessantly  abstracted from us; and if rapidly
abstracted, we have the sensation of great cold.
  From registers, kept by the illustrious founder of the University
of Virginia, Mr. Jefferson, at his residence at Monticello, lat. 37°,
58', long.  78°, 40', it appears that the mean temperature of this
part of Virginia is about  55% or 56°;  that the  thermometer varies
from 5h° in the coldest month, to 94° in the warmest.   Now the
temperature of the human body being 98°, it follows, that heat must
be incessantly abstracted from us, and that we ought  here constantly
  Vol. I.                     11 
82
sensibility.
to experience  the sensation of cold.   This we should probably
do, were we not protected by clothing, and  aided  by the  artificial
temperature of our fires during the colder seasons.   The influence
of our own bodily powers and secretions in the generation of heat
is interesting and important, but does not materially concern us here.
  Yet, accustomed as the body is to  give oft'caloric, there is a tem-
perature which, generally speaking, does not communicate to-usthe
sensation of cold, although we may still be disengaging heat to some
extent.  This  temperature may perhaps be fixed somewhere be-
tween  70° and S0° in  the  climate of  the  middle portions of the
United States.  So much, however, axe our sensations in this respect
dependent upon the temperature that  has previously existed, that
the comfortable point will be found to vary at different seasons.
If the thermometer, for instance, has ranged as high as 98°, and if,
for a few days, it has maintained this elevation, a depression of 15°
or 20°will be  accompanied by feelings of discomfort; whilst a sud-
den elevation from 30° to 75° may occasion an oppressive feeling of
heat.   During the voyages  made by Captain Parry and others to
discover a north-west passage it was found, that after having lived for
some days in a temperature of 15° or 20° below 0, it felt quite mild
and comfortable when the thermometer rose to zero, and vice versa.
  This is  the great source  of the deceptive nature of our sensations
of warmth or cold.  They enable us merely to judge of the  com-
parative conditions of the present and the past; hence it is that a
deep cellar appears warm to us in winter and cool in summer.   At
a certain distance below the surface the temperature of the earth in-
dicates the medium heat of the climate; yet although this may be sta-
tionary, oursensationson descending to it in winter and summer would
be by no means the same.  If two men were to meet each  other on
the middle of the South American Andes, the one having descended,
and the other ascended, their sensations would be very different.
The one  who had descended, coming from a colder to a warmer
atmosphere, would feel warm; whilst the traveller who had ascended
would  feel correspondent^ cold.  An  experiment often  exhibited
in the  chemical  lecture-room, although  strictly physiological, ex-
hibits the same fact.  If after having held one hand in iced water,
and the other in warm, we plunge both into  water of a medium
heat, it will seem warm to the first hand and cold to the other.
   But our sensations are not guided solely by bodies  surrounding
us.  They are often greatly dependent, especially in disease, on
the state of the animal economy itself.  If the power which the sys-
tem possesses of forming  heat, be  morbidly depressed—or  if, in
consequence of old age, or of previous sickness, the separation does
not go on regularly and  energetically, a temperature of the air,
which to the vigorous is agreeable, may produce an  unpleasant im-
pression  of cold.   Under opposite circumstances, a feeling of heat
will exist.
   By tact we  are likewise capable of forming a judgment regarding 
SENSE  OF TOUCH.
83
many of the qualities of bodies, such, as their size, consistence,
weight, distance, and motion.  This faculty, however, is not pos-
sessed exclusively  by the sense in question. We can judge, for ex-
ample, of the size  of bodies by the  sight;  of distances, to a certain
extent,  by the  ear, &c.  To appreciate these  characteristics, it is
necessary that the  sense should be used actively and that we should
call into exercise the admirable instrument with which we are pro-
vided for that purpose.
   In treating of the external senses  generally, it was remarked,
that we are capable of judging, by their aid, of impressions made on
us by portions of our own body. By the sense of touch we can de-
rive information regarding its temperature, shape, consistence, &c.
An opinion has, indeed,  been advanced,  which merits reception,
that this sense is best  adapted for proving our own  existence, as
every time that  two portions  of the body come into contact, two
impressions are  conveyed to the brain, whilst if we touch an extra-
neous body we have but one.
   The tact of the mucous membranes is extremely delicate.  The
great sensibility  of the  lips, tongue, conjunctiva,  Schneiderian
membrane, lining  membrane of the trachea and urethra is familiar
to all.  Excessive pain is produced in them by the contact  of ex-
traneous bodies; yet in many cases we have the effect of habit in
blunting sensation singularly exemplified.  The first introduction of
a bougie into the urethra will produce intense irritation;  but after
a few repetitions the sensation will become scarcely disagreeable.
   To appreciate accurately the shape and size of bodies, it is neces-
sary that they should be embraced by a part of the body, which can
examine their various  surfaces and be applied to them in every di-
rection.   In man,  the organ well fitted for this purpose is the hand.
   This is situated  at the free extremity of a long and flexible mem-
ber, which admits of its being moved in every direction, and ren-
ders it not only well adapted for the organ of touch but for that of
prehension, as will be seen in another place.   Man alone possesses
a true hand;  for although other animals have organs  of prehension
very  similar to his, they are much less complete.  Aristotle,  in-
deed, and Galen  term it the instrument of instruments.  The
chief superiority of the hand consists in the size and strength of the
thumb, which stands out from the fingers  and  can be brought in op-
position to them, so as to enable us to grasp bodies, and to execute
various mechanical processes under the guidance  of the  intellect.
So important an organ was the thumb esteemed by Albinus, that
he called it a lesser hand assisting the larger—" manusparva ma-
jori adjutrix."
   In addition  to these advantages, the  hand  is furnished with a
highly  sensible integument.  The papillae are  largely developed,
especially at the extremities  of the fingers, where they are ranged
in concentric circles, and rest upon a spongy tissue, by many phy-
siologists considered to be erectile, and if not,  serving as a cushion. 
84
SENSIBILITY.
At  the  posterior extremity of  the fingers, the nails are situated,
which support the pulp of the fingers behind, and render the con-
tact with bodies more immediate.  This happy organization of the
soft parts of the hand alone concerns the sense of touch directly; the
other advantages, which it possesses, relating to the power of apply-
ing it under the guidance of volition.
  Of the mode in which touch is effected it is not necessary to treat.
Being nothing more  than  tact,  exerted by an appropriate instru-
ment, the physiology of the two must be identical.
  Metaphysicians have differed  widely  regarding the services that
ought to be attributed to the touch. Some have greatly exaggerated
them, considering it the sense par excellence, or the first of the
senses.  It is an ancient notion  to ascribe  the superiority of man
over animals and his preeminence  in the universe—his intelligence,
in short, to the hand.   Anaxagoras  asserted, and Helvetius  re-
vived the idea, " that man is the wisest  of  animals because he pos-
sesses hands."   The notion has  been  embraced and expanded  by
Condillac, Buffon, and many  modern physiologists and metaphy-
sicians.   Buffon, in particular, assigned so much importance to
the touch, that he believed the cause why one person has more  in-
tellect than another is, his having made  a more prompt and repeated
use of his hands  from early infancy.   Hence he recommended that
infants should be allowed to  use them freely from the moment of
birth.   Other  metaphysicians have considered the hand the source
of our mechanical capabilities.
  The same answer applies to all these views. The hand can only be
regarded as an instrument by which information of particular kinds
is conveyed to the brain, and by which  other functions are executed
under the direction of the will.  The  idiot  has the sense frequently
more delicate  than the  man of genius or than the best mechanician,
whilst the most ingenious artists have by no means the most deli-
cate touch. But  we have  some striking  cases to show that the hand
is not entitled to this extravagant  commendation.  Not many years
ago, a Miss Biffin was exhibited in  London, who was totally de-
void of both upper and lower extremities.   Yet she was unusually
intelligent and ingenious.  It was surprising to observe the facility
with which she hem-stitched, turning the needle with  the greatest
rapidity in her mouth and inserting it by means of the teeth.  She
also painted miniatures faithfully  and beautifully; holding the pen-
cil between her head and neck.  All  her motions were, in fact,
confined to the tongue  and lips, and to  the muscles of the neck.
   Magendie, in the last edition of his physiology,  alludes to  a
similar case.  He says that there was, at that time, (1825,) in Paris,
a young artist, who had no signs of  arm, forearm, or  hand, and
whose feet had one toe less than usual—the second; yet his intelli-
gence was, in no respect, inferior  to that of boys of his own age;
and he  even gave indications of distinguished ability. He sketched
and painted with his feet.  At  this very time, (1832,) a Miss Ho- 
SENSE OF TOUCH.
85
neywell is advertised in the public prints, asborn without arms; and
yet who has acquired so much dexterity  in the use of the scissors,
as to be able, by holding them  in  her mouth, to cut  likenesses,
watch papers, flowers, &c. She is also affirmed to write, draw, and
execute all kinds of needle-work with the utmost ease and despatch.
How fatal are these authentic examples to the views of Helvetius
and others!
   But,  it has been said  the touch is the least subject to error of all
the senses, and that it is the geometrical sense. In part only is this
accurate.   It certainly possesses  an advantage in having the organ
brought into contact with the body that excites the impression,
whilst in the cases of vision, and olfaction, the organ receives only
the impression  of an emanation from the  body; and, in that of audi-
tion,  a vibration only of an intervening medium.
   Yet some of the errors into which it falls are as grievous as those
that happen to  the other senses.  How inaccurate is its appreciation
of the temperature of bodies!  We have attempted to show, that it
affords us merely relative knowledge, the same substance appearing
hot or cold to  us, according to  the  temperature of the substance
previously touched.  Nay, this infallibility so little exists, that we
have the same  sensation communicated to us by a body that rapidly
abstracts caloric from us, as by one  that supplies it rapidly.   By
touching frozen mercury, which requires a temperature of—40° of
Fahrenheit to congeal, we experience the sensation of a burn!
   Again, if we cross the fingers and touch a rounded body, a mar-
ble, for instance, with two of the pulps at the same time, instead of
experiencing the sensation  of one body, we feel as if  there were
two;—an illusion produced by the lateral portions of fingers being
brought in opposition which are naturally in a  different situation,
and at a distance from each other; and as these two parts habitually
receive distinct impressions, when  apart,  they  continue to do so
when applied to opposite sides of the rounded body.
   It has been asserted, again, that the touch is the great corrector
of the errors into which the other senses  fall.  But let  us  inquire
whether, in this respect, it possesses any decided superiority over
the other senses.  For this purpose,  it is well to adopt the  distinc-
tion made by Spurzheim and others, of the functions of the senses
into immediate and mediate.   Each sense has its immediate  func-
tion, which it possesses exclusively;  for which, in other words, no
other can be substituted.  The touch instructs us regarding tempe-
rature;  the taste appreciates savours; the smell, Odours; audition,
sound;  and vision,  colours.  These are the immediate functions of
the senses, each of which can be accomplished by its own  organs,
but by no other. As concerns the immediate functions of the senses,
therefore, the touch can afford no correction.   Its predominance as
regards the mediate functions of the senses is likewise exaggerated.
The mediate functions are  those that are auxiliary  to  the  senses,
consisting in the impressions they furnish to the  mind, and by aid 
86
SENSIBILITY.
of which it acquires its  notions of bodies.  The essential  differ-
ence between these two sets of functions is, that the mediate can
be effected by several senses at once.   Vision, olfaction, and audi-
tion participate in judging of distances, as well as the  touch; the
sight instructs us regarding shape, &c. It has, indeed, been affirmed
by  metaphysicians, that the touch is necessary to several  of the
senses to give them their full power; that we could form no notion
of the size, shape, and distance of bodies, unless  instructed by this
sense.   The remarks already made, have  proved the  inaccuracy
of \Jt\is opinion.  The farther examination of it will be resumed un-
der the subject of vision.  The senses  are, in truth, of  mutual  as-
sistance.   If the touch falls into error, as in the case of inaccurate
appreciation of temperature, the sight, aided by appropriate instru-
ments, dispels it.  If the fingers, crossed, convey to  the brain the
sensation of two rounded bodies, when one only exists, the sight
apprizes us of the error;  and if the sight and touch united impress
us with a belief in  the identity of two liquids, the smell or  the taste
will often detect the erroneous  inference.
  But, it has been said by some, touch is the only sense that gives
us any  notion of  the existence of bodies.  Destutt-Tracy has
satisfactorily opposed this, by showing, that our notion of the exist-
ence of bodies is a work of the mind, in the acquiring of which the
touch does not assist more immediately than any other sense. "The
tactile sensations," he observes, "have not of themselves  any pre-
rogative essential to their nature, which distinguishes them from
every other.  If a  body affect the nerves beneath  the skin  of my
hand, or if it produce certain vibrations in those distributed  on the
membranes of my  palate, nose, eye, or ear, it is a pure impression
which I receive; a simple affection which I experience; and there
seems to be no reason for believing, that one is  more  instructive
than another; that one is more adapted than another for enabling me
to judge that it proceeds from a body exterior to me.  Why should
the simple sensation of a puncture, burn, titillation, or pressure, give
me more knowledge of the cause, than that of a colour, sound, or
internal pain? There is no reason for believing it."  There are, in-
deed, numerous  classes  of bodies  regarding whose  existence the
touch affords us not the slightest information, but which are detected
by the other senses. On the whole then we must conclude that the
senses mutually  aid each other in the execution of certain of their
functions ;  but that each has its province, which cannot  be invaded
by any  of  the others;  and that too much preponderance has been
ascribed to the touch by metaphysicians and physiologists.  Ad-
ministering, however, so largely to the mind, it  has been  properly
ranked with vision and audition as an intellectual sense.
  By education, the sense of touch is capable of acquiring extraor-
dinary acuteness.   To this circumstance we must ascribe  the sur-
prising facts we  occasionally meet with  in the blind. Saunderson,
who lost his eyesight in the second year of his life,  and was Pro- 
SENSE OF TASTE.
87
fessor of Mathematics at Cambridge, England, could discern false
from genuine medals, and had a most extensive acquaintance with
numismatics. Baczko, referred to by Rudolphi, and who describes
his own case, could distinguish between samples of woollen cloth of
equal quality but of different colours.  The black appeared to him
amongst the roughest and hardest; to this succeeded dark blue and
dark brown, which he could  not, however, distinguish from each
other.   The colours of cotton and silk stuff he was unable to dis-
criminate, and he properly enough doubts the case of a Count Lynar,
who was blind, and said to be capable of judging of the colour of a
horse by the feel. The only means the blind can possess of discrimi-
nating colours must be in the inequalities  of surface produced by
them; and if these were insufficient to enable Baczko to detect the
differences between cotton and silk fabrics, it is not probable that
the sleek surface of the horse would admit of such discrimination.
   In animals the organ of touch varies.  The monkey's resembles
that of man.  In other quadrupeds it is seated in the lips, snout  or
proboscis.   In molluscous animals the tentacula, and in insects, the
antennae or feelers are organs  of touch, possessing, in some, very
great sensibility.  Bats appear to  have this sensibility to an unusual
degree. Spallanzani observed these animals, even after their eyes
had been destroyed and  ears and  nostrils shut up, fly through intri-
cate passages, without  striking against the walls, and dexterously
avoiding cords and lines placed in their way.   The membrane  of
the wings is, in the opinion  of many, the organ that receives the
impression produced by a change in the resistance  of the air; but
some experiments made by Mr. Broughton sanction the idea, that
it  may be dependent upon their whiskers.   These whiskers, which
are found on the upper lip of feline and other animals are plentifully
supplied with nerves, which seem to proceed from the second branch
of the fifth pair, and are  lost in the substance of the bristles.  In  an
experiment which Mr. Broughton made on a kitten, he found that
whilst the whiskers were entire, it was capable of threading its way,
blindfolded, out of a labyrinth, in which it was designedly placed;
but that it was totally unable to do so when the whiskers were cut
off.  It struck its head repeatedly against the sides, ran against  all
the corners, and tumbled over steps placed in  its way, instead  of
avoiding them, as it did prior to the removal of the whiskers.
   From facts like these  Mr. Broughton drew the  conclusion, that
certain  animals are supplied with whiskers for the purpose of ena-
bling them to steer clear of opposing bodies in the dark.

          Sect.  II.—sense  of  taste  or gustation.

   The sense of taste teaches us the quality of bodies called sapidity.
It  is more nearly  allied to touch, in its mechanism, than any other
of the senses, as it requires the immediate contact of the body with 
88
SENSIBILITY.
 the organ of taste; and as that organ is, at the same time, capable of
 receiving tactile impressions, distinct from those of taste.  Of this
 we have a striking example.   If  we touch various parts of the
 tongue with the  point  of a needle, we  find two distinct percep-
 tions occasioned.   In some parts we experience the sensation of a
 pointed  body without  savour;  and in others a metallic taste is
 manifested.  The organ of gustation is not, therefore, restricted to
 the production of that sense, but participates in the sense  of touch.
 Yet so distinct are those functions,  that the touch  can, in  no wise,
 supply the place  of its  fellow, in detecting the sapidity of bodies.
 This last is the immediate instruction afforded by gustation.

               Anatomy of the Organs of Taste.

   The chief organ of  taste is  the tongue, or  rather the mucous
 membrane covering the upper surface and sides of that organ.  The
 lips, inner surface of the cheeks, the palate and fauces, participate in
 the  function, especially when  particular savours  are  concerned.
 Magendie includes the oesophagus and stomach, but we know not
 on what grounds.   His subsequent  remarks, indeed, controvert the
 idea.  The lingual branch of the fifth pair is, according  to him, in-
 contestably the nerve of taste;  and as this nerve is distributed  to
 the  mouth, we can understand why gustation should  be effected
 there, but not how it can be  accomplished  in the oesophagus and
 stomach.   The tongue consists,  almost entirely, of muscles, which
 give it great mobility, and enable it to fulfil the various functions
 assigned to it; for it is not only the organ of taste, but of mastica-
 tion, deglutition, and articulation.  These muscles, being under the
 influence of volition, enable the  sense to be executed passively  or
 actively.
   As regards gustation the mucous  membrane  is the portion that
 immediately concerns us. This is formed, like the mucous mem-
 branes in general, of the different layers  already described.   The
 corpus papillare, however, requires  additional  notice.  If the sur-
 face of the tongue be examined it will be found to consist of my-
 riads of fine papillae or villi, giving  the organ a  velvety appearance.
 These papillae are, doubtless, formed like those of the skin, of the
 final ramifications of nerves, and of the radicles of exhalant and ab-
 sorbent vessels, united by means of a spongy erectile tissue. Great
 confusion exists amongst anatomists in their descriptions of the pa-
 pillae  of the tongue.  Those  concerned in  the sense of taste may,
 however, all be included in two divisions:—1st, the conical, or py-
 ramidal, the finest sort being by some caWed filiform; and 2dly, the
fungiform.  The former are broader at the base than at  the top,
 and are seen over the whole surface of the tongue, from the tip  to
 the root.   The latter, which are larger at the top than at the base,
 and resemble the mushroom,—whence their name,—are spread about, 
SENSE  OF TASTE.
89
here and there, upon the surface of the organ.  These papillae of taste
must be distinguished from a third set, thepapillas capitatae, which are
mucous follicles, and of course accomplish a very different function.
  All the nerves that pass  to
the parts, whose office it is to
appreciate savours, must be
considered to belong  to the
gustatory apparatus.   These
are the inferior maxillary, se-
veral branches of the superior,
filaments from the spheno-pa-
latine and naso-palatine gan-
glions, the lingual branch  of
the fifth pair, the whole of the
ninth  pair,  or  great  hypo-
glossus, and the glossopha-
ryngeal.  To which of these
must be assigned the function
of gustation we  shall  inquire
presently.
   Like the skin and  mucous
membranes in general, that of
the  tongue  and mouth  con-
tains, in its  substance, nume-
rous mucous follicles, which
secrete a fluid that lubricates
the organ and keeps it in  the
conditions best adapted for the
accomplishment of its func-
tions.   Some  of  these  are
placed very conspicuously in
the  mucous membrane of the tongue.  They are the papillae capi-
titse of many anatomists, erroneously named, as they are not formed
like the papillae and execute a very different office.  They are mu-
cous follicles, and ought to be so called.  They are situated near the
base of the tongue, and the last perceptible rows anteriorly unite at
an angle close to the foramen caecum of Morgagni.  (See Fig. 15.)
The fluids exhaled from the mucous membrane of the mouth, and
the  secretion of the different  salivary glands likewise aid in gusta-
tion; but they are more concerned in mastication and insalivation,
and will require notice under another head.

                          Of Savours.

   Before proceeding to explain the physiology  of gustation, it will
be necessary to inquire briefly into the nature of bodies, connected
with their sapidit}', or in other words, into savours, which are the
cause of sapidity.
  Vol. I.                     12
Fig. 15.
a. Foramen of Morgagni.
b. Fungiform papillce.
c. Conical papilla.
d. Papillce capitatce.
e. Epiglottis. 
90
SENSIBILITY.
   The ancients were of opinion, that the cause of sapidity is a pe-
culiar principle, which, according to its combination with the con-
stituents of bodies, gives rise to the various savours that are  found
to exist.  This notion  has  long been abandoned; and chiefly, be-
cause we observe no general or common characters amongst sapid
bodies, which ought to be expected if they were pervaded  by the
same principle; and because it is found that bodies may be deprived
of their sapidity by subjecting them to appropriate agents.   Many
of our culinary processes have been instituted for this purpose; the
infusion of tea is indebted for all  its attractions to the power we
possess of separating, by boiling water, its savoury from its insipid
portions. A savour must, therefore, be esteemed  an integrant mole-
cule of a body; not identical in all cases, but as heterogeneous in its
nature as the impressions that  are  made upon the  organ of taste.
When the  notion was once entertained that savour is an integrant
molecule, sapidity was attempted to be explained by  the shape of
the molecule.  It was said,  for instance, that if the savour be sweet,
the molecule must be round; if sharp, angular; and so forth. Sugar
was said to possess a spherical, acids, a pointed or angular molecule.
We know, however, that substances, which resemble each other in
the primitive shape of their crystal, impress the organ of taste very
differently;  and that solution, which must destroy most, if not all,
of the influence from shape, induces no change in the savour.
   Others have referred sapidity to a kind of chemical action, be-
tween the molecules and the nervous fluid. This view has been sug-
gested by  the fact, that as a  general  principle, sapid bodies, like
chemical agents, act only when in a state of solution; that the same
savours  usually belong to bodies possessed of similar chemical pro-
perties,  as the sulphates and nitrates; and that, in the action of acids
on the tongue and mouth, we witness a state of whiteness and con-
striction, indicative of a first degree of combination.   All these cir-
cumstances, however, admit of a more philosophical explanation.
There are unquestionably many substances, which do combine che-
mically, not with the nervous  fluid, of whose existence we  know
nothing, but with the mucus of the mouth, and the sapidity resulting
from such combination is felt by the nerves of taste; but there are
many bodies, which are eminently sapid, and yet afford us instances
of very  feeble powers of chemical combination;  nay, in numerous
cases, we have not the least evidence that such powers are existent.
Vegetable infusions or solutions afford  us strong examples of  this
kind, of which syrup may  be taken as the most  familiar.  The ef-
fect of solution is easily intelligible: the particles of the sapid body
are in this  way separated, and  come successively into contact with
the gustatory organ; but we have reason to believe, that solution is
not always requisite to appreciate sapidity.  Metals have generally
a peculiar taste, which has been denominated metallic; and this, even
if the surface be carefully rubbed, so as to free it from oxide, which
is more or  less soluble.   Birds, too, whose organ of taste is as dry 
SENSE OF  TASTE.
91
as the corn they select from a mass of equally arid  substances, are
probably able to appreciate savours.  The taste, produced by touch-
ing the wires of a galvanic pile with the tongue, has been offered as
another instance of sapidity exhibited by dry bodies. This is, more
probably, the effect of that chemical action on the fluids covering
the mucous membrane of the tongue, which always follows such
contact. Such chemical change must, however, be confined to these
fluids,  and when once produced, the nerve of taste is compelled to
appreciate the savour  developed; in the same manner as it does, in
case of morbid alterations of the secretion of the mucous membrane,
when, it is well known, that a body, possessing considerable  and
peculiar sapidity, will fail to impress the nerves altogether, or will
do so inaccurately.  The notion of any chemical combination with
the nervous fluid must of course be discarded.  There  is not the
slightest shadow of evidence in favour of  the hypothesis.  Yet the
epithet chemical was  once applied to this sense on  the strength of
it, in opposition  to the senses of touch, vision, and audition, which
were called mechanical, and supposed to be produced  by vibra-
tions of their nerves.
   The savours, met with in the three kingdoms of nature, are innu-
merable.  Each  body  has its own by which it is distinguished; but
few instances occurring in which any two can be said to  be identi-
cal.  This is the great source of difficulty, when we attempt to throw
them into classes, as  has  been  done  by  many physiologists.   Of
these classifications, the one by Linn^us is the best known. It will
elucidate the unsatisfactory character of the whole; he divided sapid
bodies into sicca, aquosa, viscosa, salsa,  aeida, styptica, dulcia,
pinguia, amara, acria, et nauseosa.   He gives also examples of
mixed  savours—the  acido-acria,  acido-amara,  amaro-acria,
amaro-acerba, amaro-dulcia, dulci-styptica, dulci-acida,  dulci-
acria, and acri-viscida; and remarks that the  majority are anti-
theses  to each other, two and two, as the dulcia and acria; the pin-
guia and styptica; the viscosa and salsa; and the aquosa and sicca.
Boerhaave again  divides them into primary and compound; the
former including the  sour, sweet, bitter, saline, acrid, alkaline,
vinous, spirituous, aromatic, and acerb; the latter resulting from
the union of some of the primary savours.   There  is, however, no
accordance amongst physiologists regarding those that should be es-
teemed primary, and those that are  secondary and  compound;  al-
though the division appears to be fairly admissible.  The acerb,for
example, which  is considered primary by Boerhaave, is by others,
with more propriety,  classed amongst the secondary or compound,
and believed to consist of a combination of the acrid and acid. Still
we understand sufficiently well the character of the acid, acrid,
bitter, acerb, sweet, &c; but when,  in common language, we have
to depict other savours, we are frequently compelled to take some
well known substance as the standard of comparison.
  According to Adelon, the only distinction, which we can make
amongst  them is, into the agreeable and disagreeable.   Yet of 
92
SENSIBILITY.
the unsatisfactory nature of this classification he himself adduces
numerous and obvious proofs.  It can only, of course, be applicable
to one animal species, often even to an individual only; and  often
again only to this individual, when in a given condition.  Animals
are known to feed upon substances, which are not only disagreeable
but noxious to other species.   The most  poisonous  plants in our
soil have an insect which devours them greedily and with impunity;
and the southern planter is well aware  that this is the case with his
tobacco, unless the operation of worming  be performed in due sea-
son. The old adage that " one man's meat is another man's poison"
is metaphorically accurate.   Each individual has by organization or
association- dislikes to particular articles of food, or shades of differ-
ence in his appreciation of tastes which may be regarded peculiar;
and in certain cases these peculiarities are  signal  and  surprising.
   Of the strange differences, in this respect, that occur in the same
individual under different circumstances, we have a  common and
forcible instance in the pregnant female, who  often has the most ar-
dent desire for substances which were previously  perhaps repugnant
to her, or at all events not relished.  The  sense too,  in certain dis-
eases, especially of a sexual character, or connected with the state
of the sexual functions, becomes remarkably depraved;  so that sub-
stances, which can, in no way, be ranked  as eatables are greedily
sought after.  Only a short time ago, a young lady was  under the
care of  the  author, whose greatest  bonne bouche was slate pencils.
At other times, we find,  chalk, brick-dust, ashes, dirt,&c. obtaining
the preference.
   Habit, too, has  considerable effect in our decisions regarding the
agreeable.   The Roman liquamen or  garum, the most celebrated
sauce of antiquity, was prepared from the  half putrid intestines of
fish; and one of the varieties of the Osro? SiA^<«», or laserpitium, is
supposed to have  been the asafoetida.  Even at this time, certain of
the orientals are fond of the flavour of this nauseous substance. Pu-
trid meat is the delight of some nations; and a rotten egg, especially
if accompanied with the chick, is highly esteemed by the Siamese.
Even in civilized countries, we find game  in asemi-putrescentstate
eaten as a luxury, which, to those  unaccustomed to  it, requires a
true education. The same may be said of the pickled olive, and of
several cheeses—thefromage de Gruyere, for example, so much es-
teemed  by the inhabitants of continental Europe.
  Magendie asserts that the distinction of savours into the agree-
able and disagreeable is the most important, as bodies whose taste
appears agreeable to us are generally useful in our nutrition; whilst
those whose taste is disagreeable are commonly noxious.  As a ge-
neral principle this is true, but there are many exceptions to it.

                     Physiology  of Taste.

  The physiology of taste being so nearly allied  to touch as effected
by the mucous membranes, it will  not be necessary to repeat here 
SENSE OF TASTE.                     93
the utility of the various layers of which the membrane consists.  In
order that taste may be satisfactorily executed, it is necessary that this
membrane should be in a state of integrity; for even if the cuticle
simply be removed, gustation is not effected, and we experience the
morbid sensation of pain.  It is also indispensable, that the fluids,
poured into  the cavity of the mouth, should be in the necessary
quantity, and possess the proper physical characteristics.  We can
farther appreciate the advantages of masticatjon and insalivation,
by dividing solid bodies into minute  portions,  dissolving them
where soluble, and bringing them successively in contact with the
organ of taste.   The gustatory nerves thus receive the impression,
and by the same agents it is transmitted to the brain. These nerves
go to the formation of the papillae, which, we have seen, are situated
in a spongy, erectile tissue.   As in the sense  of tact and touch, it is
probable that this erectile tissue is not passive during the exercise
of taste; but that, by means of it, the papillae assume a kind of erec-
tion.  Magendie believes this view to  be void of foundation; but
Sir C. Bell has properly remarked, that if we take a pencil and a
little vinegar, and touch, or even rub it  strongly on the surface of
the tongue where these papillae do not exist,  the  sensation of the
presence of a cold liquid is alone experienced; but if we touch one
of  the papillae with the point  of the brush, and at the same time
apply a magnifying glass, it is seen to stand erect, and the acid taste
is felt to pass, as it were, backward to the root of the tongue.
   This experiment confirms the one with the point of the needle
already referred to, in showing that the parts of the tongue, that
possess the power of receiving tactile impressions, are distinct from
those concerned in gustation.  The fine  conical papillae, by some
called filiform, seated at the sides and tip of the tongue, appear to
be the most exquisitely sensible.
   Although the sense of taste is almost wholly accomplished by the
membrane covering the tongue, the other parts, enumerated amongst
the organs of taste, often participate in  the function; as the palate,
lips, interior of the mouth, top of the pharynx, &c.  We find, in-
deed, that certain bodies affect one part of the mouth and  others
another. Acids, for example, act more especially upon the lips and
teeth ; acrid bodies, as mustard, on the pharynx. But we have still
more direct evidence in those cases  in which  the tongue  has been
wanting.  Roland, of Saumur, in a work published in 1630, under
the pompous title of Aglossostomographie,  gives the case of a
child, six years of age, who lost her tongue in  small-pox and yet
could speak, spit, chew, swallow and taste.  De Jussieu exhibited
to the Acadimie des Sciences of Paris, in 1718, a Portuguese girl,
born without a tongue, who also possessed all  these faculties.  In a
case mentioned by Berdot, and cited by Rudolphi, in which  no
part of the tongue existed, the individual  could  appreciate the
bitterness of sal ammoniac,  and the  sweetness  of sugar; and
Blumenbach refers, in his comparative anatomy, to the case of a
young man, who was born without a tongue,  and yet, when blind- 
94
SENSIBILITY.
fold, could distinguish between solutions of salt and aloes, put upon
the palate.
  Certain bodies leave their taste in the mouth for a length of time
after they have been swallowed.  This arriere-gout—the nachge-
schmack ofthe Germans,—is sometimes felt in the whole mouth; at
others, in a part only;  and is probably owing to the papillae having
imbibed the savory substance,—for the substances producing this ef-
fect belong principally to the class of aromatics.  This imbibition
frequently prevents the savour of another substance from being duly
appreciated; and in the administration of nauseous drugs we avail
ourselves of the knowledge of the fact, either by giving an aromatic
previously, so as to forestall  the nauseous preparation, or by com-
bining powerful aromatics with it, which strongly impress the nerves
of the papillae, and produce a similar result.
  There is a common experiment, which has formed the foundation
of numerous wagers, and elucidates this subject,  or at least demon-
strates, that the effect produced upon the nerve by the special irri-
tant, continues, as in the case of the other senses, for some time after
it has made its impression, so that the nerve becomes comparatively
insensible, for a time, to the  action of other sapid bodies. It consists
in giving to a person, blindfold, brandy, rum, and  gin, or any
other spirituous liquors in rapid succession, and seeing whether  he
can discriminate one from the other.  A few contacts are sufficient
to impregnate the nerve so completely with the impression, that all
distinction  becomes confounded.
  It has been remarked, that numerous nerves are distributed to the
organ of taste; the ninth pair, the lingual and other branches of the
fifth, and the glosso-pharyngeal.   An interesting question arises—
which of these is the nerve of taste;  or are more than  one, or are
the whole concerned? Of old, the lingual nerve of the fifth pair was
universally considered  to accomplish the function solely;  the other
nerves being  looked upon  as simple motors.   Boerhaave and
others assigned the office to the ninth pair and considered the others
to be motors.  The filaments of  the fifth pair have been described
as being perceptible even into the  papillae; but others  have de-
nied that they can be so traced.  Opinions have, generally, settled
down upon the lingual branch of the fifth pair. Such is the view of
Sir Charles  Bell, who considers  the ninth pair, which arises
from the anterior column of the spinal marrow, as the nerve of mo-
tion for the tongue; the lingual branch of the fifth, a nerve having
a posterior root, as the nerve of taste; and the glosso-pharyngeal
as the nerve by which  the tongue is associated with the pharynx in
the function of deglutition.  It is likewise maintained, that the fifth
is the first encephalic nerve, that appears in the lower classes of ani-
mated nature, as the taste is  the first of the special senses noticed in
them; that, at first, the nerve consists only of  the lingual branch;
and farther that its size, in animals, is generally in a ratio with that
of the organs of taste and mastication.
  Some experiments  by Magendie, seem  to settle the  question 
SENSE OF TASTE.
95
definitively. On dividing the lingual branch of the fifth pair on ani-
mals, he found, that the tongue continued to move, but that they
always lost the faculty of appreciating savours.  In this case, how-
ever, the palate, gums, and internal surface of the cheeks preserved
the faculty, because supplied with other branches of the fifth.  But
when the trunk of this nerve was  cut, within the cranium, the
power of recognising savours  was completely lost in every part of
the mouth,—even in  the case  of  the most acrid and caustic bodies.
He found, too, that this loss of the sense occurred in all those, who
had the fifth pair morbidly affected.
   The fifth pair may then be considered as the parent trunk for the
gustatory nerve: and not only is  it the nerve for the special func-
tion, but it is, as we have seen,  that of general sensibility. Anatomy
and physiology would consequently lead to the belief, that the touch
or general sensibility, and the taste—a function of special sensibility,
are more nearly allied than any of the other senses: some of which,
we shall find, have distinct  nerves for the two functions:  the fifth
pair, however, always endowing the organs with general sensibility.
   This  distinction between  the taste and the other senses, has led
M. De Blainville to suppose, that it is perhaps, neither sufficiently
special, nor sufficiently limited in extent to have a separate nervous
system: and therefore that  all the nerves of the tongue are equally
inservient to the sense, as the different nerves of the skin which pro-
ceed from numerous pairs, are  equally inservient to touch or tact.
   Regarding the uses of the sense of taste.  Its immediate function,
as has been remarked, is to give the sensation of savours.   This
function, like the touch, is instinctive, requires no education, cannot
be supplied by any of the other senses, and is accomplished as soon
as the tongue  has  acquired  the necessary degree of development.
To this it may be replied, that the very young infant is not readily
affected by savours.   In all cases, however, certain sapid bodies ex-
cite their usual impression : and in the course of a few months, when
the organ becomes completely developed, the sense acquires a high,
and often an inconvenient degree of acuteness.
   The mediate or auxiliary offices of gustation are few  in  number,
and limited in extent.  It does not afford much instruction to the
mind.  The chemist and mineralogist occasionally gain information
regarding bodies by its agency;  but it is never considered by the
physiologist  as  worthy of the  rank of an intellectual  sense: but,
on the contrary, is classed with olfaction as corporeal.
   To appreciate a savour accurately, the sapid substance  must re-
main for some time in Nie mouth: when rapidly swallowed the im-
pression is extremely feeble, and almost null.  Of this fact we take
advantage,  when  compelled to swallow any nauseous substance:
whilst we retain a savory article long in the mouth, in order that
we may draw from it all its  sweets.  How different, too, is the
consent of the  auxiliary  organs under these  two circumstances.
Whilst  a luscious body augments the secretion  of the  salivary 
96
sensibility.
glands, or causes the mouth " to water," as it has been  called, pro-
jecting the saliva, at times, to a distance  of some feet from the
mouth, and disposing every part to approach and  mingle with it;
a nauseous substance will produce  constriction of every secretory
organ, and this effect will extend even to the stomach itself, so that
it will often reject the offending article as soon as it  reaches the
cavity.  We can thus understand how, caeteris paribus, an article,
which is pleasing  to the palate, may be more digestible than one
which excites disgust, and  vice versa.
  Of the " consent of parts," exerted by the stomach on the organ
of taste, we have a familiar illustration in the  fact, that whatever
may  be the gout,  with  which  we commence a meal on a  fa-
vourite article of diet, we  find that  the relish becomes blunted as
the stomach becomes filled: and  hence the Romans  were in the
habit of leaving the table  once or twice during a  meal, and, after
having unloaded the stomach, of returning again to the charge—
" vomunt ut edant, edunt ut vomant."
  Among animals we see great diversities in this sense.  Whilst
none possess  the  refined  taste of man, there are many that are
capable, by taste  or smell, of knowing  those plants, which are
nutritive from those that are noxious to them; and it is very unu-
sual for us to find that an animal has died from eating those  that
are unquestionably poisonous  to it.   Yet, as we have remarked, a
substance, which is noxious to one, may be eaten with impunity by
another: and if we select animals, and place them in a field contain-
ing plants, all of which are ranked by us as poisons, and which are
poisonous to a majority of  those animals, we find that not only has
a selection  been made by each animal of that which is innocuous
to it, but that the substance has furnished nourishment  to it, whilst
to the other it would have proved fatal.   All this  must be depen-
dent  upon peculiar and inappreciable organization.
   The sense of taste is, more than any other, under the influence
of volition.  It is provided with a  muscular apparatus,  by which it
can be closed or opened at pleasure; and, in addition, it ordinarily
requires the assistance of the upper extremity, to convey the sapid
substance  to the mouth.   The sense can, therefore, be exercised
passively or actively; and by cultivation, is capable of being largely
developed.   The spirit taster  to extensive commercial establish-
ments exhibits the truth of this in a striking manner.   He has, of
course, in his vocation, not only to taste numerous samples, but to
appreciate the age, strength, flavour, and other qualities of each:
yet the practised individual is  rarely wrong in his discrimination.
With almost all, if not all, the custom is to take a small quantity of
the liquor into the mouth;  throw it rapidly around that cavity, and
then  eject it.  A portion in this way comes in contact with every
part of the membrane, and of course, impresses not only the lingual
branch, but the other ramifications of the fifth pair.
   The gourmet of the French, somewhat more elevated in the scale 
SENSE OF  SMELL.
97
than our ordinary epicure, prides himself upon  his discrimination
of the nicest shades of difference and of excellence in the mate-
rials set before him.  Many gourmets  profess to be able to pro-
nounce, by sipping  a few drops of  wine, the country whence it
comes and its age; and, according to Stelluti, can tell by  the
taste,  whether birds,  put upon the table,  are domesticated or
wild—male or female: " sapevano dire gustando li tordi s'erano
domestici d pur selvaggi, e se maschi d pur ferrimine."   Dr.
Kitchener, indeed, asserts, that many epicures are capable of
saying in what precise reach or stretch of the Thames, the salmon
on the table has been eaught.  Such acuteness  of  sense  is by no
means desirable.  Doomed to meet in his progress  through life,
with such a preponderance of what demands obtuseness rather than
acuteness of feeling, the epicure must be liable to continual annoy-
ances and discomforts, which the less favored can never experience.

      Sect. III.—of the sense of smell,  or olfaction.

   The object of this sense is to appreciate the odorous properties of
bodies. It differs from the last, in the circumstance of the body not
coming into immediate contact. It is only necessary that an odorous
emanation shall impinge upon the organ of sense.  Still it does not
essentially vary in its physiology from the sense of taste.

               Anatomy of the Organ of Smell.

   The organ of smell is a mucous membrane, which lines the na-
sal cavities, and is called the  Sohneiderian or pituitary.  It resem-
bles that which covers the organ of taste, except that the nervous
papillae are still  more delicate,  to correspond with the greater
tenuity of the body, that has to make the impression.  The  mem-
brane lines the whole of the bony cavities called the nasal fossae,
which are constantly open anteriorly and posteriorly, to permit the
air which traverses them to  proceed to the  lungs.  The anterior
aperture is covered by a kind of pent-house or capital, for the pur-
pose of collecting the odorous particles.   This capital is called the
nose.  The essential part of  the organ is the pituitary or olfactory
membrane; the other parts being superadded in animals to perfect
the sense.
   The bony portions of the nose are separated from each  other by
a bone called the vomer.  This septum is  extended, by  means of
cartilage,  to the anterior extremity  of the nose, so  that the nasal
fossae are  divided into like parts,  which have  no communication
with each other,  but open together  posteriorly into the top of the
pharynx.
   Within  each of the nares, are  two convoluted or  turbinated
bones—generally called ossa spongiosa vel turbinata; and, by the
French, cornets.   These are situated one above the other; the su-
   Vol. I.                      13 
98
sensibility.
perior being formed of a plate of the ethmoid bone—the inferior a
distinct bone.   They divide the general cavity of each nostril into
three passages or meatus, as exhibited in Fig. 15*, where figures
7 and 10 represent the superior and inferior spongy bones  respec-
tively, and 11 the vomer; the three meatus being chiefly comprised
between these  bones.  The inferior meatus is broad and long, the
least oblique and the least tortuous; the  middle is narrow, almost
as long, but more extensive from above to below; and the superior
is much shorter, more oblique and still narrower.  The narrowness
of these passages, in the living subject, is so great, that the slightest
tumefaction of the pituitary membrane renders the passage of air
through the nasal fossae extremely difficult.  This is the cause of
the difficulty of breathing through the nose, that attends a " cold in
the head."

                           Fig. 15*.
 
                       SENSE OF  SMELL.                    99

  Into the two upper passages cavities in certain bones open, which
enlarge considerably the extent of the nasal fossae. These are called
sinuses, and consist of the maxillary,  palatine, frontal, sphe-
noidal, and  ethmoidal; the last being sometimes termed ethmoidal
cells.

                           Fig. 16.
o. Frontal sinus—b. Ethmoidal cells—c. Sphenoidal sinus—d. Nasalfossce—e. Maxillary sinus.
   All the cavities are lined by the delicate membrane—the Schnei-
derian or pituitary,—or by a prolongation of it.  In the nasal fossae,
it augments the thickness of the turbinated bones. Ibresembles the
mucous membranes in general in its composition, and adheres firmly
to the bones and cartilages, which it covers.   Its aspect is velvety,
owing to a multitude of minute papillae, and it receives a great
number of vessels and nerves. The sinuses are lined by a prolonga-
tion, apparently, of the same membrane; differing, however, in
some respects from the other.  The whole of this membrane is the
seat of the secretion of the  nasal mucus, which, doubtless, per-
forms a part in olfaction as  important as the secretion from the mu-
cous membrane of the mouth does in gustation.
   The same nerve is not distributed over the whole of this mem-
brane.   In some parts, the  olfactory or first pair, can be  traced;
in others, we see only filaments of the fifth pair.
   The first of these—the olfactory or ethmoidal nerves, have  not
always been regarded as the nerves of smell. Anciently, they were
supposed to be canals for  the passage of the pituita or phlegm, 
100
sensibility.
which was supposed to be secreted by the brain.  At the present
day, anatomists are doubtful only regarding their origin; some de-
riving them from the  anterior lobe of the brain, others from the
corpora striata, which have, in consequence, been called thalami
nervorum ethmoidalium; and others, again, with Mr. Gall, and
with probability, referring them, like every other nerve of sense,
to the medulla oblongata.  Beclard affirms that in a hydrocepha-
lic patient, where a part of the brain had been destroyed by disease,
he actually detected this origin.
  The nerve  proceeds directly  forwards, (See Fig. 11,) until it
reaches the upper surface of the cribriform  plate of the ethmoid
bone, when it divides into a number of filaments, which pass through
the foramina in the plate and attain the nasal fossae, where they are
dispersed on the upper and middle part of the  Schneiderian mem-
brane, but cannot be traced on the lower.  Most anatomists are of
opinion, that here they constitute, with vessels of exhalation and
absorption, the papillae;  whilst others, as Scarpa, not having been
able to trace them thither, have been of opinion, that the filaments
interlace to constitute  a kind of proper membrane.
  Our means of observation cannot be considered sufficient to enable
us to decide this question positively.  In the case of the mouth, we
have seen, that anatomy has not succeeded in following  the  nerve
to its minute terminations;  nor has it in the case of the olfactory or
of any other nerve, if we except those of vision and audition, and
in these we see the terminations but imperfectly.
  The olfactory nerve has not been traced on the os spongiosum
inferius, on the inner  surface  of the middle spongy bone, or in any
of the sinuses.  Besides the first pair of nerves, the pituitary mem-
brane receives several branches from the fifth  encephalic pair; for
example, the nasal twig of the ophthalmic branch of the fifth, and
filaments from the frontal branch of the same,  from  the sphenopa-
latine ganglion, the palatine nerve, the vidian nerve, and from the
anterior dental branch of the superior  maxillary.  One of these
twigs enters the anterior naso-palatine  canal, and in its course to
the roof of the mouth, passes through a small  ganglion, which has
been described by  H. Cloquet, under the name  naso-palatine,
and which he conceives to be the organ of sympathy between the
senses of smell and taste.
   The pituitary membrane is  kept moist by  the nasal mucus, as
well as by the exhalation constantly  taking  place from it.  It re-
ceives, likewise,  the superfluous tears by means of the ductus ad
nasum, a duct passing from the inner canthus  of the eye and open-
ing into the nasal fossae, below the lower spongy bone.  The con-
stant evaporation which  must take place from the membrane, owing
to the passage of the air  during respiration, requires that the secre-
tion should be continuous and  copious, otherwise  the membrane
would become dry.
   The nasal fossae communicate externally by  means of the nostrils; 
SENSE OF  SMELL.
101
 the shape, size, and direction of which vary considerably, so as  to
 give rise to the aquiline, Roman, pug, and other varieties of nose.
 At the extremity of the nostrils long hairs are situated—technically
 called vibrissas—whose function, it is conceived, may be to  sift, as
 it were, the air passing through during respiration, and thus to pre-
 vent extraneous bodies from entering the fossae.  The nostrils are,
 also, capable of being expanded or contracted by appropriate muscles.
   In this sense, we have  a more clear separation between the phy-
 sical and nervous part of the apparatus than in either of those we have
 considered.  The nose proper forming the essential  physical  por-
 tion; and the nerves of smell, the organic or nervous.

                           Of Odours.

   The comprehension of the  physiology of olfaction will not be
 complete without an inquiry into odours, or those emanations from
 odorous  bodies, which give character to them, and impress the or-
 gan of smell.
   It was long maintained, as in the case of savours, that odours are
 dependent upon a peculiar principle,  which, according to  its parti-
 cular combination with the constituents of bodies, gives rise  to the
 various odours.   To this principle the terms aroma and spiritus
 rector have  often been assigned;  but  the notion has been long
 abandoned, because no general or common  characters are  observa-
 ble amongst odorous bodies, as ought to be expected, were they in-
 debted for their odour to  the same principle;  and because,  again,
 bodies can be deprived of their odour by exposing them  to ap-
 propriate agents, as when  we subject them to  infusion and  distil-
 lation.
  Walther, a German physiologist, is of opinion that an odorous
 body is only such by virtue of a vibratory motion, analogous to that
 made by a sonorous body. We have, however, the most satisfactory
 evidence, that there are special odorous, as there are special savory
 molecules.  We can, for example, prevent an  odorous body from
 impressing our olfactory nerves, by covering it with a glass receiver.
 Odours can, likewise, be separated, as has been remarked, by infu-
 sion  and by distillation.  The  fact, however, has  been  directly
 proved by an experiment  of Berthollet.  On putting a piece of
 camphor at the top of a tube and filling the remainder of the tube
 with mercury, he found that, after a time, the mercury descended,
 the camphor had diminished in size, and the space above the metal
 was occupied by an odorous gas.
  But what is  the cause  of the disengagement of  these odorous
 molecules ? By  most writers on this subject it has been considered
 dependant upon the  solvent action of caloric on the body.   The
opinion is as old as Theophrastus, that all bodies are odorous, and
it is one, which it is  very  difficult not to embrace, if we add—pro-
vided they are subjected to the appropriate agents for disengaging 
102                      SENSIBILITY.
the odorous particles; and the probability is, that the reason we es-
teem particular bodies inodorous is, that our olfactory nerves are
not organized with sufficient delicacy to enable us  to distinguish
their properties.  Heat  assists the escape of odorous particles from
a variety of bodies, and hence it has been maintained that every
body that is volatile must be odorous.  Adelon asserts, that this is
not the case, but it is difficult to accord with him.   The fact of our
not  appreciating  the  odour is  no proof of its non-existence. In
truth, bodies that  are inodorous to one animal or individual may be
the  contrary  to  another.  In  cases, too,  in which  the smell is
morbidly acute, a substance may  appear overwhelmingly odorous,
which  may not even impress the  sense  in  healthy individuals.
M. H. Cloquet refers to  the  case of a celebrated  Parisian  phy-
sician, who was subject to violent attacks of hemicrania or megrim,
and who was  dreadfully tormented, during one of the paroxysms,
by the smell of copper, exhaled from a pin that  had been dropped
in the bed!
   Caloric seems, however, to be only one of the causes of the dis-
engagement of odours.  Some are retained by so feeble  a  degree
of affinity, that they appear to be exhaled equally at all tempera-
tures.   Light influences their escape materially, in particular cases;
some plants giving off their  fragrance during the day, others per-
fuming the air only at night. Dampness, too, in many cases, assists
their escape;—hence  the  fragrance  of a garden after a summer's
shower; and the smell afforded by all argillaceous substances, when
breathed upon;—a fact, the knowledge of which, is of considerable
importance to the chemist.
   Lastly,  substances which appear to us entirely devoid of  odour,
will exhale a strong one, when rubbed together.  All these circum-
stances  tend greatly to prove, that every substance is possessed of
odorous qualities, provided we are aware of the precise mode for
causing their emanation, although our olfactory nerves may not be
sufficiently delicate to appreciate them.
   Around  the odorous  body, the molecules, as they escape, must
form an atmosphere, which, of course, will  be denser the nearer it
is to the body.  These particles are diffused around,  not, probably,
in the same manner as light or sound, but as one fluid mixes with
another; and, when the air is still, it is conceived, that their strength
will be inversely as the square of the distance from  the substance
exhaling them.   There is a great difference, however, in  odours
with regard to their diffusion in the atmosphere.  Some extend to
a great distance, whilst others are confined to a small compass. The
odours  of many  flowers are  so delieate as not to  be felt, unless
they are brought near the olfactory organs: whilst, according to
Boyle, that of cinnamon is experienced at sea, at the distance of
twenty-five  miles  from  Ceylon.  Lord Valentia affirms, that he
himself distinctly smelt  the aromatic gale at nine leagues distance.
Facts of this kind are employed by the natural philosopher to ex- 
SENSE OF SMELL.
103
hibit the excessive divisibility of matter.   Scales, in which a few
grains of musk have been weighed, have retained the smell for twenty
years afterwards, although they must have been constantly exhaling
odorous molecules during the whole of this period.  Haller kept
some papers, for more than forty years, which had been perfumed
by a single grain of amber;  and at the end of that time, they did
not appear to have lost  any of  their odour.   That distinguished
physiologist and mathematician calculated, that every inch of their
surface had been impregnated by ¥tftfs *so oth °f a grain of amber,
and yet they had scented for 14,600 days a stratum of air at least a foot
in thickness.  But how much larger must these molecules be  than
those of light, provided we regard it as consisting of molecules, see-
ing that glass is capable of retaining the former, but suffers the other
to penetrate it in every direction without obstacle!
   The air is not the only vehicle for odours.  It has been seen that
they adhere to  solid bodies;  and that, in many cases, they  can be
separated  by aqueous or spirituous  distillation.   The art  of the
perfumer  consists in fixing and preserving  them in  the most
agreeable and convenient vehicles.   Yet it was, at one time,  stre-
nuously denied, that they could be conducted  through water;  and,
as a natural consequence  of this view, that  fishes could smell.  Du-
meril, for example, maintained, that odours, being essentially of a
volatile or gaseous  nature, cannot exist in fluids; and, moreover,
that fishes have no proper olfactory organ;—that the part, which is
commonly considered as  such, is their organ of taste.  The opinion
is now entertained by few.   We have seen that odours can be re-
tained in fluids; and not many naturalists of the present day will be
hardy enough to  deny, that  fishes have an organ or sense of smell.
At all events, but few anglers, who have used their oil of rhodium,
or other attractive bait, will  be disposed to give  up the  results of
their experience,  without stronger grounds than any that have yet
been assigned by the advocates of that view of the subject.
   When it was determined, that odours consist in special molecules,
given off from  bodies, it  was attempted  to explain their  action on
the pituitary membrane in the same  manner as that of savours on
the membrane of the tongue.  It was conceived,  for example, that
the shape of the molecules of a pungent odour is pointed, that of
an agreeable, round.  Others, again, were of opinion, that olfaction
is owing to some chemical  union between the odorous  molecule
and the nervous fluid; or between it and the nasal mucus.  None,
however, have  attempted to  specify the precise chemical composi-
tion, that renders a body odorous.  The sensations are not the most
favourable  occasions for  exhibiting chemical  agency;  and, in this
particular sense, it is probably no farther  concerned  than  in the
sense of touch,  and not so much as in that  of taste. It is sufficient
for the odorous particle,—animal, vegetable, or mineral,—to come in
contact with the olfactory nerves, in  order that the odour may be
appreciated;  and  we  may,  in vain,  look  for chemical action in 
104
SENSIBILITY.
 many of those animal  and vegetable perfumes, as musk, amber,
 camphor,  vanilla, &c.  which  astonish us by their intensity and
 diffusibility.
   The same remarks, that were made on the classification of savours
 are applicable to that of odours.  They are not less numerous and
 varied; and each substance, as  a general principle, has its  own, by
 which it is  distinguished. Numerous attempts have, however, been
 made to group them, but all are unsatisfactory.
   The classification, proposed  by Linn.eus, was into Odores aro-
 matici, as those of the flowers  of the pink, bay leaves, &c; O.fra-
 grantes, as  those of the lily, jessamine, &c; O. ambrosiaci, as those
 of amber, musk, &c; 0. alliacei, as those of garlic, assafoetida,&c; 0,
 hircini, (like that of the goat,)  as those of the  Orchis hircina, Che-
 nopodium vulvaria, &c; O. tetri,  or repulsive or virous, as those
 of the greater part of the family solaneas; and lastly, 0. nauseosi, as
 that of the flowers of the veratrum,  &c. A simple glance at this di-
 vision will exhibit its glaring imperfections.   No  two individuals
 could, in fact, agree to which of any two of the cognate  classes a
 particular odour should be referred.
   None  of  the other classifications, that have been proposed, are
 more satisfactory.   Fourcroy  divided them into the extractive or
 mucous, the fugaceous oily, the volatile oily, the aromatic and
 acid, and the hydrosulphureous; !l<orry into the camphorated,
 narcotic, ethereal, volatile acid, and alkaline.
   The distinction  into animal, vegetable, and  mineral, is not more
 commendable.  Musk is the product of an animal of the ruminant
 family, but  the odour is not confined to this animal. It is contained
 in the civet, in the flesh of the crocodile, and in the musk-rat. Hal-
 ler asserts  that his own perspiration smelt of  it.   It is  met with,
 likewise, in  the vegetable kingdom—in the Erodium moschatum,
 the seeds of the Abelrnoschus,  the flowers of  the Rosa moschata,
 and of the Adoxa moschatellina, and in some of the varieties of the
 melon and the pear; and, what is perhaps more surprising, in mi-
 neral substances; as in  certain  preparations of gold, and  in some
 earths of which tea-pots are  formed  in  China and Japan.
   The odour of garlic, again, is found  not only in that  vegetable,
 but in assafoetida; in arsenic, when thrown upon hot coals; and  in
 the Bufo pluvialis, a species of toad.
   In by far  the majority of  cases we can only designate an odour
 by comparing it with that of some well known substance; hence
 the  epithets musky, alliaceous, spermatic, &c.   Adelon asserts,
 that the sole classification that can be adopted is into the agreeable
 and disagreeable.   But even the miserably imperfect division pro-
 posed by Haller is better than  this; he made three classes—Odores
 suayeolentes, 0. medii andfcetores.  The truth is, that all the ob-
jections, made to the division of savours into the agreeable and dis-
 agreeable, are equally applicable to  odours.
   Assafoetida, we have seen, was  employed by the ancients as a 
SENSE OF  SMELL.
105
condiment; and although with us it has the name deviFs dung, it
is by many of the Asiatics called the food of the gods.  We find,
too, certain animals that are  almost enravished  by certain odours.
The cat, for example, if the catmint—Nepeta cataria, or the root
of the valerian—Valeriana officinalis, be placed in its way.  These
differences, like those in the appreciation of  savours  by animals,
must be referred to minute and inappreciable organization.
   Odours have been considered possessed of medicinal and even of
poisonous properties.   Some individuals, whose peculiarity of con-
stitution renders them very liable to the action of ipecacuanha or
jalap, will experience emetic effects from the former, or the cathartic
qualities of the  latter, by merely smelling them for a short  space;
and the majority of individuals,  by pounding jalap or rhubarb for
a long  period,  will  find themselves more or  less affected.  By
smelling, for a considerable time, strong alcohol, intoxication may
be induced, as not unfrequently happens to the spirit taster, who is
young in  his vocation.  It  has  also been  asserted, that the con-
stant application of this sense to the discrimination of teas, in the
English East India company's warehouses, has laid the foundation
for numerous head affections; but the report originated in prejudice
or in accidental coincidences, and has not been found to be accurate.
  In all these cases, in which we see medicinal or poisonous effects c
actually produced by substances  inhaled  through the nostrils, we
cannot attempt to explain them by the simple impression, made by
the  odorous particle on the olfactory nerve.   They must be ac-
counted for by  the circumstance  of the minute particles of the me-
dicinal or poisonous substance being diffused in  the atmosphere and
coming into contact with the mucous membranes, from which they
are absorbed, and in this manner enter the circulation.
  Odours have, likewise, been considered to possess nutritive pro-
perties; and this chiefly, perhaps, from the effect known to be pro-
duced by savory smells upon the appetite. It is not probable, that ab-
sorption can, in this case, occur to a sufficient extent to account for the
apparent satiation.   The fact can only be explained by the effect
upon the nervous system, which influences  the appetite materially,
as we see in the operation of various mental emotions.  The first
impact  of a nauseous odour,  or even the view of a disgusting object,
will frequently convert the  keenest appetite, on  the  instant, into
loathing.   Yet, anciently, it was believed, that  life might be sus-
tained for some time, by simply smelling nutritious substances.
Democritus is said to have  lived three days on the vapour  of hot
bread; and Bacon refers to  a man, who supported  an abstinence of
several  days by inhaling the odour of a mixture of aromatic and al-
liaceous herbs.   Two hundred years ago these notions were  enter-
tained to a great extent; and they  afford the basis for the viaticum,
suggested for travellers proceeding to  the moon, according to the
plan proposed by Dr. John Wilkins, Bishop  of Chester.
  Vol.  I.                      14 
106                     SENSIBILITY.
          This learned Prelate published  a work in 1638, entitled, "  The
        discovery of a New World, or a Discourse tending to prove, that
        'tis possible there may be another habitable World in the Moon,
        with a Discourse concerning the possibility of a passage thither."
        "If we must needs feed upon something," he remarks, " why may
        not smells nourish us?  Plutarch and Pliny, and  divers other
        ancients, tell us of a nation in India, that lived only upon pleasing
        odours; and it is the common opinion of  physicians, that these do
        strangely both strengthen and repair the spirits."
          Fuller, too, a learned contemporary of the Bishop, affords an
        amusing instance of litigation, arising from this supposed  nourish-
        ing character of  odours.  " A poor man being very hungry, staid
        so long in a cook's shop, who was dishing up meat, that his stomach
        was satisfied with only the smell  thereof.   The choleric cook de-
        manded of him to pay for his breakfast; the poor man denied having
        had any; and the controversy was referred to the deciding of the
        next man  that  should pass by, who chanced to be the most noto-
        rious idiot in the whole city; he, on the relation of the matter, de-
        termined that  the poor  man's  money  should  be put betwixt two
J       empty dishes, and the cook should be recompensed with the jingling
        of the poor man's money, as he  was satisfied with the  smell of the
        cook's meat."
          It need scarcely be said, that if the vapour from alimentary sub-
        stances be capable, in any manner, of serving the purposes of nutria
        tion it can only be through the agency of the absorbents.

                          Physiology of Olfaction.

          In order that the sense of smell be duly exercised, it is necessary
        that the emanation from an odorous bod)'-  shall not only  impinge
        upon the pituitary membrane, but  that it shall impinge with some
        degree of force.  It must, in  other words, be  drawn  in with  the
        inspired air.  Perrault  and Lower found, that by  making  an
        opening into the trachea of animals, and  thus preventing the in-
        spired air from passing through  the nasal  fossae, smell  was not ef-
        fected; and that dogs, which were the subjects of the experiment,
        readily ate food they had previously refused.  These  experiments
        were repeated by Professor Chaussier, and with like results. They
        explain why we use considerable effort to draw in air loaded with
        an odour that is agreeable to us; and why, on the contrary, we ar-
        rest the respiration, or  make it pass entirely through  the mouth,
        when disagreeable.  Still odours are occasionally so diffusible  and
        expansible, that they will reach the olfactory membrane, and we are
        compelled to shut them  off by calling  in the aid of the upper ex-
        tremity.  The air being the ordinary  medium for the  conveyance
        of odorous molecules, we can understand why the organ of smell
        should form a part of the air passages. 
SENSE OF SMELL.                    107
  The use of the nose itself is to direct the air, charged with odours,
towards  the upper part of the nasal fossae.  Its situation is well
adapted for  the reception of emanations from bodies beneath it, and
its  appropriate muscles allow the nostrils to be more  or less ex-
panded or contracted.  The uses we have assigned to the  nose are
demonstrated by the fact, that they, whose noses are deformed, es-
pecially the flat-nosed, or whose nostrils are directed forwards, in-
stead of  downwards, have commonly  the sense very  feebly de-
veloped.   Sir Charles Bell, indeed, asserts, " that the  form of
a man's nose has no relation to the extent or perfection of the organ
of  smelling;" the seat of the sense lying "deep  in the  ethmoid
bone."   Yet the loss of  the nose, either by accident or  disease, is
found to  completely destroy the sense;  and by no means  the least
advantage of the Taliacotion operation is the enjoyment afforded by
the restoration of this corporeal sense.   M. Beclard affirms, that
an artificial nose, formed  of paper, or other appropriate material, is
sufficient to  restore it, so long as the substitute is attached.  Of this
we  have had no experience, but no assertion of Beclard's is in need
of confirmation.
  The mode in which olfaction is effected appears to be as follows:—
The inspired air, loaded with odorous particles, traverses the nasal
fossae; and in this passage, comes in contact with the pituitary mem-
brane, through the medium of the nasal mucus.   The use of this
mucus appears to be, not only to keep the organ properly  lubricated,
but to arrest the particles as they pass;—not  by any chemical at-
traction, but in a purely mechanical manner.  The olfactory nerves,
being distributed on the  membrane, receive the impression of the
molecules, as they impinge, and in this manner the sensation is ac-
complished.
  The use of the different spongy or turbinated bones would seem
to be to enlarge the  olfactory  surface.  According to some,  how-
ever, their office is, to form channels to direct the air towards the
openings of the sinuses.   The sinuses, themselves, afford subjects
for physiological discussion.  By many, they are considered, also,
to add to the extent of olfactory surface: by others to furnish the
nasal mucus.  No hesitation would be felt in pronouncing  both the
spongy bones and  sinuses to be highly useful in olfaction, were it
not that the olfactory nerves, or first pair, have not been traced on
the pituitary membrane covering the  middle and  inferior spongy
bones, or on that which lines the different sinuses;—that  the sinuses
are wanting in the infant, which, notwithstanding, can  appreciate
odours;—that they exist only in the  mammalia;  and that experi-
ments would seem to show, that the upper part of the olfactory
organ is more particularly destined  for the function, and  that the
sinuses, which, as well as the membrane covering the middle and
lower spongy bones, are supplied by filaments from the fifth pair of
nerves, are not sensible to odours. 
108
SENSIBILITY.
  That the upper part of the nasal fossae is the great seat of smell,
is proved  by the facts referred to regarding the uses of the nose.
Dessault, too, mentions the  case of a young  female, who  had a
fistula in the frontal sinuses, and who could not perceive an odorous
substance, when  presented at the orifice of the fistula, because there
was no communication with the proper portion of the nasal fossae,
even although she was capable of breathing through the opening.
Deschamps, the younger, also relates the case of a man, who had
a fistula of the frontal sinus, through which ether might be injected
without being appreciated, provided all communication  had been
previously cut off between the sinus and the upper part of the nasal
fossae; but if this precaution had not been taken, the sense was more
vivid when the odours passed  through the fistulous opening, than
when they reached the organ by the ordinary channel.
  Professor Richerand, again, found that highly odoriferous  in-
jections, thrown through a  fistulous opening into the maxillary si-
nus or antrum of Highmore, produced no olfactory sensation what-
ever.
  All these facts would certainly seem to lead to the belief, that the
upper  part  of the nasal  fossae, on which the first pair or olfactory
nerves are distributed, is the chief seat of olfaction, and that the in-
ferior portions of these fossae,  as well as the different sinuses com-
municating  with them, are  not primarily  concerned  in  the  func-
tion;  but doubtless, offer secondary advantages of no little import-
ance.   This conclusion would, however,  seem to admit, what is
not by any means universally admitted,  that the olfactory nerve
is the sole or  chief nerve  of  smell.   Especially difficult is it
to embrace this view, and not to believe that the spongy bones
and sinuses, on which the fifth pair  are distributed, are  agents  in
perfecting the sense, when we  find them largely developed  in
animals, that possess unusual delicacy of smell, as in the dog and
elephant.   It has already been remarked, that the ancients believed
the olfactory nerves to  be canals for conveying  away the pituita
or phlegm from the brain.  Diemerbroeck, in 1672, maintained
this opinion.   At  the early  part of the  last century, however,
the olfactory  was  supposed to be the proper nerve of smell, and
this opinion prevailed, with  scarcely  a dissentient voice, until
within the last few years.  Inspection of the origin and distribution
of this nerve  seems to indicate it as admirably adapted for a nerve
of special  sensibility connected with smell.  It is largely developed
in animals, in proportion to their acuteness of  smell, and is distri-
buted  on  the very part of the pituitary membrane to which it is
necessary to direct  air, loaded with odorous emanations, in  order
that they  may be fully appreciated.  Magendie has, however, en-
deavoured to show, by experiment, that the sense of smell is in no
wise, or but little, dependent upon the olfactory nerves, but upon
 the branches of the fifth pair.   Prior to the institution of his expe- 
SENSE  OF SMELL.
109
riments, he  had observed with astonishment, that after he had re-
moved the cerebral hemispheres with the olfactory nerves of animals,
they still preserved this faculty. He had noticed, too, that  the sense
had continued in some lunatics, who had fallen into a state of stupor,
and in whom  the substance of the brain  appeared,  on dissection,
greatly disorganized.  These facts induced him to expose  the olfac-
tory nerves  on living animals, and to experiment upon them.   In
the course of his experiments, he found, in the first place, that the
nerves were insensible to puncture, pressure, and to the contact of
the most odorous substances.  He afterwards satisfied himself, that
after their division, the pituitary membrane  not only preserved its
general sensibility, appreciated the contact  of bodies, but that it
continued to feel strong  odours, those of ammonia,  acetic acid, oil
of lavender, Dippel's oil, &c.   On the other hand, having divided
the fifth pair of nerves within the cranium, and left the  olfactory
nerves untouched, he remarked, that  the  pituitary membrane  had
lost its general sensibility;  was no longer sensible to contact of
any kind; and that it had lost the power of appreciating odours.
  From these experiments, he considered  himself justified  in in-
ferring, that the olfactory nerve does not preside over the general
sensibility  of the nose; that it  has, at the most,  but a special
sensibility as concerns odours; and that if the olfactory nerve be the
nerve of smell, it at least requires the influence  of the  fifth pair, in
order  that  it  may act:  lastly, he asks, may not the general and
special sensibility be comprised in the same nerve in the sense of
smell, as they are in that of taste:—in the fifth pair?
  These experiments are highly interesting; but they do not en-
tirely establish, that the fifth pair is the olfactory nerve.   The nu-
merous facts already mentioned, attract us irresistibly to  the first
pair, or olfactory, as they  have  been  exclusively called.  It has
been already remarked, that the fifth  is concerned in all the facial
senses: that it conveys to them general sensibility, or feeling; but
that some of them are, unquestionably, supplied with nerves of spe-
cial sensibility; the eye,  for example,  with the optic  nerve; and the
ear with the auditory; but that neither one  nor the other  can exert
its special function, without the integrity—the presidency—of the
fifth pair. The olfactory nerve is  probably in this category,—is the
nerve of special sensibility.   It is true, that in  the experiments of
Magendie, the animal  appeared to  be affected by odorous sub-
stances, after  the  division of the first pair; but a source of fallacy
might exist here, in discriminating accurately between the general
and  special sensibility.  Some of the  substances, that were  em-
ployed, were  better adapted  for eliciting the former than the lat-
ter:—ammonia and acetic acid, for example.
  The immediate function of the sense of smell, is to appreciate
odours. In this it cannot be supplied by any other sense. The function
is instinctive; requires no education;  and is exerted as soon as the 
110
SENSIBILITY.
 parts have attained the necessary degree of development.   In many
 respects this sense is intimately connected with  that of taste, and
 the impressions made  upon  each  are  frequently confounded.  In
 the nutritive function, the smell serves as a kind of advanced guard
 or sentinel to the taste, and warns us of the disagreeable or agreeable
 nature of the aliment; but if a substance, that is repugnantto the smell,
 be agreeable to the taste, the smell soon loses its aversion, or at least
 becomes less disagreeably impressed.   The smell is  not, however,
 so useful to man as a sentinel to the taste, as it is to animals: there are
 many bodies,—those containing prussic acid  for example,—which
 are extremely pleasing  by  the odours they exhale, and yet  are
 most noxious  to the human frame.  In the animal kingdom it is
 greatly depended upon, and is rarely a  fallacious guide.  It enables
 animals to make the proper selection of the noxious from the inno-
 cent:—the alimentary from that which is devoid of nutriment:—the
 agreeable from the disagreeable; and  this power appears to be in-
 stinctive or dependent upon inappreciable varieties of structure in
 the olfactory organs.
  As an intellectual sense, the smell is  not entitled to a higher rank
 than the taste.   Its mediate functions are very limited.  It enables
 the chemist, the mineralogist, and the  perfumer to discriminate
 bodies from each other.  We can, likewise, form  a slight, but only
 a slight, idea by it, regarding the distance and direction of bodies,
 owing to the greater intensity of odours near an odorous body, than
 at a distance from it.  Under ordinary circumstances, the informa-
 tion of this kind, which  we derive by  olfaction, is inconsiderable;
 but in the blind, and in the savage, who are accustomed to exercise all
 their external  senses more than the civilized individual, the sphere
 of utility and accuracy of this sense is largely augmented.   Of this
 we shall have  to speak  presently.  We  find it, too, surprisingly de-
 veloped in some animals; in which it is considered, by the eloquent
 Buffon. as an eye that sees  objects not only where they are, but
 even wherever they have been; as an organ of gustation,  by  which
 the animal tastes not only what it can touch and seize, but even what
 is remote and cannot be attained; and he  esteems it a universal
 organ of sensation, by  which  animals are soonest  and  most fre-
 quently impressed, by which they  act and determine, and recognise
 whatever is in accordance with, or in  opposition to their nature.
The  hound, amongst quadrupeds, affords us a familiar example of
 the extreme delicacy of this sense.  For hours after the passage of
 game, it is capable of detecting the traces; and the bloodhound can
be trained to indicate the human footsteps with  unerring certainty.
In the case  of many of the  carnivorous birds, we have signal in-
stances of the acuteness of  either  the  sense of  smell or of vision.
Which of these ought to have the credit, it is difficult to say; and,
of course, almost impracticable  to demonstrate, by direct experi-
ments. Those, that have been hitherto instituted, are more in favour 
SENSE  OF SMELL.
Ill
 of the latter, than of the former. The turkey buzzard of the United
 States of America, is a bird of this class; and it is surprising to see
 how soon they  collect from immense distances after an animal has
 died in the forests.
   Humboldt relates, that in  Peru, Quito, and in the Province of
 Popayan, when they are  desirous of taking the gigantic Condor—
 the Vulturgryphus, of Linn^us,—they kill  a cow, or hoise, and
 in a short time, the odour of the dead animal attracts those birds in
 numbers, and in places where they were scarcely known to exist.'
 It is asserted, too, that vultures went from Asia  to the field of battle
 at Pharsalia, a distance of several hundred  miles, attracted  thither
 by the smell of the killed!  Pliny, however, exceeds almost all his
 contemporaries in his assertions on this matter.  He affirms, that the
 vulture and the raven have the sense of smell so delicate,  that they
 can foretell the death of a man three days beforehand, and in order
 not to lose their prey, they arrive upon the spot the night before
 his dissolution!
   As the organ of smell, in all animals that respire air, is situated
 at the entrance of the organs of respiration, it is probable that  its
 seat, in  insects, is in the mouths  of the  air  tubes.   This sense
 appears to guide them to the  proper kinds of food, and to the exe-
 cution of most of the few offices they have to perform during their
 transient existence.   Occasionally, however, they are deceived by
 the resemblance between the odours of substances  very different
 in other qualities.   Some plants, for example,  emit a cadaverous
 odour, similar to  putrid  flesh, by which the flesh-fly  is  attracted,
 and led to deposit its ova in parts that can furnish no food to the
•future progeny.
   As regards the extent of the organ of smell,  man is undoubtedly
 worse situated than  most animals, and all these being, in other
 respects equal,  it may be fair to presume, that those in which the
 olfactory  membrane is most  extensive, enjoy  the sense  of smell
 most exquisitely.   It is curious, however, that animals which pos-
 sess the sense of smell in the highest degree, are those that feed  on
 the most fetid substances.  The dog, for instance,  riots in putridity;
 th1() birds of prey, to which  reference has been made, have similar
 enjoyment.  The  turkey buzzard of the United States  is so fetid
 and loathsome, that his captors have generally  been glad  to loosen
 him from bondage;  and it is affirmed, that  if his  ordinary fetor is
 insufficient to produce his release, he affords an  irresistible argu-
 ment, by  ejecting the putrid contents  of his stomach upon his
 possessor!   One inference may, perhaps, be drawn from this pen-
 chant of animals with the most exquisite olfactories for putrid sub-
 stances:—that the taste of the epicure for game, kept until it has
 attained the requisite ftimet, is not so unnatural as it might at first
 sight appear.
   Like the senses already described, that of smell is, to  a certain 
112
SENSIBILITY.
 extent, under the influence of volition:  in other words, it can be
 exerted actively and passively.   Its active exercises as when we
 smell any substance to enjoy its sweets, or to test its odorous quali-
 ties, generally requires prehension, the proper direction of the head
 towards the object;  and more or less contraction of certain  mus-
 cles of the alae nasi.   Doubtless, here again, the papillae are capable
 of being erected under the attention, as in the senses of taste and
 touch.  On the  other hand, we can throw obstacles  in the way of
 the reception of disagreeable odours; and, if necessary, can prevent
 their ingress altogether, by compressing the nostrils with the upper
 extremity.
   Lastly, like the other  senses, the smell is capable of great im-
 provement by education.   The perfumer arrives,  by habit, at an ac-
 curate discrimination of the nicest shades of odours; and the chemist
 and the apothecary employ it constantly  to aid them in distinguish-
ing bodies from each other; and in pointing out the changes that take
place in them, under the influence of heat, light, moisture,  &c.  In
this way it becomes a useful chemical test.  The effect of education
is likewise shown, by the difference between a dog, kept regularly
accustomed to the chase, and one that has not been trained.   For
the same reason, in  man, the sense is more exquisite in the savage
than in the civilized state.  In  the latter, he can have recourse to a
variety  of  means for distinguishing the properties of bodies, and
hence he has less occasion  for acuteness of smell than  in the former;
whilst, again, in the civilized state, numbers destroy the sense, in
 order to procure pleasure.  The use of snuff is one of the  most
 common of these destructive influences.
   Of the acuteness of the sense of smell in the savage, we  have an
 example, on the authority of Humboldt; he affirms, that the Peru-
vian Indians, in the middle of the night, can distinguish the different
races by their smell,—whetherEuropean, American Indian, or negro.
   To the same  cause must be ascribed the delicacy of olfaction,
 generally observed  in the blind.   The  boy Mitchell, who was
 born  blind and deaf, and  whose case will have  to be detailed at
length hereafter, was able  to distinguish the entrance of a  stranger
into the room by the smell alone.   A gentleman, blind from birth,
 from some  unaccountable  impression of dread or antipathy,  could
 never endure the presence of a cat in the apartment.   One day, in
 company, he suddenly leaped  up, got upon an  elevated seat, and
 exclaimed that there was a cat in the room, begging them to remove
 it. It was in vain that the company, after careful inspection, assured
 him he was under an illusion.   He persisted in  his  assertion and
 state of agitation;  when, on opening  the door  of a small closet
 in the room, it was found that a cat had been accidently shut up in it. 
SENSE OF  HEARING.
113
      Sect. IV.—of the sense of hearing  or audition.

   Audition makes known to us the peculiar vibrations of sonorous
 bodies, that constitute sounds.  It differs from the senses, that have
 already been described, in the fact, that contact is not required be-
 tween the organ of sense and the sonorous body;  or between the
 organ and any emanation from the body.  It is, however, a variety
 of touch, but produced by a medium, acted upon by the vibratory
 body.

              Anatomy of the  Organ  of Hearing.

   The auditory apparatus is a subject of intricate study to the young
 anatomist; and, unfortunately, when he has become acquainted with
 the numerous minute portions, to which  distinct and difficult appel-
 lations have been appropriated, he has here, as in many other cases,
 attained a mere tedious detail of names, without having added to his
 stock of philosophical information.  Happily, it is not necessary for
 our purpose  to go thus minutely into the  description of the organ
 of hearing.  According to the plan, hitherto pursued, allusion  will
 be made to those portions of it only, which concern the physiolo-
 gical inquirer.
   In the ear, as well as in the eye, we have the distinction between
 the physical  and nervous portions of the organs more clearly exhi-
 bited than in the  skin, mouth, or nose.  The  nervous portion is
 situated deeply within the organ; and the parts, between it and the
 exterior, act physically on the sonorous vibrations, in the case of the
 ear; and on the light, in  that of the eye.
   The organs of the  senses, hitherto considered, are symmetrical.
 Those of audition are two in number, distinct but harmonious, and
 situated at the sides of the head,  in a part of the temporal bone, ge-
 nerally called from its hardness, the pars petrosa; but by the French
 anatomists regarded as a distinct  bone, under the similar appellation
 of Le Rocher.  This bone is seated at the base of the skull, so  that
 the internal parts of the auditory organ are  deeply and securely
 lodged.
   For facility of description, the  ear may be divided into three  dis-
 tinct portions:—1, the external  ear, or  that exterior to the mem-
 brana tympani; 2, the middle ear—the space contained between the
 membrana tympani and  the internal ear; and 3, the  internal  ear
 itself, in which the auditory nerve is distributed.
   1. The external ear.—This portion of the auditory apparatus is
 commonly looked upon as an acoustic instrument, for collecting the
sonorous rays or vibrations, and directing them, in  a concentrated
state,  to the  parts within.   It is composed of the pavilion, and
meatus auditorius externus.
  Vol. I.                      15 
114
SENSIBILITY.


  Fig. 17.
1. The pavilion.
S. Meatus auditorius externns.
3. Membrana tympani,
4. Malleus,      ~j
5. Incus,

'bfS'ulare be- \™M bone» of tiie ear"
 tween the malleus
 and stapes,     J
 7. Cavity of the tympanum.
 B. Eustachian tube.
 P. Meatus auditorius internus.
10. 11. 12. The labyrinth.
10. Vestibule.
11. 11.11. Semicircular canals.
12. The cochlea.
13. Stapedius mussle.
  The pavilion varies in size and position in different individuals.
It is the fibro-cartilaginous, thin, and expanded portion, which is an
appendage, as it were, to the head.  It is  irregular on' its  anterior
surface; presenting several eminences  and depressions.   The emi-
nences  are five  in number, and have  been  called, by anatomists,
the helix,  ant-helix, the tragus, anti-tragus, and the lobe.
  The  helix forms the rim of the pavilion: the tragus is the small
nipple-like projection on the facial  side of  the meatus auditorius;
the anti-tragus is the projection opposite to this; forming the lower
portion of the ant-helix; and the lobule is the fatty, pendulous por-
tion, to which ear-rings are attached.   The depressions are three in
number—the groove of the helix*or cavitas innominata; the fossa
navicularis or  scapha; and the concha.  The name of the first suf-
ficiently indicates its situation;  the second is  nearer  the meatus
auditorius; and the concha is the expanded portion, which joins the
commencement of the meatus, and is bounded by the ant-helix,
tragus, and anti-tragus.
   The pavilion is supple and elastic;  and beneath the skin are nu-
merous sebaceous follicles, which  are distinctly perceptible, and
give to the skin its polish, and probably a portion  of its suppleness. 
SENSE OF  HEARING.
115
   On the different eminences, some muscular fibres are perceptible,
 which it is not necessary for our purpose to distinguish; as in man
 at least they are only vestiges—as the French term them—to indi-
 cate the uniform plan, which appears to .have prevailed in the for-
 mation of the vertebrated animals: if they have any office, it must,
 at all events, be extremely inconsiderable.
   Numerous vascular  and nervous ramifications are distributed on
 the pavilion. It is attached to the head by different ligaments, called—
 from their situation or attachments—zygomato-auricular, or ante-
 rior auricular:—temporo-auricular, or superior auricular, and
 mastoido-auricular, or posterior auricular; all of which termi-
 nate on the convex part of the concha. Three muscles are, likewise,
 attached to  the ear, so as to move the pavilion, in animals at least.
 These  occupy the  same position as  the ligaments described, and
 have similar names.  In man, these again, are mere vestiges; but in
 many animals, in the horse for example, they are largely developed,
 and are capable of moving the pavilion in various directions.
   The meatus auditorius externus extends from the inner extre-
 mity of the concha to  the membrana  tympani.  In the  adult it is
 about an inch long; narrower in its middle than at the extremities;
 longer inferiorly than superiorly, owing to the obliquity of the
 membrana tympani; and slightly curved upwards about its middle.
 The outer orifice is furnished with down or hairs, like the orifices
 of certain other canals.   The meatus is partly osseous, for the space
 of half an inch, and penetrates the temporal bone. More externally
 it is formed of fibro-cartilage—a prolongation of that of the concha.
 It is lined by an extension of the skin, which becomes gradually
 thinner as it proceeds inwards, and is ultimately reflected  over the
 outer surface of the membrana tympani.  Beneath this skin, nu-
 merous sebaceous follicles are situated, which secrete  the bitter
 humour, called cerumen.
   This humour occasionally becomes inspissated; obstructs  the
 canal; prevents the sonorous vibrations from reaching the membrana
 tympani, and is thus the cause of deafness.   Softening the cerumen
 by means of warm  water or oil dropped into the meatus, and then
 removing it by means of the syringe, restores the hearing.
   The  portion, then, of the auditory apparatus, which we have ar-
 bitrarily termed the external ear, is a complete cul-de-sac, formed
 by a prolongation of the common integument. There is no opening
 communicating with the next portion—the middle ear;—the mem-
 brana tympani, with its  dermoid envelopes, forming at once the
 medium of union and of separation between the two. A knowledge
 of this fact,  would somewhat diminish alarm  in cases where insects
 or other extraneous bodies get into  the meatus  auditorius.  The
 pain is  excruciating, owing to the great general sensibility of this
portion  of the auditory apparatus; but generally the chief dread en-
tertained is, that the irritating substance may pass into  the head.
It cannot, of course, proceed farther than the membrana  tympani; 
116                     SENSIBILITY.
and even were it able to clear this obstacle, insuperable impediments
exist to its farther progress.
  2. The middle ear  includes the cavity of the tympanum, the
small bones contained  in  the cavity, the mastoid cells, Eustachian
tube, &c.   Like the last, it belongs to the physical portion of the
ear.
  The cavity of the  tympanum, or drum of the  ear, has the
shape of a portion of an irregular cylinder.  Its name is not, indeed,
inappropriate. It has some resemblance to a drum, not only in form,
but, as will be seen, in function, likewise. The outer extremity of
this cylinder is  closed, like the drum, by the membrane already re-
ferred to—the membrana tympani. This membrane is not situated
vertically  in the meatus, but obliquely downwards and inwards, so
that the cavity is  broader above than below.  It is very thin and
transparent, and consists of three layers: the outermost formed by
the membrane lining the meatus auditorius externus; the most in-
ternal belonging to the membrane of the cavity of the tympanum;
and the middle, or membrane proper.  On its inner side is distri-
buted the  nerve, called chorda  tympani; and its centre affords at-
tachment to one extremity of the chain of small bones—to the handle
of the malleus.
  The proper tissue of the membrana tympani is dry, and it is ge-
nerally esteemed  to be devoid of fibres, vessels, and nerves.  Sir
Everard Home, however, in the Philosophical Transactions, for
1800,  and in the third Vol.  of  his  Lectures on  Comparative
Anatomy, asserts, that the membrane is muscular, that  its fibres
run from the circumference towards the centre, and are attached to
the malleus, and  that, if the membrane of the human ear be com-
pletely exposed, on both sides, by removing the contiguous parts,
and the cuticular  covering be washed off from its external surface;
then, by placing it in a clear light, the radiated direction of its fibres
may be easily detected.  This fibrous arrangement, Sir Everard
conceives to be muscular, and  on this he founds some ingenious
speculations, to  be hereafter noticed, regarding the appreciation of
sounds.  The discovery of a fibrous structure would, however, by
no means prove,  that  the membrane is capable of contracting; or
that it is formed of muscular tissue.  Many of the ligaments, which
consist of gelatine, and  are  consequently  incontractile, are dis-
tinctly fibrous in  their arrangement.  The same may be said of the
tendons, whose utility, as conductors of the force developed by the
muscle, would  be materially interfered with, were they possessed
of contractility.
  Again,  Ruysch, Sir Everard Home, and  Sir Charles Bell, af-
firm, that the membrana tympani is very vascular,—Sir Everard
asserting, that the vessels, in their distribution, resemble those of
the iris, and are  nearly half as numerous; their general direction
being from the  circumference to the handle of the malleus.   It is
not easy to account for this discrepancy amongst anatomists. A part 
SENSE OF  HEARING.                   117
of it is probably referable to some having directed their attention to
the  membrane proper; others to the membrane with its dermoid
coverings, which are highly vascular.
  The inner extremity of the drum is partly osseous, partly mem-
branous.  Nearly opposite the centre of the membrana tympani is
the foramen ovale or vestibulare, called also fenestra ovalis vel
vestibularis,  situated vertically,  and  forming  a communication
between the middle  and the internal ear.  It is closed by a mem-
brane, consisting, like the  membrana tympani, of three layers;  to
which is attached the base of the stapes—the other extremity of the
chain that stretches across the cavity.  Immediately below the
foramen ovale, is  the bony projection, called the promontory•; and
beneath this, again, a second opening, called the foramen rotundum
vel cochleare; or fenestra rotunda vel cochlearis, which forms a
communication between the middle ear and the external scala of the
cochlea.   This foramen is  closed by a membrane, similar to that of
the foramen ovale; but not, like it, parallel, or nearly so, to that of
the tympanum,—being situated  obliquely. There is no communica-
tion by a chain of bones between it and the membrana tympani.
  These small bones, or ossicles, are four in  number, so connected
with each other, as to form a bent lever; one extremity of which is
attached to the tympanic  surface of the  membrana  tympani; the
other to the  membrane of the foramen  ovale.   These  bones are
usually termed from  their shape—beginning with the  most external,
and following  their order—malleus,  incus, os  orbiculare, and
stapes.  A small muscular apparatus, consisting of three muscles,—
the anterior  muscle of the malleus; the internal  muscle of the
same bone; and the muscle of the stapes,—is attached to the chain,
which it can stretch or relax; and of course produces  a similar effect
upon  the  membranes to which  the chain is attached.  They are
animated  by  branches of the portio dura, or  facial nerve, which is
itself not a nerve of sensibility, but of motion; yet probably acquires
this function  by its union  with  the vidian twig  of the fifth pair, in
its passage through the aqueduct of Fallopius.  It is this nerve
which furnishes the chorda tympani.
  At the  anterior and  inferior  part of the cavity is  the  tympanic
extremity of a canal, through which the  drum  receives the air it
contains.   This  canal,  called the Eustachian tube, is about  two
inches long, and proceeds  obliquely forwards and inwards,  to the
lateral and superior part of the pharynx, into which it opens behind
the posterior nares.  It is partly osseous, partly  fibro-cartilaginous,
and membranous; and, towards its pharyngeal extremity, it expands,
terminating by an oval aperture, resembling a cleft.   Throughout
its course it is lined  by a mucous membrane, which appears to be a
prolongation  of that  of the nasal  fossae, and  it is capable of being
more or less  contracted and expanded by the muscles, which com-
pose and move the velum palati.
  The cavity of the tympanum, likewise, communicates by a short 
118
SENSIBILITY.
  and ragged canal, with numerous cells  contained  in  the  mastoid
  process.   These cells open  into each other;  and vary in number,
  size, and arrangement in different individuals and animals.   They
  are called the mastoid cells.
    The cavity is larger  in those animals, whose sense of smell is
  most acute.  In man, it is about a quarter of an inch deep, and half
  an inch broad.  It is lined by a prolongation of the same membrane,
  as that which'lines the Eustachian tube. This membrane, as we have
  seen, covers the membrana tympani; and the membranes of the fo-
  ramen ovale, and foramen rotundum.  It likewise lines the mastoid
  cells, and is reflected over the small bones.
   The middle  ear does not exist  in every animal endowed with
  hearing.   It does not begin  to  appear lower  in the scale  than in
  reptiles; and is by no means equally complex in all.   Frequently,
  the chain of bones  is entirely  wanting; and, at other times,  we find
  one bone only.
   3. The internal ear, or labyrinth, is the most important part of
 the apparatus.   It consists of several irregular cavities in the pars
 petrosa of the temporal  bone, in which the nerve of audition is dis-
 tributed.   It is, consequently, in this portion, that the physical part
 of audition  terminates, and the nervous begins. The labyrinth com-
 prises the vestibule, semicircular canals, and cochlea.
   The vestibule, as its  name  imports, is the  hall, that communi-
 cates with all the other cavities of the labyrinth. It would appear
 to be the most essential part  of the organ, as it often exists  alone.
 At its inner surface are numerous small foramina, which communi-
 cate with the bottom of the meatus auditorius internus, and through
 which the filaments  of  the auditory nerve reach  the  labyrinth.
 Externally, it communicates  with the cavity of the tympanum  by
 the  foramen ovale.  Posteriorly,  it opens  nto the semicircular
 canals by five foramina, and,  anteriorly, by a single foramen, into
 the internal scala -of the cochlea.  There is, also, posteriorly and
 inferiorly, near  the common orifice of the two vertical  semicircu-
 lar canals, the opening of a small, bony duct, which terminates in-
 ternally at the posterior surface of the petrous portion of the tem-
 poral bone.   This duct  is called the aquaeductus vestibuli.
   The semicircular canals are three in number, and occupy the
 hinder part of the  labyrinth.   They are called superior vertical,
posterior vertical,  and horizontal.  They are cylindrical cavities,
 curved semicircularly, and are more expanded at their vestibular
 origin, which has been therefore called ampulla.  They are con-
 stituted of a plate of bone,  situated in the spongy tissue of the pars
 petrosa, and all  of them communicate with the vestibule.
  The cochlea is the most anterior portion of the labyrinth.  It is
 so called in  consequence of its  resemblance,  in  man and  in the
 mammalia, to a snail's shell;  hence  also  its  French and German
 names, limagon and schnecke. It is the most intricate part of the
 organ of hearing, and does not, by any means, admit of easy de- 
SENSE  OF HEARING.
119
scription.   It is a conoidal canal, spirally convoluted, making two
turns upon itself and resting  on a bony nucleus or pillar, called
modiolus.   The base  of  the  nucleus is concave;  corresponds  to
the bottom of the  meatus auditorius internus, and  is pierced by
small foramina, through which the filaments of the auditory nerve
reach the cochlea.
   The spiral canal is divided, in its whole length, by a partition,
half osseous and half membranous, called the lamina spiralis:  so
that two distinct tubes are thus formed.  These are  the scalas  of
the cochlea.  At the apex of the cochlea they run into each other;
but, at the base, the one turns into the vestibule, and is hence called
the superior or vestibular, or internal scala;  the other commu-
nicates with the cavity of the tympanum by the foramen rotundum,
and is called the inferior, tympanic, or external scala. At this
scala, near the foramen rotundum, a bony canal begins, which pro-
ceeds towards the posterior surface of the pars petrosa on which it
opens.  It is the aquaeductus cochleae.
   The cochlea  does not exist in all animals that hear. It is, there-
fore,  not of essential importance. It varies, too, greatly, in compli-
cation, in different animals.  In birds, whose hearing is extremely
delicate, it merely consists of a short, hollow, bony process, divided
into two scalae, but without any spiral  arrangement.  In reptiles,
the cochlea  is still  more imperfect;  and in many species it can
scarcely be said to exist.   In fishes there is no trace of it.
   The different cavities of the internal ear are lined by an extreme-
ly delicate membrane.  In many animals this membrane alone exists
without any bony parietes.  It exhales  at its inner surface a limpid
fluid, called  the liquor  or lymph of  Cotugno or Cotunnius,
which, under particular circumstances, can reflow into  the  aquae-
ductus vestibuli and  aquaeductus cochleae.   This fluid is contained
in all the cavities of the internal ear.
   It is in these, likewise, that the auditory or acoustic nerve is
distributed.  This nerve  is the portio  mollis of the  seventh pair
of most anatomists.   It arises, like the other nerves of the senses,
from the medulla  oblongata, and near  the anterior paries of the
fourth ventricle.  From thence it passes obliquely outwards, for-
wards, and upwards, and  enters the meatus auditorius internus, the
foramen of which is situated on the  posterior surface of the pars
petrosa.   The base of this meatus corresponds to the inner surface
of the vestibule and  to the base of the  cochlea.   Through the first
foramen, near the base of the meatus, the portio dura of the seventh
pair or facial nerve passes, to gain the aqueduct of Fallopius, along
which it proceeds, giving off filaments to different parts of the mid-
dle ear, and  ultimately issuing by the  stylo-mastoid foramen, to be
lost on the muscles of the face.
   Below the part of the  meatus, where the facial  nerve emerges,
are several other foramina, through which the filaments of the au-
ditory nerve attain the labyrinth.   These are distributed to the 
120                      SENSIBILITY.
 vestibule, semicircular  canals, and  cochlea;  and  terminate,  by
 very delicate ramifications, in the tissue and surface of the mem-
 brane, that lines the labyrinth.
   Such are the organs concerned in the function of audition.  Be-
 fore proceeding to the physiology of these different parts, and the
 assistance afforded to the mind by this sense, it is necessary to enter
 into a brief physical disquisition on the subject of sound.

                           Of Sound.

   If a body, by percussion or  otherwise, be thrown  into vibration,
 every vibration will excite a corresponding wave in  the air: and
 these oscillations will be propagated, in all directions, until they
 are gradually lost in distance;  but if they  strike on  the  organ  of
 hearing with the necessary force, a sensation is produced, which is
 called sound or noise.   The term, however, is frequently used to
 signify, not only the sensation, but likewise  the affection  of the
 air, or of the sonorous body, by which the sensation is effected.
   That bodies move or oscillate, when they produce sound, admits
 of easy detection.  We can see it in drums, bells, musical strings,
 &c, whose vibrations, being extensive, are more perceptible; and
 we can arrest them, and with them the sound, by putting the hand
 upon the  body, or by muffling it.
   Whenever a sonorous body  is struck, a  change in the relative
 position of its molecules is produced.  These, by virtue of their
 elasticity, tend to return to their former condition.   This is done
 by a series of oscillations,  which are, at first, more extensive, but
 become gradually less,  until they finally  cease.  The rapidity  of
 these oscillations is greater in bodies that are  hard and elastic;
 and hence it has been concluded, that these two qualities render a
 body sonorous.  It is  not, however, a matter of facility to say,
 what is the precise cause of the difference of sound in analogous
 bodies.   It must,  of course, be dependent  upon intimate composi-
 tion, but  of a character  not easily intelligible to us.   There is but
 one individual  in Great Britain, who has been celebrated for the
 fabrication of the larger order of bells,—for churches, colleges, &c.
 and in certain countries the art is comparatively unknown.  The
 resonance is entirely owing to the intimate  composition  of the
 body; and is beautifully and singularly exhibited in the Chinese
gong; the sound of which  will continue to rise for some time after
 a succession of rapid and forcible blows has been inflicted.
   But, in order that the  oscillations of a sonorous body may affect
the organ of sense, an intermediate  body is necessary to repeat and
transmit them.   This body is called the vehicle of sound, and it is
usually the air. The air is,  indeed, by virtue of its elasticity, admi-
rably adapted for this purpose.  The loudness of the sound, conveyed
by the air, is dependent upon the density of that medium.  If we put
a bell under the receiver of an air pumpand exhaust the air,the sound 
SENSE OF  HEARING.
121
 will become gradually more and more faint, and when the air is
 exhausted will not be heard at all.  For the same  reason a pistol
 fired on the top of the Himala mountains gives a much feebler re-
 port than in the valleys beneath.   Sympathetic sounds afford ad-
 ditional evidences of the carrying power of air.  Every sonorous
 elastic body can be thrown into oscillations, provided the air around
 it be made to tremble in any manner.   Thus, if we sound a note
 near a piano forte, whose dampers are raised so as to admit of free
 vibration, the string, that is in unison with the tone produced, will
 vibrate; and a wineglass or goblet may, according to Arnott, be
 made to tremble and even  to fall from a  table by sounding on a
 violoncello near it, the note that accords with its own.
   The  strata of air, in proximity with the sonorous body, receive
 the first impulses; and from these they are successively propagated
 to others; much in the same manner as the undulations extend from
 the place in which a stone  is cast on a surface of smooth water;
 except, that the aerial undulations usually extend in every direc-
 tion, whilst the aqueous proceed  only horizontally.  In this  pro-
 pagation from stratum to stratum a portion of the  sound is neces-
 sarily lost;  so that the loudest sounds are  heard only within cer-
 tain limits; and, in all cases, the intensity of the sound is inversely
 as the square of the  distance from the sonorous body.
   By causing the sonorous undulations to proceed entirely in  one
 direction and preventing their escape in every other, a sound may
 be rendered audible at a much greater distance.  Biot found, that
 when he  spoke in a  whisper at one  extremity of  a  cylinder up-
 wards  of one thousand yards long, he was distinctly heard at the
 other.   In many large manufactories the knowledge of this fact is
 turned  to good account.  By having numerous tubes communica-
 ting with the different rooms of the establishment, and terminating
 in the  office of the principal, he is enabled to have his directions
 readily conveyed, and to receive any information he may require,
 without the slightest inconvenience.
   The velocity, with which sound proceeds, admits of easy calcu-
 lation.  Light passes with  such rapidity, that  it may be regarded
 as proceeding from objects  on the earth instantaneously to the eye.
 The velocity of sound is incomparably less.   We see the flash of
 a gun at a distance; and, some time afterwards, we hear the re-
 port.   Considering the light then to have  reached the eye instan-
 taneously, if we know the  distance of the  gun, and note the time
 that  elapsed between the appearance of the flash and the report, we
 can calculate accurately the rapidity of sound.  This is found to
 be about eleven hundred and forty-two feet in a second.  We can,
in this manner, tell the distance of a thunder cloud, by noting  the
time of the flash, and the time that elapses before hearing the clap.
If it  be  thirty seconds, the  cloud is at the distance of thirty times
eleven hundred and forty-two feet, or of six miles and a half.
  This  velocity  is the same for all kinds of sounds.   Biot found,
  Vol.  I.                    16 
122
SENSIBILITY.
on playing a flute at the end of the  tube, above  referred to, that
the tones arrived at the ear placed at the other extremity in due
succession; so that their velocity must have been uniform.
  When the aerial oscillations meet with a resisting body of a re-
gular surface, as AB, Fig. 18, they are reflected at an angle equal
to the angle of incidence: consequently an ear placed in the course
                                      of these reflected  waves
               Fig. 18.                as at  C, will  refer the
                                      sound to a distance as far
                                      nehind  the  point  of re-
                                      flection, and in  the direc-
                                      tion of  the reflected ray,
                                      as the sonorous body  is
                                      from the point  of reflec-
                                      tion.  It will seem  to be
                                      at E.   The ear at C will,
                                      however, receive the di-
                                      rect oscillations from the
     ^  ,,-"                          bell D, as well as those
     1^ ''                            that  proceed along the
       E                              lines D  F and F C; or, in
                                      other  words, it will  hear
both the sound and its echo; and, if the  surfaces on which the so-
norous undulations impinge be favourably disposed, these echosmay
be very numerous.
  The utility of the ear trumpet and speaking trumpet is to be
explained by this law of the reflection of  the  aerial undulations :
and some physiologists are of opinion, that the external ear is in-
servient to audition  on similar principles.  The ear trumpet is a
tube, narrow at one  extremity, so as to enter the concha; and ex-
panded at the other  like a trumpet.   It is  also  curved, so that it
may be easily  directed to objects.   All  the sonorous rays, which
enter the expanded extremity, after various reflections, are brought
to a focus in the auricular end ; and the  intensity of the  sound, is,
in this way, so much augmented, that a person, who, without it,
is entirely deaf to common conversation, may  be able to enjoy it.
A sheet of paper, folded like a cone, the apex  of which  is placed
in the concha, serves  a like purpose; and, to a less extent, the
hand held concavely behind the ear.
   Air  is not the only, or the most perfect, vehicle of sound.  The
personal experiments  of divers show,  that it  can be  conveyed
through water.  The blows of workmen around a diving bell are
distinctly heard above; and fishes have  manifestly an acute sense
of hearing, although this was at one time denied. An experiment,
made by Franklin, and by the Abbe Nollet, proves, that water
transmits a much stronger vibration than air.   When they struck
two stones together under water, a shock was  given to the ear,
which was almost insupportable. 
SENSE OF  HEARING.                  123
  Solids, too, are much better conductors of sound than air.   If
we scratch one  end of a wooden rod, the  sound will be distinctly
heard by the ear applied to the other, although it may be inaudi-
ble through the air.   Savage tribes are in the habit of discovering
the advance of  enemies, or of their prey, by applying the ear to
the ground; and the watchmen, in some of the towns, instead of
springing a rattle, and alarming offenders, strike the pavement with
a staff, the sound of which is heard by their fellow watchmen  at a
considerable distance. It is a common practice to ascertain whether
a kettle boils, by putting one end of a poker on the lid, and  the
other to the ear. The difference between simmering and  boiling is
in this way easily detected.  A knowledge of this fact, and of the
ready communication of sound through solids, has lately given  rise
to a valuable suggestion for the discrimination of diseases of the
chest,  and of various physiological and  pathological  conditions.
By putting the  ear to the chest we can hear the rush of the air
along the bronchial tubes: the pulsations of the heart, &c. and can
discover any aberration, that takes place in the execution of their
functions. This is what has been called, by the late distinguished
Laennec, of Paris—the proposer of the method—immediate aus-
cultation.  The direct application of the ear to the chest, is, how-
ever, frequently inadmissible.  In these cases Laennec used a  hol-
low cylinder, called a stethoscope, one end of which he applied to
the chest—the other to the ear. This plan he termed mediate aus-
cultation. The suggestion has led to most valuable improvements
in diagnosis.
   Hassenfratz and Biot  have made some  accurate experiments
on the comparative rapidity of the progress  of sound  through air
and solid bodies.  The latter found, in  the aqueducts of Paris,  that
a blow, struck upon a pipe nine hundred  and fifty-one metres, or
about ten huhdred and forty yards in length, was heard two se-
conds and a half sooner through the sides  of the pipe than through
the air; but the sound did not  extend so far.
   It has been  already observed, that the vibrations  of the  air,
caused by a sonorous body, are capable of exciting corresponding
vibrations in solid bodies within their sphere of action.  It was an
old observation, that such vibrations are excited only in bodies in
unison with the sonorous body; in other  words, in those that are
capable of producing the same tone with  the latter.  M. Savart
has, however, found, that unison is not necessary; and that when
a sound is  produced in the air,  every body receives  a vibration,
which is a repetition of the one that occasions the sound. This he
proved by using small membranes, on which he placed  fine sand.
These were  agitated, and the sand  assumed  various  regular ar-
rangements,  whenever a sound was  produced in their  vicinity.
This  law of physics  is  important in its physiological  relations.
The apparatus of audition consists of several  membranous  struc- 
124
SENSIBILITY.
 tures, which are thrown into oscillations, whenever the ear re-
 ceives the impressions of sound.
   The  vibrations, which produce sound, differ much as regards
 their extent and rapidity; and on these differences are dependent
 two of the qualities of sound—strength and tone.
   The strength or intensity of sound depends on the extent of
 the vibrations of a sonorous body.  This is easily seen in a musi-
 cal string; the sound of which becomes weaker as the  extent of
 the oscillations diminishes.
   The tone, on the other hand, is dependent on the rapidity of the
 oscillations; on their number in a given time.  The tone produced
 by a string, or other sonorous body, that vibrates quickly, is
 termed acute or sharp, when compared with the tone of one that
 vibrates slower. The latter is called grave, when compared with
 the former.
   The  gravest sound, that the  ear can appreciate, is ordinarily
 considered to  result from  thirty-two vibrations per  second; the
 most acute, from eight thousand  one  hundred  and  ninety-two vi-
 brations,  according to  some;—twelve  thousand, according to
 others.  Some well-devised experiments, however, recently made
 by Savart, largely extend these limits, and appear to indicate,
 that they  cannot yet be rigidly fixed.  In his experiments, the ear
 distinctly appreciated fourteen  or sixteen vibrations  per second;
 and the acutest note, that was audible, proceeded from upwards of
 forty thousand simple oscillations per second.
   The duration of the impression of a sonorous vibration on the
 ear,  is about the sixteenth part of a second.
   If a sonorous body be struck, and the vibrations excited be all
 performed in equal times, a simple and uniform  sensation will be
 produced  on the auditory nerve, and one musical tone will be
 heard.  But if the  vibrations be various and irregular,  they will
 fall irregularly on the organ of hearing, and will excite a  harsh im-
 pression, as if various sounds were heard together. In  other words,
 a noise  or discord will be produced.
   If two  notes, sounded together, afford pleasure, they produce
 harmony or concord.^ This arises from the agreement of the vi-
 brations of the two sonorous bodies, so that some of the vibrations
 of each strike upon  the ear at the same time. If, for example, the
 vibrations of one sonorous body take place in double the time of an-
 other, the second vibration  of the latter will strike upon  the ear at
 the same instant as the first vibration of the former.   This is the
 concord or harmony of an octave.  Between a note and its octave,
there are six intermediate  notes, constituting the diatonic scale,
 or gamut. If the vibrations of two strings are as two  to  three, the
second vibration of the former  will correspond with the third vi-
 bration of the latter, producing the harmony called a fifth. There
 are other tones, which, although they cannot be struck together 
SENSE OF HEARING.
125
 without producing discord, if struck in succession,  may give the
 pleasure called melody.   Melody is, in truth, nothing more than
 the effect produced on the brain, by pleasing musical tones, sound-
 ed in succession.
   There is another quality of sound, which the French call timbre.
 By some  of  the  translators of the works of the French phy-
 siologists,  this word has  been  inaccurately rendered  note.  It is
 essentially different from  note or tone, and  is peculiar. By Eng-
 lish philosophers it  is termed  the quality of sound.   It is  this
 quality that enables us to recognise various instruments, although
 sounding the same note or tone; and  to distinguish the voices  of
 individuals from each other.  Its cause is not evident.  By most, it
 is conceived to depend upon the nature of a sonorous body, if it be
 a surface:—and  at the same time on its shape, if a tube. Biot con-
jectures, that it is owing to the series of harmonic sounds forming
 part of every appreciable sound. When any sonorous body is made
 to vibrate, a distinct sound is heard, which is the fundamental;
 but, if attention be paid, others will be heard at the same time.
 These are called harmonics.
   It is not improbable but that  the timbre or quality may be de-
 pendent as well  upon the nature of the sonorous body, as upon 'the
 greater or less number of  narmonics, that  accompany the funda-
 mental sound.

                  Physiology of Audition.

   In tracing the progress of the sonorous  vibrations to the inter-
 nal ear, we shall follow the order of parts  described in the anato-
mical sketch of the auditory apparatus;  commencing with the ex-
ternal ear.
   The meatus auditorius externus being always open, sonorous vi-
brations can readily attain the membrana tympani.  Some of these
pass directly to the membrane without experiencing reflection, and
communicate their oscillations to it.  The pavilion has, by most
physiologists,  been regarded as a kind  of  ear trumpet, collecting
the aerial undulations, and directing them, after various reflections,
to the  bottom of the auditory canal. In the horse, and in those ani-
mals which have the power of pricking the ears, or of moving
them in various  directions, this is doubtless the case; but in man
we cannot expect any great effect of the  kind, if we regard its par-
ticular arrangement, and  the incapability  of moving  it from its
fixed direction, which is nearly parallel to the head.  Boerhaave,
indeed, pretended  to have proved by calculation, that every sono-
rous ray, which  falls upon the  pavilion, is ultimately directed to-
wards the meatus auditorius externus.    Simple  inspection of the
pavijflbn will show that this cannot be universally true.  Some part
of the anthelix is, in almost every individual, more prominent than 
126
SENSIBILITY.
the helix; and it is  therefore impossible for the undulations, that
fall upon its posterior surface, to be reflected towards the concha.
  M. Itard, a distinguished physiologist and aurist of Paris, as-
serts, that he has never seen the loss  of the pavilion affect the
hearing; and that, as is well known, many animals,  whose sense
of hearing is extremely acute,—the mole and birds, for example,
—are devoid of it.  Hence he concludes, that it is  perhaps rather
injurious than favourable to audition, and is more inservient to
the expression  than to the hearing of the animal.  M.  Itard's
view is doubtless too exclusive. The pavilion may  have  but little
agency, as an ear trumpet, but it must have some. The concha, be-
ing the expanded extremity of the meatus auditorius, must receive
more sonorous vibrations than could be admitted  by the meatus it-
self.  These are  reflected  towards  the membrana  tympani, and
reach that expansion in a state of  concentration;—to no  great ex-
tent, it is true.  In this way, and  perhaps in that suggested by M.
Savart, the pavilion  is useful in  audition.   That gentleman is of
opinion, that the whole of the external  ear, the elasticity of which
he considers to be capable of slight modification by the action of
its proper muscles, is an apparatus for  repeating sonorous vibra-
tions, and transmitting them along its own parietes to the mem-
brane of the tympanum.  According to  this view, the different ine-
qualities of surface in the pavilion admit of explanation.   When a
membrane is stretched in a direction parallel to a sonorous surface,
the oscillations, impressed  upon it, are  mpst  marked ; and, accord-
ingly, as sounds impinge upon the pavilion from various quarters,
the inequalities of surface always admit of some being disposed in
the most favourable way for the reception of the vibrations.
   It is true, however, that the pavilion  is not essential to audi-
tion ; the hearing not  suffering by its removal for more than a few
days; so that its physiological influence is much more limited than
might be conceived.
   The meatus auditorius externus conducts the  sonorous vibra-
tions directly, and by reflection, to the  membrana tympani, as well
as by its parietes. It is probable,  too, that it  is useful in protecting
the membrane  from the direct action of the air and extraneous bo-
dies. This is perhaps the cause of its tortuous character in all ani-
mals.  If too tortuous, the sense of hearing becomes impaired; the
sonorous oscillations not being properly directed  towards the mem-
brane.   Baron Larrey has published  some cases  of deafness pro-
duced in this manner, which were removed by wearing an artificial
concha and  meatus, of the  natural curvature, made of gum elastic.
The down or hairs at the entrance of  the meatus, have also been
regarded as protecting agents against the intrusion of extraneous
bodies; whilst the  cerumen has been looked, upon as a  fit  mate-
rial for entrapping insects in the  slough  formed by  it,  c% for
destroying them by its poisonous influence.  It is probable, now- 
SENSE OF  HEARING.
127
ever, that the most important function of the cerumen is to keep
the lining membrane of the meatus in a physical condition, adapt-
ed for the proper fulfilment of its functions.
   Middle Ear.—In the mode  described, the vibrations of a so-
norous  body attain  the membrana tympani.  An experiment by
Savart would seem to show, that this membrane is thrown into
vibrations chiefly by the air contained in the meatus. He made a
small truncated cone of pasteboard, and closed the smaller  extre-
mity by a  tense membrane, nearly as  the  membrana tympani
closes the inner extremity of the meatus  auditorius; and he found,
that when sounds were produced near the parietes of the cone, the
membrane vibrated  but little; whilst, if they were occasioned op-
posite the base of the cone, so  that they could  be transmitted to
the  membrane  by the air within the canal, the vibrations were
very distinct, even at a distance of thirty yards  and upwards.
   The membrane of the tympanum then receives and repeats the
sonorous vibrations.   It has, however, been supposed  to be pos-
sessed of other functions.  Dumas, for example, conceived it to be
composed of numerous cords, and  each of these to correspond to
some particular tone.  But of  this arrangement we have not the
slightest evidence from observation or analogy.
   By others, it has  been  supposed, and with  every  probability,
that the membrane is capable of being rendered tense  or the con-
trary by the bent lever, formed by the chain of small bones.  They
have farther stated,  that this tension or relaxation is adapted to the
sounds,  which the membrane has to  transmit.
   The ancients believed, that the  adaptation was produced by the
stretching of the membrane, so as to put it in unison with the sound
produced.
   Independently, however, of the experiments of Savart, which
show, that unison is not necessary for the production of vibrations,
the fact, that we are capable of distinguishing several sounds at the
same time, would be sufficient to  negative the supposition.  Nor
can we easily conceive, that the membrane could admit of as many
distinct  vibrations as the ear  is capable of accurately appreciating
tones, wdiich amount to about eight octaves.
   Bichat thought,  that the  degree  of tension  of the  membrane
corresponded with the intensity of sounds; and that its effect was
to cause the sonorous vibration to  attain the internal ear, in a de-
gree sufficiently strong to excite the  appropriate impression; but
not so  strong as to cause pain,—the membrane becoming more
tense for a feeble sound, and relaxed for  one too strong.  In sup-
port of this  view, Bichat cites the  case of several persons, who
could not hear ordinary sounds, until the ear had been impressed
by louder, which, according to him,  roused the membrane to ten-
sion.
  Savart, on the other hand, from  the fact, that every membrane
vibrates with more difficulty, and  less extensively, according to its 
128
SENSIBILITY.
tension, conjectures that the membrane is relaxed in  the  case of
very feeble or agreeable sounds, and that it is rendered tense to
transmit the too powerful or the disagreeable.
   Again, it has  been conceived, that the tension varies with the
tone of the sound;  being augmented  according  to some physi-
ologists in the case of acute, according to  others in that of grave,
sounds.
   Sir Everard Home, it has been remarked, esteems the mem-
brana tympani to be muscular; and he affirms, that it is chiefly by
means of this muscle, that accurate perceptions of sound are made
by the internal organ ; and that by it the membrane can alter its
degree of tension. It has been already observed, that the muscles,
attached to the small bones, are capable of varying this tension;
that the internal muscle of the malleus or tensor tympani, for ex-
ample, by its contraction, renders it more tense.  Sir Everard
admits, " that the membrana tympani is relaxed by the muscles of
the malleus, but not for the purpose alleged in the commonly re-
ceived theory.   It is stretched in order to  bring the radiated
muscle of the membrane itself into a state capable of acting, and of
giving those different degrees of tension to the membrane, which
empower it to correspond with the variety of external tremors;
when the membrane is relaxed, the radiated muscle  cannot  act
with any effect, and external tremors  make  less accurate impres-
sions."
   The reader is referred to the remarks already made on the views
of Sir Everard in their anatomical relations.  His speculations do
not, however, end here. He employs the  discovery to account for
the difference between a musical ear, as it is  usually termed, and
one which is incapable of discriminating,  or feeling pleasure from,
the succession of musical tones:—with  what success we shall  in-
quire presently.
   The truth is, that none of the conjectures, which have been pro-
posed, regarding the precise effects of tension or relaxation of this
membrane, can be looked upon in any other light than as ingenious
speculations, based, generally, upon the fact, that the  membrane
seems certainly capable of being varied in its tension by the move-
ments of the chain of bones, but leading  us to  no certain know-
ledge of the precise effect on audition of such tension or relaxation.
   In fact, although the integrity of the membrana tympani is ne-
cessary for perfect hearing, its perforation or destruction does not
induce deafness.   We have numerous cases of perforation from ac-
cident and otherwise, related by Valsalva, Willis, Riolan and
others, in which the hearing continued;  and in certain cases of
deafness, to be referred to  presently, the membrane  is actually
punctured for the purpose of restoring the hearing.
  The communication of sonorous  oscillations from the membrana
tympani, across the cavity of the tympanum to the internal ear, is
effected in three different ways;  1, by the air contained in  the ca- 
SENSE OF  HEARING.
129
vity of the tympanum; 2dly, by the chain of bones to the membrane
of the foramen ovale; and 3dly, by the parietes of the tympanum.
So that if the membrana tympani should be punctured or destroyed,
the aerial undulations, caused by a sonorous body, and which enter
the meatus auditorius, may extend into the cavity of the tympanum
and excite corresponding oscillations in the membranes of the fo-
ramen ovale and foramen rotundum.
  The chorda tympani, composed, as we have seen, of a branch of
the fifth pair and of the portio dura of the seventh, and distributed
on  the interior surface of the membrana tympani—probably con-
veys no acoustic impression to the brain.  To it is owing the ex-
cessive pain, caused by the contact of an extraneous body with the
membrane, and that occasioned by a loud noise, or by compressing
the air forcibly in  the meatus by passing the finger suddenly and
strongly  into the concha.
  The uses of the mastoid cells, which communicate with the
middle ear, are not known.  It would seem, that the strength of
audition  is in a ratio with their  extent.  In no animals are  they
more ample than in birds, which are possessed of great delicacy of
hearing.   This effect may be induced either  by  their enlarging
the cavity of the tympanum, and allowing the sonorous oscilla-
tions to come in contact with a larger  surface; or  by the plates,
which compose them, being thrown into vibration.
   Sir Charles Bell, with more warmth than is judicious or cour-
teous, combats the  idea of the foramen  rotundum receiving the un-
dulations of air.  The oblique position of the membrane of the fo-
ramen with  regard  to the  membrana tympani satisfactorily, he
thinks, opposes this doctrine.   The function, which, with Savart,
he assigns to it—if not accurately, at least ingeniously—is the follow-
ing:—As the membrane of the foramen ovale receives the vibrations
from the chain of small bones, these vibrations circulate through the
intricate  windings  of the labyrinth and are again transmitted to the
air in the tympanum by the foramen rotundum.  The different ca-
vities of  the labyrinth, being filled with an incompressible fluid, no
such circulation, he insists, would occur, provided the parts  were
entirely  osseous.   As it is, the membrane of the foramen rotundum
gives way, " and this leads the course of the undulations of the
fluid in the labyrinth in a certain unchangeable direction."
   The explanation of Sir C. Bell is not as  convincing to us as  it
seems to  be to himself. The membrane of the foramen rotundum does
not appear to be required for the undulation in the cavities of the la-
byrinth,  which he describes, as the liquor of Cotunnius can readily
reflow into the aqueducts of  the vestibule and cochlea.   The  prin-
cipal use of these canals would seem, indeed, to be, to form diver-
ticula for the liquor, when it receives the aerial impulses.  Sir C.
Bell cites the case, often quoted from Riolan, of an individual,
who was deaf from birth, and who was restored to  hearing by ac-
cidentally rupturing the membrana tympani, and breaking the os-
  Vol.  I.                    17 
130
SENSIBILITY.
sides with an ear-pick—" disrupit tympanum, fregitque ossicula
et audivit"
   In these and other cases, in which the membrana tympani and
ossicles have been  destroyed, and the hearing has still persisted,
the vibrations must have been conveyed to the parietes of the in-
ternal  ear, through the air in the cavity of the tympanum, and,
notwithstanding the charge of  " absolute confusion of ideas" ad-
duced  against such individuals as Scarpa, Magendie, Adelon,
and others, who believe that the foramen rotundum receives  the
undulations of the air, we must  confess, that the idea of the com-
munication of vibrations through that medium, as well as  through
the membrane of the foramen ovale and the osseous parietes of the
labyrinth, appears to us most solid and satisfactory.
   The ossicles or small bones have  given occasion to  the  wildest
speculations.   At the present day, they are considered to fulfil one
of two functions; either to conduct the vibrations from the mem-
brana tympani, or to stretch the membranes to  which the extremi-
ties of the chain are attached.   Both these offices are probably exe-
cuted by them; the malleus receiving the vibrations from the mem-
brana tympani, conveying them to the incus,—the incus to the os
orbiculare,—the os orbiculare to the stapes, and the stapes to  the
membrane of the foramen ovale;  by which they are transmitted to
the liquor of Cotunnius.  Savart conceives, that the chain is to the
ear what the bridge is to the violin.   It has been already observed,
that the ossicles are not essential to hearing; although they may be
required to perfect it; and that they may be destroyed, without deaf-
ness being produced, provided the membrane of the foramen ovale
remains  entire, and the parts within the labyrinth retain their in-
tegrity.  If in the removal of the stapes by ulceration or otherwise,
the membrane of the foramen were  to  be ruptured, the liquor of
Cotunnius would of course escape and  incurable  deafness be the
result.
  The Eustachian tube is an important part of the auditory appa-
ratus, and an  invariable accompaniment to the membrana tympani,
in animals.   Without the tube, the membrane would, indeed, be
devoid of function.  Pathology shows us, in the clearest manner,
that its integrity is necessary to audition; and that deafness is the
consequence of its closure. Dr. Bostock thinks, " it is perhaps not
very easy to ascertain in what mode it acts, but it may be concluded
that the proper vibration of the membrana tympani is, in some way,
connected with the state of the air in the tube."
  The name of the cavity to which the tube forms a communication
with the external air, might have  suggested an easy and sufficient
explanation of  its  use.  The drum of the ear, like every other
drum, requires an aperture in some part of its parietes, in order
that its membranes may vibrate.   The Eustachian tube serves this
purpose; and its closure produces the same  effect -upon the mem-
brana tympani at one end of the cylinder, and on the membrane of 
SENSE OF  HEARING.
131
the foramen ovale at the other, as would be produced on the parch-
ments of the ordinary drum by the closure of its lateral aperture.
We can, in this way, account for the temporary deafness, which ac-
companies severe cases of inflammation of the throat,—the swelling
obstructing the Eustachian tube.
   During the constant efforts of deglutition the air is  renewed in
the cavity of the tympanum ; and as the extremities of the Eusta-
chian tube terminate in the pharynx, it always enters at a subdued
temperature.
   By closing the nose and mouth, and forcing air from the lungs,
we can  feel a sensation of fulness in the ear, produced by  the pres-
sure of  the air against the internal  surface of the membrana tym-
pani; and they, who have the  membrane perforated, can  send to-
bacco smoke copiously out of the external ear.
   Besides this necessary function, the Eustachian tube has been
supposed to possess another—that of serving as  a second meatus
auditorius, by permitting sonorous  vibrations to enter through the
pharyngeal extremity;  and, in this  way, to attain the internal
ear.  A simple experiment, first  described  by  Perolle,  exhi-
bits the fallacy  of this  notion.  If we carry a watch  far back
into the mouth, taking care not to touch the teeth,  little or  no
sound will be heard; but if we draw the watch  forward, so  as to
touch the teeth, the  ticking becomes distinctly  audible. If  the
pharyngeal extremity acted as a second meatus, the sound ought
to  be heard  better when the  watch  is placed nearer to it;  but
this is  not the  case.   On  the  contrary, it is  not until the  sono-
rous body is put  in contact with the teeth, that the  sound is ap-
preciated.  This is effected by  the  vibrations of  the watch  being
conveyed along the bony  parietes  until they reach the  auditory
nerve.
   Again, if the meatus auditorius externus be completely closed,
we cannot hear the voice of one who speaks into the  mouth;  and
can  hear but imperfectly our  own.   The  fact of our gaping,
when desirous of hearing accurately, has partly led to the belief,
that the Eustachian tube acts as a second meatus.  It has  been pro-
perly remarked, however, that  this  may be merely an act of  ex-
pression; and, also, that  the meatus auditorius is rendered  more
open, when  we  depress the lower jaw, than when it  is raised, as
can be readily perceived by inserting the little finger into the mea-
tus,' when the jaw is in either situation.
   In addition to these functions, it  is probable, that the Eustachian
tube acts as a diverticulum for the air in the cavity of the tympa-
num, when it is agitated by too powerful sounds.
   Internal ear.—In the  various ways mentioned, the vibrations of
a sonorous body  reach  the  internal ear.  The membranes of  the
foramen ovale and foramen rotundum resemble the membrana tym-
pani in their physical characteristics; and, when thrown into vibra-
tion, communicate the impression to the liquor of Cotunnius, which 
132
SENSIBILITY.
 fills the cavities of the internal ear.  By this medium the vibrations
 are conducted to  the  auditory  nerve, which  conveys  the impres-
 sion to the brain.
   The views, entertained regarding the sympathetic vibrations of
 the membrana tympani, have almost all been applied to the mem-
 brane of the foramen ovale:  our knowledge, however, is restricted
 to the fact, that its  tension  can be  varied  by the chain of bones,
 without our being able to  specify the circumstances under which
 this takes place. Adelon asserts, that the membrane may be torn,
 and yet the sense of hearing not be destroyed. This seems scarcely
 possible, as the liquor of Cotunnius  must necessarily escape, and so
 much morbid action be induced  as to render audition apparently
 impracticable.
  The membrane of the foramen rotundum, which forms the me-
 dium of communication between the cavity of the tympanum and the
 cochlea, has, of course, no  chain of bones to modify its tension.
Both the vibrations into which  it is thrown, and those of the vesti-
bular membrane,  are imparted,  as we  have seen, to  the liquor of
 Cotunnius, which fills all the different cavities of the labyrinth, is
present in every ear, and appears essential  to audition.
  Of the precise  uses of the vestibule, semicircular canals, and
cochlea, we have  very limited notions.  The beauty and  complexity
of their arrangement, has, however, given  rise to various conjec-
tures. Lecat considered the lamina spiralis to consist of numerous
minute cords, stretched along it,and capable of responding to every
tone. Magendie affirms, that no one at the present day admits the
hypothesis regarding the use of this osseo-membranous  septum; but
 he is in error. Sir C. Bell asserts, that the cochlea is the most im-
 portant part of  the organ of hearing;  or rather, that it is " the re-
 fined and higher  part of the apparatus;" and he considers  the la-
 mina spiralis the  only part adapted to the curious and admirable
 powers of the human ear, for  the  enjoyment  of melody  and
 harmony.
  The subject of the musical ear will  engage us presently. It may
 be sufficient to  remark, in this place, that there is no ratio, in ani-
 mals, between the delicacy of the hearing, and the degree of  com-
 plication of the cochlea.  The cochlea of the Guinea pig is more
 convoluted than that of man, yet we can hardly conceive it to have
 abetter appreciation of musical tones; whilst in birds, whose hear-
 ing is unquestionably delicate, the organ is, as we have remarked,
 extremely simple, and has no spiral arrangement.
   Again,  the semicircular  canals  have been compared  to organ
 pipes, adapted  for producing numerous tones; and Dr. Young sup-
 posed them to be " very capable of assisting in the estimation of the
 acuteness or pitch of a sound, by receiving its impression at their
 opposite ends; and occasioning a recurrence of similar effects at dif-
 ferent points of their length, according to the different  character of
 the sound; while the greater or less pressure of the stapes must 
SENSE OF HEARING.
133
serve to moderate the tension  of the fluid within  the  vestibule,
which serves to convey the impression." •'* The cochlea," he adds,
" seems to be pretty evidently a micrometer of sound."  All these
are mere hypotheses;—ingenious, it  is true, but still  hypotheses:
and, in candour, we must admit, that  we have  no positive  know-
ledge of the precise functions of either vestibule, cochlea, or semi-
circular canals. Our acquaintance with them is limited to  this ; that
they contain the final expansions of the auditory nerve; and that it
is, within them, that this nerve receives  its impressions from the
oscillations of sonorous bodies.
   It has been  observed, that  these vibrations may reach  the nerve
by the bony parietes; and that the ticking of a watch, held between
the teeth, is, in this way, heard.  A blow  upon the head  is dis-
tinctly audible;  and Ingrassias relates the case of a person, who
had become deaf in consequence of obstruction  of the meatus audi-
torius externus, and yet could hear the sound of a guitar, by placing
the handle between his teeth, or by making a  communication be-
tween his teeth and the instrument by a metallic or other rod. The
physician has recourse to a plan of this kind for detecting whether
a case of deafness be dependent upon  obstructed Eustachian tube;
on some affection of the meatus auditorius externus; or on insensi-
bility of the auditory nerve, or of the  part of the brain that effects
the sensation.   If the latter be the case, the ticking of a watch, ap-
plied to the teeth, will not be audible; and the case will necessarily
be one of a hopeless character.   If, on the other hand, the sound be
perceived, the attention of the physician will be directed, with well
founded expectations of success, to the physical parts of the organ,
or to those concerned in the transmission of vibrations. Frequently
it will happen, in such cases, that the  Eustachian  tube is  impervi-
ous; and properly directed efforts may succeed  in removing the ob-
struction; or, if this be impracticable,  temporary, if not permanent,
relief may be obtained by puncturing the membrana tympani, and
allowing the aerial undulations, in  this way, to reach the middle
and internal ear.
   Lastly, as regards the precise nerve of hearing. In this sense we
have  the distinction, between the nerve of general, and that of spe-
cial sensibility, more clearly observed.  The experiments of Ma-
gendie have shown, that the portio mollis of the seventh  pair is
the nerve  of  special sensibility;—that it may be cut, pricked, or
torn,  without exhibiting any general sensibility; and  that it is in-
servient only to the sense of hearing.   The  same experiments de-
monstrate, that this nerve cannot act,  unless the fifth pair, or nerve
of general sensibility, be in a state of  integrity.   If the latter nerve
be divided within the cranium, the hearing is always enfeebled,
and frequently destroyed.
  The immediate function of the sense of hearing is to appreciate
sound; and we may apply to it what has been said  of  the other
senses, that, in this  respect,  it cannot be supplied  by any other 
134                      SENSIBILITY.

sense:—that it is instinctive, requires no education, and- is exerted
as soon as the parts have attained the necessary degree of develop-
ment.
  Amongst the advantages afforded by the possession of this sense,
which has been properly termed intellectual, are two of the highest
gratifications  we enjoy; the  appreciation of  music, and  the plea-
sures of conversation.  It is to this  sense that we are indirectly
indebted for the use of verbal language—the happiest of all inven-
tions—as it has been properly termed, and to  which we shall have
to advert in the course of our inquiry into the animal functions.
  Metaphysicians  and physiologists have differed considerably  in
their views regarding the  organs, more immediately concerned  in
the appreciations in question.  Many, for example, have  referred
the faculty of music to the ear; and hence, in common language,
we speak of an individual, who has a "musical ear" or the con-
trary.   Others, more philosophically we think, have  considered,
that the faculty is seated in the encephalon: that the ear is merely
the instrument for  conveying the  sonorous undulations; which, in
due  order, constitute  melody; but that  the  appreciation is ulti-
mately effected in the brain.   " That it,"  (the power of distinguish-
ing  the  musical relations of sounds,) says Dr.  Brown, " depends
chiefly or perhaps  entirely, on  the structure  or state  of the mere
corporeal organ of hearing, which  is  of a  kind, it must be remem-
bered, peculiarly  complicated,  and therefore susceptible  of great
original diversity in the parts, and relations of the parts that form
it, is very probable;  though  the  difference  of  the separate parts
themselves, or of their relations to  each other  may, to  the mere
eye, be  so minute, as never  to  be discovered by dissection."
Many physiologists  of  eminence have  regarded  the complex
internal ear as the  seat of the faculty; some  looking to  the coch-
lea;  others to the  semicircular canals, but few of them referring
it to the brain.  Sir C. Bell, indeed, asserts, that " we are not
perhaps warranted in concluding, that any one part  of the organ of
hearing bestows the pleasures of melody and harmony, since the
musical ear, though so termed,  is rather a faculty depending on the
mind."   Yet afterwards he adds—" we think that  we find  in the
lamina spiralis (of  the cochlea) the only part adapted to the curious
and  admirable powers of the  human  ear,  for the enjoyment of me-
lody and harmony..  It is  in vain to say, that these capacities are in
the mind and not in the outward organ.   It is true, the capacity for
enjoyment or genius for music  is in the mind.  All  we contend for
is, that  those curious varieties of sound, which constitute the source
of this enjoyment, are communicated through the ear, and that the
ear has  mechanical provisions for every  change of sensation."
   A cherished opinion of Sir Everard Home on this subject has
been referred to.    Conceiving the membrane of the tympanum to
be muscular, he considers the membrana tympani, with its  tensor
and radiated muscles, to  resemble a monochord, " of which the 
SENSE of hearing.
135
 membrana tympani is the string; the tensor  muscle the screw,
 giving the necessary tension, to make the string perform its proper
 scale of vibrations ; and the radiated muscle acting upon the mem-
 brane, like the moveable bridge of the monochord, adjusting it to
 the vibrations required to be produced;" and he adds, "the differ-
 ence between a musical ear and one which is too imperfect to  dis-
 tinguish the different notes in music, will appear to arise  entirely
 from the greater or less nicety with which the muscle of the mal-
 leus renders the membrane capable of being truly adjusted.  If the
 tension be perfect, all the variations produced by the action of  the
 radiated muscle will be equally correct, and the ear truly musical."
   In this view, as unsatisfactory in its basis as it is in some of  the
 details, Sir Everard completely excludes, from all participation in
 the function, the internal ear, to which the attention of physiologists,
 who consider  the faculty to be seated in the ear, has been almost
 exclusively directed.
   A single case, detailed by Sir Astley Cooper in the Transactions
 of the Royal Society for 1800'and  1801, prostrates the whole of the
 ingenious fabric, erected  by Sir Everard.  Allusion has already
 been made to the old established  fact, that the  membrane of  the
 tympanum may be destroyed without loss of hearing  necessarily
 following.  Sir Astley was consulted by  a gentleman, who  had
 been attacked, at the age  of ten years, with an inflammation  and
 suppuration in his left ear, which continued discharging matter for
 several weeks.  In the space of about twelve months after the first
 attack, symptoms of a similar kind took place in the right ear, from
 which matter issued for a considerable time.   The discharge, in
 each instance, was thin, and extremely offensive; and in  it, bones
 or pieces of bones were observable.   In consequence of  these at-
 tacks he became deaf, and remained so for three months. The hear-
 ing then began to return;  and in about ten months from the last at-
 tack, he was restored to the state he was in when the case was pub-
 lished.  Having filled his mouth with air, he closed his nostrils and
 contracted the cheeks; the air, thus compressed, was heard to rush
 through the meatus auditorius with a whistling noise, and the hair,
 hanging from the temples, became agitated by  the current of  air,
 that  issued from the ear.   When  a candle was applied, the flame
 was agitated in a similar manner.   Sir Ashley  passed a probe into
 each ear, and thought the membrane of the left side was totally de-
 stroyed, as the probe struck against the petrous portion of the tem-
 poral bone.   The space, usually occupied by the membrana tym-
 pani, was found to be an  aperture without one trace of membrane
 remaining.  On the right side, also, a probe could be passed into
 the cavity of the  tympanum; but, on  this side, some remains of
 the circumference  of the  membrane could be discovered, with a  cir-
 cular opening in the centre, about a quarter of an inch in diameter.
 Yet this gentleman was not only capable of hearing every thing that
was said in company, but  was nicely susceptible to musical tones; 
136
sensibility.
" he played well on the flute, and had frequently borne a part in a
concert;  and he sung with much taste and perfectly in tune."
  Independently of these partial objections, the views, that assign
musical ear and acquired language to the auditory apparatus, appear
liable to others that are insuperable.
  The man who  is totally devoid of musical  ear, hears the sound
distinctly.  His sense of hearing may be as acute as that of the best
musician.  It is his appreciation that is defective.  He  hears the
sound, but is incapable of communicating it to others.  The  organ
of appreciation is in this, as in every other sense,—the brain.  The
physical  part of the organ may modify the  impression, which has
to be made upon the nerve of  sense:—the latter  is compelled to
transmit the  impression as it  receives it; and  it is not until the
brain has acted, that perception takes place, or that any idea of the
physical  cause of the impression is excited in the mind.    If, from
faulty organization, such idea is not formed in the case of musical
tones, the individual is said not to possess a musical  ear.   But  the
fault lies in his cerebral  conformation.   We do  not  observe  the
slightest  relation between musical talent and delicacy of hearing.
The best  musicians  have not  necessarily the most delicate sense,
and, for the reasons already assigned, it will be  manifest, why the
idiot, whose hearing may be acute, is incapable  of singing, as well
as of speaking.  Again, we  do not  see the  least ratio in animals
between  the power and character of their music, and the condition
of their auditory sense.  We are compelled then to admit, that the
faculties  of music and speech are dependent upon  the organization
of the brain ;  that they require the ear  as a secondary instrument;
but that  their degree of perfection is by no  means in proportion
to the delicacy of the sense of  hearing.  In these opinions, Gall,
Broussais, Adelon, and other distinguished physiologists, concur.
" Speech," says Broussais, " is heard and repeated by all men, who
are not deprived of the auditory sense, because they are all endowed
with a cerebral organization, fit to procure for them distinct ideas
on that subject. Music, when viewed as  a mere  noise, is  also heard
by every one;  but it furnishes  ideas,  sufficiently clear to be repro-
duced and communicated by those individuals only, whose frames
are organized in a manner adapted to this kind of sensation."
  Yet, although we must regard the musical faculty to be intellec-
tual, and consequently elevated in the scale, it is hardly necessary
to say that its deficiency is no evidence  of that  mental and moral
degradation, which has been depicted by poets  and others;—as in
the well  known anathema of Shakespeare:—

             " The man that hath  no music in himself,
             Nor is not mov'd with concord of sweet sounds,
             Is fit for treasons, stratagems and spoils;
             The motions of his spirit are dull as night,
             And his affections dark as Erebus:
             Let no such man be trusted." 
SENSE  OF HEARING.
137
  Or in that of Beattie :—

        " Is there a heart that music cannot melt ?   ,
        Alas! how is that rugged heart forlorn;
        Is there, who ne'er those mystic transports felt
        Of solitude and melancholy born!
        He needs not woo the muse; he is her scorn.
        The sophist's rope of cobweb he shall twine;
        Mope o'er the schoolman's peevish page; or mourn,
        And delve for life in mammon's dirty mine;
        Sneak with the scoundrel fox, or grunt with glutton swine."

   In the classification of the objects of human knowledge, music
has  been  ranked  with poetry; but we meet with  striking evi-
dences  of their wide  separation.   Whilst  the professed musician
is frequently devoid of all poetical talent,  many excellent poets
have no musical ear. Nor does the power of discriminating musical
tones indicate that the  possessor is  favoured with  the finer sensi-
bilities of the mind;  nor the want of it prove their deficiency. It has
been a common remark, that, amongst professed  musicians, the in-
tellectual manifestations have been singularly and generally feeble;
—a  result partly occasioned by their attention  having been almost
entirely engrossed from childhood  by their favourite pursuit; but
not perhaps to be wholly explained by this circumstance; and whilst
we find them often unmarked  by  any of  the kindlier sympathies,
we see those, that are " not mov'd with concord of sweet sounds,"
alike distinguished as philosophers and  philanthropists.
   The defect, in these cases, differs probably in  an essential man-
ner, from one to which attention  has been  drawn by the late Dr.
Wollaston, in the Philosophical Transactions, for  1S20.  In
that communication he describes  many  curious facts,  regarding,
what he terms, a peculiarity in certain  ears; which seem to have
no defect in the general capacity of receiving sound, or  in the per-
ception of musical tones,  but  are  insensible to very acute  sounds.
This insensibility commences  when the vibrations have attained a
certain degree of rapidity, beyond which all sounds are inaudible to
ears thus constituted. Thus, according to Wollaston, certain per-
sons cannot hear the chirp of the grasshopper; others the cry of the
bat; and he refers  to one case in which the note of the sparrow was
not audible. Dr. Wollaston himself, was incapable of hearing any
sound  higher than six octaves above  the  middle E in the piano
forte.
   The defect in these cases would probably be referable to the phy-
sical part of the ear, rather than  to the auditory  nerve, or to the
part of the brain concerned in the appreciation of sounds:—the vi-
brations, that are performed with great rapidity, not being respond-
ed to by the parts of the organ destined for this purpose; and, con-
sequently, never reaching the auditory nerve.  Recent  researches
however, of Savart—one of the most dexterous and ingenious ex-
perimenters of the day—seem to show,  that the defective apprecia-
  Vol.  I.                      18                        V 
138
sensibility.
tion of acute sounds, in such cases, is not owing to their acuteness,
but to their feeble degree of intensity; that, if the sound can be
made sufficiently intense, the ear is capable of hearing a note of up-
wards  of forty thousand simple oscillations  in a second; and  that
the cases, referred to by Wollaston, are, consequently, owing to
defective hearing, rather than to insensibility to very acute sounds.
   Another acquired  perception of the ear, is that of forming a
judgment of the distance of bodies.  This  we do by attending to
the loudness of the  sound; for we  instinctively lay it down  as a
principle, that a loud sound proceeds from  a body  that is near us,
and a feeble sound from one more remote. This is the cause of nu-
merous acoustic errors,  in spite of reason and experience.  In the
theatres, the deception is often well managed, when  the object is to
give the idea of bodies approaching.   The sound—that of martial
music, for example—is rendered  faint and subdued; and, under
such circumstances, appears to proceed from the remote distance;
whilst by adding gradually and skilfully to its  intensity, we are
irresistibly led to the belief, that the  army is approaching;  and the
illusion is completed by the appearance  of the military band on the
stage, allowing its soul-inspiring strains to vibrate freely in the air.
In like manner we are deceived by the ventriloquist.   He is aware
of the law, that guides  us, in our estimation of distance, and by
skilfully modifying the intensity of his voice, according as he wishes
to make  the sound appear to proceed from a near or distant object,
he irresistibly leads us into an acoustic error.
   It requires education or experience to enable us to appreciate dis-
tances accurately by this sense, as well as to judge of their position.
In the case, detailed by Magendie in his Journal de Physiologic
for 1825,—of a boy, who after having been  entirely deaf until the
age of nine, was restored to hearing by M. Deleau, by means of in-
jections thrown  into the cavity of the tympanum through the pha-
ryngeal extremity of the Eustachian tube—one of the most remark-
able points was, his difficulty in acquiring a  knowledge  of  the po-
sition of sonorous bodies.
   In forming our judgment on this subject we  require  the use of
both ears.  In all other cases an impression  made upon  one only
would perhaps be sufficient.  To judge of the direction of a sound
we compare the intensity of the impression  on  each ear, and form
our deductions accordingly; and experiment shows, that if we close
one ear we are led into errors, which  are  speedily dissipated by
employing both.  Still we  are often deceived even under these last
circumstances, and are compelled to  call in the aid  of sight.   The
blind afford us striking examples of accuracy, in  this respect, in
their acquired perceptions  of  the  ear.  In the Belisar of  Zeune,
the case of a blind man is cited from Diderot; who, guided by the
direction of his  voice, struck his brother, in a quarrel, on the fore-
head, with a missile, which brought  him to  the ground.  If the so-
norous vibrations before reaching the ear are deflected  from their 
SENSE OF HEARING.
139
course, we are liable to deception, mistaking the echo often for the
direct or radiant sound.
  The fdeas of magnitude, acquired by the ear, are few, and to a
trifling extent only.  They occasionally enable the blind to judge
of the size of apartments, and this they are sometimes  able to  do
with much accuracy.  It is well known, that if a sound  be confined
within a small space, it appears much louder than when the sono-
rous undulations can extend farther; hence the greater noise, caused
directly by a pistol fired in a room than in the open air.  The sound in-
directly produced will necessarily be modified by the different  re-
flections or echoes, that may be excited. Hy attending to these cir-
cumstances—to the loudness of the voice and to the intensity of the
reverberations occasioned by the walls, and by calling into their aid
the experience they have had under similar circumstances;—in other
words, by effecting a strictly intellectual process, the blind attain
the knowledge in question.
  The velocity of a body is indicated by the rapid succession of the
vibrations, that impress the ear, as well as by the change in their in-
tensity if the body be moving along a surface or through the air. A
carriage, approaching us with great velocity, is detected by the ear,
from the rapidity with which the wheels strike against  intervening
obstacles; and by the gradual augmentation in the intensity of  the
sound thus produced. When opposite to us the intensity is greatest;
and a declension gradually takes place until the sound is ultimately
lost in the distance.
  Lastly, by audition we can form some judgment of the nature of
bodies,  from the difference in the  sounds emitted.   It has been
already remarked, that the timbre, or  quality  of sound, can be
accurately appreciated.   By this quality we can distinguish  be-
tween the sound of wood or of metal; of hollow or solid bodies, &c.
But in all these cases we are compelled to call in aid our  experi-
ence, without which we should be completely at a loss; and to exe-
cute a very rapid, but often a very complicated, intellectual opera-
tion.
   To conclude:—audition  may  be  exercised passively as  well as
actively; hence  the difference  between simply hearing and listen-
ing.  We cannot appreciate, in  man, the precise effects produced
on  the different  portions of the ear by volition; whether, for  ex-
ample, the advantage be limited to the  better direction  given to the
ear, as regards the sonorous body; and  to the avoiding  of  all  dis-
traction, by confining the attention entirely to the impressions made
on  this sense; or whether, by it, the pavilion may not be made
somewhat more  tense by the contraction of its intrinsic and extrin-
sic  muscles:—the membrana tympani,  and the membranes of  the
foramen ovale by the contraction of the muscles  of the  ossicles; or,
in fine, the auditory nerve be rendered better adapted for the recep-
tion of the impression; and the brain for its appreciation. All these
points are insusceptible of direct observation  and experiment, and 
140
SENSIBILITY.
are, therefore, enveloped in uncertainty.   In some animals, as the
horse, the  outer  ear  becomes  an acoustic  instrument under the
guidance of volition; and is capable of being turned in every direc-
tion in which a sonorous body may be placed.
   Like the other senses—that of hearing is largely improved by
education or cultivation.  The savage, who  is accustomed, in the
stillness of the forest, to listen to the approach of his enemies  or of
his prey, has the sense  so delicate as to hear sounds, that are inaudi-
ble to one  brought up in the din of the busy world.
   The blind, for the reasons more  than once assigned, afford ex-
amples of extreme delicacy of this as well as of their other remain-
ing senses.  They are necessarily compelled to cultivate it more;
and, lastly, the musician, by education, attains the perception of the
nicest shades of musical tones:  the  aptitude is laid in  cerebral or-
ganization ; and is developed by the education of the instrument—
the ear, as well  as of the encephalic or intellectual organ ;  without
which, as we have seen, no such appreciation could be accomplished.

        Sect. V.—of  the sense  of sight, or vision.

   The immediate function of the sense  of  sight is to give us the
notion of light and colours.  Like the other senses, it is a modifica-
tion of that of touch ; whether we regard the special irritant—light
—as an emanation from luminous bodies; or as  the vibration of a
subtle, ethereal fluid,  pervading all space.  Under the latter theory
it would most strongly  resemble the sense last considered.
   The pleasures and advantages, derived by the mind through this
inlet, are of so signal  a  kind as  to render the organ of vision a sub-
ject of universal interest. Every one, who lays the slightest claims
to a general education, has made  it more  or less the subject of
study; and is frequently better  acquainted with its structure and
properties  than the medical practitioner.  Complicated as its organi-
zation may seem, it is,  in action, characterized by extreme simpli-
city; yet,  " in its simplicity,"  as Arnott has remarked, " so per-
fect, so unspeakably perfect, that the searchers  after  tangible evi-
dences of an all-wise and good Creator, have declared their willing-
ness to be limited to it alone in the midst of millions, as their one
triumphant proof."
   Into this structure  we shall inquire so far as is necessary for our
purpose; after having described the general properties of light; and
then detail the mode in which its various functions are effected, and
the knowledge derived  by the mind through its agency.
   The eye is the organ of vision.  It varies materially in different
animals: in some consisting of a simple capsule,  with  the  final ex-
pansion of the  nerve of sight distributed on its interior, and  com-
municating externally by means of a transparent cornea, which ad-
mits the light. It is in this simple state, that M. de Blainville assi-
milates it to a bulb  of hair, modified for the new function it has to 
SENSE OF SIGHT.                    HI
perform.  In man, and in the upper classes of animals, the organ is
much more  complicated in its structure; and in it we have a still
clearer example of the distinction between  the  physical and ner-
vous or vital part of the apparatus, than in any of the other organs
of sense;  the former consisting of transparent tunics, and humours,
which modify the light according to the laws of  optics:  the  latter
being a production or expansion  of the nervous system, for the re-
ception of the impression of light, and for conveying such  impres-
sion to the proper part of the  encephalon.  There are, besides, at-
tached to  the organ a number of accessary parts or tutamina, which
are more or less concerned in the proper performance of the func-
tion.  It will be necessary, therefore, to give a succinct view, not
only of the eye, properly so called, but also of these  accessary or-
gans, which  serve to lodge, move, protect, and lubricate it.  The de-
scription will not,  however, be  clearly   understood, without pre-
mising some general observations on the properties  of light, espe-
cially as regards its refraction,  on which the  phenomena of vision
are greatly dependant.

                           Of Light.

   The sun and the fixed stars  are the great sources of light.   It is
given off also from  substances  in  a state of  combustion, and  from
phosphorescent bodies; and, by entering the eye directly or after
various reflections or refractions, impinges on the optic nerve and
gives the sensation of light.
   Two  great opinions have been entertained regarding  the nature
of light; the one, propounded  by Newton,—that it consists of ex-
tremely minute particles,  emanating from  luminous bodies; the
other,—that of Descartes, Hook, Huygens,  Euler, and  others,
that it is a subtle, eminently elastic fluid—an ether—pervading  all
space; the elastic molecules of which, when put in motion by the
internal oscillations of bodies, impress the eye as sonorous vibra-
tions affect the ear. It is not for us to discuss this question of higher
physics.   We may merely remark, that  difficulties attend both hy-
potheses.  According to that of  Descartes, it is not easy to ex-
plain, why an opaque body should prevent  the  undulations  from
reaching the eye; or the change  of direction, which the light expe-
riences  in passing from one medium into another; whilst, accord-
ing to that of Newton, it is difficult to conceive, how a luminous
body, as the sun, can shed its immense torrents of light incessantly,
without undergoing rapid diminution; and how, with the extreme
velocity of light these particles should not be possessed of sensible
momentum; for it has been found, that a large sunbeam, collected
by a burning-glass, and thrown upon the scale  of a balance, of ex-
treme delicacy, has been insufficient to disturb the equilibrium. To
the hypothesis of Newton it has also been objected, that the par-
ticles, being reflected by thousands of bodies, and in innumerable di- 
142                       SENSIBILITY.

rections, would  necessarily jostle and interfere greatly with each
other.   This objection is not, however, as valid as it appears at first
sight.   It will be seen hereafter, that the impression of a luminous
object remains upon the retina for the sixth part of a second.  Ad-
mitting it, however, to impress the eye  for the -j^th part, three
hundred particles, per second, would be  sufficient to  excite a con-
stant and uniform sensation of the presence  of light;  and since, as
we shall find, it  traverses sixty-seven thousand leagues in a second
of time, if we divide this by three hundred, we shall  find a  space
of six hundred and seventy miles between each particle; a distance
equal to that—in a straight line—between New York and Savannah;
and if we suppose six particles to be sufficient  per second, each will
be separated from the other by a space of thirty-three thousand five
hundred miles!
  Without deciding in favour of either of the great theories, that of
Newton admits of more easy application to our subject, and will,
therefore, be employed in the various explanations that may be re-
quired.
  The light, then, proceeding from a luminous body, impinges on
the substances, that are within its sphere; and these, by reflecting
the whole or a part of it to the eye, become visible to us.
  In its course, direct or reflected, its velocity is almost inconceiv-
able.  From observations made on the eclipses of Jupiter's  satel-
lites, by Ro3mer, Cassini, and other astronomers, it has  been cal-
culated, that the light of the sun  is eight  minutes and  thirteen  se-
conds in its passage from that luminary to the earth.   The distance
between the earth and sun  is thirty-three millions of leagues, so that
the velocity of light is sixty-seven thousand leagues, or two hundred
thousand miles per second;  in other words, in the lapse of a single
second,  it could pass between Washington and Albany—supposing
the distance to be three hundred miles—seven hundred times; and
could make the tour of the globe in  the time it takes us to wink.
In consequence of this extreme velocity, in all calculations, regard-
ing the light from bodies on the surface of the  globe, it is presumed
to reach the eye instantaneously; for, granting  that a luminous body
at Albany could be seen at Washington, the light from it  would
reach the eye in the T£7th part of a second.
  A series of particles succeeding each other  in a straight  line is
called a ray of light.   The light, however, which proceeds from a
radiant point, forms diverging cones, which would be prolonged in-
definitely did they not meet with obstacles.
  In its course, it loses its intensity according to a law, which seems
applicable to all  influences radiating  from a centre.   If a  taper be
placed in the middle of a box, each of whose sides is a foot square,
all the light must impinge upon the sides of the box. If, afterwards,
it be placed in a box whose sides are two feet  square, the light will
shine upon them from double the distance, but it will be distributed
over four times the surface. The intensity of the light, then, in this 
SENSE OF SIGHT.
143
case, as in every other, diminishes according to the square of the
distance from the luminous body.   According to this  rule, those
planets, which  are nearer to the sun than we are, must receive the
light and also the heat—for the same law applies  to  caloric—in
much greater intensity;  whilst the more distant luminaries can re-
ceive but  little caloric,  or light, in comparison  with  our earth;
hence, perhaps, the necessity of the satellites by which  they are ac-
companied, and by  whose agency the light of the sun is reflected to
the planet, and the  deficiency, in some measure compensated.
   In proceeding from a luminous body, the rays, cones, or pencils
of light must traverse intermediate bodies, in order to reach the eye.
These bodies are called media.  Air is the common medium; and
when, in this way, the light has reached the exterior of the organ,
the farther transmission is effected through different transparent hu-
mours, which consequently form so many media.
   In its course  through the different media,  the light  may remain
unmodified:—may proceed in the same straight line; or it may
meet with an obstacle, which arrests it altogether or reflects it; or,
again, it may traverse media of different natures and densities, and
be made to deviate from  its original course or be refracted.
   When a ray  of light falls upon an opaque body, as upon a bright
metallic or other mirror, the  light is reflected  from the mirror,
in  such a  manner, that the  angle,  made by  the incident ray,
with a  perpendicular to the surface of the  medium at the point
of incidence, is exactly equal  to that made by  the reflected ray
with the same perpendicular.
   Suppose IJ,(Fig.
19.) to  represent a
plate of polished me-
tal, or of glass, ren-
dered opaque by a  s
metal spread upon
its posterior surface,
as in the  common
looking-glass.  The
rays,    proceeding
from an observer at
K, will be reflected
back to him  in the
same line KC; that I
is, in a line perpen-
dicular  to  C,  the
point  of incidence.
The observer will,
therefore,   see  his
own image; but, for
reasons  to be hereafter mentioned,  under the head of optical illu-
sions, he will seem to be as far behind the mirror as he really is he-
Fig. 19.
 
144
SENSIBILITY.
fore it or at E.   Suppose, on the other hand, that the observer is
at A, and that a luminous body is placed at B; in order that the
rays, proceeding from it, shall impinge upon the eye at A, it is
necessary that the latter be directed to that point of the mirror,
from which a line, drawn to the eye, and  another  to  the  object,
will form equal angles with the perpendicular; in other words, the
angle A C K, or angle of incidence, must be equal to the  angle
of reflection, B C K.  In this case, again, the object will not ap-
pear to be  at B, but  in the prolongation of the line A C, at H, as
far from the point of incidence, C, as B is.
   Except in the case of illusions, the study of  the  reflection of
light or catoptrics, does not concern vision materially.  It is  on
the principles of dioptrics, that the chief modifications are effected
in the progress of the light through the physical part of the organ;
and without some knowledge of these principles the subject would
be totally  unintelligible.   It  is  necessary, therefore, to  dwell at
some length on this  topic.
   Whenever a ray of light passes through diaphanous or trans-
parent bodies of different densities, it  is bent or  made to deviate
from its course;  and such deviation is called refraction; the ray
is said to be refracted; and, owing to  its being susceptible of such
refraction, is held to be refrangible.   The point at which a ray
of light enters a medium, is called  the point  of  immersion;  and
that by which it issues from such medium—the point of emer-
gence.   Instead  of  considering the medium I  J  opaque,  let us
regard  it  as transparent.   C, in  this case,  will be the point of
immersion for the  incident rays that meet there;  and L and F
will be the points of emergence for the rays K  E and A C F G,
respectively.   If a ray of light, as K  C, falls perpendicularly  on
the surface of any medium, it continues its  course  through the
medium without experiencing any modification, and emerges in the
same straight line.  Hence, a body  at L, will appear in its true di-
rection and distance  to an observer at  K, looking directly down-
wards on a pool of water,  I J.  If, on the  other hand, a ray of
light, as A C, after having passed through air, falls obliquely upon
the surface of the water at C; by entering  a  medium of different
density, it is deflected from its course; and, instead of proceeding
in the diretion  C H, it is refracted, at the point of immersion, in
the direction C F,—that is, towards the perpendicular K E.  If,
again, the  ray emerges at F into a medium of the same density as
that through which it passed in the course A C, it will proceed in
a line parallel to A C, or in the direction F G, or it  will wander
from the perpendicular.  The cause of  this difference in the de-
flections, produced by different media, is not easy of explanation.
The fact, alone, is known to us, that bodies refract light differently
according to their densities and nature. If the light proceeds from
a rarer to a denser medium it is attracted or refracted towards the
perpendicular; if, on the contrary, it  passes from a denser to a 
SENSE OF  SIGHT.
145
 rarer medium, it is refracted from the perpendicular.  The ray
 AC passed from a rarer medium,—the air,—into a denser, I J—
 water; it was refracted in the direction C F, towards the perpendi-
 cular K  E.  On emerging at F, circumstances were reversed; it
 wandered  from the perpendicular M N, and in the direction F G,
 parallel to  A C, because the media above and  below I J were iden-
 tical.  We can now understand why water, saline solutions, glass,
 rock crystal, &c. have higher refractive powers than  air.  They
 are more dense.
    The nature or character of bodies also  influences greatly their
 refractive powers.  Newton observed this, in his  experiments
 upon the subject, and has furnished science with one of its proudest
 trophies, by his prognostic, in the  then infant state of chemistry,
 that water and the diamond would be found to contain combustible
 ingredients.  The diamond or brilliant is one of the most refrac-
 tive of known substances, and this  is one of the sources of its bril-
 liancy.   The opinion  of Newton, it  is hardly necessary to say,
 has been  triumphantly confirmed.
   This refraction of the rays, that  fall  obliquely upon a medium,
 gives rise to numerous optical illusions. The ray proceeding from
 F,  in the  bent  course F C A, will impinge on an eye at A; and
 the object F will appear to  be at /.  The pool will consequently
 seem shallower.  In like manner, an object O in the air would not
 be perceptible to an eye in the water at F, in the direction 0 C F;
 whilst one at A would  be distinctly visible; the ray from it pro-
 ceeding in  the direction A C F, but appearing to come straight
 to the eye in the direction 0 C F.
   All transparent bodies, at the same time that they refract light,
 reflect a portion of it.   This is the  cause of the reflections we no-
 tice on the  glass of our windows, and of the image perceptible  in
 the eye.
   The same  substance has always the  same  refractive power,
 whatever may  be its shape:—in all cases, the sine of the  an-
 gle of refraction holding the same  ratio to the sine of the  angle
 of incidence, whatever  may be the  incidence.  The angle of inci-
 dence is the angle formed by the incident ray with a perpendicu-
 lar raised from the point of immersion; the angle of refraction
 that formed by the refracted portion of  the ray with the same per-
 pendicular.  In Fig. 19, A C K is the angle of incidence of the ray
 AC; and L C F the angle of refraction.  The sines of these angles
 respectively are the lines P Q and L F.
   But although the media may refract the  rays  of light equally
 the form  of the refracting body will materially modify their ar-
 rangement.   The perpendiculars to the surface may approach or
 recede from each other; and if this be the  case the refracted rays
 will approach or recede from each other likewise.
   Where  the body has plane and parallel surfaces, as in the  glass
of our windows, the refraction, experienced by the ray  on  enter-
   Vol. I.                      19 
146
SENSIBILITY.
ing the glass, is corrected by that which occurs on its emergence;
and although the light may not pass in one straight line, it proceeds
in parallel lines, separated by a space dependent upon the thick-
ness of the refracting body and the obliquity of the incident  ray.
If the medium  be very thin, as in  a pane of glass, the rays do not
appear deflected from their original direction.  In Fig. 19, the in-
terval between the direct ray and the ray A C F after its emerg-
ence is  that between G and H.
   If the surfaces of the diaphanous body are plane, but inclined to-
                                            wards each other,
                  Fig.  20.                  as in the common
                                          H prism,  the refrac-
                                            tion,  experienced
                                            by  the  ray  on
                                            emerging,  instead
                                            of correcting  that
                                            experienced  dur-
                                            ing   its   passage
                                            through the body,
                                            is added to it; and
the rays are deflected from their course to an extent equal to the
sum of  the two refractions.   The ray  A B, (Fig. 20,) after, im-
pinging upon the side D  L of the prism, at B, instead of continuing
its course in the direction B J, is refracted towards the perpendi-
cular C B F; the medium being denser than air; and on emerging
into the rarer medium, instead of continuing its course in the di-
rection  G I, it is refracted in the line G H or from  the  perpendi-
cular K J.
  Again,  if the surfaces  of the [medium be  convex, the rays are
so situated, after refraction, as to converge behind  the refract-
ing body into a point called the focus, which is nearer to the me-
                                        dium  the less  the di-
                                        vergence of the rays, or
                                        in  other words,   the
                                        more distant the lumi-
                                        nous object.  Fig. 21
                                        exhibits a pencil of rays,
                                        proceeding  from a ra-
                                        diant  point at A,  and
                                        meeting  at  a focus at
                                        B: the dotted lines be-
                                        ing the perpendiculars
drawn to the surface at the points of immersion and emergence.
  Lastly, if the surfaces  of the medium be concave, as in Fig. 22,
the luminous rays, proceeding from a radiant point  as  at  A, are
rendered so divergent, that if we look for a  focus here it must be
anterior to the medium or at G.
 
SENSE OF  SIGHT.


    Fig. 22.
  A knowledge of these facts has given occasion to the construc-
tion of numerous invaluable optical instruments, adapted to modify
the luminous rays, so as to change the  situation in which bodies
are seen, to augment their dimensions, and to  render them more
luminous, and visible, when remote and minute.  It is,  indeed, to
this branch of science that we are  indebted for some of the most
important information, and advantages, that we possess in the do-
mains of science and art.   The simplest of these instruments are
bodies, shaped like a  lentil, and hence called lenses.  They are
composed of two segments of a sphere.  The medium in Fig. 21 is
a double convex lens; that in Fig. 22, a double concave.  The
manner in which they modify the  course of  the luminous rays,
passing through them, has been sufficiently described.
  The study of the refraction of light leads us to the knowledge
of an extremely important fact;—which, when  it was first made
known by Newton, excited universal astonishment;—viz. that a
ray of light is itself composed of several  coloured rays, differing
from each other in their refrangibility.
 
148
sensibility.
  If a beam of the sun's light be admitted through the hole of a
window-shutter, E F, into  a dark chamber, it will proceed in a
direct line to P, and form a white spot upon the wall, or on a whiten-
ed screen placed there for the purpose. But if a glass prism, B A
C, be placed, so  that the light may fall upon its surface, C  A, and
emerge at the same angle from its second surface, B A, in the di-
rection g G; the beam will  expand; and if, after having emerged,
it be received on the whitened screen, M N,  it will  be found to
occupy a considerable space; and, instead of the white spot, there
will be an oblong image of the sun, K L, consisting of seven co-
lours;—red,  orange, yellow, green, blue, indigo, and  violet.
Each  of these colours admits of no farther decomposition, when
again passed through the prism; and the whole lengthened image
of the sun is called the prismatic or solar spectrum.
  In this dispersion of the coloured rays, it will be observed, that
the red ray is the least turned from its course;  and is hence said
to be the least refrangible; whilst the violet is the most so.
  Such is the spectrum, as  depicted by Newton;  since his  time
it  has, by some, been  considered  to  consist  of  three colours,—
red, yellow, and blue;  as certain  of the colours  can be composed
from others,—the green, for example, from the blue and  the yel-
low. Wollaston made it to consist of four; red, green, blue, and
violet: Sir J. Herschel of four;  red, yellow, blue, and violet;
and, more recently, Sir David Brewster  has restricted  it to
three; red, yellow, and  blue. The  causes, which have led to these
various divisions, it is not our province to explain.
  Each of the rays,  of which the spectrum is composed, appears
to have  a different  calorific and  chemical action; but this is a
subject, that in nowise concerns the function we are considering.
  The decomposition of light into its constituent rays enables  us to
explain the cause of the colour of different substances.  When white
light impinges upon a body, the body either absorbs all the rays
that compose it; reflects all;  or absorbs some, and reflects others.
If it reflects the  whole of the light  to the  eye, it  is of a white co-
lour ;  if  it absorbs  all, or reflects  none, it  is  black; if it  reflects
only the red ray, and absorbs all the rest, it is red, and so of the
other colours.
  The cause, why one body reflects one  ray, or set  of rays, and
absorbs others, is totally unknown.   It is conceived  to  be owing
to the nature and particular arrangement of its molecules.  This
is probable.  But we are still as much in the dark as ever.  It
is accounting for the ignoturn per ignotius.
  Two other points  require a brief notice, being intimately con-
cerned in vision;—the aberration of sphericity, and the aberra-
tion of refrangibility.
  It has  been  remarked,  that the rays  of  light—after  passing
through a convex lens, or medium, whose surfaces are convex—
converge, and are brought to a focus behind it.  The whole of the 
SENSE  OF SIGHT.
149
rays do not, however, meet in this focus.  The rays that are near-
est the axis, R" F of the lens, Fig. 24, are refracted to a  focus
more remote from the lens, than  those that fall on the lens at a
distance from the axis.
   The rays R',
R",   and  R'",
are brought  to
a  focus at  F,
whilst the rays
R L and R""
L' converge at
the   point   /,
much   nearer
the  lens.   In
like    manner,
rays,    which
fall upon the lens intermediate between  the  rays R  and  R',
will  have their foci  intermediate  between  / and F.  This di-
versity of focal distances,  is  called the spherical aberration,
or the aberration  of sphericity:  the   distance / F  is  the
longitudinal spherical aberration; and B A the lateral sphe-
rical  aberration  of the lens.  This aberration  is  the  source
of confusion  in  common  lenses; and as  it  is dependent upon
the shape of the  lens,  it has  been obviated, by forming these
instruments  of  such  degrees  of curvature, that  the rays, fall-
ing upon the centre or margins of the lens, may all be refracted to
the same focus. This is effectually accomplished by lenses, whose
sections are  ellipses or hyperbolas.  In a common lens, the incon-
venience is obviated by employing  lenses of  a small  number of
degrees; or  by interposing an  opaque body, called, by the opti-
cians, a diaphragm, anterior to the lens, so that the rays of light
can only impinge upon the central part, and consequently be re-
fracted to the same focus.   This diaphragm  is present in all tele-
scopes, and  occupies the situation of the curves D and D' in Fig.
24, so as only to admit  the rays R', R", and R'", to fall upon  the
lens.  Such an apparatus, we shall find, exists in the human eye.
   Lastly, it has been already observed, that the different rays, con-
stituting the solar spectrum, are unequally refrangible,—the  red
being the least, the violet the most so; hence the cause of their dis-
persion in the spectrum.   It follows from this  fact, that whenever
light experiences refraction, there must be more or less dispersion
of its constituent rays; and the  object, seen  by the refracted ray,
will appear colored.  This must, of course, occur more particularly
near the margins of the lens, where the surfaces become  less and
less parallel  until  they meet.  The  inconvenience resulting from
this dispersion is called the aberration of refrangibility, and has
been attempted to be obviated  by glasses, that have been termed,
in consequence, achromatic.  These are made by combining trans- 
150
SENSIBILITY.
parent bodies of different dispersive powers, so that they may com-
pensate each other, and thus the object be  seen  in its proper co-
lours, notwithstanding the refraction.   Dr. Blair found, for exam-
                                           ple, that by  enclos-
                  Fig. 25.                  ing muriate of anti-
                                           mony B E between
                   abc                    tw0  convex lenses
                  •^-£Th                    °f crown glass* A D
                  ~mHjk—-^^            and C F, the parallel
                   plpl     ^"""""---^^     rays  R, R  and R
                      M-----------^^>. p were refracted to a
                   fjtBt       ^^^^"^   single  focus at P
                       l^-^*"           without the slightest
                  ]p|ff§r                    trace  of secondary
                    DBF                    colour.    Newton
                                           was of opinion, that
                                           the light, in travers-
ing a refracting medium, always experiences a dispersion of its
rays, proportional  to its refraction.   He therefore  believed, that
it would be impossible to fabricate an achromatic glass.   This is
one of  the  rare cases in which that illustrious philosopher erred.
Since his time, and chiefly by the labours of Dollond, such instru-
ments  have  been  formed on the principles above mentioned; so
as to greatly diminish the inconveniences sustained from the use of
common lenses; although,  still, not perfectly achromatic.   The
inconvenience is farther obviated by the diaphragm in telescopes,
already referred to.  As the dispersion is most  experienced  near
the margin of the lens, it shuts off the rays, which would otherwise
fall upon that portion and diminishes the extent of aberration. The
human eye is achromatic.   It is obviously essential that it  should
be so;  and this result is probably owing to a combination of causes.
It is formed of media of different dispersive powers. Its lens is con-
stituted of layers  of different densities, and it is provided  with a
diaphragm of singularly valuable construction.
   Such are the prominent points of the beautiful science  of optics,
that chiefly  concern the physiologist, as an introduction to vision.
Others will  have to be adverted to, when we  consider  the  eye in
action.

               Anatomy of the Organ of Vision.

   The human eye is almost spherical, except for the prominence of
its most anterior and  transparent part—the cornea.   It  has been
compared to a telescope, and with much propriety; as many of the
parts of that instrument have been added, to execute particular of-
fices, which are admirably performed by the eye—the most perfect
of all optical instruments.
 
SENSE  OF SIGHT.                     151

    Fig. 26.
a. Aqueous humour.—6. Cornea.—c. Iris.—d. Lens.—e. Ciliary processes.-^". Vitreous humour.—g. Optic
                    nerve.—A. i. Muscles above and below.
   Every telescope consists, in part, of a tube, which always com-
prises pieces, capable of readily entering into each other.  Within
this cylinder are several glasses or lenses, placed in succession from
one extremity to the other.  These are intended to refract the rays
of light and to bring them to determinate foci.  Within  the tele-
scope is a kind of partition of paper or metal, having a round hole
in its centre, and usually placed near a convex glass, for the pur-
pose of diminishing the surface of the lens accessible to the rays of
light and obviating the spherical  aberration.   The interior of the
tube and of the diaphragm is colored black, to absorb the oblique
rays, which are not inservient to vision, and thus to  prevent them
from causing confusion.
   This arrangement is nearly a counterpart of that, which exists in
the eye.  The tube of the instrument is represented by three mem-
branes  in superposition,—the sclerotic, choroid,  and retina; the
latter being the one, that  receives the  impression of light.  Within
this case are four refracting bodies, situated one- behind the other;
and all intended to bring the rays of light to determinate foci, viz.
—the cornea, aqueous humour, crystalline lens, and vitreous hu-
mour.  Lastly, in the interior of the eye,  near the anterior sur-
face of the crystalline lens, is a diaphragm—the iris, having an
aperture in its  centre—the  pupil.  These  different parts will de-
mand a more detailed notice.
   1. Coats of the eye, &c—The sclerotic is  the  outermost coat. 
152
SENSE OF  SIGHT.
that move the  eyeball, and is manifestly intended for the protec-
tion of the internal parts  of the organ.
  Immediately within the sclerotica, and feebly united with  it by
vessels, nerves  and cellular tissue, is the choroid coat;—a soft, thin,
vascular and nervous membrane.  It completely lines  the sclerotic
and  has consequently the same  shape and extent.  Behind, it is
perforated by the optic nerve; before, it has the iris united with it;
and within, it is lined by the retina, which  does not  however  ad-
here to  it,—the black pigment separating them from each other. It
is chiefly  composed of the ciliary vessels and nerves,  and consists
of two  distinct  laminae, to the innermost of which Ruysch—the
son—gave the name membrana Ruyschiana.   In fishes  these la-
minae are  very perceptible, being separated  from each  other by a
substance, which Cuvier considers to be  glandular.   The choroid
is impregnated and lined by a dark-coloured mucous pigment, called
pigmenttim nigrum.  In some  cases, as in the albino,  this sub-
stance, which is exhaled from the  choroid, is  light-coloured, ap-
proximating to  white.  Leopold Gmelin conceives, that  it  ap-
proaches the nature  of indigo; whilst Dr.  Young regards it as a
mucous substance, united to a quantity of carbonaceous matter,
upon which its  colour depends. On the outer side of the bottom of
the cavity of the eye, there is a  small shining space, destitute of
this pigment, through which the  colours  of the  membrana  Ruys-
chiana appear.   This spot is termed the tapetum.  It is  met with
only in quadrupeds.
  The retina is the last coat, if we except a highly delicate serous 
sense of  sight.
153
membrane,—lately discovered by  Mr. Jacobs, Demonstrator of
Anatomy in Trinity College, Dublin—which is interposed between
the  retina and choroid coat. The retina lines the choroid; and is a
soft, thin, pulpy, and grayish membrane, formed  chiefly, if not
wholly, by the final expansion of the optic nerve.  Ribes, indeed,
esteems it a distinct membrane, on which the optic nerve is  dis-
tributed;—a structure more consistent with analogy.   On its inner
surface, it is in contact with the membrane of the vitreous humour,
but  they  are  not adherent.   Anteriorly, it terminates  near  the
anterior extremity of the  choroid, forming a kind of ring, from
which an  extremely delicate lamina is given  off.  This is reflected
upon the ciliary  processes,  dips into the intervals separating them,
and, according to  some anatomists, passes forward as far as  the
crystalline.  About a sixth of  an inch on  the outside of  the optic
nerve, and in the direction of the axis of the eye, or of a line drawn
perpendicularly through the centre of the cornea, is a yellow spot,
about a line in extent, surrounded by several folds, and  having a
foramen in its centre.   These are the limbus luteus, and foramen
centrale of Soemmering.
   The retina receives many blood-vessels, which proceed from the
central artery of the retina, or o/Zinn.  This vessel—it is  im-
portant to observe—enters  the eye through the centre of  the optic
nerve;  and before passing directly through  the vitreous  humour,
sends off lateral branches to the retina.
   2. Diaphanous parts of the eye.—-The parts which  act as re-
fracting bodies, are either  transparent membranes, or fluids,  con-
tained in capsules, which give them a fixed shape.   These parts are
the cornea, aqueous humour, crystalline, and vitreous humour.
   The cornea is the convex transparent part of the eye: advancing in
front of the rest of the organ, as a watch-glass does before the case,
and  appearing like the segment of a smaller sphere superadded  to a
greater.   It was, for a long time, considered to  be a prolongation
of the sclerotic; but they are manifestly distinct membranes, being
separable by maceration.  The posterior surface is concave, and be-
tween it and the iris  is the small  space occupied  by the aqueous
humour, called the anterior chamber of the eye.  The  cornea is
composed of several thin laminae in super-position, which have been
compared to horn, and  hence the name of the membrane.  Like
the corneous tissue, in general, it  possesses  neither  blood-vessels
nor  nerves.  In  animals, the density and convexity of the cornea
vary with the media in which they exist, and with the condition
of the other refractive parts of the eye.
   The aqueous  humour is a slightly viscid  fluid, which  occupies
the whole of the space between the posterior surface of the cornea
and  the anterior  surface of  the crystalline.  This space is  divided
by the iris into  two chambers—an anterior and a  posterior—the
latter being the small interval  between  the  hinder surface of  the
iris, and the anterior surface of the crystalline.  Sir David Brewster
  Vol.  I.                      20 
154
sensibility.
erroneously asserts, that the posterior chamber contains the crys-
talline and vitreous humours;  and Dr. Arnott, that the anterior
and posterior chambers of the  eye, are the compartments  before
and behind the crystalline.   Anatomists are not agreed, whether
the aqueous humour has a proper membrane, which secretes it, or
whether it is not an exhalation  from the vessels of the iris and ci-
liary processes.  Ribes, indeed, derives it from the vitreous humour.
However  secreted, it is very rapidly regenerated, when evacuated;
as it must be in every operation for the cataract by extraction.  It
is not lodged in cells, and hence readily flows out when the cornea
is punctured.  The quantity of the aqueous humour in the adult, is
about five  or six grains. Its specific gravity is not rigidly established,
but it differs slightly from that of water, being a littlegreater.  Accord-
ing to Berzelius, it is composed of water 98.10; a little albumen, mu-
riates, and lactates 1.15; soda, with a substance soluble in water, 0.75.

                           Fig. 28.
Section of the eye magnified, three diameters.
  The crystalline lens is a small body, of a crystalline appearance,
and lenticular shape, whence its name. It measures, in the adult,about
1.33 of an inch in its greatest circumference; and is about 2J lines
thick at its centre.  It is situated between the aqueous and vitreous
humours; and not, as Dr. Fleming asserts,  in " the  centre of the 
sense of  sight.
155
cavity of the eye," but at about one-third of the anteroposterior
diameter of the organ.  A depression at the anterior surface ot the
vitreous humour receives it, and a reflection of the proper membrane
of this humour passes over it.                       ,
   The crystalline is surrounded by its capsule, the interior ot which
is bathed by a slightly viscid and transparent secretion, called the
liquor Morgagni.   The lens is more convex behind than before;
the radius  of its anterior surface being, according to Brewster,
0.30 of an inch; and that  of its posterior surface 0.22 of an inch.  It
consists of a number of concentric ellipsoid laminae, increasing in
density from the circumference to the centre.  Some fibres detach
themselves from the different laminae to those immediately beneath,
constituting the sole bond of union that exists between them.
   Of old it was believed, that  the  crystalline was of  a muscular
structure, and capable of modifying its own convexity, so as  to
adapt the eye to distances.  This was the opinion of Descartes;
and it has more recently been revived, with modifications, by Dr.
Young.  Its muscularity is, however, by no means established, al-
though its  fibrous character is unquestionable.
   The specific gravity of the human crystalline  is said, by Chene-
 vix, to be  1.0790.  He considered it to be composed chiefly of albu-
 men: according to an analysis, however, of Berzelius, it would ap-
 pear to contain 35.9 parts, in the hundred,  of a matter  very analo-
 gous to the colouring matter of the blood.
   The vitreous humour, so called in consequenceof its resemblance
 to melted  glass, occupies the whole of the cavity of the eye behind
 the crystalline.  It is convex behind, and  concave before, and is
invested by a delicate, thin, transparent  membrane, called tunica
 hyaloidea, which furnishes prolongations internally, that divide it
 into cells.   It is owing, indeed, to this arrangement of the mem-
 brane, and not to the density of the humour, that it has the tenacity
 of the white of egg.  Its density does not differ materially from
 that of the aqueous humour; their specific gravities being stated at
 1.0009, and 1.0003 respectively.  The cells, formed by the hyaloid
 membrane, are not all of the same shape and size.  They commu-
" nicate freely with each other, and are well represented in Fig. 28.
   At the anterior part, where the hyaloid  membrane  reaches  the
 margin of the crystalline, it is separable into  two laminae; one of
 which is reflected over the anterior, the other over the posterior
 surface of the lens.  Between these  laminae, and at their junction
 round the crystalline, a  canal exists, into which  air may be intro-
 duced ; when it exhibits a plaited arrangement; and has hence been
 called the  bullular canal of Petit; and, by the French writers, the
 canal goudronni, or simply, the canal of Petit. This canal is ge-
 nerally conceived  to be  devoid of  aperture; but Jacobson affirms,
 that it has, in its sides, a number of minute foramina, which admit
 the entrance and exit of the aqueous humour.
   The composition of the vitreous humour, according to  Berze-
 lius, is as follows:—water, 98.40; albumen, 0.16; muriates and lac- 
156
SENSIBILITY.
tates, 1.42; soda, with an animal  matter, soluble only in water,
0.02.  Its absolute weight is fifteen  or  twenty times greater than
that of the aqueous humour.
   3. It was remarked, in the comparison drawn  between the eye
and the telescope, that a diaphragm exists in the former, called the
iris; and sometimes the uvea. Generally, however, the latter term
is appropriated to the posterior lamina of the iris.  By some anato-
mists,  the iris is conceived to be a  prolongation of the choroid:  by
others, to consist of a proper  membrane  of  a  muscular character;
and, by others again, to  be essentially vascular and nervous; the
vessels and nerves being distributed on an  erectile tissue.   There
is, in the views  of both anatomists  and physiologists, much  dis-
crepancy regarding the structure and functions of this portion of.
the eye.   Mr. Edwards, of Paris, demonstrates, that it consists of
four laminae, two of which are extensions of the laminae composing
the choroid;—a third belongs to the  membrane of the aqueous hu-
mour,  and is reflected over its anterior surface; and the  fourth is
the proper tissue of the iris.   Magendie asserts,  that the most re-
cent anatomical investigations prove the membrane to be muscular;
and to  be composed of two sets of fibres;—the outermost radiating;
whose  office is to dilate the pupil;  the innermost  circular and con-
centric, for the purpose of contracting it.  The arrangement of these
                         fibres is represented in Figs. 29 &  30;
         Fig. 29.        the former of which is an internal view
                         of the human iris, magnified three  dia-
                         meters ; and the latter, an external view,
                         exhibiting the surface  to consist  essen-
                         tially of a plexus of blood-vessels;  and
                         taken from the microscopic investiga-
                         tions of Mr. Bauer and Sir Everard
                         Home.   These vessels, and the nerves,
                         are ramifications of the ciliary, the nerves
                         arising  from the ophthalmic ganglion,
                         and nasal  branch of the fifth pair.
                           The iris is the coloured part of the
                         eye, seen  through the  transparent cor-
                         nea;  and, according to the particular
                         colours  reflected from it, the eye is said
                         to  be blue, gray, hazel, &c.  In its centre
                         is an opening, called the pupil, through
                         which alone the  rays of light can reach
                         the lens. This opening can be enlarged,
                         or contracted, by the contraction or dila-
                         tation of the iris; and in this respect it is
                         perpetually varying, according to  cir-
                         cumstances.  In  man, the pupil is circu-
                         lar, but it  differs greatly in its dimen-
                         sions and  shape in different animals.
   On the posterior surface of the iris, or on the uvea, the  pigmen-
 
SENSE OF  SIGHT.
157
turn nigrum exists, as on the choroid. This layer has likewise some
effect in giving colour to the eye.  In blue eyes, for instance, the
tissue of the iris is nearly white; the pigmentum nigrum, which ap-
pears through it, being the chief cause of its colour.
   At the point of junction between the iris and the choroid coat,
they are united to  the  sclerotica  by a band of cellular  substance,
called the ciliary ligament;  and, from  the anterior margin of the
choroid, where  it unites with the base  of the  iris, numerous vas-
culo-membranous appendages arise, which appear to be prolonga-
tions  of the anterior margin of the choroid, turning inwards towards
the margin of the crystalline  lens, and terminating abruptly, with-
out being attached to that  body. They are the ciliary processes.
   These beautiful appendages are from sixty to eighty in number;
and resemble the disk of a radiated flower. On their posterior surface
they are covered by the same kind of pigment as that of the choroid
and uvea; and they impart the stain to the membranes of the crystalline
and vitreous humours. The greatest diversity of opinion, here again,
exists regarding both structure and function.  By some, these pro-
cesses have been esteemed nervous; by others, muscular, glandular,
and vascular.  Sir Everard Home asserts, on  the authority of mi-
croscopic observations  by  Mr. Bauer, that between the processes
are bundles of muscular fibres of  considerable length; which origi-
nate all around from the capsule of the vitreous humour, pass for-
ward  over  the edge of the lens, are attached firmly to its capsule,
and there terminate.  They are unconnected with  the ciliary pro-
cesses, or iris, and  he conceives that their contraction will  pull the
lens towards  the retina.  In appearance they resemble the choroid,
and are probably identical with it in structure.

   Such is an  anatomical view of the physical  part  of the eye pro-
per, so far  as is necessary  for the  physiological inquirer. We have
yet to consider the most important part of the organ: that which is
essentially  nervous and vital in its action; and which, as we have seen,
goes to constitute one of the membranes of the eyeball—the retina.
   The optic  nerves—the  second pair of Willis—arise from the
anterior part  of the corpora quadrigemina; and not, as was at one
time universally believed, from the thalami nervorum opticorum.
Setting out from this point, they proceed forwards towards the tha-
lami,  to which they adhere;  receiving filaments from  the corpus
geniculatum externum, an  eminence a little  anterior to, and on
the outside of the  tubercula; and from  a layer of cineritious sub-
stance, situated between the point of junction of the nerve of each
side and the eminentiae mammillares,—called  the  tuber cinereum.
Proceeding forwards towards  the eye,  the nerves approach, and
form a junction at the sella turcica, or on the upper surface of the
sphenoid bone.  Anterior  to this point,  they diverge, each passing
through the optic foramen to  the corresponding eye; piercing the
sclerotic and  choroid at a point about one-tenth of an inch from the 
158
SENSIBILITY.
axis of the eye on the side next the nose;  and expanding, to form
the whole, or a part of the retina.
  M. Lassaigne has recently examined the chemical composition
of the optic nerves and retina; and concludes, from his experiments,
that the retina is formed of the same elements  as the cerebral and
nervous substance; differing only in the proportion of the consti-
tuents.
  It is a question that  has often been agitated,  whether the optic
nerves, at their junction  on the sella turcica, simply lie alongside
each other; or whether they do  not decussate, so that the root of
the nerve of the left eye is on  the right side;  and that of the right
on the left.  Anatomical investigations have hitherto left the ques-
tion unsettled; whilst pathology appears to  have furnished proofs
on both sides.  Thus, where the right eye has been lost for a  consi-
derable time, the optic  nerve of the same side has been found in a
state of atrophy through its whole extent.   In  other cases of the
kind, the posterior portion  of the left nerve has been found in
this condition.  Fishes have the nerve arising from one side of the
brain, and passing to the eye of the other side; hence crossing, but
not uniting.   On the other  hand, Vesalius  gives a plate of a case
in which  he  found the optic  nerves  passing to  the  eyes of the
same side from which  they originate without adhering at all;  and
yet without any disturbance of vision.  It is not necessary, how-
ever, to adduce the numerous cases that have been published in fa-
vour of one view or the other.  It is impossible to  sift  those that
are entitled to implicit  confidence from those that are not.  We may
merely remark, that certain observations  of Valsalva, Chesel-
den, and Petit, appear to show, that where  the brain  is  injured,
it is the eye  of the  opposite side that is affected, and, in cases of
hemiplegia or paralysis of one side of the body, we  certainly have
too  many instances for  testing  the accuracy of this opinion.
  Soemmering, whose  correctness as an observing anatomist has
never been disputed, affirms, that he had an opportunity of examin-
ing seven blind persons; in all of whom the atrophy of the  nerve
was on the side or root opposite to the eye affected.   Some, again,
have advanced an opinion, that the decussation is  partial, and con-
cerns only the internal  filaments; that the others pass directly on to
half the corresponding eye; so that one-half of each eye is supplied
by straight fibres  proceeding directly from the root of the same
side; the other half by  those resulting from the  decussation of the
internal fibres.  Messrs.  Wollaston and Berard  embrace  this
opinion, for the purpose of explaining the anomaly of vision, called
hemiopia, in which  only one-half the  object  is seen.   Cuvier,
Serres, and Caldani, also assert, that they have noticed  this ar-
rangement in  the horse, and in the nerves when  subjected  to ap-
propriate maceration.
  These views are, however, opposed by the direct experiments of
Magendie.  He divided, in a rabbit, the right optic nerve, behind 
SENSE OF  SIGHT.
159
the point of decussation, or what has been  called the chiasma of
the nerves;—the sight of the left eye was destroyed.  On  cutting
the left root, the sight of the right eye was equally destroyed; and
on dividing the bond of union by a longitudinal incision, made be-
tween the nerves, vision was entirely abolished in both eyes;—a
result, which, as he properly remarks, proves  not only the exist-
ence of decussation, but, also, that it is total and not partial, as Wol-
laston had supposed.  Another experiment, which he instituted,
led to a similar result. Fifteen days before examining a pigeon, he
destroyed one eye.   The nerve of the same side, as far as the chi-
asma, was wasted; and, behind the chiasma, the root of the oppo-
site side. Rolando and Flourens, too, found in their experiments,
that when one cerebral hemisphere was removed, the sight  of the
opposite eye was lost. We may conclude, then, in the present state
of our knowledge, that there is not simply a junction, or what the
French call adossement, of the optic nerves; but that they decus-
sate at the sella turcica.
  The eye proper receives numerous vessels,—the ciliary arteries
and veins, and several nervous ramifications, the greater part  of
which proceed from the ophthalmic ganglion of the fifth pair.
   The following are the dimensions, &c. of the organ, on the au-
thorities  of Petit, Young, Gordon,  and Brewster.

                                                     Eng.  Inch.
Length of the antero-posterior diameter of the eye     -     0.91
Vertical  chord of the cornea......0.45
Versed sine of the cornea   ------     0.11
Horizontal chord of the cornea.....0.47
Size of pupil seen through the cornea  -    -    -   0.27 to 0.13
Sizeofpupildiminishedbymagnifyingpowerofcorneato0.25 to 0.12
Radius of the anterior surface of the crystalline   -    -     0.30
Radius of posterior surface  *-__---     0.22
Principal focal distance of lens    -----     1.73
Distance of the centre of the optic nerve from the foramen
   centrale of Soemmering  -    -    -    -    -    -     0.11
Distance of the iris from the cornea    -                    0.10
Distance of the iris from the anterior surface of the crystalline  0.02
Field of vision above a horizontal line   -    -    50°) ^_ 0
Field of vision below a horizontal line  -    -    70° 3
Field of vision in a horizontal plane     -     -   150°
Diameter of the crystalline in a woman above fifty years of age 0.378
Diameter of the cornea     ------   0.400
Thickness of the crystalline......0.172
Thickness of the  cornea......0.042
   It is proper to  remark, that all  these measurements were neces-
sarily taken from the dead organ, when the  parts are by no means
in the same relative situation as when alive; and this is a cause why
many of the phenomena  of vision can never  be determined with
mathematical accuracy. 
160
SENSIBILITY.
                      Accessory Organs.

  The visual organs being of an extremely delicate texture, it is of
obvious importance that they should be guarded against deranging
influences.   They are accordingly provided with numerous parts,
which afford them protection, and enable them to execute the func-
tions for which they are destined.  They are, in the first place, se-
curely lodged in the bony cavities, called the orbits, which are of a
conical figure, with the apices directed inwards.  In the truncated
apex the foramen  opticum is situated, by which the optic  nerve
enters the orbit.  Here are, also, the superior orbitar and spheno-
maxillary fissures, through which  many vessels and nerves pro-
ceed to the eye or its appendages. The base of the orbits is not di-
rectly  opposite to the apices, but tends outwards; so that the axes
of these cavities, if prolonged, would meet at the sella turcica. The
eye, however, is not placed in the direction of the axis of the orbit,
but straight  forward; and as it is nearly spherical, it is obvious that
it cannot completely fill the conical cavity. In Fig. 26, the muscles
h and i indicate the shape of the upper and lower surfaces of these
cavities;—the whole of the space, between the posterior part of the
orbit and these muscles, that is not occupied by the optic nerve, be-
ing possessed by an adipose, cellular tissue, on which the eye is
placed, as it were, on a cushion.  Under particular morbid circum-
stances, this deposit becomes  greatly augmenled, so as to cause the
eye to start  from its socket; constituting the disease  called exoph-
thalmos.
  The;parts, however, that are more immediately reckoned amongst
the protectors of the  organ—the tutamina oculi—are the eye-
brows, eyelids, and the lachrymal apparatus.
  The eyebrows or supercilia, (Fig. 27, S SS.) are situated imme-
diately on the superciliary ridge of the frontal  bone. They consist
of hair, varying in  colour according to the individual, and turned
towards the outer angle of the eye,—of common integument,—of
sebaceous follicles, situated at the root of each hair,—and of muscles
to move them, viz: the frontal  portion  of the occipito-frontalis,
(A A.  Fig. 31;) the upper edge of the orbicularis palpebrarum, C;
and the corrugator supercilii,  B.
  The palpebrse or eyelids are, in man, two in  number—an  upper
and a lower, or a greater and  a less—the palpebra major vel supe-
rior, and the palpebra minor vel  inferior—the former covering
three-fourths of the eye ; hence the transverse diameter of the eye
is not represented by their line of union, the latter being much be-
low it, and  therefore improperly termed, by  Haller, AZquator
oculi.  By the separation  of the eyelids, we judge, but inaccurately,
of the size of the eye;—one, who is capable  of separating them
more  largely from each other, appearing to us to have a larger eye,
—and the contrary. 
SENSE OF  SIGHT.


     Fig. 31.
161
A A. The frontalis muscle.
B B. Corrugator supercilii.
C C. Orbicularis palpebrarum.
 D. Levator labii superioris alaeque nasi.
 E. Compressor nasi.
 F. Levator labii proprius.
 G. Levator anguli oris.
 H. Zygomaticus.
K. Orbicularis oris.
L. Nasalis labii superioris.
N. Triangularis oris.
O. Quadratus menti.
P. Levatores menti.
Q. Buccinator.
R. Temporalis muscle.
   The edge  of the eyelids is thick, rounded, and furnished  with
hairs, resembling generally, in colour, those  of the head.   These
are the eyelashes or cilia.   On the  upper  eyelid  they are curved
upwards;  on the lower downwards, as in Fig. 27.  The eyelids are
formed of four membranous layers, in superposition, and  of a fibro-
cartilage, which extends  along the whole of the  edge and keeps
them tense.   The outermost of these layers is the common integu-
ment; the skin of which  is  very  delicate and semi-transparent
yielding readily to the motions of the eyejids and having numer-
   Vol. I.                      21 
162
SENSIBILITY.
 ous transverse folds.  The cellular tissue, beneath the skin, is very
 loose, and is, under particular circumstances, infiltrated by a serous
 fluid, giving the eyelid, especially the lower, a  dark appearance;
 but it never contains fat.  Beneath the common integument is the
 muscular stratum, formed by the orbicularis palpebrarum, (C C.
 Fig. 31.) in the lower eyelid; in  the  upper, by  the same muscle
 and the levator palpebrae superioris, which arises from  above the
 foramen opticum, and is inserted into the superior edge of the fibro-
 cartilage of the tarsus.
   Beneath the  orbicularis palpebrarum, again, there is  a  fibrous
 layer, which occupies the whole of the eyelids, passing  from the
 edge of the  orbit to the  tarsal margin,  and seems  intended to limit
 the motion of the eyelids, when they approximate each other. The
 last layer, and that which forms the posterior surface of the eyelids,
 is a fine, delicate, transparent, mucous membrane,  called the tunica
 conjunctiva, or tunica adnata; so called because it joins the eye-
 lids to the globe of the eye.   It lines, in fact, the eyelids, and is re-
 flected over the  ball; but it has been a matter of contention, whether
 it passes over the transparent cornea. The generality of anatomists
 say it does; Ribes, however, maintains the opinion, that  it extends
 only as far as the circumference of the cornea,and that the cornea itself
 is covered by a proper membrane.  Physiologically, this dispute is
 of no  moment.  At its outer surface, a humour is constantly exhaled,
 which keeps it moist, and facilitates the motions of the eyelids over
 the eyeball.   Its loose state also  favours these motions.   Both eye-
lids are kept tense by the aid of a fibro-cartilage, situated  along the
 edge of each, and called the tarsus.  That of the upper  eyelid is
 much more  extensive than that of  the lower; and both seem as if
 cut obliquely, at the expense of their inner surface; so that, in the
 opinion of most anatomists, when  the eyelids are brought together
 a triangular  canal is formed between them and the ball of the eye,
which has been conceived useful in conducting the tears towards the
 lachrymal puncta.  Magendie denies, that any such canal exists;
 and there seems but little evidence of it, when we examine how the
 tarsal cartilages come  in  contact.  Such  a canal, destined for the
 purposes mentioned, would, indeed, seem superfluous.  Besides the
 eyelashes, certain compound follicles are situated  in the  substance
 of the tarsal cartilages.   These are thirty or forty in number in the
 upper eyelid, and twenty-five or thirty in the lower.  They are in
 particular furrows between the tarsal fibro-cartilages and the con-
junctiva, (Fig. 27, T t)  and secrete a sebaceous fluid, called by the
 French chassie, in the  dry state; by  us, gum of the eye, which
 serves the purposes of the follicular secretions in general.
   The arrangement of the eyelids differs in different animals.   In
several,  both eyelids  move;  but in others, only one; either the
lower rising to join the upper, or the upper descending to meet the
lower.   In the sun-fish—tetraodon mola—the eyelid is single and
 circular, with a perforation in the centre, which can be contracted
 or enlarged, according to circumstances.   In many  animals, again, 
SENSE OF  SIGHT.
163
there is a third eyelid, called the nictitating membrane, which is
of a more delicate texture and  more largely supplied with  blood-
vessels ; and in some animals is transparent. In birds it exists, and
is well seen in the owl.  It is at the inner angle of the eye, and is
capable of being drawn over the ball like a curtain, by two particu-
lar muscles, and of thus freeing the surface of the eye from  extra-
neous substances.  In  man, it is only a vestige, destined to no ap-
parent use.   It  is represented in Fig. 27, and is called  valvula,
or plica semilunaris.
   The eye has its proper muscles, capable of moving it in various
directions.   Their arrangement is readily understood.  They are
six in number:—four recti or straight muscles, and two oblique.
1. The rectus superior or levator.   2.  The rectus inferior or de-
pressor.  3. The rectus internus or adductor; and 4, the  rectus
externus or abductor.   They all arise from the base of the orbit,
around the optic foramen; pass forward to vanish  on  the sclerotica;
and,  according to some anatomists, extend over, and form a layer
to the cornea.
                             Fig. 32.
1. Globe of the eye.
3. Optic nerve.
3. Aponeurosis of the rectus externus.
4. Posterior extremity of do.
5. One of the origins of do. on the outside of the
   optic nerve.
6. Inner origin of do. from an aponeurosis.
7. Common to it and the rectus inferior and rec-
   tus internus.
 8. Rectus superior.
 9. Posterior extremity of do.
10. Rectus inferior.
111111. Obliquus superior.
12. Trochlea.
13. Obliquus inferior.
14. Rectus internus.
15. Levator palpebras superioris.
16. Upper eyelid.
   The oblique muscles are, 1. The greater oblique, obliquus supe-
rior, patheticus, or trochlearis, which arises from the inner side of
the foramen opticum, passes forwards to the  internal orbitar pro-
cess of the frontal bone, where its tendon is reflected over a pulley
or trochlea, and crosses the orbit, to be inserted into the upper pos- 
164
SENSIBILITY.
terior, and outer part of the  globe of the eye.   2. The  lesser ob-
lique or obliquus inferior, whose fibres arise from the anterior and
inner part of the floor of the orbit, near the lacrymal groove, pass
under the eyeball, and are inserted betwen the entrance of the optic
nerve and insertion of the abductor oculi, and opposite the insertion
of the obliquus superior.
   These muscles have their proper nerves.  The third pair—mo-
tores oculorum—or common oculo-muscular, are distributed to all
the muscles except the trochlearis and abductor. The fourth pair,
or pathetic, or internal oculo-muscular, to the trochlearis singly;
and the sixth pair, or external oculo-muscular, to the abductor.
   Lastly, the office of tutamina oculi is  not wholly engrossed  by
the parts, that have been mentioned.   The apparatus for the  secre-
tion of the tears participates in it, by furnishing a fluid, which lubri-
cates the surface of the eye, and keeps it in the necessary degree of
humidity for the proper performance of its functions.  It is a beau-
tifully ingenious little apparatus, the structure of which can easily be
made intelligible.  It consists of the lachrymal gland, the excretory
ducts of the gland, the caruncula lachrymalis, the lachrymal ducts,
and  the nasal  duct;  in other words,  of two  sets of parts,—one,
forming the  fluid  and pouring it on  the anterior  surface of the
eye, the other comprising the organs for its excretion.
   The lachrymal gland is situated  in a small  fossa or depression
                               at the upper,  anterior, and  outer
           Fig. 33.            part of the orbit.  It is  an oval
                               body, of the size of a small almond;
                               of a grayish colour,  and  composed
                               of small,  whitish, granular bodies
                               collected into lobes.  From these,
                               six or seven excretory ducts arise,
                               which run nearly parallel to each
                               other and open on the inner side
                               of the upper eyelid, near the outer
                               angle of the eye and near the tar-
                               sal cartilage. Through these  ducts,
                               the  tears, secreted by the lachry-
                               mal gland, are spread over the tu-
                               nica conjunctiva.  They are com-
                               posed, according to  FouRCROYand
                               Vauquelin, of water, mucus, mu-
                               riate of soda,  soda,  phosphate  of
                               lime, and phosphate of soda, and
                               their taste is manifestly saltish, al-
though  the saline ingredients are described as  not exceeding a hun-
dredth part of the  whole.  They are not secreted by those animals
that live in water.
  At the inner angle of the eye is the caruncula lachrymalis.  It
is  a  collection  of  small  mucous follicles, which  secrete a thick,
 abed. The lachrymal canals.
   a a. The puncta lachrymalia.
tfg h i. The lachrymal duct.
   k I. The lachrymal gland. 
SENSE OF  SIGHT.
165
 whitish humour, to fulfil a similar office with the secretion of the
 meibomian follicles.  It completes  the circle  formed by the mei-
 bomian glands around the eyelids.  (See Fig. 27.)
   The  rosy or  pale colour of this body  is supposed to  indicate
 strength or debility.  This it does,  like other vascular parts of the
 system, and in a precisely similar manner.
   The puncta lachrymalia are two small orifices, situated near the
 inner angle of the eye;  (Fig. 27 & 33,) the  one in the upper, the
 other in the lower eyelid;  at the part  where the eyelids quit the
 globe to pass round the caruncula lachrymalis. They are continually
 open, and directed towards  the  eye.   Each punctum is the com-
 mencement of a lachrymal duct, which passes towards the nose hi
 the substance of the eyelids, between  the orbicularis palpebrarum
 and tunica conjunctiva.  These open, as represented in Fig. 33, into
 the lachrymal sac, which is nothing more than the commencement
 of the nasal duct or ductus ad nasum. The bony canal is formed
 by the anterior  half of the os unguis, and by the superior maxillary
 bone; and opens into the nose behind the  os spongiosum  inferius.  *
 Through these excretory ducts, all  of  which are lined by a pro-
 longation of  the mucous membrane, the tears pass into the nasal
 fossae.
   Within the last few years, Dr. Horner, the able anatomist, who
 fills the chair of anatomy in the University of Pennsylvania, has
 described a small muscle, which is evidently a part of the lachrymal
 apparatus, and to which he gives the name tensor tarsi.   It is on
 the orbital face of the lachrymal sac; arises from the posterior su-
 perior part of the os unguis; and, after having  advanced a quarter
 of an inch, bifurcates; one fork being  inserted  along each lachry-
 mal duct, and terminating at or near the punctum.  It is probable,
 that the function of this muscle is to keep the puncta properly di-
 rected towards  the eyeball, or as  Dr. Physick has  suggested,  to
 keep the lids in  contact with the globe. The office,  assigned to it
 by Dr.  Horner, of enlarging by its contraction, the  cavity of the
 lachrymal sac, and thus producing a tendency to a vacuum, which
vacuum can be more readily filled through the puncta than through
 the nose, owing  to the valves or folds of the internal  membrane of
 the sac—is ingenious, but apocryphal.

                    Physiology of Vision.

   The preceding anatomical sketch  will enable the reader  to com-
prehend this important organ in action.   In describing  the office
executed by its various  components, we shall follow the order there
observed, premising some general considerations on the mechanism
of vision;  and afterwards depicting  the protecting and modifying
influences exerted by the various accessory parts:—the different
phenomena of vision will next be explained, and lastly, the informa-
tion conveyed to the mind by this sense. 
166                      SENSIBILITY.
  In tracing the progress of luminous rays through the purely phy-
sical part of the organ, we  shall, in the first  instance, suppose a
single cone to proceed from a radiant point in the direction of the
axis of the eye;  or in other words, of the antero-posterior diameter
of the organ, B b.
Fig. 34.
                                          It is obvious, that the
                                        rays, which fall upon the
                                        transparent  cornea   can
                                        alone be inservient to vi-
                                        sion.  Those, which im-
                                        pinge upon the sclerotica,
                                        are  reflected;  and a part
                                        of those also,that fall  upon
                                        the  cornea, giving occa-
                                        sion, in the latter case, to
                                        the  image observed in the
                                        eye, and to the brilliancy
                                        of the organ.  Nor  does
                                        the  whole of the cornea
                                        admit the rays,  for  it is
                                        commonly more  or less
                                        covered,   above  and be-
                                        low, by the free  edge of
                                        the  eyelids.
                                          Again, the whole of the
                                        light, that enters the cor-
                                        neadoes not impinge upon
                                        the  retina. A portion falls
                                        upon the  iris, and is re-
                                        flected back to the eye, in
                                        such manner as to give us
                                        the  notion of the colour of
                                        the  organ.  It is, conse-
                                        quently, the light, which
                                        passes through the pupil,
                                        that can alone attain the
                                        retina.
                                          If we suppose  a lumi-
                                        nous cone to proceed from
                                        the  radiant point  B, Fig.
                                        34,  directly  in the  pro-
                                        longation  of the  antero-
                                        posterior diameter of the
                                        eye, the axis of this cone
                                        will also be the axis of the
                                        organ; sO  that a  ray of
light, impinging upon the humours in the direction of this axis, will,
as in the case of the lenses, previously referred to, pass through the
 
SENSE  OF SIGHT.                    167
humours without undergoing deflection and will fall upon the re-
tina at b.  This, however, is not the case with the other rays com-
posing the cone.  They do not fall perpendicularly upon  the  cor-
nea, and are, consequently, variously  refracted  in their passage
through the cornea, aqueous humour, crystalline  and vitreous hu-
mour; but so that they join their axis in a focus at the point where
it strikes the retina.
  The transparent parts of the eye, as has been seen, are of different
densities, and are consequently possessed of different  refractive
powers.  These powers it has  been attempted*to estimate; and the
following is the result  of the somewhat discordant  evaluations of
different experimenters: the power of air being 1.000295.
	Cornea.	Aqueous Humour.	CRYSTALLINE LENS.				Vitreous Humour.
			Capsule.	Outer Layers.	Centre.	Mean.	
Hawksbee -Jurin -Rochon Young -Chossat | Brewster ■	1.339	1.33595 1.3333 1.329 1.3333 1.338 1.3366	1.339 1.3767	1.338	1.393 1.3990	1.384 1.3839	1.33595 1.332 1.339 1.3394
   The ray of light, impinging obliquely on the surface of the trans-
parent cornea, passes from a rarer to a denser medium. It will, con-
sequently, be refracted towards the perpendicular raised from the
point of impact.  It will, from this cause, as well as from the con-
vexity of the cornea, be rendered more convergent; or,  in other
words, will approach the axis of the cone. (See Fig. 21.)   In pro-
ceeding  through the  aqueous  humour,  little variation  will  be
produced, as the densities of it and the cornea differ but little; the
latter is slightly more refractive, according to the table, and there-
fore the tendency, that exists, will be to  render the ray less con-
vergent.  This convergence gives occasion to the entrance of a
greater number of rays through the pupil, and necessarily adds to
the intensity of the  light  that impinges on the crystalline. Pursuing
the ray through the two chambers of the  eye, we  find it next im-
pinging on the surface of the crystalline, which possesses  a much
higher refractive power than the  cornea  and  aqueous humour; in
the ratio of 1.384 to 1.336.  From this cause, and  from the con-
vexity of the anterior surface of the lens, it is rendered still more
convergent or approaches still more the axis of the cone. It is pro-
bable, however, that even here, some of the light is reflected back,
and goes towards the formation of the image in the eye, and to the
brilliancy of the organ; other reflected rays perhaps impinge upon
the pigmentum nigrum lining the posterior surface of the  iris and
are absorbed  by it.  From the crystalline the ray einerges into  a
medium possessing less refractive power; and, therefore, is deflected 
168
SENSIBILITY.
 from the perpendicular.   The shape, however, of the posterior sur-
 face of the lens so modifies the perpendiculars, as to occasion such a
 degree of convergence, that the oblique ray meets the axis at a fo-
 cus on the retina.  (See Figs. 21 & 34.)   In this manner, two cones
 are formed;  the one having its apex at the radiant  point, and its
 base on the cornea,—the objective cone,—the other having its apex
 on the retina, and termed the ocular cone.
   These remarks apply chiefly to the cone  proceeding in the direc-
 tion of the axis of the different humours, from a single radiant point.
 It is easy to understand, that every portion of the object ABC,
 Fig. 34, must be a radiant point and project so many cones, in an
 analogous manner; which, by impinging upon  the retina, form a
,picture of the object upon that expansion, at gb h. It is important,
 however, to observe, that  the rays, proceeding from the upper part
 of the object, fall, after refraction, upon the lower part  of the  re-
 tina;  and those from the lower part of the  object upon the upper;
 so that the picture or representation of the  object on the retina  is
 inverted.  How the idea is excited in the mind of an erect object
 will be the subject of after inquiry.
   When  rays fall obliquely on a lens,  as A g and C h, and pass
 through the centre of the  lens, they suffer  refraction at  each of its
 surfaces, but as the twro refractions are equal and in opposite direc-
 tions,  the rays may be esteemed to pursue their course in a straight
 line.   The point a, at which these various rays cross, is called
 tine optic centre of the crystalline.  Each  of  these straight  rays,
 proceeding from a radiant point, may be assumed as the  axis of all
 the rays proceeding obliquely'from the same point, and the common
 focus must fall on some part of this axis.  In this way, the object is
 represented, in miniature  and inverted, on the retina.
   That such a representation of external  objects is formed within
 the eye,  is in accordance with sound theory, and is supported, not
 only by indirect but by direct experiment.  If a double convex lens
 be fitted into an opening, made in the window-shutter of a darkened
 chamber, luminous cones will proceed from the different objects on
 the outside of the house, and  will converge within; so that if they
 be received on a sheet  of paper, a beautiful and  distinct image of
 the object will be apparent.   This is the well known instrument—
 the camera obscura, of which the organ  of sight may be regarded
 as a modification. Making abstraction, indeed, of the cornea, and of
 the aqueous and vitreous humours, the representation of the eye in
 Fig. 34,  with the object, and its image on the retina, is the common
 camera obscura.  The eye  is, therefore, more complicated and more
 perfect than this simple instrument; the  cornea with  the  aqueous
 and vitreous humours being added for the purpose of concentrating
 the light on  the  retina; the  latter, in addition, affording a large
 space for the expansion of the retina, and preventing the organ from
 collapsing.  In the operation for cataract by extraction, which con-
 sists in removing the lens through an opening, made in the lower 
SENSE OF  SIGHT.
169
part of the cornea;  the aqueous humour escapes but is subsequently
regenerated.  If, however, too  much  pressure be exerted  on the
ball, to force the crystalline through the pupil and the opening in the
cornea, the vitreous humour is sometimes pressed out, when the eye
collapses and is irretrievably lost.  Yet how minute must these re-
presentations be; and how accurate the mental appreciation, seeing
that each impression from myriads of luminous  points is trans-
mitted by the retina to the encephalon and perceived with unerring
certainty!
   Experiments have been instituted, which are even more satisfac-
tory than those just mentioned.  These have been of different kinds.
Some experimenters have formed artificial eyes of glass, to repre-
sent the cornea and crystalline,  with water in place of the aqueous
and vitreous humours.   Another  mode is, to place the eye of an
ox or sheep in a hole in the shutter of a dark chamber; having pre-
viously removed the posterior part of the sclerotica, so as to  permit
the images of objects on the retina to be distinctly seen.  Malpighi
and Haller employed a more easy method.  They selected the
eyes of the rabbit, pigeon, puppy, &c. the choroid of which is near-
ly transparent;  and directing the  cornea towards luminous objects,
they saw them distinctly depicted on  the  retina.  More recently
Magendie has repeated these experiments by employing the eyes
of albino  animals, as those of the white rabbit, the white pigeon,
the white mouse, &c, which afford great facilities for accomplishing
the experiment; the sclerotica being thin, and almost transparent;
the choroid, also, thin, and when  the blood, which  gives it  colour,
has disappeared after the death  of the  animal, offering  no sensible
obstacle to the passage of light.  In every one  of these experiments,
external objects were found to be represented on the natural or ar-
tificial retina in an inverted position; the  image being  clearly de-
fined, and with all the colours of the original.
   In  the  prosecution of his experiments, in some  of which he
was assisted by M. Biot, Magendie  found, as  might  have been
expected, that any alteration in  the relative proportion or situation
of the different humours had a manifest effect  upon vision. When a
minute opening was  made in the transparent cornea, and a small
quantity of the aqueous humour permitted  to escape, the image had
no longer the same distinctness.  The same thing occurred when a
little  of the vitreous humour was discharged by a small incision
made through the sclerotica.  He farther found, that the size of the
image on the retina was proportionate to the distance of the object
from the eye.  When the whole of the aqueous humour  was  evacu-
ated, the image seemed to occupy a greater space on the retina, and
to be less distinct and luminous.   The removal  of the  cornea was
attended with similar results.
  When the crystalline was either depressed or extracted, as in
the operations for cataract, the  image was still formed at the bot-
  Vol. I.                     22 
170
sensibility.
 torn of the eye; but it was badly defined, slightly illuminated, and
 at least four times the usual size.
   Lastly, when the cornea, aqueous humour, and crystalline, were
 removed, leaving only the capsule of the crystalline and the vitre-
 ous humour, an image was no longer formed upon the retina; the
 light from the luminous body reached it, but it assumed  no shape
 similar to that of the body from which it emanated.
   The greater part of these results, as Magendie remarks, accord
 very well with the theory of vision. Not so, the distinctness of the
 image under these deranging circumstances.   According  to the
 commonly received notions on this subject, it is necessary, in or-
 der to have the object depicted with distinctness on the retina, that
 the eye should  accommodate itself to the distance at which the ob-
ject is placed; otherwise  indistinct vision must result.   This  is a
 subject, however, that will be discussed presently.
  Such are the general  considerations relating to  the progress of
luminous rays from an object through the dioptrical part of the or-
gan of sight to  the nervous portion—the retina.  We shall now in-
quireanto the offices executed by the separate parts that enter into
its composition, where they have not already engaged attention.
  The cornea, aqueous humour, crystalline, and vitreous humour,
 we have shown to be a series of refractive bodies, for concentrating
the luminous rays  on the  retina; to keep the parietes of the eye dis-
tended, and to afford surface for the expansion of the retina;—thus
enlarging the field of vision. It is probably owing to their different
refractive powers, that the  eye is achromatic;  or, in other words, '
 that  the  rays,  impinging upon the retina, are not  decomposed
 into  their  constituent  colours,  an inconvenience  which  apper-
 tains to the common lens. (Fig. 24.)   The eye is strictly achro-
 matic; and it has  been an object of earnest  inquiry amongst phi-
 losophers, how the aberration of refrangibility is corrected in
 it.  Euler first, perhaps, asserted, that this is owing to the dif-
 ferent refractive powers of the humours; and he conceived, that, by
 imitating this structure in the fabrication of  lenses, they might be
 rendered achromatic.  Experience has shown the  accuracy  of this
 opinion, (Fig. 25.) Others have believed that the effect is produced
 by certain of the humours, as the aqueous and the vitreous, which
 they have considered capable of correcting the dispersion produced
 by the cornea and crystalline. Others have placed it in the crystal-
 line, the layers of which, being of different dispersive powers, might
 correct each other. Lastly,  some have denied altogether the neces-
 sity for the eye's being achromatic; asserting, that the depth of the
 organ is so inconsiderable, that the dispersion of  the  rays, by the
 time they reach the retina, ought to be inappreciable. Such was the
 opinion of d'Alembert.   Maskeleyne calculated the amount of
 the aberration, that must  necessarily take place in the eye, and con-
 cluded that it would be fourteen or fifteen times less than in  a com- 
SENSE OF  SIGHT.
171
mon refracting telescope, and therefore imperceptible.  Uncertainty
still rests on this subject; and it cannot  be removed until the dis-
persive and refractive powers of the transparent parts of the organ
be mathematically determined; as well  as their exact curvatures.
It has been already shown, that the data we possess on this subject
from different observers are sufficiently imprecise.
   Our knowledge, then, is  restricted  to the fact, that the  eye is
perfectly achromatic, and  that, in  this  respect, it  exceeds any in-
strument of human  construction.   The views of  Euler are the
most probable; and the effect is doubtless much aided by the iris
or diaphragm, which prevents the rays  from falling upon the mar-
gins of the lens, where, by the surfaces meeting  at an angle, the
aberration is necessarily greatest.
   Of the coats of the eye—the sclerotic, as has  been remarked,
gives form to, and protects the organ.
  The choroid is chiefly useful by the black pigment, which lines
and penetrates it.  It will be seen, indeed, that some individuals,
on insufficient grounds, have esteemed it the seat of vision. Leaving
this question for the moment, and granting,  as we shall endeavour
to establish, that the impression is received upon the expansion of
the optic nerve—the retina—the use of the choroid would seem to
be, in ordinary circumstances, to afford surface for  thepigmentum
nigrum, whose function it is to absorb the rays  after they have
passed through the retina, and thus to  obviate the confusion that
would arise from varied reflections, were the choroid devoid of
such dark covering.  In the albinos or white animals, the pigment,
being wanting, this  inconvenience is really experienced, so that
they become nyctalopes, or at least see but imperfectly during the
day. In the night, however, or when the light is feeble, their vision
is unimpaired; and hence the albinos of our species have  been call-
ed by the Germans and Dutch, kakerlaken, or  cockroaches.
   Sir Everard Home is of opinion, that the pigmentum nigrum
of the eye is provided as a defence against strong  light, and hence
it is lightest in those countries farthest  removed from the effects of
the sun.  In confirmation of this he remarks, that  it is dark in the
monkey and in all animals that look upwards, and in all birds ex-
posed to the sun's rays; whilst the owl, that never sees the sun,
has no black pigment. The function, assigned to it by Sir Everard,
it doubtless possesses likewise.
   The use of the shining spot on the outside of the optic nerves,
in the eyes of quadrupeds, called the tapetum, has been an inter-
esting theme of speculation,  and has given rise to  much ingenious,
and to not a little ridiculous hypothesis amongst naturalists.  The
absence of the black pigment necessarily occasions the  reflection
of a portion of the rays from the membrana Ruyschiana;  and it
has been presumed, that these reflected rays, in  their passage back
through the retina,  may cause a double impression, and thus add 
172
sensibility.
to the intensity of vision. Another view has been, that the reflect-
ed rays may pass outwards through the retina without exciting any
action, to be thrown on the object in order to increase the distinct-
ness of the image on the retina, by an  increase of its light.  Dr.
Fleming, who, in his work on the Philosophy of Zoology, usually
exhibits much philosophical  acumen and  physiological accuracy,
thinks it not probable, that both surfaces of the retina are equally
adapted for receiving impressions of external objects, and that the
rays in their passage inwards alone produce the image.  More re-
cently, however, M. Desmoulins has adduced many facts and argu-
ments to show, that the tapetum really does act the part of a mirror,
and by returning the rays through the retina, subjects it to a double
contact. He affirms, that in nocturnal animals, and in many fishes and
birds, which require certain advantages to compensate for the con-
ditions of the  media in which they are  situated, the  tapetum is of
great extent, and always corresponds to the  polar segment of  the
eyeball, or to the  visual  axis; that in many animals,  as in the cat,
the pigmentum nigrum is wholly wanting; and that  it is only  ne-
cessary for the vision of diurnal  animals.  He farther remarks,
that,  in  man, the pigment diminishes  according  to age; and
that in advanced life  it becomes white; and he ingeniously pre-
sumes, that this is a means employed by nature to compensate, in
some measure, for the gradual diminution in the sensibility of the
retina,—the choroid beneath reflecting more and more of the rays
according as the pigment is removed from its surface.  The views of
M.  Desmoulins are the most satisfactory  of any that have been
propounded, and impress us the more forcibly,  when we compare
them with  some other fanciful speculations, such as that of  M.
Richerand, who supposes, that the use of the tapetum is to cause
animals to have an exaggerated opinion of man!  As if the same
effect would not be produced whatever  were the object that  im-
pressed the organ.
  The iris has been compared, more than once, to the diaphragm
of a lens or telescope.   Its function consequently must be, to cor-
rect the aberration of sphericity, which would otherwise take
place.  This it does by diminishing the surface of the lens on which
the rays impinge, so that they meet at the same focus on the re-
tina.   Biot has remarked, that this diaphragm is situated in the
eye precisely at the place where  it can best fulfil the  office,  and
yet admit the  greatest possible quantity of light.
  The iris is capable of contracting or dilating, so  as to contract
or dilate the pupil.   It has been already  observed, that the views
of anatomists, regarding the muscular  structure of  the iris, have
been very discrepant, and that some esteem it to be essentially vas-
cular and nervous, the vessels  and nerves being distributed on an
ereetile tissue.  The partizans of each opinion explain the motions
of the iris differently.  They who admit  it to consist of muscular 
SENSE OF  SIGHT.
173
fibres affirm, that the pupil is contracted by the action of the cir-
cular fibres, and dilated by that of the radiated. Those, again, that
deny the muscularity of the organ, say, that contraction of the
pupil is caused by the afflux  of blood into the vessels, or by a sort
of turgescence similar to what occurs in erectile parts in  general,
and dilatation  by the withdrawal of the surplus fluid.
  Admitting,  (and we think this must be conceded,) that the iris
is really muscular, we meet with a singular anomaly in its physio-
logy—that no  ordinary stimulus,  applied directly to it, has any
effect in exciting it to  contraction.  It  may be pricked with the
point of a cataract needle without  the slightest motion being ex-
cited ; and, from the experiments  of Fontana and Caldani, it
seems equally insensible, when luminous rays are made to impinge
on it; yet MM. Fowler, Rinhold, and Nysten,  have proved,
that it contracts, like other muscular parts,  on the  application of
the galvanic stimulus. Like them, too, it is  under the nervous in-
fluence,  its movements being generally involuntary ; but, there is
some reason to believe, occasionally voluntary. Dr. Roget asserts
that this is the case with his eye.   In the parrot, and  in certain
nocturnal birds, its motions  are manifestly influenced by volition;
and, when the cat is roused to attention, the pupil dilates, so as to
allow a  greater quantity of light to reach the retina.
  Magendie affirms, that the attention and effort, required to see
minute  objects distinctly, occasion contraction of the human pupil.
He selected an individual, whose pupil was very  movable; and
placing  a sheet of paper in a fixed position, as regarded the eye
and the light,  he marked the state of the pupil.  He then directed
the person to endeavour, without moving the head or eyes, to read
very minute characters, traced on the  paper.  The pupil imme-
diately  contracted, and continued so as long as the effort was main-
tained.
  Many experiments have been made to discover the nerve, which
presides over  the movements of the iris. These experiments have
demonstrated, that if, instead of directing a pencil of rays upon the
iris, we throw it upon the  retina, or through the  retina on  the
choroid, contraction of  the  pupil  is immediately induced.   The
movements of the iris must, then,  be to a certain extent under the
influence of the optic nerve.  It is found, indeed, that if the optic
nerve be divided, in a living animal, the pupil becomes immov-
able and expanded. Yet, that the motions of the iris are not solely
influenced by this nerve is evinced by  the fact, that  in many cases
of complete amaurosis of both eyes, there has been the freest dila-
tation and contraction of the pupil; and also that the section of the
nerve of the fifth pair, which chiefly supplies the iris, equally in-
duces immobility of the pupil.  The same effect is produced, ac-
cording to Mr.  Herbert  Mayo,  by dividing the third  pair;
and, according  to Desmoulins,  in  the eagle, whose iris is  ex- 
174
SENSIBILITY.
treinely movable, the third pair is the  only nerve distributed to
the organ.
   The general remark, made by Broussais, on the organs that
combine voluntary  and involuntary functions, is applicable here;
—that  they will be  found to possess both cerebral and  gan-
glionic  nerves.   Accordingly, Magendie  conjectures, that those
of the  ciliary nerves, which proceed from  the ophthalmic gan-
glion, preside over  the dilatation of the pupil, or are the nervesof
involuntary action;  and that those, which arise from the nasal
branch  of the fifth pair, preside over the contraction of the pupil.
We can thus understand why, in apoplexy, epilepsy, &c, the pu-
pil should be immovably dilated.   All volition and every cerebral
phenomenon are  abolished by the  attack ;  the nerve of the fifth
pair, therefore, loses its influence;  and the  iris is given up to  the
agency  of the ganglionic nerves, or nerves of involuntary action,
proceeding from  the ophthalmic ganglion.
   On the whole,  as the preceding  detail will have sufficiently evi-
denced, our notions, regarding the motions  of the iris, and  the
nerves that preside  over them, are vague and unsatisfactory.
   The  iris  contracts  or  dilates  according to   the  intensity of
the light  that strikes  the  eye.  If the light from an object be
feeble, the pupil is dilated to admit more of the luminous rays; on
the contrary, if the light be powerful, it contracts.  We see  this
very manifestly on  opening  the  eyes,  after they have  been  for
some time closed, and bringing a candle suddenly near them. It is
one of  the  means we  frequently employ in cerebral  diseases to
judge of the degree of insensibility.
   We shall  presently inquire into  the effect of contraction or  di-
latation of the pupil on distinct vision; and show that they are ac-
tions for accommodating the eye to vision at different distances.
   We may conclude, then, that the iris is one of the most import-
ant parts of the visual apparatus;  and that  its functions  are mul-
tiple:—that  it is partly the cause of the  achromatism of the organ,
by preventing the rays of greatest divergence from falling near the
marginal parts of the crystalline:—that it corrects  the aberration
of sphericity—regulates the quantity of light admitted through  the
pupil, and accommodates the eye,  to a certain extent, to vision at
different distances.
   An enumeration  of the multiform sentiments entertained, re-
garding the functions of the ciliary processes, will show how little
we know, that is precise, on this  matter, also.   They have often
been considered contractile;  some believing them connected with
the motions of the iris, others to vary the distance of the crystal-
line from the retina.   Jacobson makes them dilate the apertures,
which he conceives to exist in the canalgoudronni, so as to cause
the admission of  a portion of the aqueous  humour  into the canal,
and thus to change the situation of the crystalline.  Others believe 
SENSE OF  SIGHT.
175
that they secrete the pigmentum nigrum; and others—the aqueous
humour.  But the processes are  wanting in animals, in which the
humours,  notwithstanding, exist.  There is no opinion, perhaps,
more probable than that of Haller;—that they are destined to assist
mechanically in the constitution of the eye, and have no farther use.
   The function  of the  retina remains to be considered.   It  is
the part that receives the impression from  the  luminous  rays,
which impression is, by the optic nerve, conveyed to the  brain.
This nervous expansion was, at one time,  universally believed  to
be the most delicately sensible membrane of the animal frame.  Of
late, it has been shown by the  experiments of Magendie, that the
sensibility of both it and the optic nerve is almost entirely special,
and limited to the appreciation of light:—that the general sensi-
bility is exclusively possessed  by the fifth encephalic pair, and that
the nerve  of special sensibility is incapable of executing  its  func-
tions, unless that of general sensibility be in a state of  integrity.
That distinguished  physiologist found,  when  a couching needle
was passed into the eye at its posterior part, that the retina might
be punctured and lacerated without the animal exhibiting evidences
of pain.    The same result attended his experiments on  the  optic
nerves.   These nerves, both anterior and posterior to their decus-
sation, as  well as the thalami nervorum  opticorum, the superficial
layer of the tubercula quadrigemina, and the three pairs of motor
nerves  of the eye gave no signs of general sensibility.  On the
other hand, the general sensibility of the anterior part of the eye—
of the conjunctiva,—is well known.   It is such, that the smallest
particle of even the softest substance excites  intense  irritation.
This general sensibility Magendie found to be totally annihilated
by the division of the fifth pair  of nerves within the cranium;  so
that hard-pointed bodies and even liquid ammonia made no painful
impression on the  conjunctiva.  Nictation was arrested, and the
eye remained dry and fixed like an artificial eye behind the  para-
lyzed eyelids.  The sight, in  this case, also, was  almost wholly
lost; but by making the eye pass rapidly from obscurity into the
vivid light of the sun, the eyelids approximated, and, consequently,
some slight  sensibility to  light remained;  but it was extremely
slight.  In this sense, then, as in the senses of hearing and  smell,
we have the distinction between a special nervous system of sense,
and a nervous system  of general sensibility, without which the
former is  incapable of executing  its elevated functions.
   The expansion of the retina occupies  at least two-thirds of the
circumference of the eyeball.  It is of obvious importance that it
should have as much space as possible; and in certain animals,  in
which the sense is very acute, the membrane is plaited, so as to have
a much larger surface than the interiorof theeyeball; and thustoallow
the same luminous ray to impinge upon more than one point of the
membrane. This is seen in the  eyes of the eagle and vulture, and  in
nocturnal animals.  The inconceivable acuteness of the sense of sight 
176                     SENSIBILITY
in birds of prey,has already been referred to, under the sense of smell.
It was there stated, that the strange facts regarding the condor, vul-
ture,  turkey-buzzard, &c., which meet in numbers in the  forests,
when an animal is killed, ought rather to be referred to acuteness
of the sense of sight than of smell. Sir Everard Home affords an
additional  illustration  of this  subject.  "In the year  1778, Mr.
Baber, and several other gentlemen,  were  on a hunting party in
the Island of Cassimbusar, in Bengal,  about fifteen miles north of
the city of Marshedabad; they killed a  wild  hog of uncommon
size, and left it on the ground near the tent.  An hour after, walk-
ing near the spot  where it lay, the sky perfectly clear, a dark spot
in the air, at a great distance, attracted their attention; it appeared
to increase in size, and to move directly towards them; as it  ad-
vanced it proved  to be a vulture flying in a direct line to the dead
hog.  In an hour, seventy others came in all directions, which in-
duced Mr. Baber to remark,—this cannot be smell." How incon-
ceivably, sensible  to its special  irritant must this membrane be in
the human eye, when we consider that every part of an extensive
landscape is depicted upon its minute  surface;  not only in  its pro-
per situation, but with all its varied tints!  and how impracticable is
it for us to  comprehend how the infinitely wider range  of country
can be so vividly depicted on the diminutive  eye of the vulture,
as to enable it to  see its prey from such a remote distance!

   Having  traced  the mode in which the  general  physiology of
vision is effected, and the part performed by each of the constituents
of the eye proper, we shall briefly consider the functions of the
rest of  the visual apparatus; the  anatomical sketch of which has
been given under the head  of accessory organs; and  afterwards
inquire into the various interesting and important phenomena ex-
hibited by  this  sense.
   These organs perform  but a secondary part in vision.   The orbit
shelters the eye, and protects it from external  violence.  The eye-
brows have a similar effect; and, in addition to this, the hair, with
which they are furnished, by virtue  of its  oblique  direction to-
wards the temple, and by the sebaceous  secretion  that  covers it,
prevents the perspiration from flowing into the eye, and directs it
towards the temple or the root  of the nose.   By contracting the
eyebrows,  they  can   be thrown forwards and   downwards in
wrinkles; and can thus protect the "eye  from  too strong a light,
especially when coming from above.
   The eyelids cover the eye during  sleep, and preserve it from
the contact of extraneous bodies.   During  the waking  state, this
protection is afforded by the instantaneous occlusion of the  eyelids,
on the anticipation of danger to the ball.   The incessant nictation
likewise spreads the lachrymal  secretion  over the surface of the
conjunctiva, and  cleanses it; whilst the  movement, at  the  same
time, probably excites the gland to augmented secretion. 
SENSE OF  SIGHT.
177
  The chief part of the movementof nictation isperformed by the up-
per eyelid: the difference in the action of the eyelids being estimated,
by some physiologists, as four to one. Under ordinary circumstances,
according to Adelon, it is the levator palpebrae superioris, which,
by its contraction or relaxation, opens or closes the eye;  the orbi-
cularis palpebrarum not acting.   If the levator be contracted, the
eyelid is raised and folded between the eye and orbit, and the eye
is open:  if, on the other hand,  the levator be relaxed, or spread
passively over the surface of the  organ, the eye is closed.   In
this view, the orbicularis muscle is not contracted,  except in
extraordinary  cases, and  under  the influence of volition; whilst
the closure of the eye, during sleep, is dependent upon simple re-
laxation of the levator.   The views of Broussais on this subject
are, we think, more satisfactory.  He  considers that the open state
of the eye, in the waking condition, requires no effort; because the
two muscles of the eyelids are so arranged, that the action of the
levator is much more powerful than that of the orbicularis; and he
adduces,  in proof of this, that the  eyelids are,  at the time of
death, half open.  On the other hand,  the closure of the eye in
sleep, he conceives to be owing to the contraction of the orbicu-
laris muscle, which'acts whilst the others rest.   If the opening of
the eye were wholly dependent upon  the action of the levator pal-
pebra?  superioris muscle, its relaxation, during insensibility and
death, ought to be sufficient to completely close the  eye; and the
orbicularis palpebrarum would  be comparatively devoid of func-
tion; being only necessary for the closure of the organ under the
influence of volition.
  It has been found by experiments, instituted by Sir  Charles
Bell, and by Magendie, that nictation  is effected  under the in-
fluence chiefly of the portio dura of the seventh pair, or facial nerve:
—one of the respiratory nerves of Sir Charles Bell's system—
the respiratory  of the face.  When  this nerve is cut,  nictation is
completely arrested; and when the nerve of the fifth  pair, also dis-
tributed  to these  parts,  is divided,  it ceases likewise, but less
thoroughly; a very vivid light exciting it, but at considerable in-
tervals, and imperfectly.
  We see here something very analogous to the partition of the
nerves of the-senses into  those possessing general, and those con-
veying special sensibility.  Like the latter functionaries, the nerve
of the seventh pair appears to be specially concerned in nictation,
and not to be capable of executing its office unless the  fifth pair—
the nerve of general sensibility,—be  in a state of integrity.
  The eyelids can, by their approximation, regulate the quantity
of light that enters the pupil, when it is injuriously powerful; when
feeble, they are  widely separated, to  allow as much  as possible to
penetrate the organ.   By  their agency, again, the most diverging
rays from an object can be prevented from falling upon  the cornea;
  Vol. I.                    23  ' 
178
SENSIBILITY.
and the vision of the myopic or short-sighted can, in this way, be
assisted.  It is a means of which they often avail themselves.
  The cilia or eyelashes, it is probable, are of similar advantage
as regards the admission of light into the eye, and have some part,
probably, in preventing extraneous bodies, borne about in the air,
from reaching the sensible conjunctiva.
  The muscles of the eyeball have acquired the chief portion of
their interest of  late years, and largely through the investigations
of the eminent  physiologist—of  whose labours we have so fre-
quently had occasion to speak—Sir Charles Bell.   The arrange-
ment of the four straight muscles, and especially their names, suf-
ficiently indicate the direction in which they are capable of moving
the organ, when acting singly.  If any two of them contract to-
gether,  the eyeball  will,  of  course, be moved in the direction of
the diagonal, between the two forces; and if each muscle contracts
rapidly  after the other, the organ will execute a movement of cir-
cumduction.   The oblique muscles are antagonists to each other,
and roll the eye in opposite directions; the superior oblique direct-
ing the  pupil downwards and outwards; the inferior upwards and
inwards. But as  the different straight muscles are capable of carry-
ing the  eye in these directions, were we to regard the two sets of
muscles as possessing analogous functions, the oblique would  ap-
pear to  be superfluous.
  This, along with  other reasons, attracted the attention of  Sir
Charles Bell to the subject; and the result of his experiments
and reflections was:—that the straight muscles are  concerned in
the motions of the eye excited by volition; and that the oblique
muscles are the organs of  its involuntary motions; and, in this
manner, he accounts  for several phenomena, connected with the
play of these organs in health and disease.
  Whilst the power of volition can be exerted over  the recti mus-
cles, the eye is moved about in the waking state by their agency;
but as soon as volition fails, from any cause, the straight muscles
cease  to act, and the eye is turned  up under the  upper eyelid.
Hence it is, that  this happens at the approach of, and during sleep:
and whenever insensibility occurs, from  any cause, as in faintness,
or on the approach of dissolution; and that turning up of the eye-
ball, which we have  been accustomed to regard as the expression
of agony, is but the indication of a  state of incipient or total  in-
sensibility.
  Whenever, too, the eyelids are closed, the eyeball is moved, so
that the cornea is raised  under the upper eyelid.   If one eye  be
fixed upon an  object, and the other  be closed, with the finger so
placed as to feel the convexity of the cornea through the upper eyelid,
and the open eye be shut, the cornea of the other eye will be found
to be elevated.  This change takes  place during the most  rapid
winking motions of the eyelids^ and is obviously inservient to the 
SENSE OF  SIGHT.
179
 protection of the eye; to the clearing of the eyeball of every thing
 that could obscure vision, and perhaps, as Sir Charles Bell pre-
 sumes, to procure  the discharge from the ducts of the lachrymal
 gland. During sleep, when the closure of the eyes is prolonged, the
 transparent cornea is, by this action, turned  up under the upper
 eyelid, where it is securely lodged and kept moist by the secretions
 of the lachrymal gland and conjunctiva.
   The different distributions of the motor nerves of the eye have
 been described in the anatomical sketch.  It is there stated, that
 the superior oblique muscle receives one whole pair of nerves:—the
 fourth pair.   This nerve, then, it seemed to Sir Charles Bell,
 must be concerned in the functions we have described; and as the
 Various involuntary motions of the eyeball  are intimately concerned
 in expression, as in bodily pain, and  in mental agony,—in which
 the action  of the  direct muscles  seem,  for  a time, to be sus-
 pended,—he  was led to  consider  the fourth  pair as a  nerve of
 expression—a respiratory nerve; and, hence, intimately connected
 with the facial nerve of the seventh pair, which,  as  has already
 been remarked, is the great agent in the twinkling of the eyelids.
 Anatomical examination confirmed thisview;—the roots of the nerve
 being  found to arise from the same column as the other respiratory
 nerves.  The coincidence of this twinkling and of the motion of
 the eyeball  upwards was, therefore, easily understood.
   There is a difficulty, however, here, which has doubtless already
 suggested itself.  The fourth pair of nerves is distributed to the
 superior oblique only; the lesser oblique receives none of its rami-
 fications.  They cannot, therefore,  be identically situated  in this
 respect.   Yet they are both  considered by Sir Charles Bell as
 involuntary muscles.  The action, indeed, of the lesser oblique
 would appear to be even more important  than that of the greater
 oblique, as the function of the  latter, when acting singly, is to carry
 the eye upwards and inwards; and, when the action of its antago-
 nist is abolished, this is more clearly manifested.  Sir Charles
 Bell  found, that the effect  of dividing the superior oblique was
 to  cause the eye to roll more forcibly upwards: in other words,
 it was given  up, uncontrolled, to the action of the antagonist
 muscle.
   This difficulty, although it is not openly stated by Sir Charles,
 must have impressed him; as, after  having referred to the effect of
 the division of the superior oblique, he is constrained to suggest
 an influence to the fourth pair, which would, we think, be anoma-
 lous:—that it may,  on  certain  occasions, cause a relaxation  of the
 muscle to which it  goes, and,  in such case, the eyeball  must be
 rolled  upwards!
  We  have still, therefore, much to learn  regarding this subject,
into which so  much interest, and, at the same time, so much un-
certainty has been infused.   The views of Sir Charles regarding 
180
SENSIBILITY.
the functions of the two sets of muscles on certain optical pheno-
mena will be dwelt upon hereafter.
   The great use of the tears would seem to be to moisten the con-
junctiva, and to remove extraneous bodies from  its surface;  thus
assisting the motions of the eyelids and eyeball, just referred to.
These tears are secreted by the  lachrymal gland;.and, by means
of its excretory ducts, are poured upon the surface of the tunica
conjunctiva, at the upper and outer part of the eye. Their farther
course towards the puncta lachrymalia has been the subject of dif-
ference  of sentiment.   The generality of physiologists consider,
that, owing to the form of the tarsal cartilages, a canal must exist,
when the eyelids are  closed, of  a triangular shape, formed  ante-
riorly by the junction of the cartilages, and behind by the ball  of
the eye.  Magendie, on  the other hand,  denies the existence  of
this canal, and asserts, that the tarsal cartilages do not touch by a
rounded edge, but by  an inner plane surface.  If we were to grant
the existence of this canal, it could only aid us in our explanation
of the course of the tears during  sleep.   In the waking state, they
are not ordinarily secreted in such quantity as to require that much
should pass to the puncta; the movements of nictation  spreading
them over the surface of the eye, whence they are partly absorbed,
and the  rest perhaps is evaporated.  Under extraordinary circum-
stances, however, the gland increases  its secretion so  much, that
the tears not only pass freely through the lachrymal ducts into the
nose, but flow over the lower eyelid.   The  epiphora or watery
eye, caused by obstruction of these ducts, also proves that a certain
quantity of the secretion must  always be passing into the  puncta.
The physical arrangements of the eyelids  and tunica conjunctiva
are doubtless the cause of their course in this direction.
  It has been gratuitously supposed by some, that the humour  of
Meibomius prevents the tears  from reaching the outer surface  of
the lower eyelid; acting like a layer of oil on the margin of a ves-
sel filled with water.   A similar function has been assigned to the
secretion of the caruncula lachrymalis.  Both these fluids, how-
ever, are probably inservient to other ends.  They are readily mis-
eible with water—become consequently dissolved in the tears, and,
with the assistance of the fluid secreted by the tunica conjunctiva,
aid the movements of the eyelids over the  ball of the eye, and
keep the tarsal  margins and  their appendages in the condition re-
quisite for the due performance of their functions.
  The action of the puncta themselves in admitting the tears has
received different explanations. Adelon regards it as organic and
vital.  We ought, however, in all cases, to have recourse to this
mode of accounting for phenomena  as the ultima ratio, and the
present  appears to us to be a case in which it  is  singularly unne-
cessary.  In many of the  results of absorption we are compelled
to suppose, that a vital operation must have been concerned in the 
sense of  sight.
181
process.  Where, for example, as in the case of the lymphatic ves-
sels, we find the same fluid circulating, whatever may have been
the nature of the  substances whence it was obtained, the evidence,
that a vital action of selection and  elaboration has been going on,
is irresistible: but no  such action can have occurred in the case in
question.   The tears in the lachrymal ducts and in the ductus ad
nasum are identical with those spread upon the surface of the eye;
the only difference being in their situation.   This is one  of the
few ca*s in the human body, which admit of satisfactory explana-
tion on the physical principles  of  capillary attraction.  In vege-
tables, the whole  of the circulation of their juices is to be thus ac-
counted for. If we twist together several threads of yarn, moisten
them, and put one extremity  of the roll into a vessel of water, al-
lowing the other to hang down on the outside of the vessel, and
to dip into  an empty vessel placed below it, we  find, that the
whole of the fluid, in the first vessel, is in a short time transferred
to the second.  If, again, we  take a small tube, less than the twen-
tieth part of an inch in diameter, which  is called  capillary, and
place it  so as to touch  the  surface of water, we find,  that the
water  rises in it  to  a  height, which  is greater the smaller the
bore of the tube.   If  the diameter of the tube be the fiftieth part
of an inch, the water  will rise to the height of two inches and a
half; if the one  hundredth part of an inch, to five inches; if the
two hundredth part of an inch, to ten inches; and so on.  Now, the
punctum lachrymale is, in our view of the subject, the  open ex-
tremity of a capillary tube, which  receives  the fluid of the lachry-
mal gland and conveys it to the nose, being properly directed to-
wards the eyeball by  the tensor tarsi muscle of Horner.
  Lastly, the tunica  conjunctiva is another part of the guardian
apparatus of the eye.  It secretes a fluid,  which readily mixes with
the tears and appears  to have similar uses.  Like the mucous mem-
branes in general, it absorbs; and, in this way, a part, of the la-
chrymal secretion is removed from its  surface. An animal, for the
same reason can be readily poisoned by applying Prussic  acid to
it.   As the conjunctiva lines the eylids and is reflected over the
globe, it  supports the friction, when  the  eyeball or eyelids are
moved;  but, being highly polished and always moist, the whole
of this is but insignificant.
   The extreme sensibility of the outer part of the eye appertains
entirely to the tunica conjunctiva, and is dependent on the ophthal-
mic branch of the fifth pair.   When this  nerve was divided in a
living animal, Magendie found that  the membrane became en-
tirely insensible to every kind of  contact, even of substances that
destroyed it chemically. In his experiments on this subject, he ar-
rived at  some singular results, regarding the influence of the fifth
pair on the  nutrition of the eye. When the trunk of the nerve was
divided within the cranium, a little after its  passage  over the pe-
trous portion of the temporal bone, the cornea was found, about 
182                     SENSIBILITY.
twenty-four hours afterwards, to become troubled, and a large spot
to form upon it.  In the course of from forty-eight to sixty hours,
this part was completely opaque; and the conjunctiva, as well as
the iris, was in a state of inflammation; a turbid  fluid was thrown
out into the inner chamber, and false membranes proceeded from
the interior surface of the iris.   The crystalline and vitreous hu-
mour now began to lose their transparency; and, in the course of
a few days, were entirely opaque.
  Eight days after the division of the nerve, the cornea stparated
from the sclerotica; and the portions of the humours that remained
fluid escaped at the opening.  The organ diminished in size, and
ultimately became a kind of tubercle, filled with a substance of a
caseous appearance.   Magendie properly concludes from these
experiments, that the  nutrition of the eye is under the influence of
the fifth pair ; and he conceives, that the opacity of the cornea was
directly owing to the section of this nerve, and  not to  a cessation
of the lachrymal secretion or to the prolonged contact of air, caused
by the paralysis of the eyelids; inasmuch as when the branches of
the nerve proceeding to the eyelids  were simply  divided, or when
the lachrymal gland was taken away, the opacity did  not super-
vene.

                   Phenomena of Vision.

  It has been more than once remarked, that  the retina—the ex-
pansion of the  optic  nerve—is the part  of the  eye that  re-
ceives the  impressions  of luminous rays, from which they  are
conveyed  by the optic  nerve  to the brain.   Yet  this has been
contested.
  The Abbe Mariotte discovered the singular fact, that when a
ray of light falls,  as he conceived, upon the  centre of the optic
nerve, it excites no sensation.
   " Having often observed," he remarks, "on dissections of men
as well as of brutes, that the optic nerve does never answer just to
the middle of the bottom of the eye; that is, to the place where
the picture of the object we look directly upon is made; and that
in man it is somewhat higher, and  on the side towards the nose;
to make therefore the  rays of an object to fall upon the optic nerve
of my eye, and to find the consequence thereof,  1 made this expe-
riment.  I fastened on an obscure wall, about the  height of my
eye, a small round paper, to serve me for a fixed point of vision.
I fastened such another on the side  thereof towards my right hand,
at the distance of about two feet, but somewhat lower than the first,
to the end that I might strike the optic nerve  of  my right eye,
while I kept my left shut.  Then I placed myself over against the
first paper, and drew  back by little and  little, keeping my right
eye fixed and very steady on the same, and being about ten feet
distant, the second paper totally disappeared." 
sense of  sight.
183
   It is obvious, from what has been said regarding the axes of the
 orbits and the part of the eyeball at which the optic nerve enters,
 that rays of light from an object can  never fall, at the same time,
 upon the insensible point of each eye. The defect in vision is, con-
 sequently, never experienced except in such experiments as those
 performed by Mariotte.  In one of these he succeeded in direct-
 ing the rays to the insensible points of both eyes at once.  He put
 two round papers at the height of the eye, and at the distance of
 three feet from each other. By then placing himself opposite them
 at the distance of twelve or thirteen feet, and holding his thumb
 before his eyes, at the distance of about eight inches, so that it con-
 cealed from the right eye the paper on the left hand, and from the
 left eye the paper on the right, he looked at his thumb steadily with
 both eyes, and both the papers were lost sight of.
   These experiments certainly show, that there is a part of the re-
 tina or optic nerve, which is, in  each  eye, insensible to light; and
 that this point is on the nasal side of the axis. No sooner, however,
 had Mariotte  published  an account of his experiments  than it
 was decided, that this spot was the base of the optic nerve; a con-
 clusion was accordingly drawn, that it is incapable of distinct vision,
 and this conclusion has been embraced,  without examination, in
 almost all the books of optics to  the present time.  Although pro-
 bable, however, it is by  no means certain that  the  light, in these
 cases, does fall upon the base of the nerve.  The direction in which
 the ray proceeds is such, that it  is reasonable  to suppose it  does
 impinge there;  the suggestion of M. Thillaye, that it falls upon
 the yellow spot of Soemmering, can only be explained by his being
 in utter ignorance of its situation, which we have seen to be on the
 outer side of the nerve.  But granting  that the light falls on the
 base of the nerve, it by no means demonstrates, that  the nerve is
 incapable of receiving the impression.  It has been already shown,
 that the central artery of the retina penetrates the eye through the
 very centre of the nerve; and, through the same opening, the cen-
 tral vein leaves the organ.  It is probable, therefore, that, in these
 experiments, the ray falls upon the blood-vessels, and not upon the
 medullary matter of the nerve; and if so, we could not expect that
 there should be sensation.   That the insensible spot is of small
 magnitude is proved by the fact, that if candles are substituted for
 the round papers or wafers, the candle does not disappear, but be-
 comes a cloudy mass of light.  It is true, Daniel Bernouilli con-
 sidered the part of the  nerve insensible to distinct impressions to
 occupy about the seventh part of the diameter of the eye, or about
 the eighth of an inch ; but there must evidently have been some error
in his calculations, for the optic nerve itself can rarely equal this pro-
portion.  The estimate of Lec at, who was himself a believer in the
views of Mariotte, that its size is about one-third, or one-fourth of
a line, is probably still wider from the truth in the opposite direc-
tion.  Simple experiment, with two wafers placed upon a door at 
184
SENSIBILITY.
 the height of the eye, will show clearly, that both the horizontal
 and vertical diameters of the spot must be larger than this.
    The fact, observed by Mariotte, was not suffered to remain in
 repose.   A new hypothesis of vision was formed upon it; and as
 he considered it demonstrated, that the optic nerve was insensible
 to light, he drew the inference, that the retina was so likewise; and
 as vision was effected in every part of the interior of the eye, ex-
 cept at the base of the optic nerve, where the'choroid is alone ab-
 sent: he inferred that the choroid must be the true seat of vision.
    The controversy, at  one time,  maintained on this subject, has
 died away, and it  is not our intention to disturb its ashes, farther
 than to  remark, that M. De La Hire, who engaged in it, enter-
 tained the opinion, that the retina receives the impression of the
 light in a secondary way, and through the choroid coat as an inter-
 mediate  organ:  that by the light striking the choroid coat, it is
 agitated, and this  agitation is communicated to  the retina.   The
 views of De La Hire are embraced by Brewster, in  his recent
 treatise on optics, as well as by numerous other philosophers.
    The opinions of Mariotte have  now few, if any supporters.
 The remarks already made, regarding the optic nerve; the effect
 of diseases of the retina, of the  nerve itself, and  of its thalami,
 compel us to regard its expansions as the seat of vision: and if we
 were even  to admit, with Mariotte, that the  insensible portion
 is really a part of  the  medullary matter of the  nerve, and not a
 blood-vessel existing there; we could still satisfactorily account for
♦the phenomenon by the anomalous  circumstances  in which the
 nervous part of the organ is  there placed.  The choroid coat, of
 great importance in the function, is absent; as well as the pigmen-
 tum nigrum; and  hence we ought not  to be surprised, that the
 function  is imperfectly executed; we say imperfectly, for the ex-
 periment with the  candles exhibits, that the part is  not really in-
 sensible to light; or is so in a very small portion of its surface only.
    It may seem, at first sight, that the fact of this defect existing
 only in the centre of the optic nerve, or at the  porus opticus, as
 it has been termed, where the central artery of  the retina enters,
 and  the corresponding vein leaves the organ, militates against the
 idea of its being caused by the rays impinging upon these vessels;
 as, if so, we ought to have similar defects in every part of the re-
 tina, where the ramifications of these vessels exist.  Circumstances
 are not here, however, identical.  When the ray falls upon the
 porus opticus, it strikes the vessels in the direction of their length;
 but, in the  other  cases, it falls  transversely upon them; pierces
 them, and  impresses the retina  beneath;  so that, under  ordinary
 circumstances, no difference is perceived between the parts of the
 retina, over which the vessels creep, and the remainder of  its ex-
 tent.  We can, however, by an  experiment described by J. G.
 Steinbuch, in  his Beitrag zur Physiologie der Sinne, published
 at Niirnberg, in 1811, exhibit that under particular  circumstances 
SENSE OF  SIGHT.                    185
such difference really exists, and renders the  blood-vessels of the
organ perceptible to  its own vision.  If, without closing the eye-
lids, the  left eye  be  covered with the hand, or some other  body,
and a candle or lamp be held in the right hand within two or three
inches of the right eye, but rather below it, (keeping the eye di-
rected straight forward,) on moving the candle slowly from right
to left, (or if the candle be held on the right side of the eye, it may
be moved up and down,) a spectrum appears, after a short time, in
which the blood-vessels of the retina, with  their various ramifica-
tions, are distinctly seen projected, as  it were, on a plane without
the eye,  and greatly  magnified.  They seem to proceed from the
optic nerve, and to consist of two upper and two lower branches,
which ramify towards the field of vision, where a dark spot is seen,
corresponding to the foramen centrale. The origin of the vessels
is a dark oval spot, with an areola.
  This phenomenon  must be accounted for by the parts of the re-
tina, covered by the blood-vessels, not being equally fatigued with
those that are exposed.
  It has  been  remarked, that the rays, proceeding from the upper
part of an object,  impinge upon the lower part of the retina;  and
those from the lower part on the upper portion of the retina; hence,
that the image of the object is reversed, as in Fig. 34.
  It has, accordingly, been asked;—how is it, that in these circum-
stances, we see the  object in  its proper position, inasmuch as its
image is  inverted on the retina?   Buffon, Lecat, and others be-
lieved, that originally, we do  see them so inverted; but that the
sense of touch apprises us of our error, and enables us to correct it at
so early  a  period, and so effectually, that we are afterwards not
aware of the  process.  Berkeley again  asserted, that the po-
sition of objects  is  always judged of, by comparing them with
our own; and that,  as we see  ourselves  inverted, external bo-
dies  are in the same  relation to us as if they were erect.  It
is not necessary  to  reply, at length, to these phantasies, which
are obviously  founded  in error.  Cases enough have occurred, of
the blind from birth having been restored to sight, to show that no
such inversion, as that described by Buffon, takes place;  whilst
the boy, who  stoops down  and looks at objects between his legs,
although he may  be, at first, a little confused, from the usual posi-
tion of the images on the retina  being reversed, soon sees as well
in  that way as in any other.  The truth is, that the great error
with all  these speculatists has been, that they have imagined a true
picture to be formed on the retina, which is regarded by the mind,
and therefore  seen inverted.   It need hardly be said, that there is
no  interior eye to take cognizance of this image; but that the mind
accurately  refers the impression, made upon the retina, to the ob-
ject producing it; and if the lower part of the retina be impressed
by  a ray from the upper part of  an object,  this impression is con-
   Vol. I.                     24 
186
SENSIBILITY.
veyed by the retina to the brain as it receives it, and no error can
be indulged.
  When a cone of light proceeds from a radiant point, as from B,
Fig. 34, the  whole of the rays, whatever may be their relative
obliquity, are,  as we have seen, converged to a focus upon the re-
tina at b, yet the point B is seen only in one direction,  in  that of
the central ray or axis of the  cone B b.  If we look over the top of
a card at the point B, till the edge of the card is just about  to hide
it; or if, in other words, we obstruct all the rays that pass through
the pupil, excepting  the uppermost  ray, the  point  is  seen in
the same direction as when  it was viewed by the whole  cone of
rays proceeding from B. If we look, again, beneath the card,  in a
similar manner, so as to  see  the  object by the lowermost ray of
the cone, the radiant point will be equally seen in the same direc-
tion.  " Hence," says Sir David Brewster, " it is manifest that
the line of visible direction does not depend on the direction of
the ray, but is always perpendicular to the retina;" and as the sur-
face of the retina is a portion of a sphere, these perpendiculars
must all pass through one point, " which may be called the centre
of visible direction; because every point of a  visible object  will be
seen in the direction of a line drawn from this centre to the visi-
ble point."
  The premises, assumed by  Sir David, will doubtless have struck
the reader as entirely insufficient for the  conclusion at which he
has arrived.  It seems to us,  indeed, to be as erroneous  as it is ca-
tegorical.
  The point o, Fig. 34, is, in his view, the centre of visible direc-
tion. Where a luminous cone proceeds in the direction of the axis of
the eye, the centre of visible direction will necessarily fall in  that
line, and a perpendicular, drawn from  the point b, where the rays
of the cone meet at a focus on the retina, will pass through  this
centre of visible direction. As regards a cone so situated, then, it
is true, that the object will be seen in the direction of a line drawn
from the point of impact on the  retina through the centre of the
eyeball to the visible point; but as regards every other  cone pro-
ceeding from other points of the object, A B  C, it is palpably un-
true.   Instead  of A B C, let us take any object, D E,  nearer the
eyeball, and, according to the views of Brewster, the ray pro-
ceeding from D, and impinging  on the retina at d, will  be  seen in
the direction d o; whilst that radiating from E will be seen in
the direction e  o;—in other words, the length  of the object  will
be infinite.  The absurdity will be heightened by still farther en-
larging the sphere of vision, D E, when the lines of visible direction
will be thrown  behind the centre of the eyeball, instead of before it.
  The true mode of  explaining  the difficulty, started by  Brew-
ster, is to consider the line of visible direction to be a line drawn
from the point  at which the ray strikes the retina through the op- 
sense  of sight.
187
tic centre of the crystalline a.   This will apply to every imagina-
ble case.  The points A and C, of the object ABC, are thus seen
in the direction of  the lines g A and  h C, whatever may be the
obliquity with which some of the rays of the cones, proceeding
from these points, may fall upon the cornea; in like manner, all
the rays of the cones, from the points  D and E, that can impinge
upon the crystalline, will be referred back along the lines d D, and
e E respectively.
   This "law of visible  direction," which Sir David Brewster
has laid down, " removes at once," he conceives, every difficulty
that besets the subject we have been  considering;—the  cause  of
erect vision from an inverted image on the retina.  "The lines of
visible direction necessarily cross each  other at the centre of visi-
ble direction, so that those from the lower part of the image go to
the upper part of the object, and those  from the upper part of the
image to the lower part of the object." We have seen, that, in the
case of the object D  E, they do not cross each other; and, conse-
quently, that, according to Sir David's own law, there ought  to
be no image formed. But even were  his view correct, the expla-
nation is too physical.   As soon as the ray from an object has im-
pinged upon the retina, the physical part  of the process is com-
pleted; an impression is made upon the retina;  the brain appre-
ciates  the sensation, and the object is seen in its true position.
   A certain intensity of light is necessary, in order that  the re-
tina may be duly impressed;  and this varies in different animals;
some of which,  as we have seen, are capable of exercising the func-
tion of vision in the night, and have hence been termed nocturnal.
In man, the  degree of light, necessary  for distinct vision, varies
according to the previous state of the  organ.   A person, passing
from a brilliantly illuminated  room into the  dark, is, for  a time,
incapable of seeing  any thing; but this effect varies in individuals;
some  being much  more able to see  distinctly in the dark than
others.  This is owing to the  retina, in some, being more sensible
than in others; and, consequently,  requiring a less degree of light
to impress it.   On  the  other  hand, a very powerful light  injures
the retina, and  deprives  it, for a time, of  its function; hence the
unpleasant impression produced by the introduction  of lights into
a room, where the  company have been previously sitting in com-
parative obscurity;  or by looking at the sun.   The effect upon the
retina, thus induced, is called dazzling.
   If the light that falls upon the eye be extremely feeble,  and we
look long and intensely upon any minute object, the retina is  fa-
tigued; the sensibility of its central portion becomes exhausted, or
is painfully agitated; and the objects  will appear and disappear,
according as the retina has recovered or lost its sensibility; a kind
of remission seeming to  take place  in the reception of the  im-
pressions. 
188
SENSIBILITY.
   These affections are considered by Sir David Brewster as the
source of many optical deceptions, which have been ascribed to a
supernatural origin.   " In a dark night, where objects are feebly
illuminated, their disappearance and reappearance must seem very
extraordinary to a person whose fear or  curiosity calls forth all
his powers of observation. This  defect of  the eye must have been
often noticed by the  sportsman, in attempting to  mark, upon the
monotonous heaths,  the  particular spots where moorgame had
alighted. Availing himself of the slightest difference of tint in the
adjacent heaths, he endeavours to keep his eye steadily upon it as
he advances; but whenever the contrast of illumination is feeble,
he almost always loses sight of his mark, or if the retina does take
it up a second time, it is  only  to lose it again."
  In all these cases, in which the eye has been so  long directed to
a minute object, that the retina has become  fatigued, on turning
the axis of the eye slightly away from the object,  the light from, it
will fall upon a neighbouring part of the retina and the object will
be again perceived; whilst in the mean time the part previously in
action, will have recovered from its fatigue.
  By this fact, of the  retina becoming  fatigued  by regarding
an object  for  a long  time, we explain  many interesting pheno-
mena of vision.  If the eye  be  directed, for a time, to a white
wafer, laid upon a black ground,  and afterwards to a sheet of white
paper, it will seem to have a black spot, of the same size  as the
wafer upon it; the retina  having  become  fatigued by looking at
the white wafer.  On the other  hand, if the  eye be turned to a
black wafer, placed upon a sheet of white  paper, and afterwards to
another part of the sheet, a portion of the paper, of the size of the
wafer, will appear strongly illuminated:—the ordinary degree of
light appearing intense, when compared with the previous defi-
ciency.
  It is on this, that the whole theory of  accidental colours, as
they are called, rests. When the eye has been, for some time, re-
garding a particular colour, the retina becomes insensible to this
colour;  and if, afterwards, it be turned to  a sheet of white  paper,
the paper will not seem to be white, but will be of the colour, that
arises from the union of all the rays of the solar spectrum,  except
the one to which the retina has become insensible.   Thus, if the
eye be directed for some  time, to a red wafer, the sheet of paper
will seem to be of a bluish green, in a circular spot  of the same
dimensions as the wafer.  This  bluish-green  image is  called an
ocular spectrum, because it is impressed upon  the eye  and may
be retained for a short time; and the colour  bluish-green is  said
to be the accidental colour of the red. If this experiment be made
with wafers of different colours,  other accidental  colours will be
observed,  varying with the colour of the  wafer employed, as in
the following table:— 
SENSE  OF SIGHT.
189
Accidental colour,
 or colour of the
 ocular spectrum.
 Bluish-green.
 Blue.
 Indigo.
 Violet, with a little red.
 Orange red.
 Orange yellow.
 Yellow green.
 White.
 Black.
White
      Colour of
      the wafer.
       Red
       Orange
       Yellow   f
       Green
       Blue
       Indigo
       Violet
       Black
       White
   If all the colours  of the spectrum be ranged in a  circle, in the
proportions they hold in the spectrum itself, as in the accompany-
ing figure,—the  accidental colour
of any  particular colour will  be
found  directly opposite.   Hence
the two colours have been termed
opposite colours.
   It will  follow, from what  has
been said, that if the  primary co-
lour, or that to which the eye has Black
been first directed, be added to the
accidental colour, the result must
be the same impression as that pro-
duced by the union of all the rays
of  the  spectrum—that  of white
light.  The accidental colour, in  other words, is what the primi-
tive colour requires to make it white light. The primitive and acci-
dental colours are, therefore, complements of each other; and hence
accidental colours have also been  called complementary colours.
They have likewise been termed harmonic, because the primitive
and its accidental colour harmonize with each other in painting.
   It has been supposed,  that the formation of these ocular spectra
has frequently given  rise to a belief in supernatural appearances;
the retina, in certain  diseased states of the nervous system, being
more than usually disposed to retain the impressions, so that the
spectrum will remain visible for a long time after the  cause has
been removed.  Such appear to  be the views of Drs. Ferriar,
Hibbert, and Alderson—the chief writers, in modern times, on
apparitions.   This subject will be the theme of future discussion.
It may be sufficient, at present, to remark, that the great seat and
origin of spectral illusions is, in our  opinion, the brain, and  that
the retina is no farther concerned than it is in dreaming or in the
hallucinations of insanity.  The  retina is able to  receive  visual
impressions over its whole surface, but not with equal distinctness
or accuracy.   When  we regard an extensive prospect, that part of
it alone is seen sharply, which falls upon the  central part of the
"fPnj 
190
SENSIBILITY.
retina, or in the direction of the axis  of the eye;  hence, we al-
ways, in our examination of minute objects, endeavour to  cause
the rays from them to impress this part of the retina ; the distinct-
ness of the impression diminishing directly as  the  distance  from
the central foramen increases.  This central point, called the point
of distinct vision, is readily discriminated on looking at a printed
page. It will be found that although the whole page is represented
on the retina, the letter to which the axis of the eye is directed  is
alone sharply and distinctly seen;  and, accordingly, the axis of
the eye  is directed in succession to each letter as we read.
  In making some experiments on indistinctness of vision at a dis-
tance from the  axis of the eye, Sir David Brewster observed  a
singular peculiarity of oblique vision, namely,—that when we shut
one eye and direct the other to any fixed  point, such as the  head
of a pin, and hence see all other objects within the sphere of vision
indistinctly;  if one of these objects be  a strip of white paper or  a
pen lying upon a green cloth, after a short time, the strip  of paper
or the pen will altogether disappear,as if it were entirely removed;—
the impression  of the green cloth upon the surrounding parts of
the eye extending itself over  the part of the  retina, which the
image of the pen occupied.  In a short time, the vanished image
will reappear and again vanish. When the object, seen obliquely,
is luminous,  as a candle, it  never  vanishes entirely, unless its light
is  much weakened, by being  placed at  a great distance; but
swells and  contracts and is  encircled with a nebulous halo; the lu-
minous  impressions extending themselves to adjacent parts of the
retina not directly influenced by the light itself.
   From these and other experiments of a similar character, detailed
in his Treatise on  Optics, Sir David  infers, that oblique or in-
direct vision is inferior  to direct vision, not  only in  distinctness,
but from its inability to preserve  a sustained vision of objects. Yet
it is a singular fact, that the indirect has a superiority over direct
vision in the case of minute objects such as small stars, which can-
not, indeed, be seen by direct vision.
   It is a mode, frequently  adopted by  astronomers for obtaining a
view of a star of the last degree of  faintness, to direct  the eye  to
another part of the field,  and, in this way, a  faint star, in the
neighbourhood of a large one, will often become very conspicuous,
so as to bear a certain illumination, and yet it will entirely disap-
pear, as if suddenly blotted  out, when  the eye is turned full upon
it; and,  in this way, it can be made to appear and disappear as often
as the observer pleases.  Sir J. F. W. Herschel and Sir James
South, who describe this method of  observation, attempt to ac-
count for the phenomenon  by supposing, that the lateral portions
of the retina, being less fatigued by strong light, and less exhaust-
ed by perpetual attention, are probably more sensible to faint im-
pressions than  the central ones: and the suggestion carries with it
an air of verisimilitude. 
SENSE  OF SIGHT.
191
   Sir David Brewster, however,—from the result developed by
his experiments, that, " in the case of indirect vision, a luminous ob-
ject does not vanish, but is seen indistinctly  and produces an en-
larged image on the retina, beside that which is produced by the
defect of convergency in the pencils,"—concludes somewhat mys-
tically, "that a star, seen indirectly, will affect a large portion of
the retina from these two causes, and, losing  its sharpness, will be
more distinct."
   In order, that the image of any object may impress the retina,
and be perceived by the mind;  it must, first of all, occupy a space
on the retina, sufficiently large for its various parts to be appreciated:
in the next place,  the  image must be distinct, or sharp, in other
words, the luminous rays,  that form it,  must  converge accurately
to a focus on the retina: lastly,  the image must be sufficiently illu-
minated. Each of these conditions varies with the size of the body
and the distance at  which it is situated from the eye; and there are
cases, where they are all wanting, and where the object is conse-
quently invisible.
   An object may be so  small, that the  eye cannot distinguish it;
because the image, formed on  the  retina, is  too minute.   To re-
medy  this inconvenience the object must be brought near  to the
eye, which increases the divergence of the rays and the size of the
image; but if we bring it too close to the eye, the rays are not all
brought to a focus  on the retina,  and the image is indistinct. .  If,
therefore, an object be so small, that, at  the visual point, to be pre-
sently mentioned,  the  rays, proceeding from it, do not form  an
image of sufficient  size on the retina, the object is not seen.  To
obviate this imperfection of the sense, minute bodies may be viewed
through a small hole in a piece of paper or card, or with the instru-
ment called a microscope.  By  looking through the small aperture
in the paper or card, the object may be brought much nearer to the
eye; the rays of greatest divergence are prevented by the smallness
of the hole from impinging upon the retina;  and the rest are con-
verged into a focus upon that membrane, so  that a sharp  and dis-
tinct impression is  received.  The iris is, in this way, useful in ef-
fecting distinct vision; the most divergent rays being, by its con-
tracting the pupil, prevented from falling upon the crystalline.
   Any object, that does not subtend an  angle of the  sixtieth  of a
degree, is invisible; but it is obvious that this  must differ greatly in
individuals.   Some eyes are much more capable of minute inspec-
tion than others; and a  greater facility is acquired by practice.
   Again  there  is  a point of approximation to  the  eye beyond
which objects cease to  be distinctly seen, in consequence  of the
rays of light striking so divergently  upon the eye that the focus
falls behind the  retina.   This point, too, varies  according  to the
refractive power of the eye, and  is therefore  different in  different
individuals.  In the myopic or short-sighted eye, it is  much nearer 
192
SENSIBILITY.'
the eye than common; in the presbyopic or long-sighted, more dis-
tant. The iris, here again, plays an important part; by its action in
shutting off the most diverging rays, as above described.
 ^here is also a limit beyond which objects are no longer visible.
This is owing to the light from the object becoming absorbed be-
fore it  reaches the retina, or so feeble as not to make the necessary
impression.   The distance, consequently, at which an object may
be seen, will depend upon the sensibility of the retina and partly
on the  colour of the object;—a light colour being visible to a greater
distance than one that is dark.  A distant object may also  be im-
perceptible, owing  to the image, traced  on the retina, being too
minute to be appreciated; for the image diminishes as the distance
of the object increases.  The range of distant vision varies, likewise,
with the individual, and especially with  the  myopic  and presby-
opic; and in such cases the pupil dilates to admit as much light as
possible into the interior of the eye, and to compensate in some
measure for the defect.  Between the ranges of distant and near
vision, a thousand different distances  occur, which are seen more
or less distinctly.  In all cases, however, the ocular cone must be
brought to a focus on the retina, otherwise there cannot be perfect
vision.  It has been  already observed, in the proem on light, that
the distance, at which the ocular cone arrives at a focus behind the
lens, is always in proportion to  the length of the objective cone;
or, in other words, that the focus of a lens varies with the distance
at which  a radiant  point is situated before  it: where the radiant
point is near the lens the focus will be more remote behind it, and
the contrary.   If this occurs in the human eye it must necessarily
follow;—either that  it  is not necessary, that an object be impressed
upon the retina; or that the eye is capable of accommodating itself
to distances; or if it does not occur, we must admit that, owing to
the particular constitution  of the  eye, the  impressions are duly
made on the retina,  without any necessity for such adaptation.
  The whole bent of our observations on vision would preclude the
admission of the first of these postulates. The second has been of al-
most universal reception, and has given rise to many ingenious spe-
culations; whilst the third has been seriously urged of late years
only.
   It would occupy too  much  space to dwell, at length, upon the
various ingenious discussions and the many interesting and  curious
experiments, that have resulted from a belief in the power possess-
ed by  the eye of accommodating itself to distances. It is a subject,
however, which occupies so large a field  in the history of physio-
logical opinions, that it cannot be wholly passed over.  The chief
views, that have been entertained upon the subject, are:—1. That
the cornea or lens must recede from, or  approach the retina,  ac-
cording to the focal distance, precisely as we adapt our telescopes,
by lengthening or shortening the tube. 2. If we suppose the retina 
sense of  sight.
193
to be stationary, the lens must experience a change in its refractive
powers, by an alteration of its shape or density ;  or, 3. In viewing
near objects, those rays only may be admitted, which are nearest
to the axis of the eye,  and which are consequently the least
diverging.
   1. The hypothesis, that the adjustment of the eye is dependent
upon an alteration in the antero-posterior diameter of the organ, or
on the relative position of the humours and retina, has been strongly
supported by many able physiologists.  Blumenbach was of opi-
nion, and his views seem to have been embraced by Dr. Hosack,
that the four straight muscles of the eye, by compressing the eye-
ball, cause a protrusion of the cornea, and thus an increase in  the
length of the  axis.  Dr. Monro  believed that the iris,  recti mus-
cles, the two  oblique and the orbicularis palpebrarum have  all
their share in  the accommodation;  and Hamberger, Briggs,
and  others, that the  oblique  muscles, being thrown  in opposite
directions round it, may have the effect of elongating the axis
of the eye.
   Kepler thought, that the ciliary processes draw the crystalline
forwards, and increase its distance  from the retina.   Descartes
imagined the same contraction  and elongation to be effected by a
muscularity of the crystalline, of which he supposed the ciliary
processes to be the tendons. Porterfield, that the corpus ciliare
is contractile,  and capable of producing the same effect. Jacobson,
that the aqueous humour, by entering the canal of Petit, through
the apertures in it, distends the canal, and pushes the crystalline
forwards.  Sir Everard Home, that the muscular fibres he  has
described as existing between the ciliary processes, move the lens
nearer to the retina, and that the lens is  brought forward by other
means, (which he leaves to conjecture,) when the distance of  the
object is such as to require its being so. Dr. Knox, that the annulus
albus, or the part which unites the choroid and  sclerotic coats, is
muscular, and the chief agent in this adjustment; whilst  Sir David
Brewster thinks it " almost certain, that the lens is removed from
the retina by the contraction of the pupil."
   Without examining these and other views in detail, it may be re-
marked, that the nicest and most ingenious examination by the late
Dr. Young could not detect any change in.the length of the axis of
the eyeball. To determine this, he fixed the eye, and at the same time
forced in upon the ball the ring of a key, so as to cause  a very ac-
curately defined phantom to extend within the field of perfect vision;
then looking to bodies at different distances, he expected, if  the
figure of the eye weremodified,that the spot, caused by the pressure,
would be altered in shape and dimensions; but no such effect oc-
curred ; the power of accommodation was as extensive as ever, and
there was no perceptible change either in the size or figure of  the
oval spot.
   Vol. I.                    25 
194
SENSIBILITY.
   Sir Everard Home, again, asserts that all the ingenuity of the
distinguished mechanician, Ramsden, was unable to decide, whe-
ther, in the adjustment of the eye, there is any alteration produced
in the curvature of the cornea.
   These facts would alone induce a doubt of the existence of this
kind of adjustment, even if we had not the additional evidence,
thai many animals are incapable  of altering the shape of the eye-
ball, by the muscles at least.   The cetacea and the  ray, amongst
fishes, and the lizards amongst reptiles, have the sclerotica so in-
flexible as to render any variation in it impossible.
   With regard to many of the  particular views that have been
mentioned, they are mere "cobwebs of the brain," and unworthy
of serious argument.  In the action of the orbicularis palpebra-
rum, as suggested by Dr. Monro, there is, however, something
so plausible, that many persons have been misled by it.
   He made a set of experiments to show, that this muscle, by com-
pressing the eyeball, causes the cornea to protrude, and thus ena-
bles the eye to see near objects more distinctly. When he opened
his eyelids wide, and  endeavoured  to read letters, which were so
near the eye as to be indistinct, he  failed; but when he kept the
head in the same relation  to the book, and brought the edges of the
eyelids within a quarter of an inch of each other, and then  made
an exertion to read, he found  he could see the letters distinctly.
On this  experiment Sir Charles Bell properly remarks, that if
the eyelids have any effect upon the eyeball by their approximation,
it must be to flatten  the cornea; and that the improvement in near
vision produced by such  approximation, was owing to the  most
divergent rays being shut off,  as in the experiment of the pin-hole
through paper, and distinct vision being thus effected.
  2. The second hypothesis,  which attributes the adaptation to a
change of figure in the crystalline itself, has  been embraced by all
those  who regard that body  to  be muscular; and  therefore by
Leeuwenhoek and Descartes, and more lately by Dr. Young.
  These muscular fibres,  however, could never be excited by Dr.
Young, so as to change  the  focal power; and their existence is
more than doubtful.  The increasing density of the  lens towards
the centre indicates rather a cellular structure, the cells being filled
with transparent matter of various degrees of  concentration; and
an examination into its  intimate physical constituents affords no
evidence of muscularity.
  It is somewhat singular, that on a subject where so many oppor-
tunities  have occurred for establishing the fact definitively, such
difference of opinion should exist regarding the question, whether
an eye from  which  the crystalline has been removed, as in the
operation for cataract,  is capable of adjusting itself to near objects?
Amongst others, Haller and Knox decide the question affirma-
tively; Porterfield, Young, and Travers,  negatively. 
SENSE OF SIGHT.
195
   Magendie, as we have seen, considers the  great use  of  the
crystalline to be:—to increase the brightness and sharpness of the
image by diminishing its size.  Mr. Travers again, regards ad-
justment as a change of figffre in  the  lens; not,  however,  from a
contractile power in the part itself,  but  in  consequence of the la-
mellae, of which it is composed, sliding over each  other, when acted
upon by external pressure; while, upon  the removal of this pres-
sure, its elastic nature restores it to its former sphericity.
   The iris is conceived to be the agent  in this process;  the pupil-
lary part of the organ being, in  the  opinion of Mr. Travers, a
proper sphincter muscle, which, when it contracts and relaxes, will
tend, by the intervention of the ciliary processes, to effect a change
in the figure of the lens, which will produce a corresponding change
in its refractive power.
   3. One of the causes to which the faculty of seeing at different dis-
tances has been ascribed, is the contraction and dilatation of the pu-
pil. It has been already observed, that when we look at near objects,
the pupil contracts, so that the most divergent rays do not pene-
trate the pupil, and vision is distinct. Hence it has been conceived
probable, by De La Hire, Haller, and  others, that  the adjust-
ment of the eye to various distances, within the limits  of distinct
vision, may be effected by this mechanism; in the same manner as
it regulates the quantity of light admitted into the interior of the
organ.  Certain  it is, that if we look at a row of minute objects,
extending from the  visual point outwards,  the pupil  is seen to
dilate gradually, as  the axis of the eye recedes from the  nearest
object.
   An experiment, made by the author, when a student of medicine,
on his own eye, has been quoted  by Dr. Fleming, as confirmatory
of this view.  The extract of belladonna has the power, when ap-
plied to the eyelids, of dilating the pupil considerably.   This was
so applied, and in the space of  about  twenty minutes, the pupil
 was so much  dilated, that the iris was almost invisible.   From the
 time that it became preternaturally dilated, objects presented to
 this eye, with the other closed, were seen as through a cloud.  The
 focus was found to  be at twice  the distance of that of the sound
 organ; but in proportion as the effects  of the belladonna went off,
 and the pupil approached its natural size, vision became more and
 more distinct, and  the focus nearer the natural.   In the open air,
 all objects, except those near, were distinctly seen, but, on entering
a room, all was enveloped in mist.
   There is, indeed, more evidence in favour of the utility of  con-
traction and dilatation of the pupil in distinct  vision,  within cer-
tain limits at least, than of either of the other  supposed  methods
of adjustment; and, accordingly, the majority of opticians of the
present day embrace this view of  the  subject;  but without being
able to explain satisfactorily the  change in the interior  of the eye 
196
SENSIBILITY.
 effected  by its  movements.   " It seems difficult," says Sir Da-
 vid Brewster—the latest writer on this subject, " to avoid the
 conclusion, that the power  of adjustment depends  on  the me-
 chanism which  contracts and dilates the pupil; and as this adjust-
 ment is independent of the variation of its aperture, it must be ef-
 fected by the parts in  immediate contact with the base of the iris.
 By considering  the various ways in which the mechanism at the
 base of the iris may produce the adjustment, it appears to be almost
 certain, that the  lens is removed from the retina by the contraction
 of the pupil."  The  conclusion, drawn by Sir David,  does not
 impress us with  the same degree  of certainty.
  Pouillet, whose lectures at the FacultS des Sciences  of  Paris
 have  been recently published, explains the matter,  with  no  little
 confidence,  by the double effect of the crystalline  being  com-
 posed of different  layers, and  the mobility of the pupil.  These
 layers being thinner towards the axis of the crystalline than near
 its  edges, by detaching them successively, the curvature of the re-
 mainder becomes  greater and  greater, until the most central por-
 tion has the shape  of a sphere.  Hence, he  remarks,  such an
 apparatus will not have one focus only, but several, as many, in
 fact, as there are  superposed  layers;  the foci being nearer and
 nearer as we approach the  central  spherical  portion.  This ar-
 rangement, he says, enables us to see at all distances, inasmuch as,
 having " an infinite number of foci at our disposal, we can use
 the focus, that suits the object we are desirous of viewing."  If,
 for  example, it be a near object, the  pupil contracts, so as to allow
 the rays to fall only on the central part; if more distant, the  pupil
 is dilated to permit the rays  to  pass  through a part, that has a
 more  distant focus.
  It is obvious,  however, that in such a case, the ordinary incon-
 venience  of the aberration of sphericity must result; as when
 the pupil is dilated, the rays must pass through the central, as
well as through the more marginal parts of  the lens.  Pouillet
himself is aware of this difficulty, but he does not dispose  of it
philosophically.   " It may be said," he remarks, " that in opening
the pupil  widely, the light is not precluded from passing by the
 centre, and that  a kind of curtain would  be required to cover the
part of the lens,  which  is unemployed.   To this I reply, that there
is no necessity to prevent the rays from passing by the axis of the
 crystalline; for,  what is the light, which passes through this  small
 space  compared with that which passes through the great zone of
 the crystalline.   It may be looked upon as null."
  The whole affair, it must be admitted, is enveloped in perplexity,
 and is rendered not the less so by the fact, mentioned by Magen-
 die, that if we take the eye of an albino animal, and  direct it to-
 wards a luminous object, we find a perfect image  depicted on the
 retina, whatever may be the distance  of the object;—the image, 
SENSE  OF SIGHT.
197
of course, being smaller and less luminous when remote, but always
distinct.   Yet, in this experiment, the eye being dead, there could
be neither contraction nor dilatation of the pupil.
   This result has induced Magendie, and  not  too hastily, we
think, to draw the conclusion—that although theory may suggest,
that there ought to be such adaptation, as has been presumed and
attempted to be accounted for, observation proves, that this is not
the  fact; and, consequently, all the  speculations  on the subject,
however ingenious they may be, must fall to the ground.
   We are, indeed, not justified perhaps  in admitting more than a
slight  accomodation  from the contraction of the pupil in viewing
near objects, effected in the mode already explained.   If the acco-
modation  existed to  any material extent, it  is difficult  to under-
stand, why trifling cases of short or long-sightedness should not be
rectified.  Sir Charles Bell conceives  " that the mechanism of
the eye has not so great a power of adapting the eye to various dis-
tances as is  generally imagined, and  that much of the effect attri-
buted to mechanical  powers, is the consequence of the  motion of
the pupil, the effect of light and of  attention.  An object looked
upon, if not attended to, conveys no sensation to the mind.   If one
eye is weaker than the other, the object of the stronger eye alone
is attended  to, and  the  other  is entirely neglected: if we  look
through a glass with one eye, the vision  with the other is not at-
tended to." "The mind," he adds, " not  the eye, harmonizes  with
the state of sensation, brightening the objects to which we attend.
In looking  on a  picture  or panorama, we look to  the figures, and
neglect the  back  ground; or we look to the general landscape, and
do not perceive the near objects.  It cannot be an adaptation of the
eye, but an accommodation and association of the mind with the
state of the  impression."
   The view, we have expressed upon the subject, is strikingly con-
firmed by the calculations of M. De Simonoff, a learned Russian
astronomer, who  asserts, that from a distance of four inches to in-
finity, the changes in the angle of refraction do not exceed twenty-
three  minutes, so that the apices of luminous cones, in a properly
formed eye, must always fall  within the substance of the retina,
and hence no variation in the shape of the eye, according to the
distance of  the object, can be necessary.
   Such facts amply justify the interrogatory of Biot—whether the
aberration of  the focus for different distances may not be compen-
sated, in  the  eye, by the intimate  composition of the refractive
bodies; as the aberration of sphericity probably is? Yet, if this be
the case, how admirable must be the construction of such an instru-
ment! how far surpassing any effort of human ingenuity! an instru-
ment capable of not only correcting its own aberration of sphericity
and its aberration of refrangibility, but of seeing at all distances.
   It has been before observed, that the visual point varies in dif- 
198
SENSIBILITY.
ferent individuals.  As an average, it  may  be assumed  at eight
inches from the eye.  There are many, however, who, either
from original conformation of the organ,  or from the progress of
age, wander largely from this average; the two extremes consti-
tuting myopy or short-sightedness, and presbyopy or long-sight-
edness.
  In the myope or short-sighted, the visual  point is so close, that
objects cannot be seen, unless brought near the eye.  This  defect
                              is owing to too great a refractive
           Fig. 36.           power in the transparent  parts of
                              the organ; or to too great a depth
   s*"    >v                    of the  humours;  or it  may be
 /............;^V--~""^::^===^5ST" causea"  °y unusual  convexity of
 n^^^^-t^^^<Cr^^       *ne cornea or crystalline; or from
 Xs^^^"^"11^/?-"^^^           the retina  being too distant from
  y^  ^y                   the crystalline.  From any one or
                              more of these causes, the rays of
light, proceeding from distant objects, are brought to a focus before
they reach the retina, and the objects consequently are not distinctly
visible. (Fig. 36.) To see them distinctly, they must be placed close
to the eye, in order that the rays may fall more divergently, and the
focus be thrown farther back, so as to impinge  upon the retina.
  The defect may be palliated by the use of concave glasses,  which
render the rays, proceeding from the object, more  divergent.  It
is by no  means infrequent in youth; and the myope has been con-
soled with the common belief, that, in  the progress of life, and in
the alterations,  that take place in the eye from age, he is likely to
see well without spectacles, when others of the same age may find
them essential.   It is probable, however, that this is a vulgar error;
as we have known  different sexagenarians, who have  not expe-
rienced the slightest improvement by the progress of age.
  The presbyope, presby tic, or long-sighted labours under an op-
posite defect.   The visual point is much  more distant than the
average;  and he is unable to see an object unless it is at some dis-
tance.  This condition is owing to too  feeble a refractive power in
                                 the transparent parts of the eye;
            Fig. 37.             to insufficient depth of the eye;
                                 to too close an  approximation
                                 between the retina and crystal-
                                 line; or to too little convexity
                                 of the cornea or crystalline; so
                                 that the rays of light,  proceed-
                                 ing  from  a near object, are not
rendered sufficiently convergent to impinge  upon the retina, but
fall behind it.  (Fig. 37.)
  This defect, which is experienced by most people, more or less,
after middle age, is palliated by the use of convex  glasses,  which
 
SENSE  OF SIGHT.
199
render the rays, proceeding from an object, more convergent, and
enable the eye to refract them to a focus farther forward, or on the
retina.
  Although the presbyopic eye is unusual  in  youth, it is some-
times met with.  A young friend, at ten or twelve years of age,
was compelled to employ spectacles, adapted to advanced life; and
this was the case with several of the members of a family, to whom
the arts have been  largely indebted in this country.  One of them,
at twenty, was  compelled  to wear spectacles which were almost
microscopes.
  Both the myopic and the presbyopic conditions exist in a thou-
sand degrees, and hence it is impossible to  say, a priori, what is
the precise lens, which will suit any particular individual.  This
must be decided by trial.  The opticians have their spectacles ar-
bitrarily numbered to suit different periods of life, but each person
should select for himself such as will enable him to read without
effort at the usual distance.
  A degree of myopy may be brought on  by  long-protracted at-
tention to minute and near objects; as we observe occasionally in
the watchmaker and engraver; and again, a person, who has been
long in the habit of looking out for distant objects, as the sailor, or
the watchman at the signal stations, is rendered less fitted for mi-
nute and near inspection.
  During the domination of Napoleon, when the conscript laws
were so oppressive, the young men frequently induced a myopic
state of the eye, by the constant use of glasses, of considerable con-
cavity ; this defect being esteemed a sufficient  ground  of exemp-
tion from  military  service.
  Another question, which has given rise to much disputation and
experiment is, why, as we have two eyes, and the image of an ob-
ject is impressed upon each of them, we do not  see such object
double ?
  Smith, in his " Optics," and Buffon consider that  in infancy
we do see it double; and that it is not until we have  learned by
experience,—by the sense of touch for example,—that one object
only exists, that we acquire the power of single vision.   After the
mind has  thus become instructed of its error, a habit of rectifica-
tion is attained, until it is ultimately effected unconsciously.
  The objections to this hypothesis are many and cogent. We are
not aware of any instance on  record, in which double  vision has
been observed to occur in those, who, having laboured under cata-
ract from  birth, have received their sight by an operation; and we
are  obviously precluded from knowing the state  of vision in  the
infant; although the simultaneous and parallel motion of the eyes,
which  is  manifestly instinctive, and not dependent upon habit,
would induce us to presume, that the images of  objects—as soon
as the parts have attained the necessary degree of development—
are  made to fall upon corresponding parts of the retinae.  This, we 
200
SENSIBILITY.
 shall see, is essential to single vision.  It may, also, be remarked,
 in favour of the instinctive nature  of this parallel motion  of the
 eyes, that in the blind,—although we may find much irregularity in
 the motions of the eyeball, owing to no necessity existing for the
 eyes being directed to any particular point—the eyeballs move to-
 gether, unless some deranging influence be exerted.
  Again, are we to presume that all those animals, which  are  ca-
 pable of directing their eyes towards the same object always see
 double?  and if they do not, how is the error rectified  in  them?
 Can we suppose, for example, that the young  calf sees  two mo-
 thers, and that it is by an intellectual process,  that it knows there
 is only one ?
  The truth is, as we have already observed, that the encephalon
 is compelled to receive the impression as it is conveyed to it; and,
 even in cases in which we are aware of an illusion, the perception
 of the illusion still exists in spite of all experience.  If the finger
 be pressed on one side of the eyeball, an object, seen in front, will
 appear double,  and the perception of two objects will be made in
 the brain; although we know, from experience, that one only ex-
 ists. This occurs in all the various optical  illusions to be presently
 mentioned.
  The effect of intoxication has been adduced in favour of this hy-
 pothesis.   It is said that, in  these cases, the usual train  of mental
 associations is broken in upon, and hence double vision results.
  The proper explanation, however, of this diplopia of the drunk-
 ard rests upon other grounds. The effects of inebriating substances
 on the brain are, to interfere  with all the  functions of that organ:
 and most sensibly with the voluntary motions, which become ir-
 regularly executed.   The voluntary muscles of the eye partake of
 this vacillation  and  do not move in  harmony,  so that  the impres-
 sions are not made on corresponding points  of the retina, and double
 vision  necessarily results.
  Another hypothesis has been, that although a separate impression
 is made upon each retina,  in consequence of the union of the optic
 nerves, the impressions are amalgamated,  and arrive at  the ence-
 phalon, so as to produce but  one perception.
  This was  the opinion of Briggs and Ackermann and at one
 time was generally received.  Still more recently, Dr. Wollaston
 has supposed the consentaneous motion of the eyes to be connected
 with the  partial union of the optic nerves.  The  anatomical and
physiological facts, relating to the union and decussation of the optic
 nerves, have already engaged us.  By a reference to  that subject
 it will  be found, that a true decussation takes place between them;
 that each eye has, notwithstanding, its distinct nerve, from origin
to termination; and that no such semi-decussation, as that contended
for by  Dr. Wollaston, exists.  These facts are unfavourable to
 this  hypothesis of amalgamation of impressions: and, besides, if
 we press slightly on the eye, we have a double impression, although 
SENSE OF  SIGHT.
201
the relation of the optic nerves to each other is  the  same, and,
moreover,  the same explanation ought to apply  to audition,  in
which we have two distinct impressions, but only a single percep-
tion.  Yet no one conceives that the auditory nerves decussate.
  Another opinion has been maintained;—that we do not actually
receive  the perception of two  impressions at the  same time, but
that vision consists in a rapid alternation of the eyes, according as
the attention is directed to one or other of them by accidental cir-
cumstances.  Such was the opinion of Dutours.  A modification
of this view was entertained by Lecat, who asserts, that, although
the right  eye is not always the  most powerful,  it is the most
frequently employed: and Gall openly denies, that we use both
eyes at the same time, except in the passive  exercise  of the func-
tion. In active vision, he asserts, we always employ one eye only;
sometimes the one and sometimes the other; and thus, as we receive
but one  impression, we necessarily see but one object.  In support
of this view he  remarks, that, in many animals, the eyes are  si-
tuated at the sides of the head, so as not to be capable of being di-
rected together to the same object.  In them, consequently, one
eye can alone be used; and he considers this a presumption that
such is the case in man.  He remarks  farther,  that in many cases
we use one eye by preference, in  order, that we may see better;
as in  shooting, or  in taking the direction of  objects in a straight
line, &c; and that although, in other cases, both eyes may be open,
we still  use but one.  In proof of this he says, the shade of a small
object, placed between the eyes and a lighted body, does not fall
between the eyes on the roof of the nose,  as it ought to do if the
body were regarded with both eyes, but on each eye alternately,
according as the one or the other is directed to it: and, he adds, if,
when we squint voluntarily, we see two objects, it is because one
eye sees passively, whilst the other is  in activity.
  Amongst the numerous objections to this view of the subject, a
few may be sufficient.  Every one must have observed how much
more vividly an object is seen with both eyes than with one only.
The difference indeed according to Jurin  is a constant quantity;
and, in  sound eyes of the ordinary degree of power, amounts  to
one-thirteenth of the whole effect.  But  we have  experiment  to
show, that a  distinct impression is made upon each eye.
   If a solar beam be admitted  into a dark chamber, and  be made
to pass through two  glasses of tolerable thickness,  but  of different
colours, placed close alongside each other, provided the  sight  be
good, and the eyes of equal power, the light, which is perceived,
will not be of the colour of either of the glasses, but will be of an
intermediate  shade;  and, when this does  not happen, it will  be
found that the eyes are of unequal power.  When such is the case,
the light will be of the colour of the glass, that is placed before the
stronger eye.  These results  were obtained in the  Cabinet  de
  Vol.  I.                    26 
202
SENSIBILITY.
Physique of the Faculty de Midicine of Paris, by M. Magen-
die, in the presence of M. Tillaye the younger.
  The existence of this double impression is  proved in another
way.  If we place any tall, slender object a few feet before us, and
examine  its relative situation, compared with a spot on a wall in
the distance, we find, that, if the spot be hidden by the stick when
both eyes are open, it will become visible to each eye, when used
singly; and will be seen on the side of the stick corresponding to
the eye that is employed.
  All these facts signally  demonstrate, that two impressions are
really made in all cases:—one on each eye:—and yet the brain has
perception of but one.  How the cerebral  part of this function is
executed we have not the slightest  knowledge.  All our informa-
tion is limited to the fact, that, in the  two eyes, there are corres-
ponding points, on which if a similar impression be made, vision
is single; but if the harmony in the movements of the eyes be in
any manner disturbed, so that the rays proceeding from  an object
do not impinge upon corresponding points of the two retinae, vision
is double.  This is merely stating the physical circumstances, ne-
cessary for single vision: and farther we cannot proceed, without
entering the regions of conjecture.

                          Fig. 38.
  In Fig. 38, the star at A is seen exactly in the axes of the eyes
at a and d; and it is seen singly, because the rays from it impinge
upon the  retina opposite the pupil in both eyes.  These two are,
therefore, corresponding points—instinctively or by habit, probably
the former;  and we have already seen,  that vision is most distinct 
SENSE  OF SIGHT.
203
where the rays fall upon the centres of the retinae; and that these
centres have been called the points of distinct vision.  Now, the
other corresponding points of the retinae are not, as  Dr.  Arnott
has asserted, equidistant and in similar directions from the centres
of the retinae.  They are in similar directions, but not equidistant,
as will be obvious from the figure.  Let us suppose the axes direct-
ed to the star A, and that rays, from an object at B, strike the two
eyes.  This object,  seen  by oblique vision, will, for reasons pre-
viously stated, not be as distinct as the star A; but we know from
experience, that it will  be seen single.  Experience, therefore,
teaches us, that the points of the two retinae,  on which  the rays
from B impinge, are corresponding points. As, however, the rays
from B fall on the two eyes with different obliquity, these points
cannot be equidistant from the axes; the point c in the eye  D be-
ing necessarily more remote.   In  all cases, however, of oblique
vision, it is obvious, that in one eye the point will fall on  the inner
or nasal side of the axis; in the other, on the outer or temporal side.
This seems essential; for if we so modify the experiment, that the
rays from an object impinge upon the retina, with a different rela-
tion to the axes, the object is seen double; or, in other words, the
rays do not fall upon corresponding points. Let us suppose thelines
D e, Fig. 39,  (see next page) to be the  optic axes of the eyeballs
A and B respectively; the object at D will, of course, be  seen sin-
gle; but a nearer object at S would be seen double; because all the
rays, proceeding from it and passing through the optic centre of the
crystalline in  each eye, impinge upon the retina on the outer side
of the axes; and are, therefore, not on corresponding points.   In
like manner, the rays, from a more distant object atE, will impinge
on the inner side of the axes; and double vision will  be the conse-
quence.   That such is  the case is easily proved, by  holding the
finger before the eye, and looking at any object a few feet distant;
the finger will appear double; and, if we shift our vision to the fin-
ger, the object will appear double.
   In the course of the preceding remarks, it was said, that the eyes
are not always of the same power.  The difference is,  indeed, some-
times surprising.  M. Adelon mentions the case of  a person, one
of whose eyes required a convex glass, with a focus of five inches;
the other,  a concave glass with a focus  of four inches.  In these
cases, it is important to use one unassisted eye only; as confusion
must necessarily arise from directing both to an object. This is the
cause why we close one eye in looking through a telescope.   The
instrument has the effect of rendering the focal distance of the two
eyes unequal, and of placing them in the same situation as if they
were, originally, of different powers. 
204                      SENSIBILITY.


                          Fig. 39.
  If from any cause, as from a tumour pressing upon one eyeball,
from a morbid debility of the muscles, or from a want of corres-
pondence in the sensibility of the two retinae, the eyes are not pro-
perly directed to an object, double vision is the consequence; be-
cause the rays of light no longer fall upon corresponding points of
the retinae.  In almost all cases, however, of distortion of the eye-
balls, the image will fall upon a part of one retina, which is more
sensible than the portion of the other on which it impinges; the
consequence will be that the mind will acquire the habit of attend-
ing to the impression on one  eye only;  and  the other will be so
neglected, that it will assume a position to interfere as little as pos-
sible with the vision of its fellow—so that,  although at first, in
squinting, there may be a double impression, vision is ultimately
single. Buffon, who was of this opinion, affirms, that he examined
the eyes of many squinters, and found that they were of unequal
power; the weaker, in all cases, having turned away from  its direc-
tion, and generally towards the nose, in order that fewer rays might
reach it, and consequently vision  be less interfered with.  Yet,
it is always found, if the sound eye be closed, that  the other  re-
sumes its proper direction; a fact,  which disproves the idea of
De La Hire and others, that the cause of strabismus or squint-
ing is a difference of sensibility in the corresponding points of the
retinae, and that the discordance in the movements of the organs
occurs, in order that the images may still fall upon  points of the 
SENSE  OF SIGHT.                   205
retinae, that are equally sensible.   According to this view, both
eyes must of course act.
  The fact of the diverted eye resuming its proper direction, when
the sound one is closed, is of important practical application. Many
of the cases of squinting, that occur in infancy, have been induced
by irregular action in the muscles of the eyeball; so that some,
having been, from accident or from imitation, used more frequently
than others, the due equilibrium has not been maintained ; double
vision has resulted; and the affected eye has gradually attained its
full obliquity.  In these cases we can, at times, remedy the defect,
by placing a bright or conspicuous object in such a position as to
exercise  the enfeebled muscles; or we can compel the whole labour
of  vision to be effected by one eye, and that the  affected organ,
which under the stimulus will be  correctly exerted, and thus, by
perseverance, the inequality may often be obviated. These indeed
are the only cases in which we can expect to afford relief; for if the
defect be in the interior of the eye, in a radical want of correspon-
dence between the retinae, or in inequality of the foci, it is irreme-
diable.
   It would  appear, then,  that  in confirmed squinting, one eye
only is used; and that vision is single.  Arnott, indeed, asserts,
that " persons who squint have always a double vision;  but they
acquire the power  of attending to the sensation in one  eye at a
time."  Experience and reflection are against this assertion.
   We have said, that the eyeball of the imperfect  eye is drawn
towards  the nose, in order that as few rays  as possible may pene-
trate the organ; and the vision of the sound eye be less liable to
confusion.   Sir Everard Home, however,  conceives, that it takes
this direction in consequence of the adductor muscle being stronger,
shorter,  and its course more in a straight line than that of any of
the other muscles of the eye; and Sir Charles  Bell ingeniously
applies his  classification of the muscles of the eye to an explana-
tion of the same fact. He asserts, that the recti muscles of the eye-
ball are  in activity  during attention  to the  impression on the re-
tina; but that, when the attention is withdrawn, the straight mus-
cles are  relieved, and the eyeball is given  up to the influence of
the oblique muscles, the state of equilibrium between which exists,
when the eyeball is turned, and the pupil presented upwards and
inwards.
    Lastly, in persons who are in the habit  of taking repeated ce-
lestial observations, or in those who make  much use of the micro-
scope, the attention is so entirely directed to   one  eye, that the
other is  neglected,  and will,  in time, wander about, so  as to pro-
duce squinting at the pleasure of the individual.   In'these cases,
the eyes becomes of unequal power, so that one only can be em-
ployed where distinct vision is required.
   So far our remarks have been directed to double  vision, where
both eyes are employed. 
206
SENSIBILITY.
   We have now to mention a very singular fact, connected with
double  and multiple  vision  with one  eye only.   If  a  hair, a
needle, or any small object be held before one eye—the other be-
ing  closed—and within the point of distinct  vision, so that the
byight light of a lamp or from a window shall fall upon the object,
ill its passage to the eye, or be reflected from it, we appear to see
not one object but many.
   This fact, when it was first observed by the  author, appeared to
him to have entirely escaped the observation of opticians and phy-
siologists, inasmuch as it has not been noticed in any of the works
recently published on optics or physiology.  On  reference, how-
ever, to the excellent " system" of Smith, on  the former subject,
he found in the " Essay upon distinct and indistinct  Vision,"
by Dr. Jurin, appended to that work, the whole phenomenon ex-
plained and elucidated at considerable length.   The elaborate cha-
racter of the explanation is probably the cause why the fact has not
been noticed by subsequent writers.
   The best way of trying the experiment is that suggested by Ju-
rin.  Take a parallel ruler, and opening it slightly, hold  it di-
rectly before the eye, so as to look at a window or lamp through
the aperture.  If the ruler be held at the visual  point, the aperture
will appear to form one luminous line; but if it be brought  nearer
to the eye, it will  appear double, or as two luminous lines,  with a
dark line between  them; and according as the aperture is varied,—
or the distance from the eye,—two, three, four, five or more lumi-
nous and dark parallel lines will be perceptible.
   At first sight, it might seem, that this phenomenon should be
referred to the diffraction or inflection, which the light experiences
in passing by the edges of the small body,—as the hair or needle.
Newton had long ago shown, that, when a beam of light  shines
upon a  hair, the hair will  cast several distinct shadows upon a
screen,  and will, of course, present several images to the eye.  Dr.
Rittenhouse, in the second  volume  of the American Philoso-
phical Transactions, explains on  the same principle, a very cu-
rious optical appearance, noticed  by Mr.  Hopkinson, in which,
by the inflection of light, caused by the threads of a silk handker-
chief, a multiple image of a distant lamp was presented.
   The objections,  however, to the explanation by inflection are,—
that the image always appears single, if the object be  not within
the distance of distinct vision; and,  secondly,  the same multiple
image is presented, when the object is seen by  reflection, as when
we look at a fine line, drawn upon paper; or at a fine needle, held
in a bright light.   In this case, a considerable  number of parallel
images  of the needle may be  seen,  all equally or nearly equally
distinct, and not coloured.
   Dr. Jurin considers the phenomenon to be caused by fits of easy
refraction and reflection of light.  Newton demonstrated, that
the rays of light are not, in all parts of their progress, in the same 
SENSE OF  SIGHT.
207
disposition to be transmitted from one transparent medium into an-
other; and that, sometimes, a ray, which is  transmitted through
the surface of the second medium, would be reflected back from
that surface,  if the ray had a little farther to go before it impinged
upon  it.  This change of disposition in the rays,—to be either
transmitted by refraction, or to  be  reflected  by the  surface of a
transparent medium,—he called their fits of easy refraction, and
fits of easy reflection: and he showed, that these fits succeed each
other alternately at very small intervals in the progress of the rays.
   Newton does not attempt to explain the origin of these fits, or
the cause that produces them; but  it has  been suggested, that a
tolerable idea of them may be formed by supposing that each par-
ticle of light, after its emanation from a  luminous body, revolves
round an  axis perpendicular to the direction of its  motion, and
presents alternately to the line  of its  motion an  attractive and a
repulsive pole, in virtue of which it will be refracted, if the  at-
tractive pole be nearest any refracting surface on which it falls,
and reflected, if the repulsive pole be nearest the surface.
   A less  scientific notion of the hypothesis has also been  suggest-
ed,—by supposing a body with a sharp  and  a blunt end passing
 through space, and successively presenting its sharp and blunt ends
to the line of its motion.  When the sharp end encounters any soft
body it penetrates it:  but when the blunt end encounters the same
 body, it will be reflected or driven back.
   In applying this to  the phenomenon in  question, Jurin pre-
sumes,  that the
light,  in passing                  Fig. 39(1\
 through  the hu-
 mours of the eye,
 experiences  these
 fits of easy refrac-
 tion  and easy re-
 flection. This will
 be understood by
 the  marginal  fi-
 gure, Fig.  39W.
 From the point A,
 suppose a number
 of rays of light to               B
 proceed  and to impinge, with different degrees  of obliquity, on
 the denser medium, B C; all the rays,  which are in fits of easy
 refraction, will pass through the medium  to the point D;  whilst
 those, that are in fits of easy reflection,  will  be thrown back  into
 the medium  ABC;  so that  we may presume, that all the rays,
 which fall upon the parts of the medium B C, corresponding to the
 bases of the dark  cones will  be reflected  back, whilst those, that
 correspond to the bases of the light cones, will pass to a focus at D.
 Now, if all  the bundles of rays, transmitted through the surface
 
208
SENSIBILITY.
B C,  be accurately collected into a focus,  no other consequence
will arise from the other bundles  of rays having  been reflected
back, than that the focus will be less luminous, than it would have
been had all the rays been transmitted through it.
   This explains why, at the distance  of distinct vision, we  have
only a single impression made on the eye.
   But if we approach the object A, so that the focus is not thrown,
—say upon the screen  R T, which may be presumed to represent
the retina—but behind it; the dark and light spaces will be repre-
sented upon the screen, and, of course, in concentric circles.  This
happens  to the eye, when the hair or needle or other object, is
brought nearer to it than the visual point.  We can thus understand,
why concentric circles, of the nature mentioned, should  be formed
upon the retina; but how is it, that the objects seen preserve their
linear form ? Suppose a b, Fig.  39C2),to be a luminous cone,  which,
                       in a  fit  of easy refraction,  has  impinged
                       upon the retina:  and A B, b a, the con-
                       centric circles, corresponding to the rays,
                       that have been reflected. It is obvious that
                       every point of the object will be  the centre
                       of so many concentric circles on the retina;
                       and if we imagine the fits of easy reflection
                       and  refraction to be the same around those
                       points, we shall  have the dark and lucid
                       lines represented by the tangents to these
                       circles;  and  hence we can comprehend
                       why, instead of having one lucid line e f,
                       we have three, separated by dark lines pa-
                       rallel to them; and if the light from the
                       luminous point be  strong enough to form
                       more lucid rings than are represented in
                       Fig. 39(y, and the breadth of those rings be
                       not too  minute to  be  perceived, we may
                       have the appearance  of five,  seven,  or
                       more lucid lines, separated by parallel dark
                       lines.
  We proceed now to consider the advantages which  the  mind
derives from the possession of this sense, so pre-eminently entitled
to the epithet intellectual.
  Its immediate function is  to give us the sensation of light and
colour.   In this it cannot be supplied by any of the other senses.
The action is,  therefore,  the result of organization; or is a " law of
the constitution;" requires no education; but is exercised as soon as
the organ has acquired the proper development.  Yet, occasionally,
we  meet with  singular cases, in which the eye appears to be to-
tally insensible to certain colours, although capable of performing
the most delicate functions of vision. 
SENSE OF  SIGHT.
209
  Sir David Brewster, in his recent Treatise on Optics, and in
the article on Optics in the Library of Useful Knowledge, which
is evidently an emanation from the same mind, has collected seve-
ral of these cases from various sources.
  A shoemaker, of the name of Harris, at Allonby, in Cumber-
land, could only distinguish black and while; and, whilst a child,
could not discriminate the cherries on a tree from  the leaves, ex-
cept by their shape and size.   Two of his brothers were almost
equally defective.  One of them  constantly mistook orange for
grass green, and light green for yellow.
  A Mr. Scott, who describes his own case in the Philosophical
Transactions, for  1778, mistook pink for a pale blue, and a full
red for a full green. His father, his maternal uncle, one of his sis-
ters, and her two sons,  had all the same defect.
  A Mr. R. Tucker, son of Dr. Tucker, of Ashburton, mistakes
orange for green, like one of the Harrises; and cannot distinguish
blue from pink, but almost  always knows yellow.   He mistakes
red  for brown, orange  for green, and  indigo  and violet for
purple.
  A tailor at Plymouth, whose case is described in the Transac-
tions of the Royal Society of Edinburgh, by Mr. Harvey, of
Plymouth, regarded the solar spectrum as consisting only of yel-
low and light blue; and he could distinguish with certainty only
yellow, white, and gray. He regarded indigo and Prussian blue
as black, and purple as a modification of blue. Green puzzled him
exceedingly; the darker kinds appearing to him brown, and the
lighter kinds a pale orange. On one occasion he repaired  an arti-
cle of dress  with crimson instead of black silk; and, on  another
occasion, patched the elbow of a blue coat with a piece of crimson
cloth.
   A still more striking case is given by Dr. Nicol, in the Medico-
 Chirurgical Transactions of London, of a person in the British
navy, who purchased a blue uniform coat and waistcoat, with red
breeches to  match.
   Sir David Brewster refers to a case, that fell  under his own
observation, where the gentleman saw only the yellow and the
blue colours of the spectrum.
   This defect was experienced by Mr. Dugald Stewart, who
was unable  to perceive any difference between the colour of the
scarlet fruit of the  Siberian crab and that of its leaves.
   Mr. Dalton, the chemist and  philosopher,  cannot distinguish
blue from pink by daylight; and, in the solar spectrum, the red is
scarcely visible; the rest of it appearing to consist of two colours,
yellow and blue.   Mr.  Troughton,  the optician, is fully  ca-
pable of appreciating only blue and yellow;  and when he names
colours, the terms  blue and yellow correspond to the more or less
refrangible rays;—all those, that belong to the former, exciting the
   Vol. I.                     27 
210
SENSIBILITY.
sensation of blueness; and those, that belong to the latter, that  of
yellowness.
  The opinions of philosophers have varied regarding the cause of
this singular defect in eyes otherwise sound,  and capable  of per-
forming every other function of vision  in  the most delicate and
accurate manner.
  By some, it has been presumed to arise from a deficiency in the
visual organ; and by  such as consider the ear to be defective  in
function in those  that are incapable of appreciating musical tones,
this deficiency in the  eye is  conceived to be of an analogous na-
ture.  " In the sense of vision," says Dr. Brown, " there is a spe-
cies of defect very analogous to the want of musical ear,—a de-
fect, which consists in the difficulty, or rather the  incapacity, of
distinguishing some colours from each other—and colours, which,
to general observers, seem of a very opposite kind.   As the want
of musical ear implies no general defect of mere quickness of hear-
ing,  this visual defect, in like manner, is to be found  in persons
who are yet capable of distinguishing, with perfect accuracy, the
form, and the greater or less  brilliancy of  the coloured  object;
and  I may  remark, too,  in confirmation of the  opinion  that
the  want of musical tone depends on causes not mental but
organic,  that in   this analogous case  some  attempts, not abso-
lutely  unsuccessful,  have been made  to  explain  the apparent
confusion of  colours by certain  peculiarities of the external organ
of sight."
  Mr. Dalton, who believes the affection to be  seated  in the
physical part of the organ, has  endeavoured to  explain his  own
case, by supposing that the vitreous humour is  blue,  and there-
fore  absorbs  a great portion of the red and other least  refrangible
rays; and Sir David Brewster,  in  the Library  of  Useful
Knowledge,  appears to think, that it may  depend upon a want of
sensibility in the  retina, similar to that observed in the ears  of
those who are incapable of hearing notes  above a  certain pitch;
but  as this view  is not contained in his more recent Treatise
on Optics, it is probably no longer considered by him to be satis-
factory.
  The defect in question has  always appeared to us entirely cere-
bral, and to strikingly resemble, as Dr. Brown has suggested, the
" want of musical ear."  As we  have already endeavoured to esta-
blish, that the latter is  dependent  upon a defective mental appre-
ciation, the parity of the  two cases will,  of course, compel us to
refer the visual defect, or the want of the  " faculty of colouring,"
to the same cause.  It has been  remarked, that the  eye, in these
cases, exercises its function perfectly, as regards the form and po-
sition  of objects,  and the degree of illumination of their different
portions. The only defect is in the imperfect conception of colour.
The nerve of sight is probably accurately impressed, and  the de- 
SENSE OF  SIGHT.                    211
ficiency is in the part of the brain, whither the impression is con-
veyed, and where perception is effected, which is incapable of ac-
curately appreciating those differences between rays, on which their
colour rests; and this we are glad to find is the view taken of it by
one of the most eminent philosophers of the present day, Sir J. F.
W, Herschel.

   The mediate or auxiliary functions of vision are numerous;
and hence, the elevated rank that has been assigned to this sense.
By it, we are capable of judging, to a certain extent, of the  direc-
tion, position, magnitude, distance,  surface, and motion of bodies.
Metaphysicians have differed greatly in their views on  this sub-
ject;  the  majority believing, that, without the sense of  touch,
the eye is incapable of forming any accurate  judgment on these
points;  others, that the sense of touch  is no  farther necessary
than as an auxiliary;  but  that a correct appreciation  would be
formed  by sight alone.   The few  remarks, that may  be  neces-
sary on  this  subject,  will be deferred,  until  the  physical and
other circumstances, that enable us  to judge of distance, &c, have
been canvassed.
   The direction or position of objects has already been considered,
so far as regards the inverted image, formed by them on the retina.
The errors, that arise  on this point, are  by no  means numerous,
and seldom give rise to much inconvenience. The direction of the
light, that impinges on the retina, is  always referred,"as we have
attempted to demonstrate, in the direction of a line, drawn from
the luminous point through the optic centre of the crystalline.
Whenever, therefore,  the  luminous cone meets with reflection or
refraction, before reaching the eye, the retina conveys erroneous
information to the sensorium, and we experience an optical illu-
sion.
   To ascertain the magnitude, distance, and surface  of bodies,
we are obliged to take into consideration several circumstances con-
nected with the appearance of the object—such as  its apparent
size,  the  intensity of  light, shade and colour, the convergence of
the  axes of  the  eyes, the  size or  position  of intervening ob-
jects, &c.
   Porterfield enumerates six methods, which are employed in
appreciating the distance of objects—1, their apparent magnitude;
2, the vivacity of their colours; 3, the distinction of their smaller
parts; 4, the necessary conformation of the eye for seeing dis-
tinctly at different distances; 5, the  direction of their axes; and
6, the interposition of objects.
   Dr. Brown reduces them to three—1,  the difference of the af-
fections of the optic nerve;  2, the  different affections of the mus-
cles, employed in varying the refracting power of each eye, accord-
ing to the distance of objects, and in producing that particular in- 
212
SENSIBILITY.
 clination of the axes of the two eyes, which directs them both
 equally on the particular object; and 3, the previous knowledge of
 the distance of other objects, " which form with that we are consi-
 dering a part of one compound perception."
   Lastly, Dr. Arnott, in his  " Elements of Physics,"  enume-
 rates four modes by which this is effected—1. The space and place,
 occupied by objects in the field of view, measured by what is term-
 ed the visual angle.  2.  The intensity of light, shade, and co-
 lour.  3. The divergence of the rays of light—and 4.  The con-
 vergence of the  axes of the  eyes.  This  enumeration may be
 adopted, with some slight modifications.  The circumstances, in
 our opinion, to be considered are:—
   1. The visual angle, or that formed by two lines,  which shave
                                            the extremities of
                   Fig.  40.                  an object and cross
                                            atthe centre of the
                                            crystalline; so that
                                            the visual angle
                                            subtended by the
                                            object, as ad, Fig.
                                            40,  is exactly e-
                                            qual  to  that sub-
                                            tended by its im-
 age iu on the retina.   It is obvious, from this figure, that if all
 objects were equidistant from the'eye, and of the same magnitude,
 they would subtend the  same angle; and, if not of the same mag-
 nitude,  the difference would be accurately indicated by the differ-
 ence in the visual angle subtended by them; thus, the comparative
 size  of the two crosses  a d and b d is represented by that of the
 images i u and i o.   The cross  ce,  however, which  is  twice the
 size of b d, subtends the same visual angle, and is alike represent-
 ed on the retina by  the image io.  It is clear, then, that the visual
 angle does not, under such circumstances, give us a correct idea of
 the relative magnitudes  of bodies, unless we are acquainted with
 their respective distances from the eye; and, conversely, we cannot
judge accurately of their distances, without being aware of their
 magnitudes.
   A man on horseback, when near us,  subtends a certain visual
 angle; but as he recedes from us the angle becomes less and less;
 yet we always judge accurately of his size, because aware of it by
 experience; but if objects are at a great distance, so as not to admit
 of their being compared  with nearer objects  by simple vision, we
 are in a constant state of illusion; irresistibly believing,  that they
 are much smaller than they really are.  This is the case with the
 heavenly bodies.  The head of a pin held close to the eye, will
 subtend as large a visual angle as the planet Jupiter, which is one
thousand two hundred and eighty-one times bigger than this earth, 
SENSE OF SIGHT.
213
(Arnott says one hundred thousand times!) and is eighty-six thou-
sand miles in diameter.   In like manner, a five cent piece, held at
some distance from the  eye, will shut off  the sun, although its
diameter is eight hundred and eighty-eight thousand miles.   The
sun and moon again, by subtending nearly the  same visual angle,
appear to us of nearly the same size; and the illusion  persists in
spite of our being aware of the mathematical accuracy, with which
it has been determined,  that the former is  ninety-six millions
of miles from us,  and  the  latter only  two hundred and forty
thousand.
  The visual angle again, subtended by an object, differs greatly ac-
cordingtotheposition of the object. Aspherehasthesameappearance
or bulk, when held at a certain distance from the eye, whatever may
be the position in which it is viewed; and, accordingly, the visual
angle, subtended by it, is always identical. Not so, however, with
an oval.  If held, so that the rays from one of its  ends shall
impress the eye,  it will  occasion a  circular image,  and subtend
a much  smaller angle, than if viewed sideways, when the image
will be elliptical, or oval.  The same thing must occur with every
object, whose longitudinal and transverse diameters differ. It is ob-
vious that, if any such object be held  in a sloping position, towards
the eye, it will appear more or less shortened; precisely in the same
manner as  the slope of a mountain or inclined plane would appear
much greater, if placed perpendicularly before the eye.  This ap-
pearance is what is called foreshortening; and it may be elucidated
by thefollowingfigure.  Suppose a man to be standing on a level plain,
with his eye at c, looking down on the plain.  The portion of the
surface a d, which is next to him, will be seen without any fore-
shortening; but if we suppose him to regard successively the  por-
tions df, f g, and g b of the plain, the angle, subtended by each
portion, will diminish; so that if the angle a c d be 45°, dcf will
be IS0; fc g 8°, and so on; until, at the length, the obliquity will
be so great, that  the an-
gle becomes inapprecia-               Fig. 41.
ble.   This is  the cause
why,if we look obliquely
upon a long  avenue of
trees, we are unable to
see the intervals between
the farthest in the series;
although those between  the  nearest to us may be readily distin-
guished.
  In all paintings, of animals especially, the principle of fore-
shortening has to be rigidly attended to:  and it is owing to a ne-
glect of this, that we see  such numerous distorted  representations,
of the human figure particularly.
  It has been  already stated, that objects appear smaller according
 
214                      SENSIBILITY.
to their distance; hence, the houses of a street, or the trees of an
                                       avenue, that are nearest to
               Fig.  42.                us, or in the foreground,
                                       will  form   the   largest
                                       images on the retina, and
                                       there will  be  a  gradual
                                       diminution, so that, if we
                                       could imagine lines to be
                                       drawn along the tops and
                                       bottoms of the objects, and
                                       to be sufficiently prolong-
                                       ed, they would appear to
                                       meet in a point, as in Fig.
                                       42.  The art which traces
                                       objects with their various
                                       degrees of apparent dimi-
nution on account of  distance, and of foreshortening on account of
obliquity of position,  is called perspective.
  2.  The intensity  of light, shade,  and colour.—It has been
shown, that the intensity of light diminishes rapidly,  according to
the distance of the body, from which it emanates; so that it is only
one-fourth as powerful when doubly distant, one-sixteenth when
quadruply distant, and  so on.   This fact is early recognised; and
the mind avails itself of it to judge with much accuracy of relative
distances.
  It is, however, a pregnant source of optical illusions. In a bright
sunshine, the mountains appear  much nearer to us than when seen
through the haze of our Indian summer.*
  In a row of  lamps  along a street, if one be more uminous than
the rest, it will seem to be the nearest; and, in the night, we incur the
strangest errors, in judging  of the distance of any luminous body.
  The sky appears nearer to the earth  directly above, than it does
towards the horizon;  because the light from above  having to pass
only through the atmosphere, is but slightly obstructed, whilst  a
portion only of that,  which  has to pass through the dense hetero-
geneous air, near the  surface of the earth, arrives at the eye.   The
upper  part  of the sky being,  therefore,  more  luminous, seems
nearer; and, in the same manner,  we explain, in part, why the sun
and  moon appear larger at rising and setting.

  * A delightful season in the southern and western parts of North America, ge-
nerally happening in October or November; and having nothing similar to it, so
far as we are aware, in any other part  of the globe.  It is dependent upon some
meteorological  condition  of the atmosphere, and occurs only when the wind  is
southerly, or from the warmer regions; disappearing immediately as soon  as  it
veers to the north.  By some, this phenomenon has been supposed to be caused
by the large fires in  the western prairies; but the warmth that attends the haze
cannot be explained on this hypothesis, independently of other sufficient objec-
tions to it.
 
SENSE  OF SIGHT.
215
  The shade of bodies keeps pace with their intensity of light; and,
accordingly, the shadows of objects near us, are strongly defined;—
whilst in  the  distance they become confused, and the light [alto-
gether so  faint, that the eye at last  sees an extent of distant blue
mountain  or plain;  "appearing bluish," says Dr. Arnott, "be-
cause the  transparent air, through which the light must pass, has
a blue tinge, and because the quantity of light arriving through the
great extent of air is insufficient to exhibit the detail."   " The
ridge called Blue Mountains," he adds," in Australia, and another
of the same name in America, and many others  elsewhere, are not
really blue, for they possess all the diversity of scenery, which the
finest climates can give;  but to the discoverer's  eye, bent on them
from a distance, they all at first appeared blue, and they have ever
since retained the  name."
  As regards  the Blue  Ridge of America, within twenty miles of
which we are now situated, Dr. Arnott probably  labours under
misapprehension. Within a very few miles from the whole of this
extensive chain, as well as from a distance, the blue tinge is percep-
tible, especially when the air is dense and clear, soon after the sun
has descended behind it; so that the name is  as appropriate in the
vicinity as it  was when "the  discoverer's eye  was  bent on them
from a distance."
   It is obvious, that without the alternation of light and shade we
should be unable to judge, by the  eye,  of the  shape of bodies; to
distinguish a  flat circle  from a  globe; or any of the prominences
and depressions, that are every  where observable.   The universe
would appear a flat surface, the  outlines of which would not even
be perceptible; and the only means of discriminating objects would
be by their difference of colour.
   It is partly by attending to the  varying intensity of light and
shade, that the painter succeeds in representing the  near as well as
the  distant objects in an extensive landscape:  those in the fore-
 ground are made bold and distinct;  whilst the remote prospect is
made to become gradually less and less distinct, until it fades away
in the distance.  This  part of his art is called aerial perspective.
   3. Convergence of  the  axes.   When objects  are  situated at
a moderate distance from  us, we  so  direct the eyes, that if the
axes were prolonged they would meet at the object, as at D. Fig.
39.   This  angle will,  of course, vary inversely as the distance:
so that if the axes be  turned to the object  S,  the  angle will be
greater: if to  E, less.   By this change in the direction of the axes
the  mind is  capable of judging, to a certain extent, of near dis-
 tances. A definite muscular effort is required foreach particular case;
and the difference in the volition necessary to effect it enables the
brain  to  discriminate, precisely in the same manner as it judges
of the height  of a body, by the  muscular action, required to carry
the axis from one extremityr of the object to the other.
   We have the most satisfactory evidence, that such convergence 
216
SENSIBILITY.
of the axes is indispensable for judging accurately of distance, in
near vision.  If we fix a ring to a thread suspended from a beam,
or attach it to a stand, and endeavour, with one eye closed, to pass
a hook, fixed to the extremity of a rod four or five feet long, into
the ring, we shall find  it impracticable unless by accident or  by
touching the ring with the rod.   The hook will always be passed
on the far or near side of the ring; but if we use both eyes, we can
readily succeed. They, however, whose eyes are of unequal power,
cannot succeed  with both eyes.
  The fact is strikingly  corroborated by the difficulty experienced
by those who have lost an  eye.  Magendie says it sometimes
takes a year, before they  can form  an accurate judgment of the
distance of objects placed near the eye.   The  truth is, however,
as we have  known in one or two interesting  examples, that  the
power  is occasionally never regained; notwithstanding every  en-
deavour to  train the remaining organ.
  Itneed scarcely be said, that the convergence of the axes is no guide
to us in estimating objects at such a distance, that the axes are nearly
parallel; as the sun and  moon,  or any of the celestial luminaries.
  4.  The interposition of known objects.  Another mode of es-
timating the magnitude or distance of objects  is, by a previous
knowledge of the  magnitude or distance of interposed or neigh-
bouring objects; and if no such objects intervene, the judgment we
form is extremely inaccurate.  This is the reason, why we are so
deceived in the extent of a monotonous plain or in the distance at
which a ship, on the ocean, may be from us: it is also another cause,
why  the sky appears to  us to be nearer at the zenith than  it is at
the horizon.
  The artist avails himself of this means of judging  of magnitude
in his representations of colossal species of the animal or vegetable
kingdom; or of the  works  of human  labour  and ingenuity; by
placing a well known object alongside of them as a standard of com-
parison.  Thus, the representation of an elephant or a giraffe might
convey but imperfect notions  to the  mind, without that of  his
keeper being added as a corrective.
  It  is in consequence  of the interposition of numerous objects,
that we are able to judge more  accurately of the size and distance
of objects on the same level with us, than when  they are either
much above or much below us.
  The size and distance of a man on horseback are easily recog-
nised by the methods already mentioned, when he is riding before
us on a dreary plain; the man and the horse appearing more dimi-
nutive, but being seen in their usual position, they serve as mutual
sources of  comparison.  When,  however, the same individual is
viewed from an elevated height,  his apparent magnitude, like that
of the objects around him,  is strikingly less than the reality. How
beautifully and  accurately this effect is depicted by the great  dra-
matist:— 
SENSE  OF SIGHT.
217
                                " How fearful
           And dizzy 'tis to cast one's eyes so low!
           The crows and choughs, that wing the midway air,
           Show scarce so gross as beetles.  Half way down
           Hangs one that gathers samphire; dreadful trade!
           Methinks he seems no bigger than his head.
           The fishermen, that walk upon the beach,
           Appear like mice: and yon tall anchoring bark,
           Diminish'd to her cock; her cock a buoy
           Almost too small for sight."

  The great apparent diminution in the size of objects seen from
a height is not to be wholly explained by the foreshortening, which
deprives us of our usual methods of judging.  It is partly  owing
to the absence of intervening bodies; and still more perhaps from
our not being accustomed  to view objects so circumstanced.
  Similar remarks apply to our  estimates of the size  and distance
of objects  placed considerably above us".  A cross, at the summit
of a lofty steeple, will not appear more  than one-fourth of its real
size, making allowance for the  probable  distance: yet a singular
anomaly occurs here:—the steeple itself seems taller than it really
is, and every one supposes, that it would extend much farther along
the ground, if prostrated, than  it would in reality.   The truth,
however,  is, that if the steeple were laid along the ground, unsur-
rounded by objects  to enable us to form an  accurate judgment,
it would appear to be much shorter than when erect, on the prin-
ciples  of  foreshortening,  already explained.   The cause of this
small apparent magnitude of the cross and upper part of the steeple
is, that they are viewed without any surrounding objects to com-
pare with them: they, therefore, seem to be smaller than they are;
and, being smaller, the mind  irresistibly refers them to a greater
distance.   For these reasons,  then,  it becomes  necessary,  that
figures, placed on lofty columns, should be of colossal magnitude.
  It is  owing partly to the intervention of bodies, that the sun and
moon appear to us of greater dimensions, when rising  or setting,
although the visual angle, subtended by them, may  be the same.
  " The sun and moon," says Arnott, " in appearance from this
earth are  nearly of the same size, viz:—always occupying  in the
field of view about the  half of a degree, or as  much as is  occupied
by  a circle of a foot  in diameter, when held about two hundred and
fifty feet from the eye—which  circle, therefore, at  that  distance,
and at any time, would just hide either of them.   Now, when a
man sees  the rising  moon apparently filling up the end of a street,
which he knows to be  one hundred feet wide, he very naturally
believes, that she then subtends a greater angle than  usual, until
the reflection occur to him—which it rarely will of itself, that he
is using, as a measure of her size, a  street known, indeed, to be
one hundred feet wide, but of which the part concerned,  owing to
its distance, appears to  his eye exceedingly small.  The width of
the street near him may occupy sixty degrees in  his field of view,
  Vol. I.                     2S 
218
SENSIBILITY.
and he might see from between the houses many broad constella-
tions instead of the moon only ; but the width of the street far off
may not occupy, in the same field of view, the twentieth part of a
degree, and the moon, which always occupies half a degree, will
then  appear  comparatively  large.   The  kind of illusion,  now
spoken of,  is  yet more remarkable, when the moon is  seen rising
near still larger known objects,—for instance, beyond a town or a
hill which  then appears within her luminous circle."
   Such are the chief methods by which we form our judgment of
the distance and magnitude of bodies;—1st,by the visual angle—
2dly, by the  intensity  of light, shade, and colour—3dly, by the
convergence of the axes of the eyes—and  4thly, by the interposi-
tion of known objects.
   The eye also enables us to appreciate the  motion of bodies.  This
it does by the movement of their images upon the retina; by the
variation in the size of the image; and by  the altered direction of
the light in reaching the  eye.
   If a body be projected  with great force and rapidity, we are in-
capable of perceiving it;  as in the case of a shot fired from a gun,
especially  when  near  us.  But  if  it  is  projected  from a  dis-
tance, as the  field of view is very extensive, it  is more easy to
perceive it.   The  bombs, sent from  an  enemy's encampment,
can be seen far in the air, and for some time before they fall, in
the darkness  of night; and afford objects for interesting specula-
tion regarding their probable destination.
   To form an accurate estimate of the motion of a body, we  must
be ourselves still.   When sailing on a river, the objects, that are
stationary on the banks, appear to be moving,  whilst the boat,
which is in motion, seems to be at rest.
   Bodies,  that are moving in a straight line to or from us, scarcely
appear to be in motion.   In such cases, the only mode we have of
detecting their motion is by the gradual increase in their size and
illumination, when they approach us; and the converse, when they
are receding  from us.
   If at a distance, and the visual angle between the extreme points
of observation be very small, the motion of an object will likewise
appear extremely slow ;  hence the difference between a carriage
dashing past  us in the street, and the same object viewed from a
lofty column.  A balloon may  be  moving  along at the rate of
nearly one hundred miles per hour;  yet, except for its gradual di-
minution in size and in intensity of light, it may appear to  be  at
rest; and when bodies are  extremely  remote from us,  however
astonishing may be their velocity,  it can  scarcely be detected.
Thus the moon revolves  round  the  earth at the rate of between
thirty and  forty miles a minute, above forty  times swifter than the
fleetest horse; yet her motion, during any one moment, completely
escapes detection; and the remark applies still  more forcibly to
those luminaries, which are at a yet greater distance from the earth. 
SENSE OF  SIGHT.
219
  These are cases in which the body moves with  excessive velo-
city? yet the image on the eye is almost stationary; but there  are
others, in  which the real motion is extremely slow, and cannot be
at all observed, as that of the hour-hand of a clock or watch.
  It will be obvious, from all the remarks that have been indulged,
regarding  the  information derived by the  mind  from the sense
of sight, that  a strictly intellectual process has to  be executed,
without which no judgment can be formed;  and that nothing  can
be more erroneous than the notion,—at one time prevalent,—that
the method by which  we judge of distance, figure,  &c,  is in-
stinctive or dependent upon an original "law of the constitution,"
and totally independent of any knowledge gained through the me-
dium of the external senses.  It has already been remarked, that
metaphysicians may be considered as divided into those, who be-
lieve that, without the sense of touch, the eye would be incapable
of forming any accurate  judgment on  these points;  and those,
who think, that the sense of touch is no farther  necessary than as
an auxiliary, and that a correct appreciation can be formed by sight
alone:—Molyneux, Berkeley,  Condillac,  &c. support  the
former view; Gall, Adelon, &c. the latter.
  Of the precise condition of the visual perception, during early in-
fancy,  we are  of course entirely ignorant.   So far as our own re-
collections would carry us back, we have always been able to form
a correct judgment  of magnitude, distance, and  figure.   Observa-
tion, however, of the habitudes of infants, would  seem to show,
that their  appreciation of these points, especially of distance, is
singularly imprecise, but whether this be owing to the sense  not
having yet received a sufficient degree of assistance from touch, or
from want of the necessary development in the structure or func-
tions of the eyeball or its accessory parts, we are  precluded from
judging.
  The only succedaneum is the information to be obtained, regard-
ing their visual sensations, from  those who  have been blind from
birth and have been restored to sight by a surgical operation.
  Although in the numerous operations of this kind that have been
performed, it might seem, that cases must have frequently occurred
for examining into this question, such is not the fact; and  meta-
physicians and physiologists have generally founded  their obser-
vations on the celebrated case described by Cheselden in his
Anatomy.
  The subject of this was a young gentleman who was born blind,
or lost  his sight so early, that he had  no  remembrance of ever
having seen ; and was "couched," so says Cheselden, "between
thirteen and fourteen years of age." Magendie affirms, that there
is every reason to believe, that the operation was not that for cata-
ract, but consisted in the incision of the pupillary membrane.   It
need hardly be remarked that Cheselden must be the best possi-
ble authority on this subject. 
220
SENSIBILITV
  " When he first saw," says Cheselden, " he was so far from
making any judgment about distances, that he thought all objects
whatever touched his eyes, (as he expressed it,) as what he felt did
his skin,  and thought no objects so agreeable as those which were
smooth and regular, though he could  form no judgment of their
shape or guess what it was in any object that was pleasing to him.
He knew not the shape  of any thing,  nor any one thing from ano-
ther, however different in shape or magnitude;  but upon being
told what things were,  whose form he before knew from  feeling,
he would carefully observe, that he might know them again; but
having too many objects to learn at once, he forgot many of them;
and, (as he said,) at  first he learned  to know, and again forgot a
thousand things in a day.  At first he  could bear but very little
light, and the things he saw he thought extremely large;  but upon
seeing things larger, those first seen he conceived less, never being
able to imagine any lines beyond the  bounds he saw; the room he
was in, he said, he knew to be but part of the house, yet he could
not conceive that the whole house could look bigger."
  A much  more interesting case, in  many respects, than this  of
Cheselden's, which has  always appeared to us too poetical, was
laid before the Royal Society of London, in 1826, by Mr. Ward-
rop.  It was that of a  lady born blind, who received sight at the
age of forty-six, by the formation of an artificial pupil. During the
first months of her infancy, this lady was observed to have some-
thing peculiar in the appearance of her eyes; and, when  about six
months old, a Parisian oculist operated on both eyes, with the effect
of complete destruction of the one, and not the slightest  improve-
ment to the other.  From this time, she continued totally blind,
being  merely able to distinguish a very light  from a very  dark
room, but without the power  of perceiving even the situation  of
the window through which the light entered, though, in sunshine
or bright moonlight,  she knew its direction ; she was, therefore, in
greater darkness than  the boy in Cheselden's case, who knew
black, white, and scarlet, apart from each other; and,  when in a
good light, had that degree of sight, which usually exists in an eye
affected with cataract; whilst in this lady, the pupil was completely
shut up, so that no light  could reach the retina, except  such rays
as could pass through the substance of the iris.
   After a third operation had been performed, for the formation of
an artificial pupil, she  returned from Mr. Wardrop's  house in a
carriage, with her eye covered with only a loose piece of silk. The
first thing she noticed was a  hackney-coach passing by,  when she
exclaimed,  "What is that large thing that has passed by us?"  In
the course of the evening she requested her brother to show her his
watch, and she looked  at it a considerable time, holding it close to
her eye.  "She was asked what she saw,  and she said there was a
dark and a bright side; she pointed to  the  hour of twelve and
smiled,  Her brother  asked  her  if she saw any thing more; she 
SENSE OF SIGHT.
221
replied yes, and pointed to the hour of six, and to the hands of the
watch.  She then looked at the chain and seals, and observed that
one of the seals was bright, which was the case, being a solid piece
of rock crystal."  On the third day she observed the doors on the
opposite side of the street, and asked if they were red. They were
of an oak colour.   In the evening she looked at her brother's face,
and said she saw his nose; he asked her to touch it, which she did;
he then slipped a handkerchief over his face, and asked her to look
again, when she playfully pulled it off, and asked, "What is that?"
On the thirteenth day she walked out with her brother in the streets
of London, when she distinctly distinguished the street from the
foot  pavement, and stepped from one to the other "like a person
accustomed to the use of her eyes." " Eighteen days after the last
operation," says Mr. Wardrop, "I attempted to ascertain, by a
few experiments, her  precise notions of the colour,  size, forms,
position,  motions and distances of external objects.   As she could
only see with one eye, nothing could be ascertained respecting the
question of double vision. She evidently saw the difference of co-
lours; that is, she received and was sensible of different impressions
from different colours. When pieces of paper, one and a half inch
square, differently coloured, were presented to her, she not only
distinguished them at once from one another, but gave  a  decided
preference to some colours, liking yellow most, and then pale pink.
It may be  here mentioned, that, when desirous of examining an
object, she had considerable difficulty in directing her eye to it,
and finding out its position, moving her hand as well as her eye in
various directions, as a person when blindfolded, or  in  the  dark,
gropes with his hand for what he wishes to touch.   She also dis-
tinguished a large from a small object, when they wrere both held
up before her for comparison.  She said she saw different forms in
various objects, which were  shown to her.   On asking what she
meant by different forms, such as long, round, and square, and de-
siring her to draw with  her finger these forms on her other hand,
and then presenting to her eye the respective forms, she  pointed to
them exactly; she not only distinguished small from  large objects,
but knew what was meant by above and below;  to  prove which,  a
figure drawn  with ink was placed before her eye, having one end
 broad and the other  narrow, and  she saw the positions  as they
really were and not inverted.(!!) She could also perceive motions;
for when a glass of water was  placed on the table before her, on
 approaching her hand near it, it was  moved quickly to a greater
 distance, upon which she immediately said,  'You move  it; you
 take it away.'  She seemed to have the  greatest difficulty in find-
 ing out the distance  of  any  object; for when an object was held
close to her eye, she would  search for it  by stretching her hand
far beyond its position,  while on other occasions she groped close
to her own face for a thing far remote from her."
   We have given the particulars of this case at some length, inas- 
222
SENSIBILITY.
much as they are regarded by Dr Bostock, and apparently by
Mr. Wardrop himself, as strikingly confirmatory of those of Che-
selden, than which we cannot imagine any thing more dissimilar.
It will have been noticed, that, from the very first after  the  re-
ception  of sight, she formed an imperfect judgment of objects, and
even of distances: although she was devoid of the elements neces-
sary for arriving at an accurate estimate of the latter;—the sight
of both eyes. This was, doubtless, the chief cause of that groping
for objects, which is described by Wardrop.   Of forms, too, she
must have had at least an imperfect notion, for we find, that, on
the 13th day after the  operation, she stepped from the elevated
foot-pavement to  the street "like a person accustomed to  the use
of her eyes."
   The case is, we think, greatly in favour of the view, that the
sight does not  require much education,  to judge with tolerable ac-
curacy of the position, magnitude, distance, surface, and motion of
bodies; and that, by a combination of the methods we have already
pointed out, or of some of them, this imperfect knowledge is ob-
tained, without the aid of any of the other senses; but is of course
acquired with greater facility and accuracy with their  assistance,
especially that of touch. What other than visual impressions could
have communicated to the mind of Miss Biffin, whose case was
referred to under another head, the accurate and minute informa-
tion which she possessed  regarding the  bodies surrounding her, at
all distances? or how does the animal, immediately after birth, ac-
quire its knowledge of distance?  We observe the young of many,
immediately after they are  extruded from  the uterus, turn round
and embrace the maternal teat; whilst others, as the partridge, fol-
low the mother immediately after they  have burst the shell.
  The experience required for acquiring an  imperfect  know-
ledge of distance, shape,  &c.  must,  therefore,  be trifling;  al-
though an accurate acquaintance may demand numerous and care-
ful comparisons.    This first degree  of knowledge is probably ob-
tained, by comparing the visual angle with the intensity of light,
shade, and colour; the more accurate appreciation following the
use of the other methods  already described. That the convergence
of the axes requires education, is demonstrated  in the case of the
infant.  It has been remarked, that the eyeballs harmonize instinc-
tively in their parallel motions; but the convergence requires an
effort of volition,  and  it is  some  time  before  it can be effected,
which is probably the great cause of the mal-appreciation  of near
distances, which we notice in the infant; whilst it seems to exhibit
its capability of judging more correctly of objects, that are some-
what more remote, and where less convergence, and, consequent-
ly, less muscular effort is necessary.
  The numerous optical illusions we have been compelled to de-
scribe, in the progress of the preceding remarks, will render it ne-
cessary to refer to but few under this head. 
sense  of sight.
223
Fig. 43.
Di
  It has already been said, that we lay it down as a rule, that the
progress of light to the eye  is always in a straight line from  the
luminous object; and, accordingly, if the course of the rays be mo-
dified before they reach the organ, we fall into an optical illusion.
Such modifications arise either from the reflection or refraction of
the rays proceeding from  the object that causes the sensation.
  By reflection of the rays, we experience  the illusion always
caused by mirrors.   A ray of light, K C, Fig. 19,  falling upon a
plane mirror, I J, is reflected back in  the same line;  but,  as we
have seen, the object will not appear to be at K, but at E. Again,
a ray of light,  proceeding obliquely from B,  and  impinging on a
plane mirror at C, will be reflected in the direction C  A,  but to
an eye at A, the object B will appear to be at  H, in the  prolonga-
tion of the ray  that reaches the eye.
  If the mirror be concave, the object will appear magnified, pro-
vided the light from the upper
part of the object A B, Fig. 43,
be reflected to an eye at F, and
that from the lower part of the
object meet the other at this
point.   To an eye so placed,
the object will  appear magni-
fied, and seem  to  be at  C D,
or in the prolongation of the
rays which fall  upon the cornea.
  If the mirror, as in Fig. 44, be convex,
for like reasons, the cross will seem to
be smaller.
  The cornea constitutes a mirror of this
class, in which we have an accurate mi-
niature representation of objects.
  Rays, that  are  refracted  in  passing
through different media, also give rise to
visual illusions. We have seen, that the
ray from an object at F, Fig. 19, in the pool of water, I J, does not
proceed into the air in the direction F C  0, but in that of the line
F C A; and if we suppose the eye  to  be placed at A, the  object
will not be seen at F, but will appear  to be  at f;  the pool will,
consequently, appear shallower than it really is, by the space at
which f is situated above the bottom.
  We  can  now understand  why rivers should appear  shallower
than they really are, especially when viewed  obliquely; and why
the lower  end  of a pole, immersed  in water, should, when seen
obliquely, appear to be bent towards the surface.  In shooting fish
in  the water, or  in attempting to harpoon them,  this  source of
error has to be corrected.  Those birds, too, that live upon the in-
habitants of the waters, will have to learn, from experience,  to ob-
viate the optical illusion; or to descend perpendicularly upon their
Fig. 44.
 
224
SENSIBILITY.
prey, in which direction we have seen no refraction  take  place.
Similar remarks apply to the fish that  leap out of the  streams to
catch objects in the air.
  If the light, before reaching the eye, passes through bodies of a
lenticular  shape, it undergoes modifications, which have given occa-
sion to the formation of the useful instruments, that have been de-
vised for enlarging the sphere of vision.  If the lens be double con-
vex, the body, seen through it,  appears larger than it is, from the
illusion so often referred to, that we always refer the object in the
direction of the line, that impinges upon the retina. The object, con-
sequently  appears to be greatly augmented. (See Fig. 25.) For the
same reasons an object seems smaller, to an eye at A, when viewed
through a double convex lens, as in Fig. 22.
  Again,  if the light, before reaching  the cornea, is  made  to pass
through a diaphanous body, which  is itself  coloured, and  conse-
quently allows only the rays of its  own  colour to traverse  it, the
object is not seen of its proper colour but of that of the transparent
body.
  An impression of light continues to effect the retina for the sixth
part (M. D'Arcy says the seventh  part,) of  a second.  If, there-
fore, a live coal  be whirled round in a  circle,  six or seven times in
a second,  it will seem to be a continuous circle of fire.  It is owing
to this circumstance, that meteors seem to form a line of light,—as
in the case of the falling star,—and that the same impression is con-
veyed by a skyrocket in its course through the air.  We have an
elucidation of this fact in the instrument or toy called by Dr. Paris
—the thaumatrope, which consists of a circle, cut out of a card,
and having two silk strings, attached to opposite points of  its dia-
meter;  by twisting which with the finger and thumb the card may be
twirled round with considerable velocity.  On one side of the card
an  object  is drawn,—such as a chariot,—and  on the other side of it
the charioteer.  If the card be twirled round six or seven times in
a  minute  the  charioteer will  be seen in the chariot; the dura-
tion  of the impressions on the retina  being  such as to cause  the
figures, drawn on both  sides of the card, to be seen at the same
time.
   Lastly, it is by accurate attention to various opticaf illusions, and
to the laws of the animal economy on  which  they are founded, that
many of  them can be produced in the arts at pleasure. Painting is,
in  truth, little more than depicting  on canvass  the  various optical
errors which we are habitually incurring.
   To conclude,—the sense of sight differs materially in the scale
of animals; but in few is the organization more perfect or the func-
tion better executed than in man.   Situated  at the upper and ante-
 rior part  of  the body, it is capable of directing its regards over  a
 large extent of surface; of converging the axes of the two organs
 upon objects in various situations, which cannot be effected by many
 animals;  is very movable and under the domination of a muscular 
ADDITIONAL SENSES.
225
apparatus of admirable arrangement.   Still, it is not as delicately
organized as in some animals, which are capable of seeing objects at
a distance, that would  be totally beyond the  reach  of the  visual
powers of man.
  Like the other senses it can be  exerted actively and passively;
hence  the  difference  between  simply seeing and  looking.   In
the latter, the eye is directed to  the object  by the proper muscles;
and it is not improbable but that the  nerve may be aroused to a
more accurate and  delicate  reception of impressions, as we have
some reason for believing it to be in the case  of the other senses.
Like them, it admits of great improvement  by  education.  The
painter and the workers in colours are capable of great discrimination,
and detect the minutest  shades of difference with the greatest facility.
  In savage life, where the tracks or marks through the almost  in-
terminable forests, or over the pathless wilds,  are the only guides,
the greatest acuteness of vision is  necessary; and accordingly  we
find  the  North American Indian, in  this  respect, eminently dis-
tinguished.
  The mariner, too, accustomed to look out  for land or for a hos-
tile sail, will detect it in the distant horizon long before it  can  be
perceived by the landsman; and will appreciate its distance and
course with signal accuracy. Education, in this case, not only com-
municating to his eye  facility in being impressed, but improving
the intellectual process, by which he  arrives at the  estimation of
distances.
   The five senses, that have  been considered, constitute so many
special nervous systems, each concerned in its appropriate function;
and, although conveying ideas of the external world to the brain,
and connected with that organ, to a certain extent independent of it.
   The generality of physiologists admit only these five; but some
have suggested others, differing, in general, however, from the five,
in having no organ at the surface of the body exclusively concerned
in the function.  Buffon regarded, as a sixth sense, the intense sen-
sation experienced during the venereal act; but this can only be re-
garded as a peculiar variety of tact in the mucous membrane of the
genital organs;—differing  from ordinary tact in those parts, by  re-
quiring in both sexes a special condition of the  membrane; and, in
the male, one such, that the sperm, when excreted, shall make the
necessary impression upon it; and, consequently, appertaining to
both the external and internal  sensations;—the state of the membrane
being referable to the latter,  and the effect  of  the contact of the
sperm to the former.
   Some have spoken of a  sense of heat and cold:—this we have
described under the head of tact;—and others of a muscular sense,
by which we acquire a knowledge of the motions, to which muscu-
lar contractions give rise;  and thus learn to apportion the effort to
the degree of effect to be produced. The animal magnetizers, again,
  Vol. I.                     29 
226
SENSIBILITY.
have suggested a sixth sense, to which man owes the capability of
being acted upon by them; but this is entirely supposititious, and
the facts admit of a more ready and satisfactory explanation.
   A sense of hunger has been described  as situated at the upper
orifice of the stomach:—a sense of thirst in the oesophagus, and a
pneumatic sense, seated in the lungs; but all  these are more pro-
perly internal sensations.
   The German physiologists have suggested another sense, which
they term ccenassthesis, g e m e i n g e fu h 1, or  common feeling,
le bensgeftihl,  lebenssinn, i ndi vidualitUtssin n, and
s e 1 b s t g e f u h 1.*  This is not seated in any particular part of the
body, but  over the whole system, and hence termed gemei n, or
common.  It is indicated  by that lightness and buoyancy which
we occasionally experience, apparently without any adequate cause;
as well as by a sense  of lassitude and  fatigue, unconnected  with
muscular action or disease.   To it, likewise, belong the  involuntary
shuddering, glowing, or chilliness, experienced  under similar cir-
cumstances. It is manifestly one of the numerous internal sensations
felt  by the frame, and every portion of  it, according as they are in
a perfect state of health, or labouring under some cause  of irritation
or oppression; but ought not to be regarded as an additional or
sixth sense.
   Again,  it has been supposed  that certain  animals  may enjoy
other senses than the five we have mentioned.   Of this we can
have no  positive evidence.  We are devoid of all means of judg-
ing  of their sensations; and if we meet with  an additional organ,
which seems adapted for such a purpose, we have nothing but con-
jecture to guide us.  Under the sense  of touch it was remarked,
that Spallanzani found the bat capable of avoiding obstacles placed
in its way intentionally, when the eyes, nostrils, and ears had been
closed up, and it readily returns to the holes in  the caverns to which
it is habituated.   Spallanzani and Jurine supposed, that this was
owing to its being possessed of a sixth sense.   We have seen that
the  circumstance is explicable by these animals  being  possessed of
unusual delicacy of touch.
   Again, the accuracy with which migratory animals return  to their
accustomed haunts, has given rise to the notion of a sense of locality,
which is presumed to preside over this faculty.  This is, however,
in all probability, a cerebral faculty, and may fall under consideration
hereafter.
   Quadrupeds, the ape not excepted, have two bones in the face, in
addition to those found in man.  These  contain the  roots of the
dentes incisores, when such are present, but  they exist in animals
also, that are destitute of teeth. They are termed ossa  intermaxil-
laria, ossa incisoria, and ossa labialia, and  are situated, as their
names import, at the anterior part of the jaw, and between the ossa

     " Feeling of life, sense of life, sense of individuality, and self-feeling." 
ITCHING, TICKLING, &C
227
maxillaria or jaw bones.  Jacobson considers them to be an organ
of sense, as they communicate with the exterior, and  are largely
supplied with vessels and nerves.  Accordingly, this has been es-
teemed a sensitive apparatus, connected with the season of love in
animals; and by other naturalists as a sense, intermediate between
those of taste and smell, and  intended  to guide the animal in the
proper  selection of food.   It need  hardly be  said, that this is all
imaginary.

  Adelon, it was remarked, makes two divisions of the external
sensations:—those that convey information to the mind; and those
that do not. The former have  engaged our attention; the latter will
not occupy us long.  They comprise but two—itching and tickling.
Both of these occur in the skin and mucous membranes, and  near
the communication of the latter with the skin; or, in other words,
near the termination of the outlets which they line.
  Itching, however, is not always  an external sensation,—that is,
not always caused  by the contact of a body external to it.   It fre-
quently arises from an altered  condition of the tissue of the part in
which it is experienced,  as in  cutaneous affections; in  itching at
the  nose produced  by irritation in  the intestinal canal;  itching at
the  glans  penis in  cases of calculi in  the  urinary bladder,  &c,
but  commonly  the sensation  is caused by  an extraneous body;
and  we are  irresistibly led to scratch, however it may be  pro-
duced.   When  it  arises  extraneously, it  can  generally be  rea-
dily  allayed; but,  when  dependent upon a  morbid condition of
the texture of the part, it becomes a true disease, and the source of
much suffering.  If the itching be  accompanied with  a feeling of
motion, or of purring in the part, it is called tingling.   This kind
of purring also often occurs without the presence of itching.
  Tickling or titillation is always caused by the contact of some
extraneous substance, and is  therefore  a true external  sensation.
Although occurring in the skin and commencement or  termination
of the mucous membranes, all  parts are not equally susceptible of
it: and  some,—as  the lining membrane of the genital organs—are
only or chiefly so, under particular  circumstances.
  The sides, palms of the hands, and soles of the feet, are the most
sensitive in this respect; not, perhaps, because the nerves are more
numerous in those  parts, but because, owing to thinness or supple-
ness of skin, or to other inappreciable circumstances, they are more
susceptible of this kind of excitation.  We find, too, that individuals
differ as much as the parts of the body in this  respect:  some being
not  ticklish, or  incapable of being thrown into the spasm, which
the  act, nay, even  a threatening of the act, produces in  others.
Cases are on record, in which prolonged titillation has produced
general convulsions, and even  death.  Lecat  terms it  an herma-
phroditic sensation, inasmuch as, on the one hand, it excites laughter; 
228
SENSIBILITY.
and, on the  other, is insupportable; and, consequently, appears to
be intermediate between pleasure and pain.

                    INTERNAL  SENSATIONS.

  The external sensations make  us acquainted with the universe
surrounding us;  and convey to  the  mind a  knowledge of every
thing that can be, in  any manner, inservient to  our  necessities.
Such necessities have, however, to be suggested to the mind, before
it reacts, through the aid of the organs of prehension, or otherwise,
on external  bodies, and this is accomplished  by the agency of the
internal or organic sensations.
  Without the intervention of any external  cause, every organ of
the body is capable of transmitting to the brain a number of different
impressions, many of which  impel that organ to acts, that  are ne-
cessary not only for the preservation of the individual and of the
species, but also  for the perfect development of his faculties. Such
are the sensations of hunger and thirst; the impulse that leads to the
union of the sexes; and the feeling we have of the necessity for in-
termission in the exercise  of the  muscles and  of the intellect.
  They have been divided into three species by some physiologists:
the first arousing, or giving impulse to, the  action of organs; and
warning the brain of the different necessities of the system.   They
have been called wants or instinctive desires.  Such  are, hunger,
thirst,  the desire to evacuate the urine and faeces: that of respiration,
the venereal appetite,  accouchement, &c.  They belong to those
that arise, when  it is necessary the organs should act.
  The second species occur during the action of organs.   They are
often obscure, but sometimes very acute.  Amongst these  are the
impressions accompanying the different excretions,—as that of the
sperm, urine, &c.  (although, as we have seen, these partly belong to
the external sensations;) the impressions that warn us of our partial
or general movements, of  the progress of digestion, and of the in-
tellectual labours.
  The last species succeed to the action of organs, especially when
such action has been too long continued; hence the inward feeling
of fatigue, after too long exertion of the functions of the senses, of
the intellectual and moral faculties, and of the organs of muscular
motion; the necessity of repose after  prolonged muscular exertion;
and of sleep, to recruit the nervous system, and to fit it  for the ex-
ertions it has to make during the waking condition.
  The mode in which these sensations are effected is analogous to that
of the  external sensations.  There is an impression in the part to
which the sensation is referred; an action ofperception, accomplished
by the brain, and one of transmission, executed by a nerve passing
between the two parts. The two last actions are probably executed
in the same manner as they are in the external  sensations.   The 
INTERNAL SENSATIONS.
229
first, or the mode in which the impression is  effected, and the cha-
racter of the impression itself, are much more obscure.  In the ex-
ternal sensations, we can refer the  impression to a known irritant:
—special in some of the senses:—more general in others.  We know,
that light impresses  the  retina:—aerial undulations the acoustic
nerve, &c: but, in the internal sensations or sentiments, as some of
the French writers term them, the source of  the  irritation  is in
some modified  action of the part itself, in the  very tissue  of the
organ, and hence the result is said to be organic.   In the internal
sensation of hunger, for example, the impression is engendered in
the organ,—how, we know not,—is thence conveyed to the brain; and
the sensation is  not effected until  the latter  has acted.  The  same
may be said of all the other internal sensations.
  They differ, in other respects, from the external sensations. Whilst
the latter maybe entirely passive, or be rendered active by volition,
without either action being the  cause of particular pleasure or in-
convenience, the former are but little influenced by volition.   Con-
stituting the wants,—the instinctive desires,—which impel to acts,
that are necessary for the preservation and full  development of the
individual and of the species, such independence is of course essen-
tial.  On many  of them, however, habit or accustomed volition has
a certain degree of influence: and they  can unquestionably be aug-
mented or moderated by licentious indulgence or restraint.  The
influence of habit is exemplified by the regularity with  which  the
appetite returns at stated  intervals; and by the difference between
the calls of the gourmand  and of  the temperate  individual.-  It is
most strikingly evidenced, however, in its influence over the moral
wants;  which may even spring up from social indulgence, and
hence  are  not instinctive or organic:  and we are every day com-
pelled to notice  the striking difference between the individual, who
practises restraint upon his wants, and the libertine, who, like the
animals surrounding  him, gives unbridled sway to his natural and
acquired appetites.
   All the internal  sensations, when satisfied  or responded to in
moderation, communicate a feeling of pleasure; but  if resisted, pain
results.  If hunger be prolonged there is a  general feeling of un-
easiness, which  rapidly abates after food is  received into the sto-
mach in due proportion; but if satiety be produced, uneasiness  fol-
lows; and this applies to all the appetites or wants.
   The particular internal sensations will engage us, when the func-
tions to which they belong, fall under consideration.  Like the ex-
ternal sensations they must, of course,  administer to the intellect;
to an extent which will be seen  hereafter.  Their influence and na-
ture was entirely  neglected, until  of comparatively late years: but
attention has been attracted to them by the labours chiefly of Caba-
nis and of Destutt-Tracy,  and  they now form  subjects for in-
teresting speculation with the metaphysician.
   The morbid sensations belong, more particularly,  to pathology: 
230
SENSIBILITY.
 a brief notice of them will consequently be all tbat is necessary here.
 They are all comprised under the term pain.  In its enlarged sig-
 nification, this word, as is well known, means every uneasy or dis-
 agreeable sensation or moral affection: thus including sadness, anger,
 terror, as well as the painful impressions, felt in  the extremities or
 trunks of the nerves.  It is the  latter only  or physical pain that
 concerns us at present.
  Like  every  other sensation, although it may be  referred  ex-
 clusively to the part impressed, pain  requires the intervention of
 the brain: for if the nerves, proceeding from the  part to that organ,
 be cut, tied, compressed,  or stupefied by  narcotics; or if the action
of the brain itself be blunted from any cause, as by the use of opium,
or by any compression, accidental  or other, the sensation is no
longer experienced. We  can thus understand, why pain is  less felt
during sleep; and the astonishing cases of resistance to pain, which
we witness in the lunatic, and in  religious or other enthusiasts, who
have been subjected to bodily torture.   An opposite condition of
the nervous system  is the cause of the great sensibility  to  impres-
sions, which we witness in the nervous and  hysterical.
  It is obvious, that pain  may be either an external or internal sen-
sation, according as the cause of irritation is extraneous, or seated in
the tissue of the organs; and that it must vary considerably, both as
regards the  precise irritant, and the part affected; hence the differ-
ence between the pain caused by a burn, and that by a cutting in-
strument; and  the immense variety of pains to  which the human
frame is subject,  the attentive study of which is so indispensable to
the pathologist.

  So much for the sensations.   These we have seen are innumer-
able, for each sense  is capable of myriads of different impressions.
  We now pass to the consideration of those functions  which  en-
able man,—though worse provided with means of defence  and of-
fence than the beasts surrounding him, possessing no covering to
protect him from the solar heat or the winter's  cold,—to  provide
himself means  of defence; to render the animals around him sub-
servient to  his use; to cover  his  nakedness and  protect  himself
against atmospheric changes; to devise every  mechanical art; to
 fathom the laws, that govern the bodies by which he is surrounded,
 and to establish himself undisputed master of the earth.

               OF  THE  MENTAL FACULTIES, &C.

   The external senses convey to the brain the different impressions,
 made upon them by surrounding bodies; but, of themselves, they
 would be unable to  instruct the mind regarding the universe.  It is
 necessary, that the brain should act before any perception, any idea
 of them, can exist. The mental faculties, in other words,  convert
 the  impressions into such ideas.  The internal  sensations, on  the 
MENTAL FACULTIES, &C                231
other hand, consist, as we have seen, of the numerous wants and ap-
petites, necessary for the preservation of the individual and of the
species.  In  addition  to  these, man possesses another series of
faculties, which influence  his character and  disposition, and di-
rect his social existence:—these are the affective or emotive facul-
ties, or the faculties of the heart.
   The study of these different mental and moral phenomena em-
braces what has been  called psychology, from a notion  that they
are exclusively dependent upon the mind.  This notion was, atone
time, universal, and hence the appellation metaphysician, applied
to such as  were considered to proceed  in their investigations of
those subjects beyond what was physical, material, or corporeal.
   There is no subject, which has given  occasion to so much excite-
ment and controversy, as the connexion of the mental faculties with
the encephalon.   "It has unfortunately happened," says Dr. Bos-
tock, " that this subject, which is one of great interest and curiosity,
has seldom been viewed with that philosophical spirit, which should
always direct our investigations and by  which alone we  can expect
to arrive at truth.   It is admitted that certain errors may be so in-
terwoven with our  accustomed associations,  on topics connected
with morals and religion, as to render it doubtful,  on some  occa-
sions, how far we ought to attempt their removal: but if this con-
cession be  made, on the one hand, it is incumbent upon  us, on the
other, not  to inflame the prejudices which may exist  on these to-
pics, but to use our  endeavours  to correct all undue excitement,
and thus to bring the mind into that tranquil state, which may en-
able it to receive truth without the fear  of injury."
   In such a spirit ought every discussion on this interesting subject
to be conducted; and in such a spirit will the few remarks, we have
to make, be offered.
   The chief opinions that have been indulged on this subject, are,—
1st.  That all  the mental phenomena are immaterial  and  the  exclu-
sive product of the mind.  2dly. That the sentient principle, within
us, requires the intervention of an organ, through which it acts; in
other words, that mind is a principle superadded to organization ;
and  3dly.  That where there is no organization there is  no percep-
tion:—that wherever an organized structure, like the  brain, exists,
perception exists;  that  where the organization  is imperfect, per-
ception is imperfect; where the organization is sound and vigorous,
perception is clear and vigorous; where it is impaired, perception
is impaired;  and that,  when the organization ceases, perception ap-
pears to cease also.   This last view is materialism.  It supposes
that a certain condition of matter is capable of thinking, reasoning,
and understanding.
   The doctrine,—that our intellectual and moral acts are superadded
to organization, during life, and that there is an organ of the  body
concerned  in  their  manifestation,—is  the one  embraced  by the
generality of physiologists, and is most consistent with reason and 
232
SENSIBILITY.
analogy; it is but justice, however, to admit, that  the  views of
those, who consider that a certain organization produces thought,
are not deserving of the anathemas, that have been directed against
them on the score of irreligion.  The charge would rather apply to
those, who could doubt the power of Omnipotence to endow mat-
ter with  such attributes.
   Were  the mental and moral phenomena  the  exclusive products
of the immaterial principle within us, they would hardly form sub-
jects for  physiological inquiry. That they are allied to organization
is inferred from the following reasons.  As they constitute so many
functions, were they not provided with an  organ or  organs, they
would form so many exceptions;—each of the sensations requiring
an organ for  its accomplishment.   Again, our  inward feeling  in-
duces us to refer them  to  a  particular part of the frame: whilst
thought appears to us to be effected  within the head, the  chief  ef-
fects of the passions are felt in the region of the heart or stomach.
They are, moreover, not the same in every individual.  One man
will be a poet, another a mathematician; or one will be benevolent,
another cruel.  If these faculties were the exclusive product of the
mind, and of course not to be ascribed to diversity of organization, we
should have to admit, that each individual has a different immaterial
principle, and of course, that there must be as many kinds as there  are
individuals.  Lastly. The faculties vary in  the same  individual  ac-
cording to circumstances.  They are not the same in the child as in
the adult; nor in the adult as in one advanced in life; in  health as
in disease;  in waking as in sleep.  During an attack  of fever they
become temporarily deranged, and permanently so in all the varie-
ties of insanity.   These  facts are inexplicable under the  doctrine,
that they are the exclusive product of the mind or immaterial prin-
ciple.  An immaterial or spiritual principle is necessarily immuta-
ble; yet we should have to suppose it capable of alteration; of grow-
ing with the growth of the body, and of becoming old with it; of
being  awake  or  asleep; sound  or diseased.  All  these  modifi-
cations are impressed  by varying  organization—of the  brain in
particular.
   We may conclude, then, that the intellectual and moral faculties
are not the exclusive product of the mind, but that they require  the
intervention of an organ.
   That this organ is the encephalon, or a part of  it—the  brain—is
announced  by many circumstances.
   In the first place, they are  phenomena of sensibility, and hence
we should be disposed to refer them to a nervous organ; and being
the most elevated phenomena of the  kind,  to  the highest of  the
nervous organs.
   In the second place, inward feeling induces us to refer them thi-
ther.   We not only feel the process there,  during meditation, but
the sense of fatigue, which succeeds to hard study, is experienced
there likewise. 
MENTAL FACULTIES,  &C
233
   The brain, again,  must be in a state of integrity, otherwise the
faculties are deranged; or, for the time, abolished.   In fever, the
brain becomes  affected directly or indirectly, and the consequence
is perversion of the  intellect, in the form of delirium.  If the or-
gan be more permanently disordered, as by the pressure of an ex-
ostosis or of a tumour, or by some alteration in its structure or func-
tions—less appreciable in its nature—insanity,  in some of its forms,
may be the result.
   In serious accidents to the encephalon, we  observe the import-
ance of the cerebral organ to the proper exercise of the mental fa-
culties most clearly evinced.  A man falls from a height, and frac-
tures his skull.   The consequence of this is depression of a portion
of bone, which  exerts a degree of compression upon the brain; or
the extravasation  of blood from some of the encephalic vessels,
attended with similar results.  From  the moment of the infliction
of the injury, the whole of the mental and moral manifestations are
suspended, and do not return until the compressing  cause  be re-
moved, by the operation of the trephine. Richerand cites the case
of a female, who had a portion  of the brain accidentally exposed,
and in whom it was found, that pressure upon the brain completely
deprived her of all consciousness;  and this was not restored until
the pressure was removed.
   We notice, however, an  important difference  in the effect, ac-
cording to the  suddenness  or tardiness with which the amount of
pressure is produced.  Whilst a  sudden compression destroys the
intellectual  and moral manifestations for a time, any slow pressure,
produced by the gradual formation of a tumour, may exist without
exhibiting, in any manner, the evidences of its presence.  Accord-
ingly,  the anatomist is sometimes surprised to discover such mor-
bid formations in the brains of those who have never laboured un-
der any mental aberration whatever.
   A negative argument in favour of this function of the brain has
been deduced from the fact, that  disease of other portions  of the
body, even  of the principal, may exist and pass on to a fatal termi-
nation, leaving  these faculties almost wholly unimpaired.   Such is
proverbially the case with phthisis pulmonalis, the subject of which
will be flattering himself with hopes never to  be realized,  and de-
vising schemes  of future aggrandizement and pleasure, until within
a few hours of his dissolution.
   The intellectual faculties differ in each individual, and vary ma-
terially with the sex.  The  brain is, in all these cases, equally dif-
ferent.  Much may depend  upon education; but it may, we think,
be laid down as an incontrovertible position, that there is an origi-
nal difference in the  cerebral organization of the man of genius and
of him who is less gifted; and, as a general principle, that in the
former the brain is much more developed than in the latter. Whilst
the brain of the man of intellect may measure  from nineteen  to
twenty-two inches in circumference,  that of  the idiot frequently
  Vol. I.                     30 
234
SENSIBILITY.
does not exceed thirteen, or is not greater than  in the child one
year old.
  It was an ancient observation, that a large development of the
anterior and superior  parts of the head is a characteristic of ge-
nius; and, accordingly, we find, that all the statues of the sages and
heroes of  antiquity are represented with high and prominent fore-
heads.   The relation between the size of the head and the mental
manifestations  has, indeed,  interwoven itself  into  our  ordinary
modes of speech.
  Perhaps, as a general observation,  it may be found true, that the
mental capacity is in a ratio with the size of the brain, compared to
that of the rest of the body.   It is obvious, however, that to this
there must be numerous exceptions, and that independently of bulk
there may be an organization, which may be productive of the same
results, and in  which the largely developed organ may be greatly
deficient.  Size is only one of the elements of the activity of an
organ.
  The difference between the morale of the male and female is sig-
nal; and there  is no less in the shape of the encephalon in the two
sexes.   Observation, not only by anatomists but  by sculptors and
painters, shows, that the superior and anterior parts of the brain are
less developed  in the female, whose forehead is, therefore, as a ge-
neral principle, smaller; whilst the posterior parts are larger than
in the  male.  According to the system of Gall,  we shall see, that
the anterior and superior parts are considered to be connected with
the  intellectual manifestations, which  are more active in  man;
whilst the posterior are concerned  in  the  softer feelings,  which
predominate in the character of the female.
  The mental and moral faculties vary in the same individual, ac-
cording to age, health, and disease;  and in the waking and sleeping
state.  In  all  these  conditions we have  reason to  believe,  that
the slate of the encephalon  is as various.  The  anatomist notices
a manifest difference between its organization in the infant and
in the  adult or  aged.  Like the other organs of the body, it is gra-
dually developed until the middle period of life;  after which it de-
cays, along with the rest of the frame.  Our acquaintance with the
minute organization of the body does not enable us to say on what
changes these  differences are  dependent.  We see  them only  in
their results.   By the minutest examination of the special  nerves
of  the senses we are incapable of saying, why one should  be ca-
pable of appreciating the contact of sapid bodies—another that of
light, &c.
   During sleep, again, in  which the functions of the brain are more
or less suspended, the condition of the organ is modified; and ma-
nia or delirium probably never occur, without  the physical condi-
tion of the brain having undergone  some change, directly or indi-
rectly.  It is true, that, on careful examination of the brains of the
insane, it has often happened that no morbid appearance has pre- 
MENTAL  FACULTIES, &C
235
 sented itself; but the same thing has been observed on inspecting
 those, who have died of apoplexy or paralysis, in which cases, not
 a doubt  could be entertained respecting the cause being seated in
 the encephalon, and that it consisted in a physical alteration of its
 tissue.  These are a few of the cases, that make us sensible of the
 limited  nature of our powers of observation.  They by no means
 encourage, in the most sceptical, the belief, that the tissue of the
 organ is not implicated.  The investigations of the morbid anato-
 mist consequently afford us but few data, on which to form our
 opinions on this subject.
   The effect of  intoxicating  substances must  be  entirely exerted
 upon the brain.  When taken in moderation, we find all the facul-
 ties excited; but, if pushed too far, the intellectual and moral mani-
 festations become perverted.  This can only be through the action
 of those  substances upon the cerebral organ.  We can  thus  under-
 stand, how regimen may cause important modifications in the brain.
 Climate  has probably a similar influence, and hence  the difference
 between the characters of different nations and races.  The skull of
 the Mongol is strikingly different from that of the Kelto-Goth  or
 of the Ethiopian ; and the brain, as well as its functions, exhibits
 equal  diversity.
   Again, it has been  argued, that the facts we notice in the  animai
 kingdom are in favour of the brain  being the organ, concerned  in
 the manifestations of the mind; that, if each animal species  has its
 own psychology, in each  the  encephalon has a  particular organiza-
 tion; and that in all those that exhibit superior powers, the brain
 is found  large and more complicated.  To a great  extent  this is
 doubtless true.  Nothing is, indeed, more  erroneous than the no-
 tion, that even sensibility to pain is equal in every variety  of the
 animal creation.  As  we descend in  the scale, we find the nervous
 system becoming less and  less complicated until  ultimately it as-
 sumes the simple original character, which has laid the foundation
 for one of the divisions of Sir Charles Bell's system; and, al-
 though it is impossible to change places with the animal, we have
 the strongest reasons for believing, that their sensibility diminishes
 as we descend; and that the feeling, expressed by the poet, that the
 beetb, which we tread upon—

             " In corporal sufferance finds a pang as great,
              As when a giant dies"—

 however humane it may be, is physiologically untrue.  The  frog
 will continue sitting, apparently unconcerned, for hours after it has
 been eviscerated; the tortoise walks about after losing its head; and.
 the polypus, when divided by the knife, forms  so  many separate
animals.   All have noticed the independence between the parts of
a wasp when the head has been severed from the body.  The head
will try to bite, and for a considerable period the abdomen will at-
tempt to  sting.   An illustrative instance of this  kind occurred to 
236
SENSIBILITY.
 Dr. Harlan, of Philadelphia. He cut off the head of a rattlesnake,
 and grasping the part of the neck, attached to the head, with his
 finger and thumb, the head twisted itself violently, endeavouring to
 strike him with its fangs.  A live rabbit  was afterwards presented
 to the head, which immediately plunged  its fangs deep into the rab-
 bit;  and when the tail was laid hold of, the headless neck bent it-
 self quickly round as if to strike him.
   The instances of a similar kind, that occur to the naturalist, are
 numerous and interesting; and afford signal evidence of creative
 wisdom, in endowing the frames of those beings of the animal king-
 dom, that are most exposed to injury and  to torture,  with a less sen-
 sible  organization.
   On all the above accounts, then, we may conclude,—that the brain
 is the organ, through which the mind acts, in the production of the
 different mental and moral manifestations.
   Yet amongst those, who admit the accuracy of this conclusion, a
 difference of sentiment exists. Some  conceiving that other organs
 participate in the function.   Some have ascribed to each of the
 known temperaments as many intellectual and moral  dispositions.
 Others have affirmed, that, if the brain be manifestly the  organ of
 the intellect, the passions must be referred to the organs of internal
 or organic life; whilst others again have  considered the brain as a
 great central apparatus, for the reception and elaboration of the dif-
 ferent impressions, made upon the external senses; thus conceiving
 the latter to be direct agents in the execution of the function, as
 well as the brain.
  The influence of the temperaments upon the mental and bodily
 powers is much less invoked at the present day than it was of old.
 The ancients regarded organized  bodies  as an assemblage of ele-
 ments, endowed with different qualities, but associated and com-
 bined so  as to moderate and temper each other.   Modern physio-
 logists mean, by the term, the reaction  of the different organs of the
 body  upon each other, consistent with health; so that if one set or
 apparatus of organs predominates, the  effect of such predominance
 will be exerted over the whole economy.  In the  description of the
 temperaments in different authors, we find a particular character of
 the intellectual and moral faculties  assigned to each.  The man of
 the sanguine temperament is described as of ready conception, re-
 tentive memory,  and lively imagination,  inclined to pleasure, and
 generally of a good disposition, but inconstant and restless.  He of
the bilious,  on the other hand,  is  said  to be hasty, violent, am-
bitious, and self-willed; whilst the lymphatic bestows feeble pas-
sions, cold imagination, tendency to idleness; and the melancholic
disposes to dullness of conception, and to sadness and moroseness
 of disposition.
  Gall has  animadverted on this assignment of any intellectual or
moral faculty to  temperament.  If we look abroad,  he affirms, we
find the exceptions more numerous than  the rule itself; so numer- 
MENTAL FACULTIES, &C
237
ous, indeed, as to preclude us from establishing any law on the sub-
ject; and, moreover, the  idiot,  who  possesses a temperament like
other persons, has no intellectual faculties. The temperament doubt-
less influences the brain, within  certain limits, as it does other func-
tions;  but, he suggests, it does  this probably by impressing them
with a character of energy or of languor, but without, in any re-
spect, regulating the intellectual sphere of the individual; and it
may be regarded as  one of the  media of connexion  between  the
mind and the body.
   Bichat, again, maintained, that whilst the encephalon is evi-
dently the seat of the intellectual functions, the  organic nervous
system, and, consequently, the different organs of  nutrition, which
are supplied from this system, are the seat of the  emotions or pas-
sions.   That distinguished'physiologist, than whom, as Corvisart
wrote to the  First Consul, in announcing his death,  "personne en
si peu de temps n'a fait  tant de choses et aussi  bien," rests his
views upon the three following  considerations:—1st,  That whilst
inward feeling induces us to refer the intellectual acts to the brain,
the passions are felt  in the viscera of the thorax and abdomen.  2dly,
That the effects of intellectual labour are referred to the encephalon,
as indicated by the redness and heat of the face and the beating of the
temporal arteries, in violent  mental contentions, &c.; whilst  the
passions affect the organic functions, the heart is oppressed, and its
pulsations retarded or suspended;  the respiration becomes  hurried
and interrupted; the digestion impeded or deranged, &c.; and, 3dly,
That whilst our gestures and language refer the intellect to the en-
cephalon, they refer the  emotions  to the nutritive organs.  If we
wish to express any action of the mind, or if we are  desirous of re-
calling something that has escaped the memory, the hand is carried
to the head, and we are in the constant habit of designating a strong
or weak intellect by the terms a " strong or weak head;"  and we
say that the possessor has " much or little brain."  On  the other
hand, if we are desirous of depicting the passions, the hand is car-
ried to the region of the stomach or heart; and the possessor of be-
nevolent or uncharitable sentiments is said to have a "good or a
bad heart."  Bichat properly adds, that this idea is not novel, in-
asmuch as the ancients conceived the  seat of the  passions to be in
the epigastric centre; that is, in the nervous plexuses, situated in
that region;  and he  remarks, that, amidst  the varieties presented
by the passions, according to age, sex, temperament, idiosyncrasy,
regimen, climate, and disease, they are  always in a ratio with the
degree of predominance of the different nutritive apparatuses ; and
he concludes with a deduction,  which ought not to  have been ha-
zarded without the fullest reflection—that  as  the  functions of the
nutritive organs, in  which he places the passions,  are involuntary,
ami consequently uninfluenced by education, education can have no
influence over the passions, and  the disposition is consequently in-
capable of modification. 
238
SENSIBILITY.
   The answer of Gall and  Adelon to the views of Bichat ap-
pears to us irrefragable.  How can we conceive that viscera, whose
functions are known, and which differ so much from each other,
are the agents of moral acts ? The passions are sensorial phenomena,
and like all phenomena of the kind must be presumed to be seated
in nervous organs.
   Again, when any injury befalls the brain, and the intellectual fa-
culties are perverted or suspended by it, the same thing happens to
the affective faculties; and if the viscera fulfil the high office assign-
ed to them, why are not the passions manifested from the earliest
infancy, a period when the viscera are in existence and very active?
The argument of Bichat,  that  the phenomena which attend and
succeed to the passions, are referable to the organs of internal life,
is not absolute.   The functions of animal  life are frequently  dis-
turbed by the passions, as well as those  of organic life.   It is not
uncommon for  them to induce  convulsions, mania, epilepsy,  and
other affections of the  encephalon.  The effect here, as Adelon
remarks, is mistaken for the cause.  The heart certainly beats more
forcibly in anger, but the legs fail us in fear; and if we refer anger
to the heart, we must, by parity of reasoning, refer fear to the  legs.
By reasoning of this kind, the  passions might be referred to the
whole system, as there  is no part which does not suffer more or less
during their violence.
   The error arises from our being impressed with the most promi-
nent effect of the passion—the feeling accompanying it—and  this
is the cause of  the gesture and the descriptive language, to which
Bichat has given unnecessary weight in his argument.
   If, then, the views of Bichat, regarding the seat of the passions,
be unfounded, the mischievous doctrine deduced from them—that
the passions are irresistible, and  cannot be  modified by education,
falls to the ground likewise.  His notion was, that the nutritive or-
gans are the source of irritative irradiations, which compel  the
brain to form the determinations that constitute the passion,  and
to command  the  movements by which it is appeased or satisfied.
A similar view is embraced by Broussais, who, however,  con-
ceives, that the passions can  be  fomented and  increased by atten-
tion, until they become predominant.
   Daily experience shows us the powerful  effect produced on the
passions by a well-directed moral restraint.  How  many  gratifying
instances have we of those, whose habitual indulgence of the lowest
passions and propensities had rendered them outcasts from society,
having become restored to their proper place in the community by
exerting the due control over their vicious inclinations and habits?
We can, indeed, not only curb the expression of the passions, as we
are constantly compelled to do in social intercourse; we can even
modify the internal  susceptibility, by well-directed  habits of re-
pression.
   Lastly.  Many physiologists, we have seen, have considered the 
MENTAL FACULTIES,  &C                239
brain as a great nervous centre, for the reception and elaboration of
the different impressions, conveyed thither by the external senses;
and absolutely requiring such impressions for the mental manifesta-
tions.  They consequently rank, amongst the  conditions necessary
for such manifestations, not only the brain, which elaborates them,
but  the parts, that convey to  it the impressions or materials on
which it has to act; conceiving, that a necessary connexion exists
between these two orders of parts.
   The differences, observed  in  the intellectual and moral faculties
of different individuals, the supporters of these opinions ascribe, as
much to diversity in the number and character of the impressions,
as to differences in the encephalon itself.
   They do not all, however,  agree as to  the source of the impres-
sions, which they conceive to be the raw material for the intellec-
tual and  moral manifestations.   Condillac and  his  school admit
only one kind;—those proceeding from  the external senses;  and
which they term external impressions.   Cabanis, on the other
hand, in addition to these,  admits others proceeding from  every
organ in the body, and which he terms  internal impressions, in
contradistinction to the first.
   The school of Condillac set out with the maxim ascribed to
Aristotle,  " nihil est in intellectu  quod non prius fuerit in
sensu;" and they adopt as  an elucidation of their doctrine, the in-
genious idea of Condillac—of a statue, devoid of all sensation, but
which is made to receive each of the five senses in succession; and
which, he attempts to show,  can thus, from the  received impres-
sions, develope  the different intellectual and  moral faculties.  All
these, he affirms, are derived from the impressions made on the ex-
ternal senses; and he  considers,  that the whole of human conscious-
ness is mere sensation, variously transformed.
   The  views of Condillac have  been largely embraced, with
more or  less modification;  and, at the  present  day, perhaps the
majority of metaphysicians  believe, that  the impressions  of the
senses are the necessary  and exclusive materials of all the intellec-
tual acts.
   Condillac's case of the statue seems, however, to be by no means
conclusive.  It  must of course be possessed of a centre for the recep-
tion of the impressions made upon the different senses, otherwise
no perception could occur; and if we can suppose it possible for such
a monstrous formation to exist,  as a being totally devoid of the ex-
ternal senses, such a being must not only be defective in the nerves
which, in the perfect animal, are destined to convey the impressions
to the brain, but would probably be so in the  cerebral or percipient
part likewise.   From defective cerebral conformation, therefore,
the different mental phenomena might not be elicited.
   If, however,  we admit the possibility of the cerebral structure,—
particularly those portions  that are especially concerned in the func-
tion of thought—being  properly organized,  it appears to us, that 
240                      sensibility.
certain mental or moral manifestations would exist.  Of course, all
knowledge of the universe would be precluded, because deprived
of the instruments for obtaining such knowledge;  but  the brain
would still act, as regarded the internal sensations.   In  order that
such a being  may live, he must be  supplied with  the  necessary
nourishment; he must possess all those internal sensations or wants
that are inseparably allied to  organization;  he must consequently
feel the desires of hunger and thirst; but we have seen,  that these
sensations require the intervention of the brain, as much as the ex-
ternal sensations.  Supposing him, again, to survive the period of
puberty, he must experience the instinctive changes, that occur at
that period, and which are doubtless dependent upon encephalic
organization.  It seems to us, then, that in this  assumed case, a
certain degree of mental action might exist;  and, under the  suppo-
sition of a properly organized brain, that ideas—limited, it is true,
in consequence of the privation of the  ordinary inlets  of  know-
ledge—might be formed; and memory, imagination,  and judgment,
be not altogether incompatible within certain limits.
  There are many objections to the idea, that the intellectual and
moral sphere of  man and animals is  proportionate to the number
and perfection of the external senses. Many animals  have the same
number of senses as man, and frequently have them more perfect;
yet, in none, is the mental sphere co-extensive. The idiot, too, has
the external senses as delicate as the man of genius, and often much
more so; many of those,  of the greatest talents, having  the senses
extremely obtuse. It has been already remarked, that the superiority
of the human intellect has  been referred entirely  to the sense of
touch, and to the happy organization of  the human  hand; but the
case of  Miss Biffin,  more than once referred to, and that  of the
young artist cited by Magendie,  completely negative this pre-
sumption.
  The senses  are important secondary instruments, indispensably
necessary for accomplishing certain faculties of the  mind; but,  in
no way, determining its power.
  The example of the deaf and dumb is illustrative  of this matter.
If a child be born deaf, he is necessarily dumb, inasmuch as he is
unable to hear those sounds which, by their combination, constitute
language, and cannot therefore imitate them; yet this  connexion
between the functions of hearing and speech was not well  known
to the ancients. For a length of time, these objects of compassionate
interest were esteemed to be beyond the powers of any kind of in-
tellectual culture, and were  permitted to remain in a state of the
most profound ignorance.  The ingenuity of  the scientific  philan-
thropist has, however, devised modes of instruction,  by which their
mental manifestations have been exhibited  in the most gratifying
manner, and in one which proves, that  the sense of hearing is not
absolutely  necessary "for the mental  development; and that its place
may be supplied, to a great extent, by the proper exercise of others. 
MENTAL FACULTIES, &C.
241
  The deaf and dumb, being deprived of the advantages of spoken
language, is compelled to have recourse to the only kind availa-
ble to him—that addressed to the eye.   In this typical way, by a
well-devised system of instruction, he can be taught to preserve his
ideas, and  to multiply them,  as we do  by the two combined—the
spoken and written language,—without one or other of which the
human mind would have remained in perpetual infancy.  In this
way the  deaf and dumb have not only our ideas,  but the  same
words to convey them to others.
   Yet the deaf and the dumb are not so much objects of our  com-
miseration  as those who have  been deprived, from birth  or  from
early infancy, of the senses of sight and hearing, and who have thus
been devoid of two of the most important inlets for the entrance of
impressions from  the surrounding world.  In such case, it is ob-
vious, they are shut out from  all instruction, except what can be
afforded by the sense of touch; yet even here we have the strongest
evidence of independent intellect.
   One of the most striking cases of this kind is that of the  Scot-
tish boy  Mitchell, the object of much interest to Spurzheim and
to Dugald Stewart, both of whom  have described  his case in
their writings.  It is  a  matter of  uncertainty whether either his
deafness  or blindness was total.  The evidences of the sensation of
sound were, in a high degree, vague and unsatisfactory, but he gave
more convincing  proofs of the possession of  partial vision.  He
could, for example, distinguish day from night; and, when  quite
young, amused himself with looking at the sun through  crevices in
the door, and by  kindling a fire. At  the age of twelve,  the tympa-
num of both ears was perforated, but without  any advantage.  In
his fourteenth year, the  operation for cataract was performed on the
right eye, after which he recognised  more readily the presence of
external  objects, but never made use of his sight to become acquaint-
ed with the qualities of  bodies.  Before and after this period, red,
white, and yellow, particularly attracted his attention. The senses,
by which he judged of  external bodies, were  those of touch and
smell.  His desire to become acquainted with objects  was signal.
He examined every thing he met with,  and every action indicated
reflection.   In his infancy, he smelt at every one who approached
him,  and their odour determined  his affection or aversion.  He
always recognised his own clothes by their smell, and refused to
wear those that he found to belong to others.  Bodily exercises,
such as rolling down a small hill, turning topsy-turvy, floating  wood
or other  objects on the river, that passed his father's  house, gather-
ing round,  smooth stones, laying them in a circle, and placing him-
self in the middle, or building houses with pieces of  turf, &c. were
always a source of amusement to him.   After the operation on his
right  eye, he could better distinguish objects. His countenance was
very expressive, and his natural language was not that of  an idiot,
but of an intelligent being.   When hungry, he carried his hand to
  Vol. I.                     31 
242
SENSIBILITY.
his mouth, and then pointed to the cupboard, where the provisions:
were kept; and, when he wished to lie down, he reclined his head
on one side upon his hand, as if he wished to lay it upon the pillow.
He easily recollected the signification of signs, that had been taught
him, all of which were of course of the tactile kind.
  To make him  comprehend the number of days before any event
would happen, they bent his head as a sign, that he would have to
go to  bed so many times.  Satisfaction was expressed by patting
him on the shoulder or arm, and discontent by a sharp blow.  He
was sensible to the caresses of  his parents, and susceptible of dif-
ferent emotions—of hatred, passion, malice, and the kindlier feel-
ings.  He was fond of dress, and  had great fears of death, of the
nature of which he had manifestly correct notions.
  Mitchell's case has  been pregnant with interest to the  meta-
physician, but it  is not so elucidative as it would have been had the
privation of the senses in question been total.
  There is, at present, in  the  American Asylum at Hartford in
Connecticut,  a being,  not less  deserving of attention than the one
to whom allusion has just been  made.  Her name is Julia Brace.
She is the daughter of John and Rachel Brace, natives of Hart-
ford, and was born in that town in June, 1807; so that she is now,
(1832,) twenty-five years old. At four years of age, she was seized
with typhus fever, was taken sick on the evening of Monday, No-
vember 29, 1811, and, on the Saturday morning following, became
both blind and deaf.
  Prior to her illness, she had not only learned to speak, but to re-
peat her letters, and to spell words of three or four syllables; and,
for some time after the loss of  her sight  and hearing, she was fond
of taking a book, and spelling words and  the names of her acquaint-
ances.   She  retained her speech pretty well for about  a year, but
gradually lost it, and  appears  to be  now condemned to perpetual
silence.   For three years she  could still utter a few words, one of
the last of which was  " mother."   At first she was unconscious of
her misfortune, appearing to think, that a long night had come upon
the world; and often said, "//  will never be day." She would call
upon  the family  to " light the lamp," and was impatient at their
seeming neglect, in not even answering her.  At length, in passing
a window, she felt the sun shining warm  upon her hand, and point-
ed with delight to indicate that the sun shone.   From the January
after her illness,  until  the following August, she would sleep during
the day and be awake through  the night; and  it was not until au-
tumn, by taking  great pains to keep her awake during the day, that
she was set right.  At present, she is as regular, in this respect, as
other persons.  From the period of her recovery, she seemed to
perceive the return of  Sabbath; and, on Sunday morning, would
get her own clean clothes and those of the other children.  If her
mother was reading, she would find a book and endeavour to do so
likewise. 
MENTAL  FACULTIES, &C.
243
   Even now, the intervention of a day of fasting or thanksgiving
 will confuse her reckoning, and some time elapses before she gets
 Tight.
   During the first winter after her recovery, she  was irritable al-
 most to madness; would exhibit the most violent  passion, and use
 the most profane language.  The next summer she became calmer;
 and her mother could govern her, to some extent, by shaking her,
 in sign of disapprobation; and stroking or patting her head, when
 she conducted herself well.  She is now habitually mild, obedient,
 and affectionate.
   During the first summer after her illness, she was very unwilling
 to wear clothes and would pull them off violently.  At length her
 mother took one of her frocks and tried it on her sister, with a view
 of altering it for her.   Julia had ever been remarked for her sense
 of justice in regard to property.  This seemed to be awakened, and
 she took the frock and put it on  herself.  After this, she was wil-
 ling to wear clothes, and even cried for new ones.   She has ever
 since been fond of dress.   At nine years of age, she was taught to
 sew; and, since that time, has learned to knit.  She has been resi-
 dent for several years in  the American asylum at  Hartford,  where
 she is supported, in part, by the voluntary contributions of visitors;
 and, in part, by her own  labours in sewing and knitting.  A lan-
 guage of palpable signs was early established, as a means of com-
 munication  with her friends; and this has been so improved as to
 be  sufficient for all  necessary purposes.   Her  countenance, as she
 sits at work, is said to  exhibit the strongest evidence of an active
 mind and a  feeling heart; " thoughts and feelings," says a  writer
 who describes her case, " seem to flit across  it  like the clouds in a
 summer sky.  A shade of pensiveness will be followed by a  cloud
 of anxiety or gloom; a peaceful  look will perhaps  succeed; and,
 not unfrequently, a  smile lights up her countenance, which  seems
 to make one forget her misfortunes.  But no one has  yet penetrated
 the darkness of her  prison house, or been able to find an avenue for
 intellectual or moral light. Her mind seems, thus far, inaccessible
 to all but her Maker."
  How strongly do these cases demonstrate the  independence of
 the organ of intellect;  requiring, indeed, the external senses for its
 perfect development, but still capable of manifesting itself, without
 the presence of many and probably of any of them;  and how inaptly,
 although humanely, does the law regard such beings. " A person,"
 says Blackstone, " born deaf, dumb, and blind, is looked upon
 by the law as in the same state with an idiot,he being supposed in-
 capable of any understanding, as wanting all  those  senses  which
furnish the human mind  with ideas."  But if he grow deaf, dumb,
and blind, not being born so, he is  deemed  non  compos mentis,
and the same rules apply to him  as to other persons  supposed to be
lunatics.
  With regard to the deaf and dumb, they are  properly held to be 
244
SENSIBILITY.
 competent as witnesses, provided they evince sufficient understand-
 ing, and to be liable to punishment for a breach of the criminal laws.
   Cabanis embraces the views of Condillac regarding the exter-
 nal senses; but he thinks, that the impressions from these are insuffi-
 cient to constitute the matiriel of the mental and moral manifestar
 tions.  In confirmation of this opinion, he observes,  that the young
 infant and animals, at the very moment of birth, frequently afford
 evidences of complicated intellectual processes; and yet the external
 senses can  have been scarcely at all impressed.   How can  we, he
 asks, refer  to the operation of the external senses the motions of the
 foetus in  utero, which are perceptible to  the mother, for the latter
 half of utero-gestation; or the act of sucking, executed from the first
 day  of existence ? Can  we refer to this cause the fact of the chick,
 as soon as it is hatched, pecking the grain, that has to nourish it ?
 or that, so frequently quoted from Galen, of the young kid, scarcely
 extruded from the  maternal womb, which was able  to distinguish
 a branch of the cytisus from amongst other vegetables presented
 to it?
   Man and animals, continues Cabanis, during the  course of their
 existence, experience mental changes as remarkable as they are fre-
 quent: yet nothing in the condition of the senses can account for
 such difference.  For example, at the period of puberty, a new ap-
 petite is added; and this, even, when  the being is kept in a com-
 plete state of isolation.  This, he argues, it is impossible to refer
 to any change in  the external senses; which,  if they furnished
 the  materials at all, must have been doing  so from  early infancy;
 and  he concludes,  that  the  difference  observable  in  the mental
manifestations, according  to  sex, temperament, climate, state  of
health or disease, regimen, &c. cannot be referable to the senses, as
 they remain the same ; and that, consequently,  we must look else-
 where for the causes of such difference.
   These  Cabanis conceives to be, the movements  by which the
organs of internal life execute their functions.  Such  movements,
he says, although deep-seated and imperceptible, are transmitted to
the brain, and furnish that organ with a fresh set of materials.  At
puberty,  for example, when the testicles become developed, and
their function is  established, by the secretion  of the sperm, the
 organic movements, in  the process of this secretion,  are the ma-
 terials of the new desires, that appear at that age.  These impres-
sions Cabanis calls internal, in contradistinction to the external,
or those furnished by the senses; and  he considers that, whilst the
 external senses serve as the base of all that we  include under the
term intellect, the internal impressions are the  materials of what
are called instincts; and, as the organs of internal life, whence the
internal impressions proceed, vary more than the senses, according
 to age, sex, temperament, climate, regimen, &c.  it is  more easy, he
 thinks, to find in them, organic modifications, which coincide with
 those exhibited by the mind, under these various circumstances. 
MENTAL  FACULTIES, &C.
245
   In proof of these opinions, Cabanis adduces, besides others, the
following specious affirmations.   First.  As the venereal appetite
appears, in man and animals, synchronously with the development
of the testicle, and is never exhibited when the testicles are removed
in infancy, we have reason to believe, that the  impressions, which
constitute the materials for this new catenation  of ideas,  must pro-
ceed from the testicle.   Secondly. Numerous facts demonstrate,
that the condition of the uterus has much influence on the mental
and moral manifestations of the female.   For example, the period
of the development of that organ is the one at which new feelings
arise, and when the whole of these manifestations assume more ac-
tivity; and there is generally a ratio between their activity and that
of the uterus.   If the state of the uterus be modified, as it is at the
menstrual period or during pregnancy or after delivery the mind is
so likewise. All these facts ought to induce a belief, he thinks, that
impressions are continually emanating from this  organ,  which by
their variety,  occasion the diversity in the state of the mental and
moral  faculties, observed in these  different cases.   Thirdly. It is
impossible in  the hypochondriac and melancholic constitutions, to
mistake the influence exerted upon the mind by the  abdominal or-
gans;  according as these organs execute their functions more or less
perfectly, the thinking faculty is more or less languid  or brilliant;
and the affections are more or less vivid and benevolent, or the con-
trary; hence the expressions melancholy* and hypochondriasis^
assigned to the state of the mind characterizing these constitutions,
and which denote that the cause must be referred to the  organs of
the abdomen.   The origin of the alternations of inactivity and en-
ergy in the intellect, of benevolent and irascible fits of humour, as
well as of insanity, are also referable to the abdominal viscera.
  Hence, Cabanis concludes,  it is evident, that the  abdominal or-
gans are to the brain the source of fortuitous and irregular impres-
sions, which excite it to irregular acts; and is it not, he asks, pro-
bable, that what takes place in excess, in these morbid  movements,
may happen to a less and more appropriate extent in the state of
health; and that thus, impressions  may emanate, in a continuous
manner, from  every organ of the body, which are indispensable to
the production of the mental and moral faculties ?
  Cabanis, therefore, considers,  that  the axiom  of  Aristotle
should be extended; and that the statue of Condillac is incomplete,
in not having internal organs for the emanation of the internal im-
pressions, which are the materials of the instincts.
  In this way he accounts for the instincts, which by  some meta-
physicians have been  looked  upon as ordinary judgments, so ra-
pidly executed, that  the process has ceased from habit to be per-
ceptible.
  Finally, he  remarks, that there is a ratio between the duration

    • From /uthett, black, and £<*», bile.   f Disease of the hypochondres. 
246
sensibility.
 and intensity of the intellectual results and the kind of impressions,
 that have constituted the materials of them.  All the mental and
 moral acts, for instance, that are derived from impressions engen-
 dered in the very bosom of the nervous system or in the brain,—
 such as those of the maniac,—are the strongest and most durable.
 After  these come the  instincts, of which the internal impres-
 sions are the materials.  They are powerful and constant.  Lastly;
 the acts of the intellect are more transient, because they emanate
 from the external impressions, which are  themselves fickle and
 somewhat superficial.
  According  to the  views, then, of Cabanis and his  followers,
amongst the organic conditions of the mental and moral manifesta-
tions must be placed, not only the encephalon and  the external
senses, but the different organs of the body, that furnish the differ-
ent internal impressions.
  The influence of the external senses on the intellectual and moral
development has already been canvassed; and we have  seen, that
 they are only  secondary instruments for  making us acquainted
with external bodies, but in nowise regulating the intellectual or
moral sphere. The notion of internal impressions is ingenious, and
has led to important improvements in the mode of investigating the
different mental and moral phenomena.   It was suggested by Ca-
banis, in consequence of the external senses appearing to him in-
sufficient to explain all the phenomena.
  By Gall, Adelon, and others, however, all these cases are con-
 sidered explicable, by the varying condition of the  brain itself. In
the foetus in utero, in the new-born animal, there are already parts
of the brain, they say, sufficiently developed and capable of action;
 and, accordingly,  we witness  the  actions to which reference has
been made by Cabanis; and if  the intellectual and moral manifes-
tations vary according to sex,  temperament, climate, regimen, state
of health, &c. it is because the encephalon is, under these circum-
stances, in different conditions.
  The chief facts, on which Cabanis rests  his doctrine, are,—the
 coincidence between the development of  the testicle  and the ap-
pearance of the venereal appetite; and the suppression of this appe-
tite after castration. It must be recollected, however, that these are
 not the only changes, that happen simultaneously at puberty.  The
voice also assumes a very different character; but the change in the
voice is not a cerebral phenomenon.  It is dependent upon the de-
velopment  of its organ, the larynx.  Yet castration, prior to puberty,
has a decided effect upon it; preventing it from becoming raucous
 and unmelodious.  All  these  developments are  synchronous, but
 not directly consequent upon each other.   The generative function
 has two organs,—one  encephalic, the other external; and it is not
 surprising, that both of these should undergo their development at
 the same period.  We  shall see hereafter, that Gall offers us rea-
sons for believing, that the instinct of propagation  has its seat  in 
MENTAL FACULTIES, &C.               247
the cerebellum; and as the most intimate connexion and dependence
must exist between the encephalic and external apparatus, it is not
surprising, that the removal of the latter should prevent the deve-
lopment of the former, and of the instinct of which it is the organ.
If, however, the operation of castration be performed after puberty,
the instinct is not suppressed; because the necessary development
has already taken place, and the cerebellum is  in a  condition for
fulfilling the function.  The continuance of the instinct, under such
circumstances, Adelon conceives to be strong evidence against the
existence  of such internal impressions.
  The influence which Cabanis has ascribed to the uterus in fe-
males, and to the abdominal organs  in the melancholic and hypo-
chondriac, are esteemed to  belong to that excited by the tempera-
ment, or by the different organs of  the body on the  brain; which
has already fallen under discussion.
  On the  whole, then, we are perhaps justified  in concluding, that
the encephalon alone is the organ of the intellectual  and  moral fa-
culties. The interesting topic of  the various instinctive operations
of the frame, will be considered in another part of this treatise.  We
shall there find that instinct cannot be defined, in the language of
Broussais,—to consist in sensations originating in the internal and
external sensitive surfaces, and which solicit the cerebral centre to
acts necessary for the exercise of  the functions; such acts being
frequently executed without the participation of the mind,  and
even in its absence;—inasmuch as it is not confined to beings pos-
sessed of brain, but exists also in  the vegetable.
  Having now decided upon the organ;—according  to the system
adopted in this work, it would be necessary to describe its anatomy.
But this has been done elsewhere.  We  pass on, therefore, to the
consideration of the

       Physiology of the Intellectual and Moral Faculties.

  When the organ of the intellect is  exposed by accident, and we
regard it during the reception of sensation, the exercise of volition,
or during any intellectual or  moral operation, the action is found to
be too molecular to admit of detection.  At times, during violent
mental contention, a redness has been apparent, as if the blood were
forced more violently into the vessels; but no light has been thrown,
by  such examinations, on the wonderful action which constitutes
thought. We ought not, however, to be surprised at  this, when we
reflect, that the most careful  examination of a nerve  does not con-
vey to us the slightest notion how  an impression is  received by it
from an external body; and how such impression is conveyed to the
brain.
  All that we witness in these cases, is the result; and we are thus
compelled to study the intellectual  and moral acts by themselves,
without considering the cerebral movements  concerned  in them. 
248                     sensibility.

Such study is the basis of a particular science—the science of meta-
physics, ideology, or philosophy.  Apart  from organization, this
subject does not belong to physiology; but  as some of the points of
classification, &c. are concerned in questions that will  fall under
consideration, it may be well to give a short sketch of the chief ob-
jects of metaphysical  inquiry; which are,  indeed, intimately con-
nected in many of their bearings,—as commonly treated of by the
metaphysician,—with  our subject.  Broussais  has considered that
metaphysics and physiology should be kept distinct; and that all
the investigations of the metaphysician should  be confined to the
ideal. "I wish metaphysicians, since they so style themselves," he
remarks somewhat splenetically," would never treat of physiology;
that they would only  occupy  themselves with  ideas as  ideas, and
not as  modifications of our  organs: that  they would  never speak
either of the brain, the nerves, the temperaments, nor of the influence
of climates, of localities, or of regimen; that they would never  in-
quire whether there are innate  ideas, or whether they come through
the medium of the senses; that they would not undertake to follow
their developments according to age or state of health; for I am
convinced that they  cannot reason justly on all  these points.  Such
questions belong to  physiologists, who  can unite a knowledge of
the moral nature with  that of the structure of  the  human  body."
" It is possible," he adds, " that particular circumstances may oblige
them to introduce physiological considerations in their calculations;
such are the cases in which it is necessary to estimate the influence
of certain laws or customs in relation to temperature, to  the nature
of the soil, the prevailing diseases, &c. but  then they should  avail
themselves of the experience of physiologists and physicians."  A
more appropriate recommendation would have been, that the meta-
physician should make a point of becoming acquainted  with  phy-
siological facts and  reasoning; and, conversely, that metaphysics
should form a part of the study of every physiologist.
   The cerebral manifestations  comprise two very different kinds of
acts;—the intellectual and the moral: the former being the source
of all the knowledge we  possess regarding ourselves and the  bo-
dies surrounding us: and the latter comprising our internal feelings,
our  appetites, desires,  and affections, by which we  are  excited to
establish a relation with the  beings around us:—the two sets of acts
respectively  embracing the qualities of  the mind and  of the
heart.
   Under the intellect  or understanding, then, is included the as-
semblage of faculties  by which  we  acquire all the notions  we
possess.
   If we attend to the different modes in which these intellectual
manifestations are evinced in  our  own persons, we shall find that
there are several operations which differ essentially from each other.
We are conscious of the difference between perceiving an impres-
sion, made upon one of the external senses, which constitutes per- 
MENTAL  FACULTIES, &C
249
 ception, and recalling such impression to  the mind, which is the
 act of memory; as well as the distinction between feeling the rela-
 tions that connect one thing to another,  constituting judgment;
 and the tendency to act in any direction,  which we call  the will.
 The consciousness of these various mental acts  has induced philo-
 sophers to admit the plurality of the intellectual faculties, and to
 endeavour to reduce them  all to certain primary faculties; in other
 words, to faculties, which are fundamental or elementary; and which,
 by their combination, give rise to other and more complex manifes-
 tations.   To this analytical method they have been led by the fact,
 that these different acts, which they have esteemed elementary, ex-
 hibit great variety in their degrees  of activity; that one, for exam-
 ple, may be impressed with a character of great  energy—as the
 memory—whilst another, as the judgment, may be singularly fee-
 ble, and vice versa.
   Broussais, indeed, conceives, that without the memory we can-
 not-exercise a single act of judgment; since it is  always necessary,
 in order to judge, that we should experience two successive percep-
 tions; that is, that  we should feel them alternately, which we could
 not do, unless possessed of the faculty  of renewing that, which we
 felt an instant before;  or, in other words, unless we possessed me-
 mory. Hence the loss of this faculty, he says, necessarily occasions
 that of judgment, and reduces man to a state of imbecility.  '
   To a certain extent this  is doubtless  true. Total privation of me-
 mory must  be attended with the results described; that  is,  if the
 individual has no consciousness of that which has impressed him
 previously; for it is obvious, that in such  a case, there can be no
 comparison. A man,  however, may have an unusual memory for
 certain things, and not for  others; he may  astonish  us  by the ex-
 treme accuracy of his recollection of numbers, places, or persons, and
 yet he may be singularly deficient in judging of ordinary matters;
 his memory suggesting only one train of objects for comparison.
   In enumerating  the  faculties,  which, by their union, constitute
 the intellect, we observe the  greatest  discrepancy amongst meta-
 physicians;  some admitting volition, imagination, understanding,
 and sensibility; others sensibility, imagination, memory, and rea-
 son; others  will, intelligence,  and memory; others, again, imagi-
 nation, reflection, and memory.
   The views of Condillac, on this subject, have perhaps excited
 more attention than those of any other individual.  Professing, as
 we have seen, that all  our  ideas are derived  from the successive
 operations of the senses and the mind, he admits the following con-
 stituent faculties in the intellect:—sensation, attention, compari-
 son, judgment, reflection, imagination, and reason.  Sensation
 he defines the faculty of the mind, which affords the perception of
any sensitive impression.   Attention, the faculty of sensation, ap-
plied exclusively to a determinate object; being, as the word im-
ports, the tension of the mind  upon  a particular object.  Compari-
   V OIi* 1,                     oA 
250
SENSIBILITY.
son, the faculty of sensation applied to two objects at once.  Judg-
ment, the faculty by which the mind perceives the connexions that
exist between the objects compared. Reason, the faculty of running
through a succession of judgments, which are connected with, and
deduced from each other.  Reflection, as the word indicates, is the
faculty by which the mind returns upon itself,  upon its own pro-
ducts, to prove their correctness, and to subject them again to its
power:—and imagination, to which Condillac attaches memory,
is the faculty possessed by the mind of reproducing at will the dif-
ferent impressions, and all the products of its own operations.
  With regard to the order of catenation of these different faculties,
he considers sensation to be first put in play; and if, amongst the
perceptions, there is one of which we have a more lively conscious-
ness,  and  which attracts the mind to it  alone, it  is the product of
attention; then comes comparison,  which is nothing more than a
double attention; comparison is irresistibly succeeded by judgment;
if, from  one  judgment, we pass to  another deduced from it, we
reason; if the mind turns back on its own products, we reflect; and,
lastly, if the mind spontaneously awakens its different perceptions,
imagination is in action.   All these faculties are thus made to be
deduced from each other;  to originate  in the first, or in sensation;
and all are but this first sensation successively transformed.
  The doctrine of Condillac, abstractedly considered, has already
engaged attention.  The division of the  faculties,  which he con-
ceives, by their aggregation, to form  the intellect, is simple and in-
genious,  and  appears to be more easily referable to physiological
principles than that of other metaphysicians; accordingly, it has
been embraced with more or less modification by certain physiolo-
gical writers.
  The power of reflection, according to  Broussais, is the charac-
teristic of the human intellect; and to reflect is to feel.  Man not
only feels the stimulation produced by  external  organs, and by the
movements of his own organs, which constitutes sensation or percep-
tion, but he is conscious that he has felt these stimulations; or, in other
words, he feels that he has felt; he has consequently a perception
of his actual perception. This, he says, constitutes mental reflection.
This process  man can repeat as often as he thinks fit, and can ob-
serve all his sensations, and the different modes in which he felt,
whilst occupied with his feelings.  From this study he derives an
idea of his own existence.   " He distinguishes himself in the midst
of creation, and, paying regard only to his own existence, compared
with  all that is not himself, he pronounces the word /,  (moi,) and
says,  I am; and, viewing himself in action, says, I act, I do" &c.
Perception of himself and of other bodies procures him what are
denominated ideas.   This is, therefore, another result of reflection;
or, in other words,  of the faculty he possesses  of feeling  himself
feel; but man feels, besides, that he has already felt—this constitutes
memory.   In comparing two perceptions with  each other, which
are felt in succession, a third perception results, which is judgment. 
MENTAL  FACULTIES, &C                251
 Consequently, to judge is only to feel.   Hence he concludes " sen-
 sation, reflection, and judgment, are absolutely synonymous, and
 present to the physiologist nothing more than the same phenome-
 non.   The will, or that faculty by virtue of which man manifests
 his liberty by choosing, among  different  perceptions,  the one he
 must obey—that faculty, which gives him the power of resisting,
 to a certain extent, the suggestions of instinct, is founded on reflec-
 tion.   Consequently, when we consider it in a physiological point
 of view, we can only discover in it the faculty of feeling ourselves,
 and of perceiving that we feel ourselves."
    Some of the later French metaphysicians  have proposed certain
 modifications in the system of Condillac. M. De La Romiguiere,
 for instance, denies that sensation is the original faculty, and derives
 all from attention.   The mind, he remarks,  is passive  during the
 reception of sensation, and does not commence action until directed
 to some object, or until it attends.  According to him, the intellect
 consists of only three faculties—the attention; comparison, or
 double attention;  and reason, or double comparison.   Judgment,
 imagination, and memory, are not primary  faculties : judgment is
 the irresistible  product  of comparison; memory is but the trace,
 which every perception necessarily leaves behind it; and imagina-
 tion is but a dependence on reason.
    M. Destutt-Tracy,  again, reduces the number of primary fa-
 culties to four—perception, memory, judgment, and will or desire.
 According to him, attention is not an elementary faculty. It is but
 the active exercise of the intellectual faculties.   The same applies
 to reflection and  reason, which  are only a judiciously combined
 employment of those faculties; and to comparison  and  imagina-
 tion, both of which enter into the judgment.
  • The division of M. Destutt-Tracy is embraced by Magendie
 in his Precis Ettmbntaire de Physiologic
   Stewart's classification is into,  1. Intellectual powers, and, 2.
 Active and moral powers; including in the former, perception, at-
 tention, conception, abstraction, the associating principle, me-
 mory, imagination, and reason.  Brown reduces all the intellec-
 tual states to simple suggestion and relative suggestion, compris-
 ing in the former,—conception, memory, and imagination,—in
 the latter, judgment, reason, abstraction, and taste; whilst Kant
 has " twenty-five primary faculties or forms; pure  conceptions or
 ideas a priori."
   These are a few only of the discrepant divisions of psychologists.
 The list might have been extended by the classifications of Aris-
 totle, Bacon, Hobbes, Locke, Bonnet, Hume, Vauvenargues,
 Diderot,  Reid, and others.   Perhaps the most prevalent opinion
 at present  is, that the original faculties are—perception, memory,
judgment, and imagination.  It is impossible for  us, were it even
 our province, to reconcile these discrepancies.  They are too con-
 siderable for us to hope that this will ever be effected by metaphy-
 sical inquiry.  We must, therefore, look  to physiological investiga- 
252                      sensibility.
tion, if not with well founded—with the only—hopes, we can enter-
tain, for the elucidation of the subject; and we shall find presently
that the minds of metaphysical physiologists have been turned in
this direction, and that many interesting facts and speculations have
been the result.
  A second topic of metaphysical inquiry regards the formation of
all the intellectual notions we possess.  On this, there have  been
two principal opinions.  Some, as Plato, Descartes, the Kantists,
Kanto-platonists, &c. believing in the existence  of innate ideas of
things:—others, as Bacon, Locke, and  Condillac, denying the
existence of such innate ideas, and asserting, that the human intel-
lect, at birth, is a tabula rasa, and that the mind has to acquire and
form all the ideas it possesses from impressions made on the senses.
  The truth lies probably between these two extremes:—the action
of the senses and of the intellectual faculties being alike necessary;
the former receiving the external and internal impressions, and trans-
mitting them to the mind, which, through the cerebral organ, pro-
duces the different intellectual acts.
  Under the terms affective faculties,  affections, passions, are
comprehended all those active and moral powers, which connect us
to the beings that surround us, and are the incentives of our social
and moral conduct.  To this class belong the feeling that  attaches
the parent to the child; that which draws the sexes together; and
the feeling of compassion, by which we are led to assist a suffering
fellow creature.   They are, in truth, internal sensations, but of a
higher cast than those of hunger and thirst; the latter being purely
physical and announcing physical necessities, the former suggesting
social and moral relations.   Such affective faculties are the founda-
tion of what are called  moral wants; and like the internal sensations
in general are the source of pleasure, when satisfied, ofpain, when
resisted; and it is only when they are extreme and opposed, that
they acquire the name of passions*
  The analysis of these, is attended with the same difficulties as that
of the intellectual faculties.  Their plurality is universally admitted,
but still greater discrepancy exists as to their precise  number and
connexion.
  Many moralists have united the moral faculties under the  head
of will or desires.   Condillac is one of those.   Every sensation,
he observes, having the character of pleasure or  pain,—none being
indifferent,—as soon as a sensation is experienced the mind is ex-
cited to act.  This tendency is at first but slightly marked, and is
only an uneasiness, {malaise;) but it soon increases, becomes rest-
lessness or inquietude; in other words, a difficulty experienced by
the mind of remaining in the same situation. This gradually becomes
desire, torment, passion, and finally will, excited to the execution
of some act.
  Many moralists have endeavoured by ultimate analysis, to derive
* From potior, I suffer. 
mental  faculties, &c.
253
 all the affective faculties of the mind, from one principal faculty—
 that of self-love,—the inward feeling, which induces all men to at-
 tend to themselves, their own preservation, and welfare.  All the
 faculties, they assert, are returns of this self-love upon  itself; and,
 as in the case of the intellectual faculties, attempts have been made
 to classify them; but no two  scarcely agree.   Some have divided
 them into the agreeable and distressing; others into those of love
 and hatred; many, regarding their  effects upon society, into the
 virtuous, vicious, and mixed.  The first comprising those, that are
 useful to  society,—as filial, paternal, and conjugal love, which
 form the foundation  of families; goodness, pity, and generosity,
 which, by inducing men to assist each  other, facilitate the social
 condition; and the love of labour, honour, and justice, which have
 the same result by constituting so  many social  guaranties.  The
 vicious passions, on the contrary, are such as injure man individu-
 ally and society in general, as pride, anger, hatred, and malice.
 Lastly, the mixed passions are such as are useful or injurious, accord-
 ing to their use or abuse; such as ambition, which may be a laudable
 emulation or insatiable passion, according to its extent and direction.
   Again, the passions have been divided into the animal or such
 as belong to physical man, and the social or  such as appertain  to
 man in society.  The first are guides to him in his own preserva-
 tion as well as that of the  species.   To them belong fear, anger,
 sadness, hatred, excessive  hunger, the  venereal desires, when ve-
 hement, jealousy, &c.  In the second  are included all the social
 wants, when inordinately experienced.   These vary according  to
 the state of civilization of the individual and the community. Am-
 bition, for instance, it is said, may be regarded, when inordinate, as
 excessive love of power:—avarice, as an exaggeration of the desire
 for fortune:—hatred and vengeance, as the natural and impetuous
 desire of injuring those that injure us, &c.
   Stewart's division of the active and moral powers embraces,
 1. Instinctive principles, and 2. Rational principles: the former
 including appetites, desires, and affections, the latter self-love and
 the moral faculty; all  of which  Brown comprises under emo-
 tions, immediate, retrospective,  or prospective.
   It is obvious, that the analysis of the moral faculties has been still
 less satisfactorily executed   than that of the intellectual; and that
 little or no attempt has been made to specify those, that are primary
 or fundamental, from  those that are more complex.   The remarks,
 consequently, which were  made regarding the only quarter we have
 to look to, for any improvement in our knowledge of the intellec-
 tual acts, apply a fortiori to the moral; although it must be admit-
 ted, that the difficulties attendant upon the investigation of the latter
 are so great as  to appear to be almost, if not wholly, insuperable.
  As the brain, then, is admitted to  be the organ of the intellec-
 tual and moral  faculties, its structure probably varies according to
the number and character of those; and  if there be primary or fun-
damental faculties they may each have a special organ concerned in 
254
SENSIBILITY. «
their production, as each of the external senses has  an  organ con-
cerned in its production.   According to this view, the cerebral or-
ganization of animals ought to differ according to their psychology:
where one is simple the other should be so likewise,  and vice versa.
   This seems, so far as we can observe, to  be essentially the fact.
"In the series of animals," says Adelon,  "we observe the brain
more complicated as the mental sphere  is more extensive; and in
this double respect  a scale of gradation may be  formed from the
lowest animals up to man.   If this being has the most extensive
moral sphere, if he alone possesses elevated  notions of religion and
morality,  he has also the largest brain, and  one composed of more
parts; so that if the physiology of  the brain were more advanced,
we might be able, by comparing the brains  of animals with his, to
detect the material condition,  which constitutes humanity.   If the
brain were not constructed, a priori, for a  certain psychology, as
the digestive apparatus is for a  certain alimentation, if  the mental
and moral faculties were not as much innate as the other faculties,
there would be nothing absolute in legislation or morals. The brain
and its faculties are, however, in each animal species, in  a ratio with
the role, which such species is called upon to fulfil in the universe.
If man is, in this respect, in the first rank;  if he converts into the
delicate affections of father, son, husband, and country,  those brute
instincts, by which  the animal is attached to its young,  its female,
orits kennel; if,in short,he possesses faculties  which animalsdo not,—
religious and moral feelings, with allthose that constitute humanity,—
it is owing to his having a more elevated vocation, to his being not
only the king of the universe,  but  destined also for a future exist-
ence, and specially intended to live in society.  Hence it was ne-
cessary that he should not only have an intellect sufficiently exten-
sive to make all  nature more  or less  subject to  him,  but also  a
psychology such, that he might establish social relations with his
fellows.   It was necessary  that he should have notions  of the just
and  unjust,  and  be able to elevate  himself to the  knowledge of
God;—those sublime feelings, which cause him so to regulate his con-
duct as to maintain with facility his mortal connexions,  and  to de-
serve the future  life to which he is called."
   But if the intellectual sphere be regulated by the  cerebral deve-
lopment, can we not, it has been asked, estimate the  connexion be-
tween them ? And if there be different  primary cerebral faculties,
each of which must have an organ concerned in its production, can
we not point out such organ in the brain? Several investigations of
this character have been attempted, with more or less success.  Ge-
nerally, however, they have added but little to our positive know-
ledge, and this, principally, from the intricacy of the subject.
   Until of late years,  attention was chiefly paid  to the mass  and
size of the encephalon;  and it was,  at one time, asserted, that the
larger this organ, in any species  or individual,  the  greater the in-
tellect.  Man, however, has not absolutely  the largest encephalon,
although unquestionably the most intelligent of beings. The weight 
MENTAL FACULTIES, &C                255
of the encephalon of a child six years of age is given by Haller
at two pounds three ounces and a half; whilst that of the adult is
estimated by Soemmering at from two pounds three ounces, to three
pounds three ounces and three-quarters; and that of the elephant, ac-
cording to Haller, weighs from seven to ten pounds. This, conse-
quently, overthrows the proposition; and, besides, in certain insects
with very minute brains,as the beeand the ant, wemeetwith evidences
of singular intelligence.'The proposition was therefore modified, and
it was laid down that the  larger the encephalon, compared with the
rest of the body, the greater the mental sphere.  When  the subject
was first investigated in this way, the result in the case of the more
common and domestic  animals was considered so satisfactory, that,
without farther comparison, the proposition was considered  to  be
established.   More modern researches have shown, however, that
it admits of numerous exceptions, and that several of the mammalia,
and many diminutive and insignificant animals have the advantage
over man in this respect.  It has, indeed, been properly observed by
Mr. Lawrence, that it cannot be a very satisfactory mode of pro-
ceeding to compare the body, of which the weight varies so consi-
derably, according to illness, emaciation, or embonpoint, with the
brain, which is affected by none of these circumstances, and appears
to remain constantly the same.  This is the cause why in the cat,
the weight of the encephalon,  compared with that of the body, has
been  stated  as 1 to 156 by one comparative anatomist, and as 1 to
82  by another;  that of the dog as 1 to  305 by one, and as 1 to 47
by another,  &c.
  The following table, taken  chiefly from  Haller and Cuvier,
exhibits the proportion which  the  encephalon bears to the rest of
the body, in man and certain animals.
      22
      1
•   •   TT
      1
   '   4~S"
-1 to -1-
4T lU 2?
tV to
TOT
 1
 ■g"4
-rtO
2 4
 1
TS
Child, 6 years old
Adult  ....
Gibbon ....
Sapajous, from  .
Apes  ....
Baboons  .   .  .
Lemurs  .   .  .
Bat (vespertilio)
Mole  ....
Bear   ....
Hedgehog .   .   .
Fox.....
Wolf  ....
Beaver.......ajo-
Hare  ....
Rabbit ....
Rat.....
Mouse.......
Wild boar.....
Domestic do.    .   .  7|j to
1  in -J_
- to g^-
205
_1_
2 30
T5Vto
22'S'
 1
15~2~
43
 1
 i
4~12
TJo
to
T6-7
 1
To?
to
Elephant......Tfa
Stag •.......2T0
Roebuck (young) .  .  .   .  9^
Sheep   .  .
Ox   .   .  .
Calf .   .  .
Horse   .  .
Ass  ...
Dolphin
Eagle   .  .
Goose   .  .
Cock   .  .
Canary bird
Humming bird
Turtle  .  .
Tortoise  .   .
          47To
           1
        ' 154
 1111
2T' "ST* Fo' To?
          _1
        * 260
          _1
        * 3T0"
 TT
_ 1
5 37 ff
Frog
Shark
Pike
Carp
 172"
__1
24"§"5" 
256
SENSIBILITY.
  Wrisberg and Soemmering proposed another point of compari-
son :—the ratio of the mass of the encephalon to that of the rest  of
the nervous system;  and they asserted that, in proportion as any
animal possesses a larger share of the  former; or, in other words,
in proportion as the percipient and intellectual organ exceeds the
other or the organ of the external senses—the mental sphere may
be expected to be more diversified and developed.  But although
man is, in general, pre-eminent in this respect, he is not absolutely
so.   It would be still more important to know the ratio, that the
cerebrum or brain proper bears to the  cerebellum and medulla ob-
longata.  The first  is essentially the  organ of intellect; and the
most striking character of the human brain  is the large development
of the cerebral hemispheres, of which we have no parallel in the
animal kingdom. The last is the encephalic part in which all the
nerves of the senses arise or terminate.
  The assertion, that man has the largest cerebrum in  proportion
to the cerebellum is not  at all accurate.   The Wenzels found the
ratio, in man, to be as 6Ty^ or 8T\2T to 1; in the horse, A\ to 1;  in
the cow, 5\\\ to 1:  in the dog, 6¥%- to 1;  in the cat, 4T47 to 1;  in
the mole, 3f to 1; and in the mouse, 6| to 1.  Nor is it true that
man has the largest cerebrum in proportion to the medulla oblon-
gata and medulla spinalis; although to this position there are per-
haps fewer objections than to any of the others.   None of them, it
is obvious, are distinctive between man and animals, or  assist us  in
solving the great problem of the source and seat  of the numerous
psychological differences we observe in different animals and  men.
Yet numerous plans have been devised for appreciating the compa-
rative size of the cranium,—which is in a direct ratio  with that  of
the brain,—and  of the bones of the face.  As the former contains
the organ of the  intellect, and the latter those of the external senses
and of mastication ; it has  been presumed, that the excess of the
former would indicate the  predominance of thought over  sense;
and, conversely, that the greater development of the face would
place the animal lower in the  scale.
  One of these methods,  which was first proposed by Camper, is by
taking the course of the facial line and the amount of the facial an-
gle.  The facial  line  is a line drawn from the projecting part of the
forehead to the alveoli of the incisor  teeth of the upper jaw; and
the facial angle is that formed between this line and another drawn
horizontally backwards from the upper jaw.  The course of the ho-
rizontal line and its point of union with the facial line is not uni-
form in all the figures given by Camper; sometimes it  is made  to
pass through the meatus  auditorius externus, but often  it  falls far be-
low it; yet Dr. Bostock thinks, " we cannot hesitate to admit the'
correctness of Camper's observations, and  we can scarcely refuse
our  assent to  the conclusion  that he deduces  from them."   In
man, whose face is situated perpendicularly under the cranium, the
facial angle is very large.   In animals, the  face  is placed in front 
MENTAL  FACULTIES, &C
257
of the cranium;  and, as we              Fig. 45.
descend from man, the angle
becomes less and less, until
it is finally lost: the  cra-
nium and face being in most
reptiles and fish completely
on a level.  The marginal
figure  exhibits  the differ-
ence between the facial an-
gle of  those of  European
descent, and that of the ne-
gro. By covering with the
finger the parts  below  the
nose alternately, we  have
the  countenance  of   the
white or of the negro, in
which   the  facial  angle
differs  as much  as 10, or
15°.  Figure  46  exhibits
the  facial   line  and   an-
gle of  the  ourang-outang.
Those  animals,  that have
the snout long and the fa-
cial  angle  consequently
small,  have  been  prover-
'bially  esteemed  foolish,—
such as the snipe, stork, crane, &c; whilst  superior intelligence
is ascribed to those in which the angle
is more largely developed,—as  the
elephant and  the  owl; although  in
them, the large  facial  angle is caused
by the size of the frontal sinuses or by
the wide separation between  the two
tables of the skull, and is  necessarily
no index of the size of the brain.  Yet,
from this cause, perhaps, the owl was
chosen as an emblem of the goddess of
wisdom; and the elephant has received
a  name in the Malay  language, indi-
cating an opinion, that he is possessed
of reason.   The following table  ex-
hibits the facial angle in man and cer-
tain animals, taken by a line drawn
parallel to the floor of the nostrils, and
meeting another, drawn from the greatest prominence of the alveoli
of the upper jaw to the prominence of the forehead.
   Vol. I.                     33
Fig. 46.
 
25S
SENSIBILITY.
Man  .  .  65° to 85° and more.
Sapajou.......65°
Ourang-outang  .  .   56° or 58°
Guenon  ....... 57°
Mandril  ....   30° to 42°
Coati........28°
Pole cat.......3V
Pug dog.......35°
Mastiff.......41°
Hare........30°
Ram.........30°
Horse........23°
  The facial angle may, then, exhibit the difference between man
and animals;  and, to a certain extent, between the species or  indi-
viduals of the latter; but, farther, it is of little or no use."
  In man it may be considered to vary from 70°  to  85°  in the
adult, but in children it reaches as high  as 90°;—a sufficient proof,
that it cannot be regarded  as a  measure of the intellect.   In the
European, it is, on  the average perhaps, 80°, in  the Mongol, 75°,
and in the negro, 70°; not many degrees above the ourang-outang.
It is found, however, that the skulls of different nations,and of in-
dividuals of the same nation, may agree  in  the facial angle, whilst
there are .striking distinctions in the shape of the cranium and face,
in the air and character of the whole head, as well as in the parti-
cular features; the inclination of the facial line being obviously  more
dependent on the prominence of the upper jaw and frontal  sinuses
than on the general form of the head.  The ancients had manifestly
been impressed with the intellectual air exhibited by the open facial
angle ; for we find in all their statues of legislators, sages, and poets,
an angle of at least 90°,  and in those of heroes and of superhuman
natures, it is carried as high as 100°.
  This angle, according to Camper, never existed in nature; and
yet he conceives it to be the beau ideal of the human countenance,
and to have been the ancient model of beauty.   It was more-pro-
bably the model of superior intellectual endowment, although ideas
of beauty might have been connected with  it.  Every nation forms
its notions of beauty, derived from this source, chiefly from the fa-
cial angle to which it is accustomed.  With the Greeks it was large,
and therefore the vertical facial line was highly estimated.  For the
same reason it is pleasing to us; but such would not be the universal
impression.   Most savage tribes,  on our own continent, have pre-
ferred the pyramidal shape of the head, and made use of every en-
deavour, by unnatural compression in early infancy, to produce it;
whilst others, not satisfied with  the  natural shape of the frontal
bone, have forced back the forehead, either by applying a flat piece of
board to it, like the Indians of our own continent, or by iron plates,
like the inhabitants of Arracan.  By this practice, the Caraibs are
said to be able to see over their heads.
   Daubenton again,  endeavoured, by taking the occipital line
and angle, to measure  the differences between  the skulls  of man
and animals.  One line is drawn  from the posterior margin of the
foramen magnum of the occipital  bone to the inferior margin of the 
MENTAL  FACULTIES, &C
259
orbit, and the other from the top of the head to  the space between
the occipital condyles.  In  man  these  condyles, as well as the
foramen magnum, are so situated, that a line drawn perpendicular
to them would  be a continuation of the spine; but in animals they
are placed more  or less obliquely: the perpendicular would neces-
sarily be  thrown farther forward, and the angle be thus rendered
much more acute.* Blumenbach  says, that Daubenton's method
may be adopted to measure the degrees of comparison betwixt man
and brutes, but not  the varieties of  national character; for it was
different in the skulls of two Turks and of three Ethiopians.
   Blumenbach found the methods of both Camper and Dauben-
ton insufficient to indicate the varieties in the national and indivi-
dual character.   He, accordingly, describes a new method,—which
he calls the norma verticalis,—in the " Decas Collectionis suae cra-
niorum diversarum gentium" It consists in selecting two bones,
the frontal from those of the cranium, and the superior maxillary
from those of the face, and comparing these with each other,—by
regarding them vertically,—placing the  great convexity of the cra-
nium directly before him, and  marking the  relative  projections  of
the maxillary bone beyond the arch  of the forehead.  The Georgian
is thus found to be characterized by  the great expanse of the upper
and outer part  of the  cranium,  which hides the face.   In the Ethio-
pian, the narrow, slanting forehead allows the face to appear, whilst
the cheeks and jaws  are  compressed  laterally and elongated  in
front; and in the Tungoose,  the maxillary, malar, and nasal bones
are widely expanded on each side;  and the two last rise to the same
horizontal level with the  space between the frontal sinuses—the
glabella.
   Blumenbach's method, however, only affords us the compara-
tive dimensions of the two bones in one  direction.  It does not in-
dicate the depth of the maxillary bone or of the  os frontis, or their
comparative areas.  The view  thus obtained  is therefore partial.
   Finding the inapplicability of other  methods to the greater part
of the animal creation,—to birds, reptiles, and fishes, for example,—
Cuvier suggested a comparison  between  the  areas of the face
and cranium under the  vertical section of  the  head.  The result
of his observations is,—that, in  the  European,  the area of the
cranium  is  four  times  that of  the face,—excluding the lower
jaw.  In the Calmuck, the area of the face is  one-tenth greater than
in the European; in the negro, one-fifth, and in the  Sapajou, one-
half.  In the Mandril, the two areas are equal;  and in proportion
as we descend  in the scale of animals, the area of the face gains over
that of the cranium; in the hare, it is one-third greater; in the  ru-

   * By some writers, Daubenton's method is said to consist of " a line drawn
from the posterior margin of the occipital foramen to the inferior margin of the
orbit; and  another drawn horizontally through the condyles  of the occipital
bone."  It is obvious that' no comparative  judgment of  the cranium and face
could be formed from this. 
260
SENSIBILITY.
minant animals double; in the horse, quadruple, &c; so that the
intelligence of the animal is said to be greater or less, as the pre-
ponderance of the area of the face over that of the  skull diminishes
or increases.
  The truth is, according to Sir Charles  Bell, that the great
difference between the bones of the cranium and face in the Euro-
pean and negro is in the size of the jaw bones.  In the negro these
were  found to bear a much greater proportion  to the head and
to the other bones of the face than those of the European skull; and
the apparent size of the bones of the negro face was discovered to
proceed solely from the size and  shape of the jaw bones, whilst the
upper bones of the face, and, indeed, all, that had not  relation to
the teeth and to mastication, were less than those of the European
skull.
  Other methods, of a similar kind, have been proposed by natu-
ralists, but they are all insufficient to enable us to  arrive at  an ac-
curate comparison.  Blumenbach asserts that he  found the facial
and occipital angles nearly alike in three-fourths of known animals.
Moreover,  it by no means follows, that, in the same species, there
should be a correspondence between the size of the  cranium and
face.  In the European, the face  may be unusually large; and yet
the mental  endowments may be brilliant.  Leo the Xth, and Mon-
taigne and Leibnitz, Racine, Haller  and  Franklin, had all
large features. All the methods, again, are confined to the estimation.
of the size of the whole encephalon; whereas we.have seen, that
the brain alone is concerned in the intellectual and moral manifes-
tations; although Gall  includes, also, the cerebellum.   It  has al-
ready been remarked, that no animal equals  man  in  the develop-
ment of the cerebral hemispheres.  In the ape, they  are less pro-
minent; and below it, in the scale of creation, they become less and
less;  the middle lobes are less arched downwards; and the poste-
rior lobes are ultimately wanting, leaving the cerebellum uncovered;
the convolutions are less and less numerous and deep, and the brain
at length is found entirely smooth.  The experiments of Rolando
of Turin, and of Flourens of Paris, are likewise confirmatory  of
this function of the brain proper.  These gentlemen experimented
upon  different portions of the encephalon, with the view of detect-
ing their functions; endeavouring, as much as possible, not to im-
plicate any part except the one which  was the  subject of investi-
gation;  and they  found, that if the cerebral hemispheres were alone
removed, the animal was thrown into a state of stupor or lethargy;
was insensible to all impressions; was to every appearance asleep, and
evidently devoid  of all intellectual and  affective faculties.   On the
other hand, when other parts of  the encephalon were mutilated,—
the cerebellum, for example,—leaving the cerebral hemispheres un-
injured, the animal was  deprived of some other faculties,—that of
moving, for instance,—but retained its consciousness,  and the exer-
cise of all its senses. 
MENTAL FACULTIES, &C
261
  M. Desmoulins, in a recent publication on the nervous system
of vertebrated animals, is in favour of a view, originally suggested
by M. Magendie, that the intellectual sphere of man and animals
depends exclusively on  the cerebral convolutions;  and that exami-
nation of the convolutions will point out the intellectual differences,
not only between different species, but  between individuals of the
same species.
  According to him, the cerebral convolutions are numerous in
animals in proportion to their intelligence; and, in animals of simi-
lar habitudes, have a similar arrangement. In the same species they
differ sensibly, according to the degree in which the individuals
possess the qualities of their nature; for example, they vary in the
foetus and the adult;  are manifestly less  numerous and  smaller in
the idiot, and become effaced in protracted cases of insanity.  He
farther remarks, that the morbid conditions of the encephalon, which
occasion mental aberration, are especially such as act upon the con-
volutions; and that, whilst apoplectic extravasation into the centre
of the organ induces paralysis of sensation and motion, the least in-
flammation of the arachnoid membrane causes delirium.  Hence he
deduces the general principle,  that the  number and perfection of
the intellectual faculties are in  proportion to the extent of the cere-
bral surfaces.
  This view of M. Desmoulins, so far as regards the seat  of the
intellectual and moral faculties, accords with one to which attention
must now be directed, and which has given rise to more philoso-
phical inquiry, laborious investigation, and, it must be admitted, to
more idle enthusiasm and intolerant opposition, than any  of the
psychological doctrines advanced in  modern times:—we allude to
the views of Dr. Gall on the  functions of the brain.
  These,  as expressed  in his large  work,  Sur les fonctions du
Cerveau et sur celles de chacune  de ses Parties, are, 1st, That
the intellectual and moral faculties are innate. 2dly, That  their ex-
ercise or manifestation is dependent upon organization.  3dly, That
the brain is the organ of all the appetites, feelings and faculties; and,
4thly, That the brain is composed of  as  many particular organs as
there arcappetites, feelings and faculties, differing essentially from
each other.
  The importance of Gall's propositions; the  strictly physiologi-
cal  direction which they have taken,—the only one, as we have said,
which appears likely to aid us in our  farther acquaintance  with the
psychology of man,—require that the physiological student  should
have them placed before him as they emanated from the author.
The work of Gall, however, on the functions of the brain, com-
prises six octavo volumes, not distinguished for unusual method or
clearness of exposition.  Fortunately, the distinguished physiologist,
Adelon, to whom we have so frequently referred, has spared us the
necessity of a tedious and difficult analysis, by the excellent and im-
partial view which he has given in the Dictionnaire de Medecine,and 
262                      sensibility.
which has been since transferred to his Physiologie de I'Homme;
both being abridgments of the Analyse d'un cours du Dr. Gall,
published by him in 1S08.
  The foundation of this doctrine is,  that the brain is not a single
organ, but is composed of as many nervous  systems as there are
primary and original faculties of the  mind.   According to Gall,
the brain is a groupe of several organs, each of which is concerned
in the production of a special moral act; and, according as the  brain
of an animal contains a greater or less number of these organs, and
of a greater or less degree of development,  the  animal  has,  in its
moral sphere, a greater or less number, or more or less active,  facul-
ties.
   In like manner, as there are as many sensorial nervous systems
and organs of sense as  there are  external senses,  there are as  many
cerebral nervous systems  as there are special moral faculties  or in-
ternal senses. Each moral faculty has, in the brain, a nervous part,
concerned  in its production, as each sense  has  its special nervous
system;  the sole difference being, that the nervous systems of the
senses are separate and distinct, whilst those of the brain are crowd-
ed together in the small cavity of  the cranium, and appear to form
but one mass.
   The proofs adduced  by Gall  in favour  of his  proposition are the
following:—1st, It has been established as a principle, that the dif-
ferences  in the psychology of man and animals correspond to  varie-
ties  in the structure of the encephalon, and that the latter are de-
pendent  on the former.  Now, the differences of the brain consist
less  in changes of the general form of the organ than in parts which
are present in some and not in others; and if the presence or absence
of such parts is the cause  why  certain animals  have a greater  or
less number of faculties  than others, they ought  certainly  to  be
esteemed the special organs of such faculties.  2dly, The intellec-
tual and moral  faculties are multiple. This every one admits.  Each,
consequently, ought to have its special organ; as the admission of a
plurality of intellectual and  moral faculties must induce that of a
plurality of cerebral organs,  in  the same  manner as each external
sense has its proper nervous system.  3dly,  In different individuals
of the same species,—in different men,—much psychological variety
is observable.  The cause of this is doubtless in the brain; but we
can  hardly ascribe it to a difference in the general shape of the or-
gan, the form of which is sensibly the same.  It is owing rather to
differences in the  separate parts  of the brain.  Are not such parts,
therefore, distinct nervous systems? 4thly, In the same individual—
in the same man—the intellectual and affective faculties have never
the  same degree of activity;  whilst one predominates, another may
be feeble.   Now, this fact, which is inexplicable under the hypo-
thesis, that the brain is a single  organ, is  readily intelligible  under
the  theory of the plurality of organs; whilst the cerebral part,  which
is the agent of the one faculty, is  proportionably more voluminous 
MENTAL  FACULTIES, &C                263
or more active, that which presides over the other is less so. Why,
he asks, may not this happen with the cerebral organs, as with the
other organs of the body—the senses, for example? Cannot one of
these be feeble and the other energetic? 5thly, In the same indivi-
dual, all the faculties do not appear, nor are they all lost at the same
periods.   Each age has its own psychology.  How can we, then,
explain these intellectual and moral varieties, according to'age, un-
der the hypothesis that the brain is a single organ? Under the doc-
trine of the plurality of cerebral organs, the explanation is simple.
Each cerebral system has its special period of development  and
decay. 6thly, It is a common observation, that when we are fatigued
by one kind of mental occupation, we have recourse to another;
yet it often  happens,  that the new labour, instead of adding to the
fatigue experienced by the former, is a relaxation.  This would not
be the case, if the brain were a single organ and acted as such, but
is readily explicable under the doctrine of a plurality of organs. It
is owing to  a fresh cerebral organ having been put in action.  7thly,
Insanity  is frequently confined to one single train of ideas, as in the
variety, called monomania, which is often caused by the constancy
and  tenacity of an original  exclusive idea.  This is frequently re-
moved by exciting another idea opposed to the first, and which dis-
tracts the attention from it.  Is it possible, Gall asks, to compre-
hend these facts under the hypothesis  of the unity of the  brain?
8thly, Idiocy and dementia are often only partial; and it is not easy
to conceive, under the idea of unity of the brain,  how one faculty
remains amidst the abolition of all the others.  9thly, A wound or  a
physical injury of the brain will frequently modify but one faculty,
paralyzing  or augmenting it, and leaving  every  other uninjured.
lOthly, and lastly, Gall invokes the analogy of other nervous parts;
and, as the great  sympathetic, the  medulla oblongata, and medulla
spinalis are, in his view at least, groupes of special nervous systems,
it is probably, he says, the same with the brain.
   Such are the arguments employed by Gall for proving, that the
brain consists of  a plurality  of organs, each of which is concerned
in the production of a special intellectual or moral faculty, and
should they not carry conviction, it must be admitted, that many of
them are ingenious and forcible, and all merit attention.
   It is a prevalent idea, that this notion of a plurality of organs is  a
phantasy, which originated with  Gall.   Nothing  is more erro-
neous; he has adduced the opinions of numerous writers who pre-
ceded him, some of whom have given figures of the cranium, with
the seat of  the different organs and faculties marked  upon  it.  To
this list  we might add  numerous others.  Aristotle, in  whose
works we find  the germ of many discoveries  and speculations,
thought that the  first or anterior ventricle of the brain, was the ven-
tricle  of  common sense; because from  it, according to him, the
nerves of the five senses branched off.  The second ventricle, con- 
264
SENSIBILITY.
 nected by a minute opening with  the  first, he fixed upon as the
 seat of imagination, judgment, and reflection; and the third ven-
 tricle as a store-house into which the conceptions of the mind, di-
 gested in the second ventricle, were transmitted for retention  and
 accumulation; in other words, he  regarded it as  the  seat of  ?ne-
 mory. Bernard Gordon, in a work written  in 1296, gives nearly
 the same account of the brain.   It  contains, he says, three cells or
 ventricles.   In the anterior part of the  first ventricle, lies common
 sense; the function of which is to  take cognizance  of the various
 forms or images, received by the several senses.   In the posterior
 part of the first ventricle, he places phantasia; and in the anterior
 part of the second, imaginativa; in the posterior part of the mid-
 dle ventricle lies estimativa.   It  would be a waste of time  and
 space to adduce the absurd notions, entertained by Gordon on  this
 subject.  He thinks there are three faculties or virtues,—imagina-
 tio, cogitatio, and memoria,—each of  which  has  a special organ
 engaged in its production.
   For many centuries it was believed, that the cerebrum was the
 organ of perception, and the cerebellum that of memory.
   Albert the Great, in the thirteenth  century, sketched a head on
 which he represented the seat of the different intellectual faculties.
 In the forehead and first ventricle he  placed common  sense  and
 imagination; in the second, intelligence  and judgment; and in
 the third, memory and the motive force.
                               The head in the margin is from
          Fig. 47.           an old sketch contained in the Book
                             Rarities, of the University of Cam-
                             bridge.
                               Servetus conceived that the two
                             anterior cerebral cavities  are for the
                             reception of the images of external
                             objects;  the third  is  the  seat of
                             thought; the aqueduct  of Sylvius,
                             the seat of the soul, and  the fourth
                             ventricle that of memory.
                               In 1491, Peter  Montagnana
                             published an  engraving, in which
                             were represented  the  seat of  the
                             sensus communis, a cellula imagi-
                             nativa, cellula estimativa seu cogi-
                             tativa,  a cellula memorativa,  and
                             a cellula rationalis.  A head, by
                             Ludovico Dolci exhibits a similar
                             arrangement.
                                The   celebrated  Dr.   Thomas
                             Willis, in  1681, asserted that  the
corpora  striata are the seat of perception; the medullary part of the
 
MENTAL FACULTIES, &C.
265
 brain that of memory and imagination; the corpus callosum that
 of reflection; and the cerebellum, according to him, furnished the
 vital spirits necessary for the involuntary motions.
   These examples are sufficient to show, that the attempt to assign
 faculties to different parts of the brain, and consequently the belief,
 that the brain consists of a  plurality of  organs, has been long in-
 dulged by anatomists and philosophers.   The views  of Gall are
 resuscitations of  the  old;  but  resembling them,little more  than
 in idea.  Those of the older philosophers were the merest phanta-
 sies, unsupported by the slightest observation;  the  speculations of
 the  modern physiologist have certainly been the result of long and
 careful investigation, and of the deepest meditation. Whilst, there-
 fore, we may justly  discard the former, the latter are worthy of
 rigid and unprejudiced examination.
   Admitting, with Gall, the idea of the plurality of organs in the
 brain,  the inquiry would next be,—how  many special nervous sys-
 tems are there in the human brain, and what are the primary in-
 tellectual and moral  faculties over which they preside? This Gall
 has attempted.  To  attain this double object, he had two courses to
 adopt; either, first of all to indicate anatomically the  nervous  sys-
 tems,  that constitute the brain, and then to trace  the faculties of
 which they are the agents;  or, on the contrary, to first point out
 the primary faculties and afterwards to assign to each  an organ  or
 particular seat in the brain.  The first course  was impracticable.
 The cerebral organs  are not distinct, isolated in the brain; and, if
 they were, simple inspection could not inform us of the faculty  over
 which they preside; any more than the appearance of a nerve of sense
 can exhibit the kind of sensation for which it is destined.  It  was,
 only, therefore, by observing the faculties, that he could arrive at a
 specification of the cerebral organs.   But here, again, a source of
 difficulty arose.   How many primary intellectual and moral facul-
 ties are there in man? and, what are they? The classifications of the
 mental philosophers, differing, as we have seen they do, so intrinsi-
 cally and essentially from each other, could lead him to no conclu-
 sion.  He first, however, followed the notions  on which they ap-
 peared  to be in accordance;  and endeavoured to find particular or-
 gans for the faculties  of memory, judgment, imagination, &c.
 But  his researches in this direction were fruitless.  He, therefore,
 took for his guidance the common notions of mankind; and having
 regard to the favourite occupations  and the different  vocations  of
 individuals,  to those  marked dispositions, which give occasion  to
 the remark, that a man is born a poet, musician, or  mathemati-
 cian, he carefully examined the heads  of such as presented these
predominant qualities, and endeavoured to discover in them  such
parts of the brain as  were more prominent than usual, and which
might be considered as special nervous systems:—the organs of these
faculties. After multitudinous empirical researches on living indivi-
  Voi. I.                     34 
266                      sensibility.
 duals; on a collection of crania, and on casts, made for the purpose,
 attending particularly to the heads ofcsuch as had one of their faculties
 predominant, and who were, as he remarks, geniuses on one point,—
 to the maniac, and monomaniac;—after a careful study, likewise, of
 the heads of animals, comparing especially those that have a parti-'
 cular faculty with such as have it not—in order  to see if there  did
 not exist in the brain of the former, some part that was wanting in
 that of the latter; by this entirely experimental method, he ventured
 to specify, in the brains of animals  and man,  a  certain  number of
 organs;  and, in their psychology, so many faculties, truly primary
 in their  character.
   But in order, that such a mode of investigation be applicable, it
 must be  admitted, 1st. That one of the elements  of the activity of a
 function  is the development of its  organ.  2dly.  That the cerebral
 organs end and are distinct at the surface of the brain. 3dly. That the
 cranium  is moulded to the  brain, and is a faithful  index of its shape;
 for it is, of course, through the skull and the integuments covering it,
 that Gall attempts, in the living subject, to appreciate the state of the
 brain. Within certain limits these positions are true. In the first place,
 we judge of the activity of a function by the size of the organ that
 executes  it: the greater the olfactory nerve, the more acute we find
 the sense of smell. In the second  place, according to the anatomical
 theory of Gall, the  cerebral convolutions  are the final expansion
 of the cerebrum: if we trace back the original fasciculi, which,
 by their expansions, form the  hemispheres of the brain; they are
 observed to  gradually increase in  size in their progress towards
 the circumference of the organ, and to  terminate in  the  convolu-
 tions.  Lastly, to a certain extent, the cranium  is moulded to  the
 brain; and participates in all the changes, which the latter under-
 goes, at different periods of life and  in disease.   For example, dur-
 ing the first days after the formation of the  brain in the foetus,  the
 cranium  is membranous, and  has  exactly the shape of  the viscus.
 On this membrane ossific points  are deposited,  so that, when  the
 membrane has  become bone,  the cranium has still the shape of  the
 brain. In short, nature, having made the skull  to contain the brain,
 has fitted the one to the other; and this so accurately,  that its in-
 ternal surface exhibits sinuosities, corresponding to the vessels, that
 creep on  the surface  of the  brain;  and digitations, corresponding to
 the cerebral convolutions.  The brain, in fact, rigidly regulates  the
 ossification of the cranium; and when, in  the  progress  of life,  the
 brain augments, the  capacity of the cranium is  augmented likewise;
 not by the  effect  of mechanical  pressure, but owing to the two
 parts being catenated in their increase and nutrition.  This remark
applies not only to the skull and brain, regarded as a whole, but to
their separate parts. Certain portions of the brain are not developed
simultaneously  with the rest of the organ; and the same thing hap-
pens to the portions of the skull that invest them.  The forehead, 
                  MENTAL FACULTIES, &C.                  267

for example, begins to be developed after the  age of four months:
but the inferior occipital fossae do not increase in proportion until
the period of puberty.
   When the brain, again, fades and wastes, in advanced life, the
cavity of the cranium contracts; its ossification taking place on a
less and less outline.  In advanced life, however, according to Gall,
the correspondence between the brain  and the inner table  of the
skull is alone maintained: the outer table appearing to be a stranger
to all nutritive movement; and preserving its dimensions.   Lastly,
the cranium partakes of all the variations experienced by the brain
in disease.   If the brain be wanting, as in the acephalous monster,
the cranium is wanting also. If a portion of the brain exist, the cor-
responding portion of the cranium exists.  If the brain be smaller
than natural, as in the idiot, the cranium is so likewise.  If the brain,
on the contrary, be distended by hydrocephalus, the cranium has
a considerable capacity; and this, not owing to a separation  at the
sutures of the bones composing  it, but owing  to ossification taking
place on a larger outline.   If  the brain be much developed  in any
one  part, and not in another, the cranium  is protuberant  in the
former;  restricted in  the latter.  Lastly, in case of mania, the cra-
nium is often affected: seeming, for example, to be unusually thick,
dense, and heavy.
   These reasons, adduced  by Gall, may justify the admission,
that, within certain limits, the skull  is moulded to the brain: and if
we admit this, the method, followed by him, of specifying the or-
gans of the mental faculties, may be  conceived practicable.
   Such is the basis of the system of craniology, proposed by Gall.
It also  bears the  name cranology,  organology, phrenology, and
cranioscopy: though, strictly speaking, it is  by cranioscopy that
we acquire a knowledge of craniology;—the art of prejudging the
intellectual and moral aptitudes of man and animals, from  an exa-
mination of the cranium.  It is, of course, limited in its application.
Gall admits that it is not available in old age; owing to the phy-
siological fact before stated;—that the external table  of the skull  is
no longer modified by the changes that happen to the brain; and
he acknowledges that its employment is always difficult, and liable
to numerous errors. We cannot, in fact, touch the cranium directly,
for it is covered by hair and integument.  The skull is, likewise,
made rough, in particular parts, by  muscular impressions;  which
must not be confounded with what are  termed protuberances; in
other words, with the prominences that are formed by a correspond-
ing development of the brain.   In this respect  craniology presents
more difficulties  in animals, from their heads being more covered
with muscles, and from the inner table of the skull being,  alone,
in a ratio with the brain beneath.   Other errors may be indulged
from  the existence of the frontal  sinuses, of  the superior longitu-
dinal sinus, and from  the possible separation of the hemispheres on
the median  line.   The difficulty is,  of course, extremely great in
appreciating the parts of the brain, that are situated behind the eyes; 
268
SENSIBILITY.
and craniology must be entirely inapplicable to those organs of the
brain that do not terminate at the surface.
  Gall has taken especial pains to remark, that, by craniology, we
can only prejudge the dispositions of men, not their actions; and
that we can appreciate but one of the elements of the activity of the
organs—their size—not what belongs to their intrinsic activity, and
to the impulse or spring they may receive  from  the temperament
or general formation.  Setting out, however, from  the  principle,
that the predominance of a faculty is in a great measure dependent
on the  development of the portion of the brain, which is its organ,
he goes so far as to particularize, in this development, what is owing
to the length of the cerebral fibres, and what to their breadth; re-
ferring the activity of the faculty to  the former circumstance,  and
its intensity  to the latter.
  In applying cranioscopy to animals, he  observes,  that the same
cerebral organ frequently occupies parts of the head, that seem to
be very  different,  on account  of the difference  between 'station
in animals and man, and of the greater or less number of systems
that compose their brain.
  The cerebral organs, enumerated by Gall, with the correspond-
ing faculties, are as follows:—the numbers corresponding with those
of the accompanying  engravings.
1.  Instinct of generation, of
  reproduction; amativeness.
  Instinct of  propagation;
  venereal instinct.
(Crmwaw.)Zeugungstrieb,
  Fortpflanzungstrieb,
  Geschlechtstrieb.
2. Love of progeny ;philo-pro-
  genitiveness.
(G.) Jungenliebe,  Kin-
  derliebe.
3. Attachment, friendship
•i
4.  Instinct of defending self
  and property; love of strife
  ana  combat;  combative-<
  ness; courage.
{G.) Muth, Raufsinn.

5.  Carnivorous instinct;  in-
  clination to murder;  de-
  structiveness; cruelty,
(G.) Wurgsinn.
Seated in the cerebellum. It is ma-
  nifested at the surface of the cra-
  nium  by two  round protuber-
  ances, one on  each  side of the
  nape of the neck.
Indicated at the external occipital
  protuberance.

About the middle of the posterior
  margin of the parietal bone; an-
  terior to the last.

Seated a little above the ears; in front
  of the last, and towards the mas-
  toid angle of the parietal bone.

Greatly developed in all the carni-
  vorous animals; forms a promi-
  nence at the posterior and supe-
  rior part of the squamous sur-
  face of the temporal bone, above
  the mastoid process. 
I'KAXIOI.OGICAL   DIVISION of  GALL.
Tagt 266.
 
 
MENTAL FACULTIES, &C.
269
6.  Cunning;finessefaddress; f Ab(mj ^ meatug auditorius ex.
  secretiveness.             I    ternus  upon the sphenoidal an-
( i^u' •♦ Schlauheit' |    gle of the parietal bones.
  Klugheit.              >
                           ^Anterior to that of cunning,  of
                               which it seems to be a prolonga
i
7.  Desire of property; provi
  dent instinct; cupidity; in
  clination  to  robbery;  ac
  quisitiveness.
(G.) Eigenthumssinn,
  Hang zu stehlen.
8.  Pride; haughtiness;  love
  of authority; elevation.
(G.) Stolz,  Hochmuth,
  Herrschsucht.
9.  Vanity; ambition; love of f shuated gt ^ gide of ^ lagtj near

,J>for&'..  ,,   .,   t, i-    <    ^e posterior internal angle  of
(G.) Eitelkeit,  Ruhm-l
  sucht, Ehrgeiz.
10.  Circumspection;   fore-
  sight.
(G.)Behutsamkeit, Vor-"
  sicht, Vorsichtigkeit.
11.  Memory of things; me-
  mory of facts;  sense of
  things; educability; perfec-
  tibility; docility.
(G.)   Sachgedachtniss,
  Erziehungsfahigkeit.

12.  Sense of locality; sense of
  the relations of space; me-
  mory of places.
{G.) Ortsinn, Raumsinn.

13.  Memory of persons; sense
  of persons.
(G.) Personensinn.
  tion, and above that of mecha-
  nics, with which  it contributes
  to widen the cranium, by the
  projection which they form at
  the side of the frontal bone.
Behind the top of the head,  at the
  extremity of the sagittal suture,
  and on the parietal bones.
the parietal bone.
Corresponds to the parietal protu-
  berances.
Situated at the root of the nose, be-
  tween the  two eyebrows, and a
  little above them.


Answers to the frontal sinuses, and
  is indicated externally by two
  prominences at the inner edge
  of the  eyebrows, near the root
  of the nose, and outside the or-
  gan of memory of things.

At the inner angle of the orbit.
14.  Sense of words; sense of
  names; verbal memory.
(G.) Wortgedachtniss.
                            Situated at the posterior part of the
                              base of the two anterior lobes of
                              the brain, on  the frontal  part of
                              the bottom of the orbit, so as to
                              make the eye prominent.
15. Sense of spoken language; f
  talent of philology; study | Also at the top of the orbit, be-
  of languages.             <\   tween the preceding and  that of
(G.)  S p r a c h f o r s c h u n g s- j   the knowledge of colour.
  sinn.                    I 
270                      SENSIBILITY.
16. Sense of the relations of
  colour; talent of painting.
(G.) Farbensinn.
17. Sejise of the relations of
  tones; musical talent.
(G.)Tonsinn.
18. Sense of the relations of
  numbers; mathematics.

19. Sense of mechanics; sense
  of construction ; talent of
  architecture; industry.
(tr.)Ku nstsinn,Bau sin n.
20. Comparative sagacity.
(67.)  Vergleichender
  Scharfsinn.

21. Metaphysical   penetra-
  tion; depth of mind.
(G.)  Metaphysischer*
  Tie fs i n n.
22. Wit.
(67.) Witz.

23. Poetical talent.
(67.) Dichtergeist.

24. Goodness;   benevolence;
  mildness; compassion; sen-
  sibility; moral sense; con-
  science; bonhomie.
(67.)   Gutmiithigkeit,
  Mitleiden,  Moral is-
  cher  Sinn,  Gewissen.
25. Imitation; mimicry.

26. God and religion;  theo-
  sophy.

27. Firmness; constancy; per-
  severance; obstinacy.
. The middle part of the eyebrows;
   encroaching a little on the fore-
[   head.
 A little above and to one side of
   the last; above  the outer third
   of the orbitar arch.
 On the outside of the organ of the
   sense of the relations of colour,
   and below the last.
 A round protuberance at the lateral
   base of the frontal bone; towards
   the temple, ;ind behind the or-
   gans of music and numbers.
 At the middle and anterior part of
   the frontal bone, above that of
   the memory of things.
 In part, confounded with the pre-
   ceding.  Indicated, at the outer
   side of this last, by two protu-
   berances, which  give to the fore-
   head a  peculiar hemispherical
   shape.
 At the lateral and outer part of the
   last; and  giving greater width
   to the frontal prominences.
 On the outer side of the last; divi-
   ded into two halves by the co-
   ronal suture.


 Indicated by an oblongprominence
   above the organ of comparative
   sagacity; almost at the frontal
   suture.


 At the outer  side of the last.
 At the top of the frontal bone and
   at the superior angles of the pa-
   rietal bones.
 The top of the head; at  the ante-
 *  rior and most elevated part  of
   the parietal bones.
  The first nineteen of these, according  to Gall, are common to
man and animals;  the remaining eight man possesses exclusively.
They are, consequently, the attributes of humanity.
  Spurzheim, a fellow labourer with Gall, who  accompanied
him in his travels, and was associated with him in many of his pub- 
MENTAL FACULTIES, &C.
271
lications, has added some other faculties, so as to  make  the  whole
number thirty-five; but they have not been embraced by Gall in
his most recent publication, whence many of these details are taken.
   On  the  situation of these different cerebral organs, Gall re-
marks,—-1st. That those which are common  to man  and animals
are seated  in parts of the brain that are common  to both:—at the
posterior inferior, and anterior inferior, portions.  On the contrary,
those, that are exclusive  to man, are situated in parts of the brain,
which exist only in him:—in the anterior superior parts, that form
the forehead. 2dly. The  more indispensable a faculty and the more
important  to the animal economy, the nearer is its organ to the me-
dian line and to the base of the brain.  3dly and lastly. The organs
of the faculties, that aid,  or are similar to each other, are generally
situated in  proximity.
   In his exposition of each of these organs, and of the  reasons, that
induce  him to assign it as the seat of a special faculty, he sets out
by demonstrating the necessity of the faculty, which he regards to
be fundamental and primary, and to which he assigns a special ner-
vous system or organ in  the brain.   2dly. He endeavours to show,
that this faculty is really primary.  He considers  it  to be  such,
whenever  psychological  facts show, that it has its exclusive source
in organization; for example, when it is not common to all animals
and sexes;  when, in the individual possessing it, it does not exhibit
itself in a ratio with the other faculties with which he is endowed;
when it has its distinct periods of development and decrease, and
does not, in this respect, coincide with the other faculties; when it
can be exerted  alone,  be  diseased  alone, continue sound alone, or
be transmitted alone from parent  to child, &c.  Lastly, he  points
out the part of the brain, which he considers to  be its organ, founding
his decision on numerous empirical observations  of the brains of
men and animals, which  have possessed, or been devoid of, the fa-
culty and organ in question;  or have had them in unequal degrees
of development.
  It is  impossible for us, in a work of this kind, to exhibit  all the
views of Gall, and the arguments he has adduced in favour of the
existence of his twenty-seven faculties.  The  selection of one—the
instinct of generation,—will be sufficient to  show  how he treats
of the  whole.
  Gall's instinct of generation  is that, which, in  each  animal
species, impels the individuals of different sexes towards each other
for the purpose of effecting the work of reproduction. The necessity
of such an  inclination for the general preservation of animals is
manifest. It is to the preservation of the species what the sensation
of hunger is to  that of the individual.  Again, it is certainly pri-
mary  and  fundamental, for it  is independent  of  all external
influences.   It  does not  make its  appearance until puberty, and
it disappears long before other faculties.   In many animals it re- 
272                      SENSIBILITY.
 turns periodically.   In each animal species and in each individual,
 it has a special and different degree  of energy; although external
 circumstances may be much the  same in all, or at least may not
 present differences, in any manner proportionate to those of the in-
 stinct.  It may be either alone active, amidst the languor of other
 faculties, or it may be alone languishing.  Lastly, it cannot be re-
 ferred to the genital organs, for it has been observed  in children,
 whose organs have not been developed ; it has frequently continued
 to be felt in eunuchs; and has been experienced by females, who,
 owing to original monstrosity, have had neither ovary nor uterus(?)
   The  part of the brain which  is the organ of this instinct, is,
 according to Gall, the cerebellum.   His reasons for this belief are
 the following.  1st. In the series of animals a cerebellum exists only
 in those, that are reproduced by copulation, and which, conse-
 quently, must have the instinct in question.   2dly.  There is a per-
 fect coincidence between the periods at which the cerebellum  be-
 comes developed and the appetite appears.  In infancy, it does not
 exist, and the organ is therefore small.  3dly. In every species  of
 animal and in every individual, there is a ratio between the size of
 the cerebellum and  the energy of the inclination.  In males,  in
 whom it  is generally more imperious, the  cerebellum is always
 larger.  4thly. A ratio exists  between the structure of the cerebel-
 lum and the kind of generation. In oviparous animals,  for instance,
 the cerebellum is smaller at its median part; and it is  only in the
 viviparous that the hemispheres exist.   5thly. A similar ratio ex-
 ists between the cerebellum and the external genital organs. If the
 latter are extirpated at an early age, the development of the  cere-
 bellum is arrested and it continues small for the remainder  of life.
 Neighbouring parts, too, which are attributes of the male sex, as
 the horns of the stag, and the  crest of the cock, are often similarly
 stunted. On the other hand, the cerebellum, in its turn, exerts a close
 influence on the venereal appetite, and modifies the external genital
 organs.  Injuries of the cerebellum  either render the individual impo-
 tent or excite an erotic mania.   In nymphomania, the patient often
 complains of acute pain in the  nape of the neck; and  this part is
 more tumid and hot in animals at the rutting season. Gall asserts,
 that he has noticed in birds, that the cerebellum differs both in size
 and excitation, during the season  of love  from what it is at other
 times;  and he affirms, that if erection is observed  in those who
are hanged, or in  consequence of the application of a blister or a se-
 ton to the nape of the neck, or of  the use of opium, or when threat-
ened with apoplexy, especially when  the  apoplexy is  cerebellous,
or during sleep, the effect is, in all these cases,  owing to congestion
of blood in the brain in general, and in the cerebellum in particular.
From these facts, Gall concludes, that the cerebellum is the organ
of the instinct of reproduction; and he remarks, that as this organ
presides over one of the most  important faculties, it is  situated on 
MENTAL  FACULTIES, &C.
273
the median line; and at the base of the skull.  In this manner he
proceeds, with more or less success, in  his  investigation of other
cerebral organs and faculties.
  But Gall does not restrict himself to the physiological applications
of his system.  He endeavours, likewise, to  explain the differences
that exist between him and other philosophers. He altogether rejects
the primary faculties of instinct, intelligence, will,  liberty, rea-
son, perception, memory, judgment, &c.  of the metaphysician, as
mere generalizations of the mind, or common attributes of the true
primary faculties.   Whilst, in the study of physics, the general and
special qualities of matter  have  been carefully distinguished, and
the latter have been regarded as  alone founding the particular  na-
ture of  bodies; the metaphysician, says Gall, has restricted him-
self to general qualities.  For example, it is asserted  that "to think
is to feel."  Thought is doubtless a phenomenon of sensibility; but
it is a sensitive act of a certain kind.  To  adhere rigidly to this ex-
pression, says Gall, is but to express a generality, which leaves us
in as much ignorance as to  what is thought, as we should be of a
quadruped or  bird, by  saying that it is an animal; and as, to become
acquainted with such animals, their qualities must be specified, so
to understand thought,  the kind  of sensation must be specified that
constitutes it.   Instinct, according to him, is a general expression,
denoting every kind of internal  impulse;  and consequently, there
must be as many instincts as there are fundamental faculties.  In-
telligence is likewise a general expression, designating the faculty
of knowledge; and, as there are many instincts, so are there many
kinds of intelligence.   Philosophers, he thinks, have erroneously
ascribed instinct to animals, and  intelligence to  man.  All animals
have, to a certain extent, intelligence; and in man  many faculties
are instincts.  Neither  is the will a fundamental faculty.  It is only
a judgment, formed amongst several motives, and the result of  the
concourse of actions of several faculties. There are as many desires
as faculties; but there is only one will which is the product of  the
simultaneous action of the  intellectual forces.  So that the will is
frequently in opposition to  the desires.  The same thing applies to
liberty  and reason; the former merges  into what has  been said of
the will, and the latter is only the judgment, formed by the superior
intellectual faculties. In this respect, however, he remarks, it must
not be confounded with intelligence; many  animals are intelligent,
but man alone is rational.
   On the other hand, what are termed,  in the intellect,perception,
memory, judgment, imagination, &c. are attributes common to
all the intellectual faculties, and  cannot  consequently be considered
primary faculties.   Each faculty has its perception, memory, judg-
ment and imagination;  and, therefore, there are as many kinds of
perception, memory, judgment,  and  imagination, as there are  pri-
mary intellectual faculties.   This is so true, he remarks, that we
may have the memory  and the  judgment perfect upon one point,
  Vol.  I.                    35 
274                      SENSIBILITY.
and be totally deficient in them  upon  another.  The memory of
tones, for instance, is not the same as that of language; and he, who
possesses the one, may not have the other. The -imaginations, again,
of the poet, musician, and philosopher, differ essentially from  each
other.   These faculties  are, therefore, according  to  him, nothing
more than different modes of the activity of all the faculties.  Each
faculty perceives the notion to which it has  been  attracted, or has
perception; each preserves and renews the recollection of this no-
tion, or has memory.  All are disposed to act without  being excited
to action from without, when the organs are largely  developed or
have considerable intrinsic activity, which gives rise  to  imagina-
tion; and, lastly, every  faculty exerts its function  with more or less
perfection, whence  results judgment.   Attention, in his view, is
only the active mode of exercise of the fundamental faculties of the
intellect; and, being an attribute of all, cannot be  called a primary
faculty.
   As regards the affective faculties, or what have been called the
passions and affections, Gall, in the first place, asserts, that the
term passion is faulty, when used to indicate a primary faculty. It
ought only to designate the highest degree of activity of any faculty.
Every faculty requires to be put in action, and according to the de-
gree of activity, which it possesses, it is a desire, a taste, an incli-
nation, a want, a passion.  If it be only of the medium energy it
is a taste.  If, on the other hand, it be  extremely active  it is a
passion.  There may, consequently, be as many passions as there
are faculties.   We  speak of a passion for study,  or a passion for
music, as we do of the passion of love, or that of ambition. Gall
objects, also, to  the word affection, which, according to him, ex-
presses only  the modifications, that the primary faculties may pre-
sent,according to the mode in which external and internal influences
affect them.
   Some of these affective modes are common to  all  the faculties,
as those of pleasure and pain.  Every faculty may be the occasion
of one or the other.  Other affections are special to some faculties;
as pretension, which, he says, is an affection of pride; and repent-
ance an affection of the  moral  sense.  Finally, these  affections are
simple or compound:  simple when they only bear  upon  one fa-
culty, as anger, which  is a simple affection of the faculty of self-
defence;—compound, when several  faculties are affected, at the
same time, as shame, which is an affection of the primary faculties
of the moral sense, and of vanity.
   Gall reproaches the moralists, with having multiplied too much
the number of the primary affective  faculties:—in  his view, the
modifications of a single faculty, and the combination of several,
give rise to many sentiments,  that are apparently different.  For
instance, the  primary faculty of vanity begets coquetry, emula-
tion, and  love of glory.   That of self-defence gives  rise to teme-
rity, courage, a quarrelling spirit, and fear.   Contempt is the 
MENTAL  FACULTIES, &C
275
product of a combination of the faculties of pride and of the moral
'sense, &c.
  Lastly, as regard's their psychological differences, Gall divides
all men into five classes.   First.  Those in whom all the faculties
of humanity predominate;  and in whom, consequently, organiza-
tion renders the development of the mind and the practice of virtue
easy.   Secondly.  Those in whom the organs of the animal facul-
ties predominate; and  who, being less  disposed to goodness, will
need the  aid  of education  and legislation.   Thirdly.  Those in
whom  all  the faculties are equally energetic, and who may be
either  excellent individuals, or great criminals, according to the
direction they may take.   Fourthly. Those who, with the rest of
the faculties  nearly equal and mediocre, may have one predomi-
nant.   Fifthly and lastly. Those  who have the faculties alike
mediocre; this is the most  numerous class.   It is rare, however,
he remarks, that the characters and actions of men proceed from a
single  faculty.  Most  commonly, they  are  dependent  upon  the
combination  of several;  and as the possible combinations of so
many faculties are almost innumerable,  the psychological varieties
of mankind  may  be extremely various.  Again, as each of the
many organs of the brain may have, in different men, a particular
degree of development and activity, seeing that each of the facul-
ties, which are their products, has, most commonly, a special shade
in every individual; as these organs can establish between  each
other a considerable number of combinations;  and as men, inde-
pendently of the differences in their cerebral organization, which
gives rise to their dispositions, never  cultivate and  exert  their
faculties in an equal and similar manner; it may be conceived, that
nothing ought to be more variable than the intellectual and moral
characters of men; and we can thus explain, why there are not two
men alike in this respect.
   Such is an imperfect sketch of the physiological doctrine of
Gall, which we may sum  up  in the language of the author, in his
Revue Sommaire, appended to the sixth and  last volume of his
work on the " Functions of the Brain."
   11 I have established, by  a great number of proofs, as well nega-
tive as positive, and by the refutation of the most important objec-
tions, that the brain alone has  the immense advantage of being the
organ of the mind.  Farther researches on the measure  of the de-
gree of intelligence of man  and animals have shown, that the brains
of animals are more simple or complex, as their instincts, desires,
and faculties are more simple or more compound; that the different
regions of the brain are concerned in different categories of func-
tion;  and, finally, that the  brain of  every species of  animal, and,
consequently, that of man, constitutes an aggregation of as many
special organs as there are  essentially different moral qualities and
intellectual faculties in the man or animal.   The  moral and intel-
lectual dispositions are innate.  Their manifestation is dependent 
276
SENSIBILITY.
upon organization.   The brain is the exclusive organ of the mind.
Such are four  incontestable principles, forming the basis  of the
whole physiology of the brain;" and  he adds, "the detailed de-
velopment of the physiology of  the brain  has unveiled the defi-
ciencies of the hypotheses of philosophers regarding the moral and
intellectual powers of man; and has been the means of bringing to
light a philosophy of man, founded on his organization, and, con-
sequently, the only one in harmony with nature."
   It is impossible for us to enter, at length, into the various facts
and hypotheses developed in  the preceding exposition. A few re-
marks are, however, necessary.   The great points of doctrine  in
the system of Gall, are:  First. That the  brain consists of a plu-
rality  of organs, each  engaged  in  a  separate, distinct office, the
production of a special intellectual  or moral faculty.   Secondly.
That each of these organs ends at the periphery of the brain, and
is indicated by more or leas development of the part; and Thirdly.
That by observation of the skull,  we may be enabled to detect the
protuberance, produced by such  cerebral development, and thus
to indicate the seat of the cerebral organs of the different faculties.
   It has been shown, in the preceding history, that the notion of
the plurality of organs has extensively prevailed  in all ages; and
whatever may  be the merits of  the arguments adduced by Gall
on this subject, it is difficult not to conceive, that different primary
faculties  may have their corresponding organs.   Simple inspection
of the  brain, indicates that it  consists of numerous parts, differing
essentially in structure and appearance from each other; and it is
but philosophical to presume, that these are  adapted to equally dif-
ferent  functions, although our acquaintance with the physiology of
the organ may not be sufficiently extensive to enable us to desig-
nate them.  Of the innate character of several of the faculties, de-
scribed by Gall, it  is scarcely  possible for us to admit a  doubt.
Take,  for instance, the instinct  of generation, or  of -motherly
love, philo-progenitiveness, as it has  been termed.   Without the
existence of these instincts, it is manifest that every animal species
would be soon extinct.  It is fair, then, to presume, that these in-
stincts, or innate faculties, have encephalic organs, specially con-
cerned in their production.   Gall places  them  in the posterior
part of the head:  the instinct of generation  in the cerebellum; and
his causes for so doing have been cited: yet striking as his reasoning
on this topic seems to be, it has been contested by many physiolo-
gists; by Broussais, FoviLLE,and Pinel-Grandchamp, Rolando,
Flourens, Desmoulins, and others;  and not  only by argument,
but by that which must ultimately test the validity of the doctrines
of the  phrenologist—direct experiment.  The views of these gen-
tlemen, regarding the influence of  the cerebellum,  will be given
under the head of muscular motion.
   One of the greatest objections  that has been brought against the
system of Gall, is the independence in it of the different faculties 
MENTAL  FACULTIES, &C
277
of each other.   Each is made to form a separate and independent
state; with no federative jurisdiction to produce harmony in their
actions, or to regulate the numerous independent movements and
complicated associations which must inevitably occur in the various
intellectual and moral operations. He appears,  indeed, to have en-
tirely lost sight  of the important doctrine of association, which ap-
plies  not only to the  ideas, but to every other  function of  the
frame; and with which it is so important, for the  pathologist par-
ticularly, to be acquainted.
   The second point of doctrine:—that each of the cerebral organs
ends at the  periphery of the  brain, and is  indicated by more or
less development of the part, is attended  with equal difficulties. It
is admitted, as we have seen, by the most eminent physiologists,
that the exterior part of the brain is probably chiefly concerned in
the mental and moral manifestations.  Almost all believe that  this
function is restricted to the brain proper.  Gall and his followers
include the cerebellum.  Yet we meet with cases that appear to
militate strongly against this  notion. Hernia of the brain is one of
these; in which, owing to a wound of the cranium and dura mater,
a portion of the  cerebral substance will protrude and be removed;
yet the individual will do well;  and to all  appearance retain his
faculties unimpaired.   This  is  explained by the  craniologist, by
presuming, that as the fibres  of  the brain are vertical, their extre-
mities have alone been removed, and a sufficient amount of fibres
has remained for the execution of the function; and he farther en-
trenches himself in the difficulty that exists of observing accurate-
ly, in these cases, whether the faculties are really in their pristine
integrity.  He asserts, that it is frequently extremely difficult to
prove the existence of mental aberration; that  the precise line of
demarcation between reason and unsoundness of mind, is not easily
fixed; and that commonly, in these cases, attention is paid only to
the most general qualities; and  if the patient is seen to take food
and  medicine when offered to him, to reply to questions put to
him, and to have consciousness, it is asserted, that the moral sense
is free, and in a state of integrity.
   It must, however, be admitted, that the explanation of the  cra-
niologists on these  topics is  feeble  and unsatisfactory.   It is, of
course, gratuitously assuming, that observation in  such cases has
been insufficient; and if he finds that the fact in question militates
against the faith he has embraced, he is too apt to deny its authen-
ticity altogether.  With all the  candour that Gall possessed,  this
failing is too perceptible in his writings.
   Again, in many of the cases of severe injury to  the brain  that
are on record, but one hemisphere has been implicated;  and, ac-
cordingly, the impunity of the  intellectual and  moral manifesta-
tions has been ascribed to the cerebrum  being  a double organ; so
that, although one hemisphere may have been  injured, the other,
containing similar organs, may still be capable  of  carrying on the 
278                      SENSIBILITY.
function; as one eye can execute  the function of vision when the
other is diseased or lost.  Many cases, however, are recorded, in
which this mode of explanation would not avail;  and where the
loss appears to have been sustained by both  hemispheres, and in
corresponding parts; yet the faculties have persisted.
  Cases of hydrocephalic patients are, likewise, cited, who have
preserved their faculties entire.  These Gall explains, by affirm-
ing, that the brain  is not dissolved in the fluid of the dropsy;  that
it is only deployed and distended  by the presence of the fluid; and
as the distention takes place very slowly, and the pressure  is mo-
derate, the organ may be so habituated to it as to be able to conti-
nue its functions.
  Lastly, some experiments of Duverney have been adduced as
objections to the view of Gall.  These consisted in removing the
whole of the brains of pigeons; yet no change seemed to be  pro-
duced in their faculties;  but in reply to this, it is asserted,  that
Duverney could only have removed some of the superficial parts
of the organ; as whenever the experiment has been repeated, so as
to implicate the deeper-seated portions, opposite results have been
obtained.
  The truth is, that under any view of the subject, these facts are
equally mysterious. We cannot understand why, in particular cases,
such serious effects should result  from severe injury done  to the
brain: and,inothers,thecomparativeimmunity attendantupon injury
to all appearance equally grave. Pressure, of whatever nature, seems
to be more detrimental than any other variety of mechanical  mis-
chief; and it is not uncommon for us to observe a total privation
of all mental and moral acts, by the sudden effusion of blood,—of
no greater magnitude than that of a pea,—into the substance  of
the brain; whilst a gun-shot wound, that may occasion  the  loss of
several tea-spoonfuls  of brain, or a puncture  of the organ  by a
pointed instrument, may be entirely consistent with perfect  con-
sciousness.
   Thirdly.  The doctrine that, by observation of the skull, we may
be able to detect the protuberance produced by the cerebral organs
of the different faculties, has, as we have seen, laid the foundation
for the whole system of craniology, with all the extensions given
to it by  absurdity  and vain  enthusiasm.   It  has been remarked,
that the size of an organ is but one of the elements of its activity;
and  that, by cranioscopy, we can of course judge of this element
only; and it need scarcely be said, that myriads of observations are
necessary before we can arrive at any accurate specification of the
seats of  the cerebral  faculties, even if we grant, that  separate or-
gans can be detected  by the mode of examination, proposed by the
cranioscopist.  Gall, indeed, asserts  that the whole " physiology
of the brain is founded  on  observations, on  experiments, and on
researches a thousand and a thousand times repeated on  man and
animals;"  yet the topographical division of the skull, which he 
MENTAL FACULTIES, &C.                279
 has proposed, can hardly be regarded  otherwise  than  premature,
 to say the least of it; and the remark of course applies a fortiori
 to that of Spurzheim, who enumerates thirty-five original and in-
 nate faculties.
   It is this mapping of the skull, accompanied with the self-con-
 ceit and quackery of many/of the soi-disant phrenologists or cra-
 niologists, that has excited the ridicule of those who are  opposed
 to the doctrine of innate faculties, and to the investigation of points
 connected with the philosophy of the  human mind in any other
 mode  than that  to  which  they have been  accustomed  and  are
 adapted.   " When Gall," says Dr. Burrows,—in a recent work
 on insanity,—"was in England, he went in company with Dr. H.
 to visit the  studio of the  eminent sculptor, Chantry.   Mr. C.
 being at the moment engaged, they amused themselves in  viewing
 the various  efforts of his skill.   Dr. Gall was requested to say,
 from the organs exhibited in a certain bust, what was  the predo-
 minant propensity or faculty of the individual.   He pronounced
 the original must be a great poet.   His attention was directed to
 a second bust.  He declared the latter to be that of a great mathe-
 matician.   The first  was the  bust of Troughton, the eminent
 mathematician, and the second that of Sir Walter Scott."
   This kind of hasty judgment,  from manifestly inadequate data,
 is the every day practice of the itinerant physiologist, whose ora-
 cular dicta too often draw down ridicule not only upon the empi-
 ric himself, but on a system which is worthy of a better fate.  Ridicule
 is, indeed, the harmless but attractive weapon, which has usually
 been wielded against it; and too often by those, who have been ig-
 norant both of its principles and details.
   It is not above twenty years since one of the  most illustrious
 poets,  that Great Britain has produced, included, in his satire, the
 stability of  the cow-pox, galvanism, and gas, along with that of
 the metallic tractors of Perkins:—

            " The cow-pox, tractors, galvanism and gas,
             In turns appear to make the vulgar stare
             Till the swol'n bubble bursts and all is air:—"

 Yet  how secure  in  its  operation,  how  unrivalled  in  its results,
 has vaccination every where exhibited itself.
  The views of Gall are by no  means established. They require
 numerous and careful experiments,  which it is not easy for every
 one to institute; and this is one of the causes, why the minds of
 individuals will long remain in doubt regarding the merits or de-
 merits of his system.  From the mere metaphysician, who has not
attended to  the organization and functions of the frame, especially
of its encephalic portion, it has ever experienced the greatest hos-
tility;  although his conflicting views regarding the intellectual and
moral faculties was one of the grounds for the division of the
phrenologist. It is now, however, we believe, generally admitted 
280                      SENSIBILITY.
by the liberal and scientific, that if we are to attain a farther know-
ledge of the mental condition of man, it must be by a combination
of sound psychological and physiological observation and deduc-
tion.   It is time, indeed, that such a union should be effected, and
that the undisguised and inveterate hostility which exists between
certain of the professors of these interesting departments of anthro-
pology should be abolished.
  " To fulfil, definitively, the object we had proposed to ourselves
in this  supplement," says  Broussais,  in  the supplement to his
work, De VIrritation et de la Folie,—" we must infer  from all
the facts and reasoning, comprised in  this work,—1st. That the
explanations of psychologists are romances, which teach us nothing
new.  2dly. That they have no means of affording the explanations
they promise.  . 3dly. That they are the dupes of the words they
employ in disserting on incomprehensible things.  4thly.  That
the physiologist alone can speak authoritatively  on the origin of
our ideas and knowledge; and5thly.  That men, who are strangers
to the science of animal organization, should confine themselves to
the study  of the instinctive and  intellectual phenomena, in  their
relations with the different social states of existence."
  This is  neither the language nor the spirit that should prevail
among the promoters of knowledge.
  Lastly.  Physiologists have inquired whether there is not  some
particular portion of the  brain,  which  holds the rest  in subser-
vience; some part in which the mind exclusively  resides;—for
such was probably the  meaning of the researches of the older phy-
siologists into the seat of the soul.   It is certain, that it is  seated
in the encephalon, but  not in the whole of it; for the organ may
be sliced away to a certain extent with impunity. Gall, we have
seen, does not admit any central part in the encephalon, which
holds the other in subordination.   He  thinks, that  each  cerebral
organ, in turn, directs the action of the others, according as it is,
at the time, in a state of greater  excitation.  On  the other hand,
different physiologists admit of a central cerebral part, which they
assert to be the seat of  the moi, or mind.   They differ, however,
regarding the precise situation of its domicile.  At one time the
notion prevailed, that the seat of perception is not in the brain it-
self, but in its investing membranes.  Descartes, again, embraced
the singular hypothesis, that the pineal gland is entitled to this
pre-eminence. This gland is a small projection, seen in Fig. 12, at
the posterior part of the third ventricle, and, consequently, at the
base of  the brain.   Being securely lodged, it was conjectured by
that philosopher, that it must be inservient to some important pur-
pose;  and upon little better grounds  he supposed, that the soul is
resident there.   The conjecture was considered to be confirmed
by the circumstance, that, on examining the brains of certain idiots,
the pineal gland  was found to contain a quantity of sabulous mat-
ter. This  sand was supposed to bean extraneous substance, which, 
MENTAL FACULTIES, &C.
281
owing to accident or disease, was lodged in the gland and impeded
its functions; and the inference was thence drawn, that the part,
in which such functions were impeded, was the seat of the soul.
Nothing, however, is now better established, than that the pineal
gland of the adult always contains such earthy matter.
  Others, again,  as Bontekoe, La Peyronie, and Louis, place
the mind in the corpus callosum; Vieussens  in the centrum
ovale; Digby in  the septum lucidum;  Drelincourt in the cere-
bellum ; Soemmering in the fluid of the ventricles; and the greater
part of physiologists in the point, where the sensations are received
and volition sets  out;  the two functions, which, together, compose
the sensorial power of Dr. Wilson Philip.*
  The discrepancy amongst physiologists sufficiently demonstrates,
that we have no positive knowledge on the subject.

  • Darwin had previously employed this term in a more extended sense, as
including the power  of muscular contraction; but in Dr. Philip's acceptation, it
is restricted to those  physiological changes in which the mind is immediately con-
cerned.
Vol. I.
36 
282
muscular  motion.
                 OF  MUSCULAR MOTION,

    especially  of  locomotility or voluntary motion.

   The  functions, we have hitherto considered, give  occasion to
those, that have now to attract our attention.   The first instruct
us regarding the  bodies that surround us; and the second enable
us to  act upon  them; to execute all the partial motions, that are
necessary for nutrition and reproduction;  to move about from  one
place  to another, &c. &c.  All these are acts of the same character:
they are all varieties of muscular contraction;  so that sensibility
and voluntary motion comprise the whole of the life of relation.
Magendie includes the voice and movements  under the same
head; but there is convenience in  separating them, and in treat-
ing the functions  of locomotility and expression distinctly, as has
been done  by Adelon.

             Anatomy of the Motory Apparatus.

  The organs that are  essentially concerned  in  this function, are
the encephalon, the spinal marrow, the nerves, and the muscles.
The three first  of these have been sufficiently described.  The last,
therefore, will alone engage us.

                       Of the Muscles.

  The muscles constitute the flesh of animals.  They are distin-
guished  by their peculiar structure  and composition; being formed
of the elementary or  primary fibrous tissue, already described.
This tissue has  the power of contracting, and thus of  moving the
parts into which it is inserted; hence the muscles have been termed
the active organs of locomotion, in contradistinction to the bones,
tendons, and ligaments, which are passive.
  The elementary constituent of the whole muscular system is this
primary, fibrous, or muscular tissue, the precise size and intimate
texture of which have been the occasion of innumerable researches;
and as most of  these have been of a microscopic character, they
are highly discrepant.   A few of these speculations will  exhibit
this truth.
  Leeuwenhoek asserts, that  some thousands of the ultimate  fila-
ments are required to form the smallest fibre, that is visible to the
naked eye.   He describes the fibre as serpentine and cylindrical;
and affirms, that the fibres lie parallel to each other, are  of the same
shape in  all animals, but differ greatly in their size.  The size, 
MOTORY APPARATUS.
283
however, bears no proportion to that of the animal to which they
belong.   Muys affirmed, that each apparent fibre  is composed of
three kinds of fibrils, progressively smaller  than each other; and
that those of the medium size, although not larger than the ninth
part of a very delicate hair, are composed of one hundred filaments.
He supposes  the ultimate filament to be always of the same size.
Prochaska says, that the ultimate fibre or filament is discernible,
and that it is  about the -y^th part of the diameter of the red globule
of the blood in thickness; and MM.  Prevost and Dumas,  from*
the result of  their microscopic observations, affirm, that 16,000
fibres may be contained  in a cylindrical nerve, one millimeter, or
0.039 of an inch in diameter.  The intimate  structure has likewise
given rise  to extraordinary contrariety of  sentiment;—some, as
Santorini,Heister,Cowper,Vieussens,Mascagni, Prochaska,
Borelli, John Bernouilli,&c. believing the filaments to behollow;
others as Gottsched, Sir A. Carlisle, Fontana, and Berthier,
to be solid; some believing them to be straight;  others zig-zag,
spiral, or waved; some jointed; others knotted, &c. &c.
   Borelli and J. Bernouilli announced,  that the  fibre consists
of  a series  of hollow vesicles, filled with a kind  of spongy sub-
stance or marrow;—the  shape of these vesicles being, according
to  the  former,  rhomboidal, to the latter spheroidal.   Deidier
conceived it to be a fasciculus,  composed of an artery,  vein,
and lymphatic,  enveloped by a nervous  membrane,  and  held
together by nervous filaments.  Prochaska,  to consist of blood-
vessels  turned spirally around an axis of gelatinous  or  fibrinous
substance, into the interior of which the blood rushed at the time
of contraction.  He says, that the visible fibres are not cylindrical,
as they  had been described by many observers, but of a polyhedral
shape; and that they are generally flattened, or thicker in one di-
rection  than in the other.  They are not all of the  same diameter;
differing in different animals, and in  different parts of the  same
animal: they are smaller, too, in young subjects.   The filaments,
or ultimate fibres, which can only be seen  with the microscope,
have the same shape as the visible fibres; they are, however, al-
ways of the same magnitude.
   Sir Anthony Carlisle, whose  opinions, on many subjects at
least, are not entitled to much weight, describes the  ultimate fibre
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.   The extreme branches
of the blood-vessels and nerves, he says, are seen ramifying on the
surface  of the membrane inclosing the pulp, but could not be traced
into the substance of the fibre.  Mr. Bauer, and  MM.  Prevost
and Dumas,  again, differ essentially from the observers already
mentioned.   Mr. Bauer found, that the  muscular fibre was com-
posed of a series of globules, arranged in straight lines; the size of
the globule being TTVntn Part °^ an incn m  diameter. 
284
muscular  motion.
   The views of Milne Edwards, Dutrochet, Hodgkin, &c. on
 the elementary globules, have been  considered in an early part of
 this work.   The subject is enveloped in no less uncertainty, than
 the whole of that which has just been canvassed.
   The ultimate fibres, or filaments, when united in bundles, form
fasciculi or lacerti; and these, by their aggregation, constitute the
 various muscles.   Each fibre, each lacertus, and each  muscle, is
 surrounded  by a  sheath  of cellular tissue, which  enables it to
 move readily  upon each  other, and preserves  it in situ.  The
 fibres are not, however, the same at the extremities, as they are at
 the middle.  The latter  only consist of the proper  muscular tis-
 sue; the extremities being  formed of cellular tissue. If we examine
 a muscle, we find, that the proper muscular fibres become gradually
fewer, and  at length cease to be perceptible, as they approach the
 tendon at one or other extremity.   In this way, the cellular mem-
 brane, which surrounds every fibre, becomes freed from the mus-
 cular  tissue—its divisions  approximate, and become closely united
and condensed, so as to form the cord or tendon, which, of course,
holds a relation to each fibre of the muscle; and when they all con-
tract,  the whole force  is exerted upon it.  This  arrangement will
 explain the  close  union that  exists between the muscle and its
 tendon, and which has given occasion to the belief, that the latter
is  only the former condensed.   An examination of some of the
physical and vital properties of  the two will show, that they differ
as  essentially as any two of the constituents of the body that could
be selected.
  The tendon consists chiefly of gelatine, and does not exhibit the
slightest irritability; whilst the muscle is  formed essentially of
fibrine, and contracts under the  will, as well as on the application
of certain mechanical and chemical irritants.   The differences, in
 short, that exist between the two, are such as distinguish  the pri-
 mary fibrous and cellular tissues; yet the opinion of their  identity
prevailed in antiquity,  was embraced by  Boerhaave  and his
school, and, as  Dr. Bostock observes, was so generally admitted,
even in the middle of the last century, that Haller and Sabatier
scarcely ventured to give a decided opposition to it.
   Similar remarks are applicable to the notion of Cullen, that mus-
cles are only the moving extremities of nerves. Thefibres of the mus-
cle were supposed by him to be continuous with those of the nerve;
to  be, indeed, the same substance, but changed in  structure, so that
when the nerve is converted  into  muscle,  it loses the power of
communicating feeling, and acquires that of producing motion.
  Every muscle and every fibre of a muscle is probably supplied
with blood-vessels, lymphatics and nerves. These cannot be traced
into the ultimate filament,  but as this must be possessed of life and
be contractile under the will, it  must receive through  the blood-
vessels and  nerves the appropriate agents.  MM.  Dumas and
Prevost,  however, affirm, that the microscope shows, that nei- 
M0T0RY APPARATUS.
285
ther the one nor the other terminates in the muscle.  The vessels
merely traverse the organs; the arteries terminating in correspond-
ing veins;  so  that the nutrition of the muscles is effected merely
by the transudation of the blood through the parietes of the artery;
—a notion, which is liable to weighty objection, inasmuch as blood
is not muscle, but requires a true action of selection or of elabora-
tion to be exerted upon it, before it can  become so.   A similar
distribution they  assign to the nerves.   All the branches, they as-
sert, enter the muscle in a direction perpendicular to that of the
fibres composing  it; and their final ramifications,  instead of ter-
minating  in the  muscular fibres, surround them loopwise and re-
turn to the trunk, that furnished  them, or anastomose with some
neighbouring  trunk.  In their view, each  nervous filament, distri-
buted to the muscles, sets out  from the anterior column of the spi-
nal  marrow, forming part of a nervous trunk, turns round one or
more muscular fibres, and returns along  the same or a neighbouring
trunk to the posterior column  of the marrow.
  The red colour of muscles is usually ascribed to the blood dis-
tributed to them, as it may be removed by repeated washing and*
maceration in  water or alcohol, without the texture of the muscle
being modified.  By some,  it has  been thought, that a quantity
of red blood remains attached to the fibres, and extravasated from
the vessels; by others, it is presumed, with more probability,  per-
haps, to be still  contained  in  the vessels.   Bichat,  however,
conceived, that the colour is dependent  upon some foreign  sub-
stance  combined  with the fibre; and he grounds his opinion upon
the circumstance, that, in the same animal, some of the muscles are
always much redder than others; and yet they do not appear to
have a greater quantity  of blood  sent to them; and  also that, in
different classes of animals, the colour  of the muscles does not ap-
pear to correspond  with the quantity of red blood circulating
through their vessels. The fact, however, that, when muscles have
been long in a state of inaction, they become pale; and that, on the
other hand, the colour  becomes deeper, when they are exercised,
is an additional evidence, that their colour is dependent upon the
blood they receive, which is found to diminish or increase in quan-
tity, according to the degree of inactivity  or exertion.
  The muscles differ, like the primary fibre,  at their extremities
and centre; the former being formed of condensed cellular mem-
brane,  the latter of the  muscular or fibrous tissue.  The centre of
a muscle is usually called its venter or belly, and the cellular tex-
ture at the extremities is variously termed;  the part, from which
it appears to rise, being  called  the head or origin; and that,  into
which  it is inserted, the tail,  termination, or insertion.  These
terms  are  not sufficiently discriminative.  We  shall find,  that
a muscle   is   capable of acting in both  directions,  so that the
head and the  tail—the origin  and insertion—reciprocally change
places.   In ordinary  language, however,  the  extremity at which 
286
MUSCULAR  MOTION.
the albugineous tissue, (if we adopt Chaussier's nomenclature,)
assumes a round form so as to constitute a cord or tendon, is call-
ed the insertion.  When this tissue is expanded into a membrane,
it is termed an aponeurosis; and in  this state it exists at the head
or origin of the  muscle;  so that by tendon and aponeurosis the
muscles are  inserted into the  parts which they are destined to
move, if we except those that are inserted into the skin.
  Muscles are divided into simple and compound.   The simple
are those whose fibres have a similar course and arrangement.  They
may be either flat or ventriform, or radiated or penniform. The
compound arise from different parts; their origins are, consequent-
ly,  by distinct fasciculi, or they may terminate by distinct  inser-
tions.   Fig.  48, which is a representation of the biceps—a  flexor
muscle of the forearm—is one of these.  It has, as its name imports,
two heads running into one belly.  It is, also> an example of the
ventriform muscle.
                          Fig. 48.
  In the pectoralis major, Fig. 49, we have an example of the ra-
diated muscle, or of one in which the fibres converge towards their
tendinous insertion.
                          Fig. 49.
  In the penniform muscle, the fibres run in a parallel direction,
but all are inserted obliquely into the tendon,  like the feathers of
a quill.  Fig. 50 is a representation of a double penniform muscle.
Muscles may, also, be complicated; that is, with one belly,  and
several tendons, having the fibres variously inserted into them, or
having several bellies with the tendons interlaced.

                          Fig. 50.
 
M0T0RY APPARATUS.
287
   They are, again, partitioned into the long,  broad, and short.
The long muscles are situated chiefly on the limbs, and are largely
concerned in locomotion.   The broad generally form the parietes
of cavities; they are not so much enveloped as the long muscles,
by strong fibrous aponeuroses or fasciae, owing to their being ob-
viously less liable to displacement; and the short muscles are situ-
ated in parts, where considerable force is required,  and  but  little
motion; so'that their fibres are very numerous and short.
   The number of muscles of course varies in different animals; and
is in proportion to the extent and variety of motion they  are called
upon to execute.   In man, the number is differently estimated by
anatomists: some  describing several distinct muscles under one
name; and others dividing into many what ought to  belong to one.
According to the arrangement of Chaussier, three hundred  and
sixty-eight  distinct  muscles are admitted: but others reckon as
many as four hundred and fifty.
   When muscles are subjected to analysis, they are  found to con-
sist of fibrine, osmazome, jelly, albumen; phosphates of soda, am-
monia and lime, carbonate of lime, muriate, phosphate, and lactate
of soda;  and, according to Fourcroy  and Vauquelin, sulphur
and potassa are present. The great constituents of the pure muscu-
lar tissue are,—the fibrine, and probably the osmazome;—the gela-
tine, which is met with, being ascribable to the cellular membrane
that envelopes the muscular fibres and lacerti.   The membranous
structures  of young animals contain a  much greater quantity of
jelly than those of the adult; and it is  probably  on this account
that the flesh of the former is more  gelatinous;—not  because the
muscular fibre contains more gelatine.
   Thenard assigns the muscles, on final analysis, the  following
constituents:—Fibrine, albumen, osmazome, fat, substances capa-
ble of passing to the state of gelatine, acid (lactic,) and different
salts.   In  this, and every analogous case, it must be  borne in
mind, that the analysis only affords us evidence of the constituents
of the dead animal matter; and that some of the products may have
even been formed by the new affinities that result from the opera-
tions  of the analyst.  They can afford us but an imperfect judgment
of the constitution of the living substance.
   The muscular structure is liable  to a  singular kind of conver-
sion,  under particular circumstances, to which  it may be well to
advert.  When, about the latter part of the last century,  it was  de-
termined, for purposes of salubrity, to remove the bodies from  the
church yard of Les Innocens at  Paris, which had been  the ceme-
tery for a considerable part of the population of Paris for centuries,
the whole area, occupying about seven thousand square yards, was
found converted  into a mass, consisting  chiefly of animal matter,
and raising the soil several feet above its natural level.  On open-
ing the ground, for removing the prodigious collection of dead bo-
dies, they were found to be strangely altered in their nature and 
288                  muscular  motion.
 appearance.  What had constituted the soft parts of the body was
 converted into  an unctuous matter, of a gray colour, and  of a pe-
 culiar, but not highly offensive, smell. According to their position
 in  the  pits, (for the bodies were deposited in  pits or trenches,
 about thirty feet deep, each capable of holding  from twelve hun-
 dred to fifteen hundred  bodies,) and according  to the length of
 time they had been deposited, this transformation had occurred to
 a greater or less extent. It 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.  In such case, every part, except
 the  bones, the hair, and  the nails,  seemed to  have lost  all its
 properties, and to  be  converted into  this gras des cimeiitres,
 which was found to be a saponaceous compound, consisting of am-
 monia, united to adipocire,—a substance, as its name imports, pos-
 sessing properties intermediate  between  those  of fat and  wax.
 When the adipocire was freed from the ammonia, and obtained in
 a state of purity, it was  found to resemble strongly spermaceti,
 both in physical and chemical qualities.
  It was afterwards found, that the conversion  of muscular flesh
 into adipocire might be caused by other means.  Simple immersion
 in cold  water, especially in a  running stream, was found by Dr.
 Gibbes to produce the conversion more speedily than inhumation.
 It can be caused, too, still  more rapidly by the action  of dilute
 nitric acid.
  The chemical, however, is not the only, interest attached  to this
 substance.   It has been invoked  in a court of justice, for the pur-
 pose of enabling some judgment  to be formed regarding the period
 that a body may have been  immersed in  the water.   It is pro-
 bable that this must differ greatly according  to various circum-
 stances;—the time that has elapsed between the death of the indi-
 vidual, and the period of immersion; the conditions of the fluid as
 to rest or motion, temperature, &c.; and  the temperature  of the
 atmosphere; so that any attempt to fix a  period for such conver-
 sion must be liable to much inconclusiveness.  Yet the opinion of
 a medical practitioner, on this subject, has been the foundation of
 a juridical decision.  At the lent assizes, holden at Warwick,
England, in the year 1805, the  following case  came before the
 court.   A gentleman, who was insolvent, left his home, with the
 intention,—as was presumed from his previous  conduct and con-
 versation,—of destroying himself.  Five weeks and four days after
that period, his body was found  floating down a river.  The face
 was disfigured by putrefaction, and the hair separated  from the
scalp by the slightest pull; but the other parts  of  the body were
firm and white, without any putrefactive appearance. On examin-
ing the body it was found that several parts of it were converted
into adipocire.
  A commission of bankruptcy having been taken out against the
deceased a few days  after he  left home, it became an important 
MOTORY APPARATUS.
289
question, to the interest of his  family, to ascertain whether or
not he was living at that period.   From the changes sustained by
the body, it was presumed that he had drowned himself on the day
he left home; and to corroborate  the presumption, the evidence of
Dr. Gibbes was requested, who,  from his experiments on this sub-
ject, it was thought, was better acquainted with it than  any other
person.  Dr. Gibbes stated  on the trial, that he had procured a
small quantity of this  fatty matter, by immersing the muscular
parts of animals in water for a month, and that it required five or
six weeks to make it in any large quantity.  Upon this evidence,
the jury were  of opinion that the deceased was not alive at the
time the commission was taken out, and  the  bankruptcy  was ac-
cordingly superseded!

                        Of the  Bones.

  The bones are the hardest parts of the animal frame ;  and,  con-
sequently, serve as a base of support and attachment to  the soft
parts. They constitute the frame-work  of.the body and determine
its general shape. The principal functions they fulfil are,—to  form
defensive cavities for the most important organs of the body,—the
encephalon, spinal marrow, &c. and to  act as so many  levers for
transmitting the weight of the body to  the soil,  and for  the differ-
ent locomotive and  partial movements.   To them are attached the
different muscles, concerned in those functions.   In man  and the
higher classes  of animals, the bones are, as  a general  principle,
within the body; his skeleton is, consequently, said to be inter-
nal.   In the Crustacea, the testaceous mollusca, and in  certain in-
sects, however, the  skeleton is external, the whole of the soft  parts
being contained within it.  The  lobster and crab  are familiar in-
stances of this arrangement.
  The stature of the human skeleton is  various, and may be taken,
on the average, perhaps,—in those of European descent,—at about
five feet eight  or nine inches.  We find, however, examples of
considerable variation from this average.   A skeleton of  an  Irish
giant, in the museum of the Royal College of Surgeons of London,
measures eight feet  four inches.   On the other hand,  Bebe, the
dwarf of Stanislaus, king of Poland, was only thirty-three inches
high; and a Polish nobleman, Borwlaski, measured twenty-eight
French inches.  He had a sister, whose height was twenty-one
inches.
  The bones may be divided into the  short, broad or flat, and
long.   The short bones are met with in parts of the body, which
require to be both solid and movable:—in the hands and  feet for
example, and in the spine.   The flat or broad bones form the pa-
rietes of cavities, and they aid materially in the movements and
attitudes by affording an extensive surface for the attachment of
muscles. The long  bones are chieflv intended for locomotion, and
  Vol. T.                    37 
290                  muscular motion.
are met with only in the extremities.   The shape of the body or
shaft, and of the extremities, merits attention.   The shaft or mid-
dle portion is the smallest in diameter, and is usually cylindrical.
The extremities, on the other hand, are expanded; a circumstance,
which not only adds to the solidity of the articulations,  but dimi-
nishes the obliquity of the insertion of the tendons, passing over
them, into the bones.  In their interior is a medullary canal or
cavity, which contains the medulla, marrow, or pith:—a secre-
tion, whose office will be  a theme  for after inquiry.   One  great
advantage of this canal is, that it makes the bone a hollow cylin-
der, and thus diminishes its weight.   On many of the bones, pro-
minences and cavities are  perceptible.  The eminences bear the
generic name of apophyses or processes.  Their great  use is, to
cause  the tendons of muscles to  be  inserted at a much greater angle
into the bones they have to move.   It will be seen hereafter, that
the nearer such insertion is to the perpendicular  to the lever, the
greater will be the effect produced.
  The cavities are of various kinds.  Some are articular; others
for the insertion, reception, or transmission  of parts.  Those
of insertion  and reception afford  space for  the  attachment of
muscles; those of transmission, &c. are frequently incrusted with
cartilage, converted into canals  by  means of a  ligament, and  fur-
nished with a synovial membrane,  which lubricates them, and fa-
cilitates the play of the tendons, for the passage of which they are
destined.
  The mechanical structure of bone is a laminated frame-work, in-
crusted by an earthy substance, and penetrated  by exhalant and
absorbent vessels, arteries, veins, and nerves. Herissant, in 1758,
appears to have been one  of the first  who stated, that bone is es-
sentially composed of two substances:—the one  a  cartilaginous
basis or parenchyma, giving form to the part,—the other a peculiar
earthy matter,deposited in thisbasis,andcommunicatingto it itshard-
ness.  These two constituents can be readily demonstrated; the first,
by digesting the bone in dilute  muriatioacid, which dissolves the
earthy part, without acting on the  animal matter; and the second,
by burning  the bone, until all  the animal matter is consumed,
whilst the earthy part is left untouched.
  If we take a long bone and divide it longitudinally, we find, that
it is composed of three different substances, all of which may, how-
ever,  be regarded as the same osseous tissue, in various  degrees of
condensation.  These are,—the hard or compact substance,  the
spongy or areolar, and the reticulated.   The first is in the most
condensed form; it exists at the exterior of the bone, and constitutes
almost the whole of the shaft.   The second is seen towards the ex-
tremities of the long bone, and  in  almost the whole of the  short
bones. In it, the laminae are less close, and have a cancellated ap-
pearance,—the cellules bearing  the name of cancelli.   The reti-
culated substance is a still looser formation; the laminae being situ- 
motory apparatus.
291
ated at a considerable distance, and the space between filled up
with a series of membranous cells, which lodge the marrow.
  We have seen the advantages of the expanded extremities of long
bones, as regards the insertion of muscles;  but it is obvious, that
if these portions of the bone had consisted of the heavy compact
tissue, the increased weight of the limbs would have destroyed the
advantages, which would otherwise have accrued; whilst, if the
shaft of the bone, exposed, as it is, to  external violence, had con-
sisted  of the spongy tissue only, it would  not have been able to
offer  the necessary  resistance.   It is,  therefore,  formed almost
entirely of the compact tissue; so that a section  of one inch in
height, taken from the body of the bone, will not differ essentially
in weight from an inch taken from the extremity.  Nor does the
cavity, within the bones, diminish their strength as might be at
first sight presumed.  By enlarging the circumference, the con-
trary effect is produced; for we shall see, in  the mechanical proem
to the particular movements, that of two hollow columns, formed
of an equal quantity of matter and of the same height, that, which
has the larger cavity, is actually the stronger.   A very important
use of the cancellated or spongy texture of the bones has been sug-
gested by a distinguished individual of this country, to whom sur-
gical  science, in particular, has  been so  largely indebted.  Dr.
Physick asserts, that it serves to diminish, and, in many cases, to
prevent, concussion of the brain, and of the other viscera, in falls
and blows.   The demonstration, which he gives of this, is simple
and satisfactory.   If we suspend a series  of six  ivory balls by
threads; raise the ball at one extremity, and allow it to fall on the
next to it, we find, that the farthest ball in the series is impelled
to a distance, which corresponds to the momentum  communicated
by the first  ball to the second.   But if we substitute, for the mid-
dle ball of the series, a ball made of the cellular structure of bone,
we find that almost the  whole of the momentum is lost in this os-
seous structure; especially, if it be  previously filled with tallow or
well soaked in water, so as to bring it to a closer approximation to
the natural, living condition.
   Bones consist of earthy salts and animal matter intimately blend-
ed.   The latter is chiefly cartilage,  gelatine, and the peculiar fatty
matter—the marrow. On reducing bones to powder and digesting
them  in water, the fat rises and swims  upon its surface, and  the
gelatine is dissolved.
   According to the  analysis of Berzelius, 100 parts of dry hu-
man  bones consist of animal  matter,  33.3;  phosphate of lime,
51.04; carbonate of lime, 11.30;  fluate of lime, 2; phosphate of
magnesia, 1.16; and soda, muriate  of soda, and water,  1.2. Four-
croy and Vauquelin did not  detect any fluoric acid, but they
found oxides of iron and manganese, silica, and albumen.   Hat-
chett detected, also, a small quantity of sulphate of lime.
   The bones are enveloped by a dense fibrous membrane, tejrmed, 
292                  muscular  motion.
in the abstract, periosteum; but assuming different names accord-
ing to the part it covers.  On the skull, it is called pericraniutt;
and its extensions over  the cartilages of prolongation, are  called
perichondrium.  The chief uses of this expansion are, to support
the vessels in their passage to the bone, and to assist in its forma-
tion;  for we find, that if the periosteum be removed from a bone,
it becomes dead at the  surface  previously covered by the  mem-
brane, and exfoliates.  In the foetus, it adds materially to the strength
of the bone, prior to  the completion of ossification.  In  the long
bones, ossification commences at particular points; one generally
in the shaft,  and others at the different articular and  other pro-
cesses.  These ossified portions are, for some time, separated from
each other by the animal  matter, which, alone, composes the in-
termediate portions of the bone; and, without this fibrous envelope,
they would be too feeble perhaps to resist the strains to which they
are exposed.   The periosteum, moreover, affords a convenient in-
sertion  for the muscles  destined to act upon the bones;  and en-
ables  them to slide more readily when in action; hence friction is
avoided.
  The  cavity  of  long  bones is lined by  a  membrane—called
the medullary membrane or  internal periosteum, which is
supplied, with numerous vessels, adheres to the interior surface
of the bone, and is not only concerned in its nutrition,  but also in
the, secretion of the marrow, and likewise of a kind of oily matter,
which differs from marrow merely in being more fluid, and is con-
tained in the cells, formed by  the spongy substance, and  in the
areolae of the compact substance.   This is called the oil of bones.
  The marrow is considered  to  be lodged  in membranous cells,
formed  by an extension  of the internal periosteum; whilst, accord-
ing to Howship, the oil of bones is probably deposited  in longitu-
dinal  canals,  which pass through the solid substance of the  bone,
and through  which its vessels are transmitted.
  The nature and fancied uses of  the  marrow  and of the  oil of
bones will be considered in another part.
  The bones, periosteum and marrow are, in  the  sound  state,
amongst the  insensible parts of the frame. They are certainly not
sensible to ordinary irritants;  but, when morbid, they exhibit in-
tense sensibility.  This, at least, applies to the bones and perios-
teum; the  sensibility, which has been ascribed to the marrow, in
disease, being probably  owing to that of the prolongations of the
membrane, in which it  is contained.
  The number of the  bones in the body is usually estimated at two
hundred and forty, exclusive of the sesamoid bones,  which  are
always found in pairs at the roots of the thumb and great toe,  be-
tween the tendons of  the flexor muscles and joints, and, occasion-
ally, at the roots of the fingers and small toes.
  The hones are connected with each other by means of articula-
tions or joints, which  differ materially from each other.  To all 
motory apparatus.
293
 the varieties, technical names are appropriated, which form a diffi-
 cult task for the memory of the anatomical student.  Technically,
 every part at which two bones  meet and are connected, is called
 an articulation, whether any degree of motion  is permissible or
 not.   This capability, indeed, is the foundation of the division that
 prevails at the present day, all the articulations being separable
 into two classes:—the immovable or synarthroses; and the mova-
 ble or diarthroses.
   The synarthroses are variously termed, according to their shape.
 When the articular surfaces are dove-tailed into each other, the joint
 is called a  suture.   This is the articulation that  prevails between
 the bones of the skull.  Harmony is when the edges of the bones
 are even, and  merely touch, as  in the bones of the head in quadru-
 peds and birds.   When a pit in one bone  receives the projecting
 extremity of another, we have a case of gomphosis. It is exhibited
 in the union between the teeth and the sockets.  Lastly, schin-
 dylesis, is  when the lamina of  one  bone is received into a groove
 of another; as in  the articulation of the vomer, which separates
 the nasal fossae from each other.
   The movable articulations comprise  two orders:—the am-
 phiarthroses, in which  the two bones are  intimately united by an
 intermediate substance,  of  a soft and flexible character—as in the
 junction of the vertebrae with  each other—and  the  diarthroses,
 properly so called.   The last  admit of three subdivisions—the
 enarthroses or ball and socket joints;—the condyloid, in which,
 owing to the head being oval,  the movements are not as easy in
 all directions as where the head is spherical;  and the ginglymoid
 or ginglymus, in which the motion can occur only  in one direc-
 tion as in a hinge.  The farther subdivision of the joints  belongs
 more to anatomy than physiology.
   The articular surfaces of the  bones never come  into immediate
 contact.  They are tipped with  a  firm, highly elastic substance,
 called cartilage; which, by its smoothness, enables  the bones to
 rub  easily upon each other,  and may have some influence in dead-
 ening shocks, and defending the bones, which they  cover.  The
 arrangement of  the  cartilage varies according to the shape of the
 extremity of the bone.   If it be spherical, the cartilage is thick at
 the centre,  and gradually diminishes towards the  circumference.
 In a cavity the reverse is the case: the cartilage is thin at the cen-
 tre,  and becomes thicker  towards the  circumference; and  if a
 trochlea or pulley, its thickness is nearly every where alike.
   An admirable provision, against displacement of  the bones at
'the articulations, exists in the ligaments. These are, by the French
 anatomists, distinguished into  two  kinds—the fibrous capsules,
 and  the ligaments properly so called.   The  former are a kind of
 cylindrical sac^ formed of a firm, fibrous membrane;  open  at each
 extremity, by which they closely embrace the articular end of the 
294
MUSCULAR  MOTION.
bones; and loose, when the joint admits of much motion.   In this
way, the articulation  is completely inclosed: they generally bear
the name of capsular ligaments.
  The ligaments, properly so called, are bands of the same kind
of tissue, which extend from one bone to another;  by their resist-
ance preserving the bones in situ;  and by their suppleness admit-
ting of the necessary motion.
  The interior of all these articulations is lubricated by a viscid
fluid, called the synovia.  This is secreted by a  peculiar mem-
brane, of a serous nature; and its use is to diminish friction, and,
at the same time, to favour adhesion.  The mode in which it is se-
creted, and its chief properties and uses,  will be the subject of fu-
ture inquiry.
  In certain of the movable articulations, fibro-cartilaginous sub-
stances, frequently called interarticular cartilages, are found be-
tween the  articular surfaces, and not adherent to either of them.
These have been supposed to form a kind  of cushion, which, by
yielding to pressure,  and returning upon themselves, might thus
protect the joints to which they belong; and, accordingly,  it is as-
serted, that they are  met with in the joints that have to sustain
the greatest pressure; but Magendie  properly remarks, that they
do  not exist in the  hip-joint, or in the ankle-joint, which have
constantly to support the strongest pressure. The use which he sug-
gests is more specious;—that they may favour the extent of motion,
and prevent displacement.
  The stability of the joints is  likewise  aided  by the manner in
which the muscles or tendons pass  over them. These are contained
in an aponeurotic sheath, to  prevent their displacement; and thus
the  whole limb becomes well protected, and dislocation infrequent,
even in those  joints, which, as  that of the  shoulder, ought to be
very liable to displacement,  as regards their osseous arrangement.

               Physiology of Muscular Motion.

  By voluntary motion we mean a  contraction of  the muscles
under the influence of volition or the will.  This influence is pro-
pagated along  the nerves to the muscles, which are excited by it
to contraction. The encephalon, spinal marrow, nerves, and mus-
cles, are, therefore, the organs of voluntary contraction.
  Volition is one of  the  functions of the encephalon, and might
have been, with much propriety, included  under the physiology
of the intellectual and moral acts; but as it is so intimately con-
cerned with muscular motion, it was judged advisable to defer its
consideration until the present occasion.
  That volition  is a  product of encephalic action, is proved by
many facts.   If the brain be injured in any manner;—by fracture
of the skull, for example, or by  effusion of blood, producing apo- 
SEAT  OF VOLITION, &C.
295
plectic pressure in some part of it;—or if it be deprived of its func-
tions by the use of a strong dose of any narcotic substance;—or if,
again, it be in a state of rest, as in sleep:—volition is no longer
excited, and voluntary motion is impracticable.   This is the cause
why the erect attitude cannot be maintained during sleep;  and why
the head  falls forward upon the chest, when the somnolency is
to such an extent as to deprive the  extensor muscles of the back
and head of their stimulus to activity.
   That an emanation from  the  encephalon is necessary, is like-
wise proved by the effect of tying, cutting, compressing, or  stupe-
fying the  nerve proceeding to a muscle: it  matters not, that the
will may  act: the muscle does  not receive the excitant, and no
motion  is  produced;  a fact, which proves, that the nerves are the
channels of communication between the  brain and the muscles.
   If, again, we destroy the medulla oblongata and medulla spina-
lis, we abolish  all muscular motion, notwithstanding the brain
may will, and the muscles be in a state of physical  integrity; be-
cause we have destroyed the parts from which the nerves proceed.
In like  manner, by successively  slicing away the medulla spinalis
from its base to the occiput, we paralyze, in succession, every muscle
of the body which receives its nerves from the spinal marrow.
   The experiments of different  physiologists have confirmed the
view, that the encephalon is  the  chief seat of  volition.   When
it has  been  sliced  away to  a  certain  extent,  the  animal has
been  thrown  into a state of stupor; attended  with the loss  of
sensibility; of the power of locomotion;  and especially of sponta-
neous  motion; and  in writing, dancing, speaking, singing, &c.
we have indisputable evidence of its direction by the intellect.
   It is not so clear, that the seat of volition is entirely restricted
to the encephalon. There are, indeed, many actions of the yet liv-
ing trunk, which appear to show, that an obscure volition may be
exerted, even after the brain has been separated  from the rest  of
the body;  and acephalous children have not only moved percep-
tibly when in utero, but at birth.  Without referring to the lower
classes of animals, which, as we have already had occasion  to re-
mark, execute voluntary motions for a long  time after they have
been bisected; every one must have noticed the motions of decapi-
tated fowls, which will continue to run and leap; and, apparently,
to suffer uneasiness in the incised part.
   The feats of the emperor Commodus are elucidative of this mat-
ter. Herodian relates, that he was in the habit of shooting at the
ostrich, as it ran across the circus,  with an arrow having a cutting
edge; and, although the shaft  was true to its destination, and the
head was  severed from the body, the ostrich usually ran several
yards before it  dropped.  Kaauw Boerhaave,.—the  nephew of
the celebrated Hermann,—and himself an eminent medical teacher
at St. Petersburgh, asserts, that  he  saw  a  cock, thus decapitated,
run for  a distance of twenty-three feet afterwards.   Some cases are 
296                  muscular motion.
also recorded, of men walking a few steps after decapitation, strik-
ing their breasts, &c; but they can scarcely be regarded as authentic.
In those countries, where judicial execution consists in decapitation
by the sword, sufficient opportunities must have presented them-
selves  for-testing this  question; but  no zealous Naturforscher
appears to have been present to record them.   Similar opportuni-
ties must have  likewise occurred, under  the  operations of the
guillotine.
  Legallois, in some experiments  which he  instituted, for the
purpose of determining the nervous influence on the heart, &c,
found, that rabbits, which he had decapitated and deprived of their
hinder extremities, but still kept alive by artificial  respiration,
moved their fore paws, whenever he stimulated them by plucking
some of their hairs.
  With regard  to  complete acephali,  or  those foetuses which
are totally devoid of encephalon,—although they may vegetate in
utero, they quickly expire after birth, owing to their being devoid
of the organs of  the animal  functions, and the consequent impos-
sibility of respiration.  Some monsters have, however, been born
without the brain, but with  a part  of the encephalon.   These have
been called, by way of distinction, anencephali, or hemicephali.
Where the medulla oblongata exists, they possess the nervous sys-
tem of the senses, and  are, consequently, able to live  for some
time after birth, and to exert certain muscular movements, such as
sucking, moving the limbs, evacuating the excretions, &c.
  Professor Adelon asserts, that none of these facts ought to shake
the proposition, which he embraces; that in the superior animals, and
consequently in man, the medulla spinalis and the nerves are merely
the conductors of volition, or of the locomotive will; and that, in the
encephalon  alone, volition is produced.  His  arguments on  this
point, however, are not  characterized  by that ingenuousness and
freedom fromsophism, for which his physiological disquisitions are
generally  distinguished.
  "Firstofall,"he observes,"the factof the progression and motions
of men and quadrupeds, after decapitation, is manifestly apocryphal;
and even if we must admit, that certain animals still execute some
movements after decapitation, are such movements evidently regu-
lar and ordained?   And, supposing them to be so, may not this
have arisen from the conformation of the parts, or from habits con-
tracted by the organs?   This last appears to us most probable; for
if, from any cause whatever, the  muscles of a part contract, they
will cause the part to execute such motions, as the joints, entering
into its composition, require; and which will, therefore, be similar
to those that the will produces."  He farther attempts to deny the
facts related of the lower classes of animals, and asserts, that" they\
are not evinced in the experiments instituted in our day."
   The  cases which are adduced to prove the defective sensibility
of the lower tribes of animated nature, are, however, incontestable; 
SEAT  OF VOLITION, &C.
297
—the trunk of the wasp will attempt to sting after the head is re-
moved; and the experiment, which was made by Dr. Harlan, in
the presence of Capt. Basil Hall, certainly demonstrates some-
thing like design in the headless trunk.
   Our conclusion ought probably to be, from all these cases,—that
volition  is chiefly seated in the encephalon, but that an obscure
volition may, perhaps, extend over the whole of the cerebro-spinal
axis.  This conclusion, of course, applies only to the higher classes
of animals; for we have seen, that the polypus is capable of division
into several portions, so as to constitute as many distinct beings;
and it is probable, that  the principal seat of volition may extend
much lower down in the inferior tribes.
   Attempts, and of a successful nature, have been made to discover
whether the whole brain is concerned in volition, or only a part.
Portions of the brain have been disorganized by disease, and yet
the individual has not been deprived of motion; at other times, as
in paralysis, the faculty has been impaired;  and again,considerable
quantities of brain have been lost, owing to accidents, (in one  case
the author knew nineteen tea-spoonfuls,) with equal immunity, as
regards the function in question.
   The experiments, executed on this subject, go still farther to  con*
firm the idea, that volition is  not seated exclusively in  the ence-
phalon.  Rolando and  Flourens performed several, with the
view of detecting the seat of the locomotive will; or of that which
presides over  the general movements of station and progression;
and they fixed  upon the cerebral  lobes.  Animals, from which
these were removed, were thrown into a sleepy, lethargic condition;
were  devoid of sensation and spontaneous motion, and moved only
when provoked.
   On the other hand, Magendie affirms, that the cerebral hemi-
spheres may be cut deeply in different parts of their upper surface,
without any evident alteration  in the movements. Even their total
removal,if itdid notimplicate the corporastriata,he found to produce
no greater effect; or, at least, none but what might be easily referred
to the suffering induced by such  an experiment.   The results,
however, are not alike  in  all  the classes of vertebrated  animals.
Those, detailed, were observed on quadrupeds, and particularly on
dogs, cats, rabbits, Guinea-pigs, hedge-hogs, and squirrels.
   In  birds, the removal  or  destruction of  the hemispheres—the
optic tubercles remaining untouched—was often followed by the
state of stupor and immobility, described by Rolando and Flou-
rens; but in numerous cases,  the birds ran, leaped, and swam, af-
ter the hemispheres had been removed, the sight alone appearing
to be  destroyed.
   In reptiles and fish, the removal of the hemispheres seemed to
exert but little effect upon their motions. Carps swam with agility;
frogs leaped and swam as if uninjured, and  the sight  did not ap-
pear to be affected.
  Vol.  I.                     38 
298
MUSCULAR  MOTION.
  Magendie  properly concludes, from  these  experiments, that
the spontaneity of the movements does not belong exclusively to
the hemispheres; that in certain birds, as the pigeon, the adult
rook, &c. this seems to be the case; but not so in other birds; and
as regards  the mammalia, reptiles, and fish,—at least  in such of
them as were the subjects of his  experiments,—the deduction  is
universally applicable.
  Of the nature of the action of the brain, in producing volition* wc
know nothing.  It is only in the prosecution of direct experiments
upon the organ, that we can have an opportunity of seeing it, during
the execution of the function ; but the process is too minute to ad-
mit of observation.   Our knowledge is confined to the fact,  that
the encephalon does act,  and that  some influence is projected from
it along the muscles, which excites them to action, and accurately
regulates the extent and velocity of muscular contraction. Yet voli-
tion is not the sole excitant of such contraction. If we irritate any
part of the encephalon or spinal marrow, or any of the nerves pro-
ceeding from them, we find, that muscular movements are excited;
but they are not regular, as  when under the  influence.of volition.
The whole class of involuntary motions is of this kind, including
the action of many of the most important organs—the heart, intes-
tines, blood-vessels, &c.  All the involuntary muscles equally re-
quire a stimulus to excite them into action; but, as their name im-
ports, they are removed from the influence of volition, and instead
of receiving their nerves directly from the brain or spinal marrow,—
as the organs of voluntary motion do,—they are supplied from the
organic  nervous system,  or  the system of the great sympathetic.
In certain diseased conditions, we find, indeed, that all the volun-
tary muscles assume involuntary mdtions;but this is owing to the
ordinary volition being interfered with,  and to some direct or in-
direct stimulation, affecting  the parts of  the  cerebro-spinal  axis,
concerned in muscular contraction ;  or, if the effect be  local, to
some stimulation of the nerve proceeding from the axis to the part.
Of this kind of general involuntary contraction of  voluntary mus-
cles, we have a common example in the convulsions of children;
and, of the partial kind, in cramp or spasm.
  The will, then, is the great but not the sole regulator of the sup-
ply  of nervous influence.   This  is confirmed by experiment.   If
a portion of the  spinal marrow be divided, so as to separate it from
all communication with the encephalon, the  muscles cannot be af-
fected by the will;  but they contract on irritating the part of the
spinal marrow, from which  they proceed. It has, hence, been pre-
sumed,  by some physiologists, that volition  is only the exciting
and regulating cause of the  nervous  influence; and that the latter
is the immediate agent in producing contraction ;  and they affirm,
that as,  in the sensations, the impression is made on the nerve, and
perception is effected in  the brain; so, in muscular motion, voli-
tion is the act of the encephalon, and the nervous influx corres-
ponds to the act of impression. 
                SEAT OF THE MOTIVE FORCES.            299

  With regard to the seat of this nervous centre of muscular con-
traction, much discrepancy has arisen amongst recent physiologists.
It manifestly, however, does not occupy the whole encephalon; as
certain parts of it may be irritated, in the living animal, without
exciting convulsions.   Parts, again, may be removed  without pre-
venting the remainder from  exciting muscular contraction when ir-
ritated.  In the experiments  of Flourens, the cerebral lobes were
removed,  yet the animals  were susceptible of motion  when stimu-
lated ; and whenever the medulla oblongata was  irritated, convul-
sions were produced.  Its seat is not, therefore,  in the whole en-
cephalon.
  Rolando, of Turin, refers it to the cerebellum. He asserts that,
on removing the cerebellum of living animals, without implicating
any  of the other parts of  the encephalon, the animals preserved
their sensibility and consciousness, but were deprived  of the power
of motion.  This occurred to a greater extent in proportion to the
severity of  the injury inflicted on the cerebellum.  If the injury
was  slight, the loss of the  power was slight; and conversely. Im-
pressed with the resemblance between the cerebellum of birds and
the galvanic apparatus of the torpedo ; and  taking into considera-
tion the lamellated structure of the cerebellum,  which, according
to him, resembles a voltaic  pile; and the results of his experi-
ments, which showed, that the movements diminished in propor-
tion to the injury done to  the cerebellum, Rolando drew the  in-
ference, that this part of the encephalon is an electro-motive appa-
ratus, for the secretion of a fluid  analogous to the galvanic.   This
fluid is, according to him,  transmitted along the nerves to the mus-
cles and excites them to contraction. The parts of the encephalon,
concerned in volition, would, in  this  view, regulate  the quantity
in which the motive fluid is secreted, and  govern the motions;
whilst the medulla oblongata which, when alone irritated, always
occasions  convulsions, would put the encephalic extremity of the
conducting nerves in direct  or indirect communication with the
locomotive apparatus.
  This ingenious and  simple theory is, however, overthrown  by
the fact, mentioned by Magendie, that he is annually in the habit
of exhibiting, to his class, animals deprived of cerebellum, which
are still capable of executing very regular movements.   For ex-
ample, he has seen the hedge-hog and Guinea-pig, deprived not only
of brain but of cerebellum, rub its nose with the paw, when a bot-
tle of strong acetic acid has been held to it; and he properly  re-
marks, that a single positive fact of this kind is worth all the ne-
gative facts that could be adduced. He farther observes, that there
could be no doubt of the entire  removal of the brain in his expe-
riments.
  These experiments  of  Magendie are equally adverse to the
hypothesis of Flourens, that the cerebellum is the  regulator or
balancer of the movements. 
300                  MUSCULAR MOTION.
   Others, again, have  esteemed the encephalon to be the sole or-
 gan of volition, and have referred the nervous action, which pro-
 duces the "locomotive influx," as it is termed, exclusively to the
 spinal marrow; and, hence, they have termed the spinal marrow
 and the nerves issuing from it, the " nervous systems of locomo-
 tion."  It is manifest, however,  that the encephalon must partici-
 pate with the medulla spinalis in this function; inasmuch as not
 only does direct irritation of several  parts of the former excite
 convulsions, but we see them frequently as a  consequence of dis-
 ease of the encephalon; whilst, as has been remarked, there is some
 reason for believing,  that, in the upper classes of animals, an ob-
 scure volition may be exercised  for a time,  even when the ence-
 phalon is separated from the body.   It need scarcely be said, that
 we  are as ignorant of the character of this locomotive  influx, as we
 are  of that of the nervous phenomena in general.
   The parts of the encephalon  and spinal marrow concerned in
 muscular motion, are very distinct from those that receive the im-
 pressions of external bodies.  The function of sensibility is com-
 prised in the medulla oblongata and in the posterior column of the
 spine, whilst the encephalic organs of muscular motion are the cor-
 pora striata, the thalami nervorum opticorum, at their lower  part;
 the  crura cerebri, the pons varolii, the peduncles of the cerebellum,
 the  lateral parts of the medulla oblongata, and the anterior column
 of the medulla spinalis. This is proved by direct experiment, as
 will be seen presently; but, in addition to this, pathology furnishes
 us with  numerous examples of their distinctness.  In various  cases
 of hemiplegia or palsy of one side of the body,—which is of an en-
 cephalic character,—we find motion almost lost, and yet the sensi-
 bility slightly or not  at all  affected; and, on  the  other  hand, in-
 stances of loss of sensation have been met with, in which the power
 of voluntary motion has continued.  The recent discoveries in the
 system of vertebral nerves exhibit clearly how this may happen;
 and that a considerable space may exist between the  roots of a
 nerve,  one of which shall be destined for sensation, the other for
-motion; yet both  may pass  out enveloped  in one sheath;—the
 same  nervous  cord thus  conveying the two irradiations, if they
 may be  so termed.   According  to Sir Charles Bell's system,
 the  spinal column is divided into three columns; the anterior for
 motion; the posterior for sensibility ; and  the two are  kept  sepa-
 rate and united by the third, the column for respiration.
   The experiments, performed, of late years,—by the French phy-
 siologists especially,—for the purpose of discovering the precise
 parts of the encephalon concerned in  muscular motion, have at-
 tracted great and absorbing interest.   We wish it  could  be  said,
 that the  results have been such as to afford us  determinate notions
 on the subject.
   According to those of Flourens, the cerebral lobes preside over
 volition, and the medulla oblongata over the locomotive influx; to 
SEAT  OF THE  MOTIVE FORCES.
301
the latter organ he assigns, also, sensibility. We have already seen,
that the results of his  experiments have been contested, and with
them, of course, his deductions.   The facts and arguments, which
we have stated, will have shown, too, that the last proposition is
alone correct—which  refers  sensibility to the medulla oblongata;
and even it is not restricted  to  that organ or groupe of organs,
whichever it may be considered.
   MM. Foville and Pinel-Grand-Champ have affirmed, that the
cerebellum is the seat of sensibility. To this conclusion they were
led by the remarks  they had made, in the course of their practice,
that the cases of paralysis of sensibility, which fell under their no-
tice, succeeded more especially to morbid conditions of the ence-
phalon.  In this view  they conceive themselves supported by the
discovery of columns in the spinal marrow, destined for particular
functions;  and, as the  posterior column is found to be the column
of sensibility, and as the cerebellum seems to be formed from this
column, they  think it ought to  be  possessed of the same func-
tions.   Professor Adelon remarks, that Willis professed a simi-
lar notion, and that he considered the cerebral lobes to  be the point
of departure for the movements, and the cerebellum the seat of sen-
sibility. In his first volume, however, he had cited, more correctly,
the views of Willis.—"Willis says positively," he remarks,
" that the corpora striata are  the seat of perception; the medullary
mass of the brain, that of memory and imagination; the corpus
callosum, that of reflection; and the cerebellum, the source of the
motive spirits."  Willis, in truth, regarded the cerebellum as sup-
plying animal spirits to the nerves of involuntary functions, as the
heart, intestinal  canal, &c.
  The opinions of  Foville  and Pinel-Grand-Champ  are sub-
verted by the experiments of Rolando, Flourens, and  Magen-
die, which show, that  sensation continues, notwithstanding serious
injury, and even entire removal of the cerebellum.
  By  other physiologists, the two functions have been  assigned
respectively to the cineritious and medullary parts of the brain;
some asserting, that the seat of sensibility is, more especially,  in
the latter; and the motive force in the former.  According to Tre-
viranus, the more medullary matter an animal has in its brain and
spinal marrow, in proportion to the cineritious, the greater will be
its sensibility. To this, however, M. Desmoulins properly objects,
that in many animals, the spinal marrow is composed exclusively of
medullary matter; and consequently they ought not only to be the
most sensible of all, but to be wholly devoid of the power of motion.
  Others, again, have reversed the matter; assigning sensibility to
the cineritious substance; and motility to the medullary.
  From these conflicting opinions, it  is obviously impossible to
sift any thing categorical; except that we are ignorant of the spe-
cial seat of these functions.  A part of the discrepancy, in the re-
sults of the experiments, must, however, be ascribed to  organic 
302                  MUSCULAR MOTION.
 differences in the animals, which were the subjects of the experi-
 ments.   This was strikingly exemplified in those, instituted by
 Magendie, and which have been described.
   Similar contrariety exists  in the experiments and  hypotheses,
 regarding the particular parts of the encephalon, that are concern-
 ed in determinate movements of the body   The results of many
 of those are, indeed, so strange, that did they not rest on such
 eminent authority, they might be classed  amongst the romantic.
   It has been already remarked, that Rolando considered the ce-
 rebellum to be  an electro-motive apparatus, producing  the whole
 of the galvanic  fluid necessary for the motions. Flourens, on the
 other hand, from similar experiments, independently-performed,
 and without any knowledge of those of Rolando, affirmed it to
 be the  regulator  and  balancer  of the  locomotive movements;
and  he  asserted, that, when removed from  an animal, it could
 neither  maintain  the erect attitude, nor  execute  any  movement
 of locomotion;  nor, although possessing  all  its sensations, could
 it  fly from the  danger  it saw menacing  it.  The same view has
 been  advocated by Bouillaud, who has detailed  eighteen  ex-
 periments, in which he cauterized the cerebellum, and found that,
 in all, the functions of equilibration  and  progression were disor-
 dered.
   The experiments of Magendie, on  this subject, are pregnant
 with important  novelty. We have already referred to those which
 concern the cerebral hemispheres and cerebellum,  as the encepha-
 lic organs of the general  movements, in  the  mode suggested by
 Rolando and  Flourens, and  others.   In addition, he  affirms,
 " that there exist, in the brain, four spontaneous impulses or forces,
 which are situated at the extremity of two lines, cutting each other
at right angles;  the one impelling forwards; the second backwards;
the third from  right to left, causing the body to rotate; and  the
fourth from left to right, occasioning a similar movement of rota-
tion."  The first of these impulses he fixes in the  cerebellum and
medulla oblongata; the second in the corpora striata; and the third
and fourth in each of the peduncles of the cerebellum.
   1. Forward  Impulse.—It has often been observed by those
who have made experiments on  the  cerebellum, that  injuries of
that organ cause the animals to recoil, and manifestly against their
will.  Magendie asserts, that  he has  frequently seen animals,
wounded in the cerebellum, make an  attempt to advance, but be
immediately compelled to run back; and  he says, that  he kept a
duck for eight days, the greater  part of whose cerebellum he had
removed, which did not move forwards during the whole of that
time, except when placed upon water.   Pigeons, into whose cere-
bella he thrust  pins, constantly walked, and flew backwards, for
more  than a month afterwards.   Hence, he concludes,  that there
exists, either  in the cerebellum or medulla oblongata,  a force of
impulsion, which tends to cause animals to go forwards. 
SEAT  OF THE  MOTIVE  FORCES.
303
  Magendie thinks it not improbable but that this force exists in
man;  and he states, that Dr. Laurent, of Versailles, exhibited to
him, and  to  the  Academie Royale de Mtdecine, a young  girl,
who,  in the attacks of a nervous  disease, was obliged to recoil so
rapidly as to be incapable of avoiding bodies or pits behind her;
and was, consequently, exposed to serious  falls and bruises.   This
force, he affirms,  only exists in the mammalia and in birds;—cer-
tain fish and reptiles, on which he experimented, appearing to be
unaffected by the entire loss of the cerebellum.
  2. Backward Impulse.—When the corpora striata are removed,
Magendie found that  the  animal darted  forward with great ra-
pidity; and, if stopped, still maintained the attitude of running.
This was particularly remarked in young rabbits; the animal ap-
pearing to be impelled forward by  an inward  and  irresistible
power; and passing over obstacles without noticing them. These ef-
fects were  not found to take place, unless the white, radiated part
of the corpora striata was cut: if the gray matter was alone divided,
no modification was produced  in the movements.   If only one of
the corpora was removed, it remained master of  its movements,
and directed them in different ways; stopping when it chose; but,
immediately after the abstraction of the other, all regulating power
over  the motions appeared to cease, and it was irresistibly im-
pelled forwards.
  In the disease  of the horse, called,  by the French, immobility,
the animal is often capable of walking, trotting, and galloping for-
wards with rapidity; but he does not back; and frequently it is im-
practicable to arrest his progressive motion.  Magendie asserts,
that he has opened several  horses that died in this  condition; and
that he found, in  all, a collection  of fluid in the lateral  ventricles;
which had produced a morbid change on the surface of the corpora
striata, and must have exerted a degree of compression on them.
   Similar pathological cases appear to occur in man.  Magendie
relates that of a person who became melancholic, and lost all power
over his movements; continually executing the  most irregular and
fantastic antics; and frequently compelled  to walk exclusively for-
wards or backwards until stopped by  some obstacle.  In this case,
however, the patient got well; and accordingly there  was no op-
portunity for investigating the encephalic  cause. M. Itard, also,
describes two cases, in which the  patients were  impelled, in pa-
roxysms, to run  straight forward, without the power of changing
their course, even when a  river or precipice was immediately be-
fore them.
   A  case is related by M.  Piedagnel, in the third volume of the
Journal de Physiologie, which is more to the purpose than  those
just mentioned,  inasmuch  as an opportunity  occurred for post
mortem inquiry. The subject of it was, also, irresistibly impelled
to constant motion.  "At  the time of the greatest stupor," says
M. Piedagnel,  "he suddenly arose, walked about in  an agitated 
304
MUSCULAR MOTION.
manner; made several turns in his chamber, and did not stop until
he was  fatigued.  On another occasion  the  room did not satisfy
him; he went out, and walked as long as his strength would per-
mit. He remained out about two hours, and was brought back on
a litter."  M. Piedagnel adds, " that he seemed impelled by an
insurmountable force" which kept him in motion, until his powers
failed him. On dissection, several tubercles were found in the right
cerebral hemisphere, especially at its anterior part; and at the side
of the corpora striata.  These  had produced considerable morbid
changes in this hemisphere; and had, at the same time, greatly de-
pressed the left.
  From these facts, Magendie infers it to be extremely probable,
that, in  the mammalia and in man,  a force of impulsion always ex-
ists, which tends to impel them backwards, and which is, conse-
quently, the antagonist to the force seated in the cerebellum.
  3. Lateral Impulse.—Again, if the pedundes of the cerebellum
—the crura cerebelli—be divided in a living animal, it immediately
begins to turn round, as if impelled by a considerable force.  The ro-
tation or circumgyration is made in the direction of the divided pe-
duncle;  and, at times, with such rapidity, that the animal makes as
many as sixty revolutions in a minute.  The same kind of effect is
produced by any vertical section of the  cerebellum, which impli-
cates, from before to  behind, the whole substance of the medullary
arch, formed by  that organ above the fourth ventricle, (See Fig.
12,) but the movement is more rapid, the nearer the  section is to
the origin of the peduncles; in other words, to their point of junc-
tion with the pons varolii.
  Magendie affirms, that he has seen this movement continue for
eight days, without  stopping,  and, apparently, without suffering.
When any impediment was placed  in the way,  the motion was ar-
rested ;  and, under such circumstances,  the  animal  frequently re-
mained  with its paws in the air and ate  in this attitude.  What he
conceives to have been one of his most singular experiments was,
the effect of the  division  of the cerebellum into two lateral and
equal halves; when the animal appeared to be alternately impelled
to the right and left, without retaining any fixed position.  If he
made a turn or two on one side, he soon changed his motion and
made as many on the other.
  M. Serres, who is well known  as a writer on the  comparative
anatomy of the brain, and must have unusual opportunities for ob-
servation at the Hospital  La Pitii, to which he is attached—gives
the case of an apoplectic,  who presented, amongst other symptoms,
the singular phenomenon of turning round, like the animals in the
experiments just described; and, on dissection, an apoplectic effu-
sion was found in this part of the encephalon.
  On dividing the pons varolii vertically, from before to  behind,
Magendie found that the same rotatory movement was produced;
when the section was to the left of the median line,  the  rotation 
SEAT  OF THE  MOTIVE FORCES.
305
was to the left, and  vice versa; but he could never  succeed  in
making the section accurately on the median line.
  From these facts he concludes, that there are two forces, which
are equilibrious by passing  across the circle formed by the pons
varolii and cerebellum.  To put this beyond all  question, he cut
one peduncle, when the animal immediately rolled in one direc-
tion; but on cutting the other, or the one on the opposite side, the
movement ceased, and the animal lost the power of keeping itself
erect and of walking.
   From the'results of all his experiments,  Magendie infers that
an animal is a kind of automatic machine, wound up for the per-
formance  of  certain mo-
tions, but incapable of pro-               Fig. 51.
ducing  any  other.  The
marginal figure of the base
of the  brain, will explain
more directly the impulses,
described  by  that physio-
logist. The corpora striata
are situated in each  hemi-
sphere,  but their  united
impulses  may be  repre-
sented  by  the arrow  A ;
the impulse, seated  in the
cerebellum, by the  arrow
B; and those in each  pe-
duncle  of the cerebellum,
p p, by the arrows  C and
D respectively.  When the
impulse backwards is from
any cause destroyed,  the
animal  is given up to  the
forward impulse, or to that represented by the arrow B, and vice
versa.   In like  manner, the destruction of one lateral  impulse
leaves  the other without an antagonist, and the animal moves in
 the direction of the arrow placed over the seat of the impulsion that
remains.   In a state of health, all  these impulsions being nicely
 antagonized,  they are subjected to the influence of volition; but in
 disease they may, as we have seen, be so modified, as to be entirely
withdrawn from its controul.
   The four general  movements are not the only  ones, excited by
particular injuries done to  the nervous system.  Magendie states
that a circular movement,  to the right or left, similar  to that of
horses  in a circus, was caused by the division  of  the  medulla  ob-
longata, to the outer side  of the corpora pyramidalia anteriora.
When  the section was made on the right side, the animal turned,
in this  fashion, to the right; and to the left, if it was made on that
side.
   Vol. I.                    39
 
306
MUSCULAR  MOTION.
  Pathology has, likewise, indicated the brain as the seat of dif-
ferent bodily movements.   Diseases of the encephalon have been
found not only to cause irregular movements or convulsions, but,
also, paralysis of a part of  the body, leaving the rest untouched.
Hence it has been concluded, that every motion of every part has
its fixed point in some portion of the brain.
  The ancients were well aware, that in cases of hemiplegia, the en-
cephalic cause of the affection is found in the opposite hemisphere.
Attempts have accordingly been made to decide upon the precise
part of the encephalon, where the decussation takes place.  Many
have conceived the commissures to be the parts; but the greater num-
ber, perhaps, have referred it to the corpora pyramidalia. These, the
researches of Gall and Spurzheim had pointed out, as decussa-
ting at the anterior surface of the marrow,  and as being apparently
continuous with the radiated fibres of the corpora striata; and  an
opinion has prevailed, that the paralysis is of the same side as the
encephalic affection or of  the opposite, according as the affected
part of the brain is a continuation of fasciculi, which do not decus-
sate—of the corpora olivaria for example—or of the corpora pyra-
midalia,  which do.  Serres, however, affirms, that affections of
the cerebellum,  pons varolii, and the tubercula quadrigemina,
exert their effects upon the opposite side of the body; and he sup-
ports his opinion by pathological  cases  and  direct experiment.
Evidence of the latter kind has been afforded by Magendie, which
completely overthrows the idea that the decussation occurs at the
corpora pyramidalia.   He divided  one pyramid from the fourth
veatricle; yet no sensible effect was produced on the movements;
certainly there was no paralysis, either on the affected side or  on
the opposite one; more than this, he divided both pyramids about
the middle, and no apparent derangement occurred in the motions;—
a slight difficulty in progression being alone observable.
  The section of the posterior pyramids, or  corpora restiformia,
was equally devoid of perceptible influence on the general move-
ments; and to cause paralysis of one-half the body, it was necessary
to divide the half of  the medulla -oblongata,  and then the corres-
ponding side became,—not immovable, for it was affected by irre-
gular movements, and not insensible, for  the  animal moved  its
limbs when they were pinched,—but  incapable of executing the
determinations of the will.
  So far then, as these experiments go, they disprove the idea of
decussation in the medulla oblongata.  Its seat must, consequently,
be looked for elsewhere, and probably in the commissures.
  The result of the examination of morbid cases, again, has  in-
duced  some physiologists to proceed still  farther  in their location
of the  encephalic organs of muscular motion; and  to attempt some
explanation of paraplegia,  or of those cases, in which one-half the
body, under the transverse bisection, is paralysed.  MM. Serres,
FoviLLE,and Pinel-Grand-Champ assert, that the anterior radiated 
SEAT  OF THE  MOTIVE  FORCES.
30T
portion of the corpora striata presides over the movements of the-
lower limbs; and the optic thalamus over those of the upper; and
that, according as the extravasation of blood, in a case of apoplexy,
occurs in one of these parts, or in all, the paralysis is confined to
the lower or to the upper limbs, or extends to the whole body. In
1768, Saucerotte presented a prize memoir  to the Acadimie
Royale de Chirurgie, of Paris, in which a  similar view was ex-
pressed.   He had concluded, from experiments, that affections of
the anterior parts of the  encephalon  paralyzed  the lower limbs,,
whilst those of the posterior parts paralyzed the upper.   M. Cho-
part,—in a prize essay, crowned in 1769, and  contained in the
same volume with the last—the fourth of the Prix de VAcadimie
Royale de Chirurgie—refers to the result of some experiments by
M. Petit, of Namur, which appeared to show, that paralysis of the
opposite half of the body was not induced by injury of the cerebral
hemisphere, unless the corpora striata were cut or removed.
   The experiments of Saucerotte were repeated by M. Foville,
and are detailed  in a memoir, crowned by the Acadimie Royale
de Midecine, of Paris, in 1826. They were attended with like re-
sults.  In cats  and rabbits, he cauterized,  in  some, the  anterior
part of the encephalon; in others, the posterior part; and in every
one of the former, paralysis of the posterior, in  the latter, of the
anterior extremities succeeded.  Having, in one animal, mutilated
the whole of the right hemisphere,  and only the anterior part of
the left, he found, that the animal was paralyzed in the hinder ex-
tremities, and in the paw of the left fore-leg,  but that the paw of
the right remained active.
   Lastly, the motions of the tongue, or of  articulation, are some-
times alone affected in apoplexy.  The seat of this variety of mus-
cular motion has been attempted to be deduced from pathological
facts.  Foville places it in the cornu ammonis and temporal, lobe j
and Bouillaud in the anterior lobe of the brain, in the medullary
substance; the  cineritious being concerned, he conceives, in the
intellectual  part of speech.
   It is sufficiently obvious, from the whole of the preceding detail,
that the mind must still remain in doubt, regarding the  precise part
of the encephalon engaged in the functions of muscular motion.
The experiments of Magendie are, perhaps, more  than any of
the others, entitled to consideration.  They appear to have been
instituted without  any particular bias;  to subserve no particular
theory; and they are supported by pathological facts furnished by
others.   M. Magendie is, withal, an accurate and practised expe-^
rimenter, and one to whom physiology has been largely indebted.
His vivisections have been more numerous, perhaps, than those of
any other  individual.   His investigations, however, on  this, sub-
ject clearly show, that owing to the different structures of animals,
we cannot draw as extensive analogical  deductions from compara-
tive anatomy and physiology as might be anticipated.  The greatest 
308
muscular  motion.
source of discrepancy, indeed, between his experiments and those
of MM. Rolando and Flourens, appear to have arisen in the em-
ployment of different animals.  Where the same animals were the
subject of the vivisections, the results were in accordance.   The
experiments demand careful repetition, accompanied by watchful
and assiduous observation o£ pathological phenomena;  and, until
this is effected, we can, perhaps, scarcely feel justified in deducing,
from all these experiments and investigations, more than the gene-
ral propositions, regarding the influence of the cerebro-spinal axis
on muscular motion, which we have already  enunciated.
  The nerves, it has been shown, are the  agents  for  conducting
the locomotive  influence  to  the muscles.   At one time, it was
universally believed, that  the same nerve conveys both sensation
and volition; but the pathological cases, that not unfrequently oc-
curred, in which either sensation  or voluntary motion was lost,
without the other being necessarily implicated,—and of late years,
the beautiful additions to  our knowledge of the spinal nerves, for
which we are indebted to SirCHARLEsBELL and Magendie,—have
satisfied the  most sceptical, that there are separate nerves for the
two functions, although they may  be enveloped in the  same neu-
rilema, or nervous  sheath;  or, in other words,  may constitute the
same nervous cord.   We have  more than once asserted, that  the
posterior column of the spine, with the nerves proceeding from it,
is chiefly concerned in the function of sensibility, and that the an-
terior column, and the nerves connected with it, are inservient to
muscular motion; whilst a third  column intervenes, which  is the
source of all the respiratory nerves of Sir Charles Bell, and of
the various movements connected with respiration and expression.
It is proper here, again, to observe, that although these two distin-
guished physiologists agree in their assignment of function to  the
anterior and posterior columns of the spinal marrow, Bellingeri
has deduced very different  inferences from the same experiments.
He asserts, that having divided, on  living animals, either the ante-
rior roots of the spinal nerves, and  the anterior column of the me-
dulla spinalis, or the posterior roots of these nerves, and the pos-
terior column of the marrow; he did not occasion, in the former
case, paralysis of motion, and in the latter, that of sensation;  but
only,  in the one, the loss of all the movements of  flexion; and in
the other, of those of extension.   In his view, the brain and  its
prolongations, as the crura cerebri, corpora pyramidalia, the ante-
rior column of the  spinal marrow, and the nerves, connected with
it, preside over  the movements of flexion; and,  on the contrary;
the cerebellum and  its extensions, as the posterior column of the
medulla spinalis, and the  nerves connected  with it, preside over
the movements of extension.
  The prima facie evidence is  against the  accuracy of Bellin-
geri's experiments.  The weight of authority in opposition to him
is, in  the first place, preponderant; and in  the second place, it 
CONTRACTION OF MUSCLES.
309
seems highly improbable that distinct nerves should be employed
for the same kind of muscular action.
  In the ordinary cases  of the action  of a voluntary muscle, the
nervous influence, emanating from some part of the cerebro-spinal
axis, under the guidance of volition, proceeds along the  nerves,
with the rapidity of lightning, and excites the muscle to contrac-
tion.  The muscle, which was before smooth, becomes rugose, the
belly more tumid, the ends approximate, and  the whole organ is
rendered thicker, firmer, and shorter.
  With regard to the precise degree of contraction or shortening,
which a muscle experiences, some difference of sentiment has pre-
vailed.   Bernouilli and Keill estimated it at  one-third of the
length; and Dumas carried it still higher.   It must, of course, be
proportionate to the length  of the fibres,—being greater the longer
the fibres.  It has, also, been a subject of experiment and of specu-
lation, whether  the bulk and the specific gravity of a muscle are
augmented during its contraction.  Borelli  and Sir Anthony
Carlisle affirm, that the size of the muscle is increased.   In the
experiments  of the latter, the arm was immersed  in ajar of water,
with which a barometrical tube was connected; and when the mus-
cles were made to contract  strongly, the level of the water in the
tube was raised.
   Glisson, however, from the same experiment, deduced opposite
conclusions; and Swammerdam and Ermann appear to be of his
opinion; whilst Sir Gilbert Blane, Mr. Mayo, Barzellotti,
and MM. Dumas and Prevost, during the most careful experi-
ments, have  seen no variation in the level of the fluid; and, conse-
quently, do not believe, that the size of a muscle is modified by its
contraction.   Sir Gilbert Blane inclosed a living eel in a glass
vessel, filled with water, and 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 excite strong contraction; during
which he noticed, that  the water in the vessel remained entirely
stationary.  He, likewise, 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 their specific
gravity was  precisely the same.
   The experiment of Barzellotti was the following:—He sus-
pended, in a glass vessel, the posterior half of a frog, filled the jar
with water,  and closed  it with a stopper, traversed by a narrow,
graduated tube. The muscle was then made to contract by means
of galvanism, but in no case was the level of the  liquid in the tube
changed.
   It may, then, be concluded, that the bulk  of a  muscle is not
greater when contracted than when relaxed.
   During the contraction, the muscle  is sometimes so rigid and
elastic as to be capable of vibration, when struck.   The ordinary
firm state is  well exhibited by the masseter, when  the jaws are 
310
MUSCULAR  MOTION.
forcibly closed, and some men possess the power of producing so-
norous vibrations by striking the contracted biceps with a me-
tallic rod.
  It has been a matter of dispute, whether the quantity of blood,
circulating in a muscle, be diminished during its contraction.  At
one time,  it was universally believed, that such diminution existed,
and accounted for the diminished size of the muscle during contrac-
tion.  This last allegation we have already shown to be inaccurate;
and no correct deduction can, consequently, be drawn from it.  Sir
Anthony Carlisle adopted the opinion, that the muscles become
pale  during  contraction; but he offers no  proof of it.    The proba-
bility is, that he implicitly obeyed, in  this respect, the dicta of his
precursors, without observing the incongruity of such a supposi-
tion  with his idea, that the absolute size of the muscle is augment-
ed during contraction.  The truth is, we have not the  slightest evi-
dence, that the colour of a muscle, or the quantity of blood circu-
lating in it,  is at  all  altered during  contraction.  Bichat, who
adopted the opinion, that the blood is forced out during this state,
relie.s chiefly upon the fact, known  to  every one,  that,  in the
operation of blood-letting from the arm,  the flow  of  blood is aug-
mented, by working the muscles; but the additional  quantity, ex-
pelled in this case, is properly ascribed, by Dr. Bostock, to the
compression of the large venous trunks, by the swelling out of the
bellies of the muscles.
  The prevalent belief, amongst physiologists of  the present day,
is, that there is no change of colour in the muscle during contrac-
tion.
  When the extremities of a muscle are made to approximate, the
belly, of course, swells out, and would probably expand to such an
extent, that the fasciculi, of which it is composed, would separate
from each other, were  it not for the  cellular  membrane and apo-
neuroses, with which they and the whole muscle are enveloped.
  The phenomena, attendant upon the relaxation  of a muscle, are
the reverse of those, that accompany its contraction.  The belly
loses its rugose character,  becomes soft, and the swelling subsides,
the ends recede, and the organ is as it was prior to contraction.  It
is obvious, however, that after a part, as the arm, has been bent by
the contraction of appropriate muscles,  simple relaxation would
not be sufficient to restore it to its original  position ; for although
the relaxation of a muscle has  been  regarded, by  Bichat and
others, to  be, in  part  at least,  an active effort, and to consist in
something more than  the  mere cessation of contraction,  the evi-
dence in favour of this view is extremely feeble and unsatisfactory.
The  arrangement  of the  muscular system is,  in this as in  every
other respect, admirable, and affords signal evidence of Omnipotent
agency. The arm, as in the case selected above, has not only mus-
cles  to bend, but also to extend it; and,  accordingly, when  it has
been bent, and it becomes necessary to extend  it,  the flexor mus- 
CONTRACTION OF  MUSCLES.
311
cles are relaxed and rest, whilst the extensors are thrown into ac-
tion.   This disposition of antagonist muscles prevails in almost
every part of the frame, and will require notice presently.
  Muscles are not, however, the sole agents in replacing parts.
Many elastic textures exist, which, when put upon the stretch by
muscular contraction, have a tendency to return to their former con-
dition, as soon as the  extending cause is removed.  Of this, a good
example occurs in the cartilages of prolongation, which unite the
ribs to the sternum. During inspiration, these elastic bodies are ex-
tended ;  and, by returning upon themselves, they become active
agents of expiration;  tending to restore the chest to its unexpand-
ed state.
  The production of  the phenomena of muscular contraction is,
so far as we know, unlike any physical process with  which we are
acquainted. It has, therefore, been considered essentially organic
and vital; and, like other operations  of  the kind, will, probably,
ever elude our researches.  Yet here,  as on every obscure subject,
hypotheses have  been  innumerable; varying  according to the
fashionable systems of the day, or the views of the propounder.
  They who believed that the muscular fibre is hollow, or vesicu-
lar, ascribed its contraction to distention, by the influx of the animal
spirits, or of the blood; and relaxation to the withdrawal of those
fluids.  Such were  the hypotheses  of  Borelli,  Stuart, and
others.   Independently, however, of the 'great  objection to these
views,—that we  have  no positive evidence of the  existence  of
rhomboidal or other vesicles, or of the tubular form of the elemen-
tary fibre,—it is obvious, that the explanation is defective, inasmuch
as we have still to look to the cause which produces this mechani-
cal influence.   Again, how are we  to account  for the surprising
efforts of strength executed by muscles, under this hypothesis?
The mechanical influx of animal or other spirits, granting for a mo-
ment their existence, might develope  a certain degree of force; but
how can we understand them, as in the case of the muscles insert-
ed into the foot, to develope such a degree of force  as to project
the body from the ground?  In all these cases,  a new and occult
force is generated in the brain;  and this, by acting on the muscu-
lar fibre,  is the grand, efficient cause of the contraction.  More-
over, what an inconceivable amount of fluids would  be necessary
to produce the contraction of the various muscles,  that are con-
stantly in action; and what, it has been asked, becomes of these fluids
when relaxation succeeds contraction ? Some have  affirmed, that
they are absorbed by the venous radicles; others, that they run  off
by the tendons; and others, again, that they become neutralized in
the muscle, and communicate to it the greater size it possesses, in
proportion as it is more exercised. These phantasies are too abor-
tive to require comment.
  When the chemical hypotheses were in fashion in medicine, phy- 
312
MUSCULAR MOTION.
siology participated in them largely. At one time it was imagined
that an effervescence was excited in the muscle by the union of two
substances, one of which was of an acid, the other of an alkaline
nature.  Willis, Mayow, Keill, Bellini, &c.  supported opi-
nions of  this kind; some ascribing the effervescence to a union of
the nervous fluid with the arterial  blood; others to a union of the
particles  of the muscular fibre with the nervous fluid; and others,
to the disengagement  of an  elastic gas, primitively contained in
the blood,  and separated from it by the nervous spirits.  It would,
however, be unprofitable, as well  as uninteresting, to repeat the
different  absurdities of this period,—so prolific in physical obscu-
rities.  Medicine has generally kept pace with physics, and where
the latter science has been dark and enigmatical, the former  has
been so likewise.  In physiology this is especially apparent; most
of the  natural philosophers of eminence having applied their  doc-
trines in  physics to the explanation of the different functions of
the human frame.  Newton,  Leibnitz, and Descartes, were all
speculative physiologists.
  The discovery of electricity gave occasion  to its application to
the topic in question;  and it  was imagined, that the fibres of the
muscle might be disposed in  such a manner as to form a kind of
battery, capable of producing contraction  by its explosions;  and
after the  discovery of galvanic electricity, Valli attempted to ex-
plain muscular contraction, by supposing, that the muscles have an
arrangement similar to that of the  galvanic pile.
  Haller endeavoured to resolve the problem by his celebrated
doctrine of irritability, which will engage our attention hereafter.
He conceived, that the muscles possess, what he calls, avis insita;
and that  their contraction is owing to the action of this force, ex-
cited by  a stimulus, which stimulus is the nervous influx directed
by volition.  This, it is manifest, affords us no new light on  this
mysterious process.  It is, in fact,  cutting the gordian knot.   We
should still have to explain the precise mode  of action of this vis
insita.
  The hypothesis of Prochaska is entirely futile. He gratuitously
presumes, as we have seen, that the minute ramifications of the ar-
teries are every where connected with the  ultimate muscular fila-
ments, twining around them, and crossing  them in all directions.
When these vessels are rendered turgid by an influx of blood, by
passing among the filaments,  he conceives they must bend the lat-
ter  into a serpentine shape, and thus diminish  their length,  and
that of the  muscle likewise.
  Sir Gilbert Blane, again, throws out a  conjecture, deduced
from  those experiments,—in  which  he  found  that  the actual
bulk of a muscle is not changed during contraction, but  that it
gains in thickness exactly what it loses in length,—that this may
be owing to the muscle  being composed of  particles of  an  ob- 
CONTRACTION  OF MUSCLES.
313
long shape; and that, when the muscle is contracted, the long dia-
meter of the particle is removed  from a perpendicular to a trans-
verse direction.
  But the same objection applies to this as to other hypotheses on
the subject; that it is entirely gratuitous—resting on no anatomi-
cal  support whatever. There  are two views,  however, which may
be esteemed as the most prevalent  at the present  day; the  one,
which considers muscular contraction to be a kind of combustion,
the latter, that it is produced  by electricity.  The  former, which
was originally propounded by Girtanner, and zealously embraced
by  Beddoes, who  was more celebrated for his enthusiasm than for
the solidity of his  judgment,  has  now but few supporters.  This
hypothesis supposes, that muscular contraction depends upon  the
combustion of the combustible elements of the muscle, hydrogen,
carbon, and azote, by the oxygen  of the arterial blood:—the com-
bustion being produced by the nervous influx, which acts in the
manner of an electric spark:—at least, such is the view adopted by
Richerand, one of the most  fanciful of physiological speculators.
Of course, we have neither direct nor analogical evidence of any
such combustion, which, if it existed at all, ought to be sufficient,
in a short space of time, to entirely consume the organs, that af-
ford the elements.   The idea is as unfounded as numerous others,
that have been entertained, and  is worthy only of particular no-
tice, from its being professed  in one of the few works on physio-
logical science, which we  possess.
  The second hypothesis refers muscular contraction to electricity.
Attention has  been already directed to the electroid or galvanoid
character of the nervous agency;  and we have some striking ex-
amples on record of the analogous effects produced by the physical
and by the vital fluid on the phenomena under consideration.  Gal-
vanism, we shall see hereafter, is one of the great tests of muscular
irritability, and is capable of occasioning contraction, for some time
after the death of the animal,  as well as of maintaining, for a time,
many of the phenomena peculiar  to life.  Hence the reason  why
muscular contraction, which is provoked by this nervous, electroid
fluid, has been regarded as an electrical phenomenon.   Much dis-
crepancy has, however, arisen  amongst the partisans of this opinion,
regarding its modus operandi.   Rolando, we have seen, assimi-
lates the cerebellum to an electro-motive apparatus, which furnishes
the fluid, that excites the muscles  to contraction.  Some  have com-
pared the spinal column to a voltaic pile, and have supposed the
contraction of a muscle to be owing  to  an  electric or galvanic
shock.  The views of MM.  Dumas and Prevost  are the most
recent and novel.   By a microscope, magnifying ten  or twelve
diameters, they first of all examined the manner in which the nerves
are  arranged in a muscle; and found, as has been already observed,
that their ramifications always entered  the muscle  in a direction
perpendicular to its fibres.  They satisfied themselves, that none
  Vol. I.                    40 
314
MUSCULAR MOTION.
 of the nerves really terminate in the muscle ; but that the final ra-
 mifications  embrace the fibres, like a noose, and return to the
 trunk, that furnishes them, or to one in its vicinity; the nerve set-
 ting out from the anterior column  of the spinal marrow, and re-
 turning to  the  posterior.  On farther examining the muscles, at
 the time of their contraction, the parallel fibres, composing them,
 were found, by the microscope, to bend in  a zig-zag  manner, and
 to exhibit a number of regular undulations ; such flexions forming
 angles, which varied according  to  the degree  of  contraction, but
 were never under fifty degrees.  The flexions,  too, always oc-
 curred at the same parts of the fibre, and to them the shortening of
 the muscle was owing, as MM. Dumas and Prevost proved  by
 calculating the angles.
  The angular points were always found to correspond to the parts,
 where thesmall nervous filamentsenter,or are fixed into,themuscles.
 They therefore believed, that these filaments, by their approxima-
 tion, induce contraction of the muscular fibre ; and this approxima-
 tion they have ascribed to a galvanic current running through them;
 which, as the fibres are parallel and very near each  other, they
 have thought, ought to cause them to attract each other, according
 to the law laid down by Ampere, that two currents attract each
 other when they move in the same direction.   The living muscles
 are, consequently, regarded by them as galvanometers, and galva-
 nometers of an  extremely sensible kind, on  account  of the  very
 minute distance and tenuity of the nervous filaments.
  They, moreover, affirm that, by anatomical arrangement, the
 nerve is fixed  in the musde in the very position required for the
 proper performance of its function; and they esteem the fatty mat-
 ter, which envelopes the nervous fibres, and which was discovered
 by Vauquelin,  as a means of insulation, preventing the  electric
 fluid from passing from one of the fibres to the other.
  With regard to the hypotheses, that ascribe muscular contracti-
 lity to the chemical composition of the fibre, or that which  main-
 tains, that the property is dependent upon the mechanical  struc-
 ture of the fibre, they are undeserving of citation, notwithstanding
 the  respectability of the individuals who have written and expe-
 rimented on the subject.   They merely seem to show, that here,
 as in  every  case, a certain chemical and  mechanical constitution
is necessary, in order that the vital operation, peculiar to the part,
may be developed.
  But not only is it necessary, that the muscle  shall possess a
proper physical organization, it must, likewise, be endowed with
one, that is  essentially vital—in  other  words, with irritability.
The cause of the ordinary contraction of muscles is, doubtless, the
 nervous influx, but if we alter the condition of the muscle, by tying
the  vessels that supply it with blood, although the nervous influx
may be properly transmitted  to it, there will be  no  contraction.
We, moreover, find, that after a muscle has acted for some time it 
CONTRACTION  OF MUSCLES.
315
becomes fatigued, notwithstanding volition  may regularly direct
the nervous influence to it; and that it requires repose, before it
is again capable of executing its functions.
  In the upper classes of animals, contractility remains  for some
time after dissolution; in the lower classes,  especially in the am-
phibia, the period during which it is  evinced, on the application
of appropriate stimuli, is much greater.  One of the most interest-
ing of the many experiments that have been made, in this and other
countries, on  the  bodies of criminals recently deceased, for the
purpose of exhibiting the.effects of galvanism  on muscular irrita-
tability, is detailed by Dr. Ure.  The subject was a  murderer,
named Clydesdale, a middle-sized athletic man, about thirty years
of age.   He was suspended from the gallows nearly an hour, and
made no convulsive struggle after he dropped.  He was taken to
the  theatre of  the Glasgow University in about ten minutes after
he was cut down.  His  face had a perfectly  natural  aspect, being
neither livid nor tumefied; and there was no dislocation of the neck.
  In the first experiment, a large incision was made  into the nape
of the  neck, close below the occiput, and the spinal marrow was
brought into view. A considerable incision was made,  at the same
time, into the left hip, through the glutaeus maximus muscle, so as
to expose the sciatic  nerve, and a small cut was made in the heel,
from neither  of which  any blood flowed.   A pointed rod, con-
nected with one end  of a galvanic battery, of two hundred and se-
venty pairs of four inch plates, was now placed in contact with the
spinal marrow, whilst the other rod was applied to the sciatic nerve.
Every muscle of the body was immediately  agitated with convul-
sive movements, resembling a violent shuddering from cold. The
left side was most powerfully  convulsed at  each  renewal  of the
electric contact.  On removing the second rod from the hip to the
heel, the knee being  previously bent, the leg was thrown out with
such violence, as nearly to overturn one of the assistants,  who in
vain attempted to prevent its extension.
  In the next experiment, the  left  phrenic  nerve was exposed at
the outer edge of the sterno-thyroideus muscle.  As this nerve is
distributed to the diaphragm,  and communicates with  the heart
through the pneumo-gastric nerves, it was expected that, by trans-
mitting the galvanic  fluid along it,  the respiratory  process might
be renewed.  Accordingly, a small incision having been made un-
der the cartilage of the seventh rib, the point of one rod was brought
into contact with the great head of the diaphragm, whilst the point
of the other was applied to the phrenic nerve in the neck.  The
diaphragm, which is a main agent in respiration,  was instantly
contracted, but with less force  than was expected.   " Satisfied,"
says Dr. Ure, "from ample experience on  the living body, that
more powerful effects can be produced in  galvanic excitation, by
leaving the extreme communicating rods  in close contact with
the parts to be operated on, while the electric chain  or circuit is 
316
MUSCULAR  MOTION.
 completed, by running the end of the wires along the top of the
 plates in the last trough of either pole, the other wire being steadily
 immersed in the last cell of the opposite pole, I had immediate re-
 course to this method.   The success of it was truly wonderful.
 Full, nay, laborious  breathing, instantly commenced.   The chest
 heaved and fell; the  belly was protruded and again collapsed, with
 the relaxing and retiring diaphragm.  This process was continued
 without interruption, as long as I continued  the electric discharges.
  In the judgment of many  scientific  gentlemen who witnessed
 the scene, this respiratory experiment was perhaps the most striking
 ever made with a philosophical apparatus.  Let it also be remem-
 bered, that for full half  an  hour before  this period, the  body had
 been well nigh drained of its blood, and  the spinal marrow severely
 lacerated. No pulsation could be perceived meanwhile at the heart
 or wrist; but it may be supposed, that, but for the evacuation of the
 blood,—the essential stimulus  of that  organ,—this phenomenon
 might also have occurred."
  In a third experiment, the  supra-orbital  nerve was laid bare in
 the forehead. The one conducting rod being applied to it,  and the
other to the heel, most extraordinary grimaces were  exhibited.
 Every muscle in the face was  simultaneously thrown into fearful
 action. "Rage, horror, despair, anguish, and ghastly smiles, united
their hideous expression in the murderer's face, surpassing far the
wildest representations of a Fuseli or a Kean."  At this period,
several of the spectators were forced to leave the room from terror
 or sickness, and one gentleman fainted.
  The last experiment consisted in transmitting the electric power
 from the spinal marrow to  the ulnar nerve, as  it passes by the in-
 ternal condyle at the elbow, when the fingers moved nimbly, like
 those of a violin performer; and an assistant, who tried to close the
 fist, found the hand to open forcibly in spite of every effort to pre-
 vent it.   When the one rod was applied to  a slight incision in the
 tip of the forefinger, the first being previously clenched, that finger
 was instantly extended; and  from the convulsive agitation of the
arm, he seemed to point to the different spectators, some of whom
thought he had come to  life.
  What important reflections are  suggested by the perusal of this
and similar cases!  The strict  resemblance, that exists between the
galvanic and the nervous fluids, and the absorbing idea, to the phi-
lanthropist,  that galvanism may  be found successful in  resusci-
tating the apparently dead  in  cases where other means would pro-
bably fail!  Unfortunately, however, it can rarely happen, that
the means will be at hand, and  can, consequently, be  available.
It must, however, be borne in mind, that, in the case just narrated,
many of the effects were produced, two hours after respiration had
been finally arrested.
  An experiment, described by  Dr. George Fordyce, signally
exhibits the power of the contractility, which is resident in the 
CONTRACTION  OF MUSCLES.
317
tissue.  He slightly scratched, with a needle, the inside of a heart
removed from the body, when it contracted so strongly as to force
the point of the needle deep into its substance.  This experiment
has been often cited, for the purpose of showing, that the mechani-
cal effect, in such cases,  is infinitely greater than  the  mechanical
cause producing it; and hence, as we have endeavoured already to
show, that all mechanical explanations  must be insufficient to ac-
count for the phenomena of muscular contraction;  and that we are
compelled  to infer, that a new force must be always generated.
   Between twenty and thirty years ago, a cause was  tried before
the court  of exchequer in England, in which a better knowledge
of the properties  of muscle would have led to a different result.
According to the English  law, where a man marries a woman,
seised of an estate of inheritance, and has, by her, issue born alive,
which was capable of inheriting her estate; in  such case he shall,
on the death of his wife, hold the lands for his life, as tenant by
the courtesy of England. It has, consequently, been a point of mo-
ment for the husband to show that the  child was  born alive; and
the law authorities have, with singular  infelicity, attempted to de-
fine what shall be regarded evidences of this condition. According
to Blackstone, " it must be born alive. Some have  had a notion
that it must be  heard to cry, but that  is a mistake.   Crying, in-
deed, is the strongest evidence of its being born alive, but it  is not
the only evidence." According to Coke, " if it be born alive it is
sufficient,  though it be not heard to cry, for peradventure it may
be born dumb.*  It must  be proved that the issue was alive; for
mortuus  exitus  non  est exitus; so  as the crying is but a proof
that the child was born alive, amd  so is motion, stirring, and  the
like."   This  latitudinarian definition has given occasion to most
erroneous decisions, as in the trial alluded to, in which the jury
 agreed that the child was born alive; because, although, when im-
 mersed in a warm bath, immediately after birth,  it did  not " cry
 or move,  or show any symptoms  of life;" yet, according to  the
 testimony of two females,—the nurse  and the cook,—there twice
 appeared a twitching and tremulous motion of the lips; and this
 was  sufficient to make it fall under Lord Coke's definition.
    It is manifest, that, granting such motion  to have actually oc-
 curred, it was of itself totally insufficient to establish the existence
 of vitality.   We have seen, tlftt on the application of stimuli, the
 muscles of a body may be thrown into contraction for  two hours
 after the cessation of respiration.  Instead, therefore, of referring
 the irritability to the existence, at the time, of the vital principle:
 it must be regarded simply as an evidence, that the parts have pre-
 viously and recently formed part of a living system.

   • It need scarcely be said, that the deaf-dumb cry at the moment of birth the
 same as other children. The natural cry is effected by them as well as by the in-
 fant that possesses all its senses.  It is the acquired voice, alone, which they are
 incapable of attaining. 
318                  MUSCULAR MOTION.
  The contraction of a muscle is followed by its relaxation:—the
fibres returning to their former parallel condition.   This appears
to be a passive state; and to result from the suppression of the ner-
vous  influx by the will: in  other words, to be  produced by the
simple cessation of contraction.  Some have, however, regarded
both states to be active,  but without any proof.   Barthez  main-
tains, that the relaxation of  the muscle is produced by a nervous
action the reverse of that which occasions its contraction: the will
relaxing the muscles as  well as contracting them.   The  muscle is
the  only part susceptible of contraction.  The tendon conveys the
force, developed by impassively to the lever which has to be moved.
  Lastly, a sensation instructs the mind that a muscle has contract-
ed, and this has given rise to the notion of a muscular sense, and a
sensation of motion;—the Muskelsinn orBewegungssinn
of Gruithuisen,  Lenhossek, and other German writers.   It ap-
pears to be an internal sensation, produced by the muscle pressing
on the sensible parts surrounding  it; which parts convey the sen-
sation to the brain.
  The force or intensity of muscular contraction is dependent
upon two causes:—the physical condition of the  muscle, and the
energy of the brain.  A muscle, which is composed of large, firm
fibres,.will contract,—the energy of the brain being equal,—more
forcibly than one with   delicate, loose fibres.   Volition  generally
determines the degree of power developed by the voluntary mo-
tions; and is accurately regulated so as to raise a weight of one pound
or of one hundred.  Again, we notice the astonishing  efforts  of
strength of those that are labouring, at the time,  under strong ce-
rebral excitement; under mania, rage, delirium, &c. In such cases,
the  delicate muscles of  the female are capable of  contracting with
a force far transcending  that of the male.  The power  of muscular
contraction is, therefore, in a compound ratio with the strength of
the  organization of the muscle, and the degree of excitation of the
brain.  Where both are considerable, the feats of strength surpass
belief; and where both are small, the results are insignificant.
  The extensors of the  knee and foot occasionally contract with so
much violence, as to fracture the patella and the  tendo-achilles re-
spectively.  The force, developed in the calf of the leg, must  be
great, when a person stands on tiptoe with a burden  on his head
or shoulders; or when he projects his body from the soil, as in leap-
ing.  Rudolphi asserts, that he has seen a horse which  fractured
its under-jaw by biting  a piece of iron.
  We have  a number  of cases  of the  exhibition of surprising
strength on record: of these, that of Thomas Popham, referred to
by Dr. Desaguliers, is one of the most authentic and extraordi-
nary.  Dr. Desaguliers saw him,  by the strength of his fingers,
roll up a very strong and large pewter dish.  He broke seven  or
eight short and strong pieces of tobacco pipe with the force of his
middle finger, having laid them on his first and third finger.  Hav- 
force of muscular  CONTRACTION.          319
 ing thrust under his garter the bowl of a strong tobacco pipe, his
 legs being bent, he broke it to pieces by the tendons of his hams
 without altering the flexure of his knee.   He broke another such
 bowl between his first and  second  finger, by pressing his fingers
 together sideways.  He lifted a table six  feet  long,—which had
 half a hundred weight hanging at the end of it,—with his teeth,
 and held  it in a  horizontal  position for a considerable time, the
 feet of the table resting against his knees.  He took an  iron kitchen
 poker, about a yard long and  three  inches in circumference;  and,
 holding it in his right hand, he struck upon his  bare left arm, be-
 tween the elbow and wrist, till he bent the poker nearly to a right
 angle.  He took such another poker, and,  holding the ends of it in
 his  hands, and the middle against the back of his neck, he brought
 both ends of it together before him; and afterwards pulled it nearly
 straight again.  He broke a rope, about two inches in circumfer-
 ence, which was in part wound about a  cylinder of four inches in
 diameter, having fastened the other  end of it to straps that went
 over his shoulders.  Lastly,  he lifted a rolling-stone, eight hun-
 dred pounds in weight, with his hands only, standing in a frame
 above  it, and taking hold of a  chain that was fastened to it.
   That much  depends upon physical organization, as regards the
 force of muscular  contraction, is evinced  by the fact of the great
 difference in this respect in the various races of mankind.  On our
 own continent, numerous opportunities have occurred for witnes-
 sing the inferiority, in strength, of the aborigines to  the white
 settlers.
   Peron took with him, in his voyage round  the world, one  of
 Regnier's dynamometers, which indicates the relative force of men
 and  animals.  He directed his attention to the strength of the arms
 and  of the loins, making trial  with several individuals of different
 nations; viz. twelve natives of Van Diemen's land, seventeen  of
 New Holland, fifty-six of the island of Timor, seventeen French-
 men, belonging to the expedition, and fourteen Englishmen in the
 colony of New South Wales.   The following was the mean result.

                                             STRENGTH
                                    ,-------------K.--------^
                                    Of the arms,     Or the loins,
                                   kilogrammes.*    myriagrammes.
 1. Van Diemen's land,  -     -    -    50.6
 2. New Holland,       -     -    -    50.8     -    -    10.2
 3. Timor,.....58.7     -    -    11.6
 4. French,.....69.2     -    -    15.2
 5. English,.....71.4     -    -    16.3

   The highest numbers, in  the first and  second divisions, were
respectively 60 and 62;  the lowest, in the fifth, 63; and the highest

  • The approximate value of a kilogramme is about two pounds avoirdupois;—
of a myriagramme about twenty. 
320                  muscular motion.
83, for the strength of the arms.  In the power of the loins, the
highest  amongst  the New Hollanders was 13;  the lowest of the
English 12.7.
  The force of muscular contraction is, also, largely increased by
the proper exercise of the muscles.  Hence the utility of the an-
cient gymnasia.  In early times,  muscular energy  commanded
respect and admiration.   It was regarded as the safeguard of fami-
lies, and the protection of nations: and it was esteemed a matter of
national policy to  encourage its acquisition.  In modern times, the
invention  of gunpowder having altered the system of warfare, and
given to agility the superiority which strength communicated in
personal combats, institutions for the development of the muscular
system have  been abandoned, until of comparatively late years.
They afford us striking examples of the value of muscular exertion,
not only in giving energy and pliancy to  the frame, but as a means
of preserving health.
  The mean effect of the labour of an active man, working to the
greatest possible advantage, and without impediment, is generally
estimated  to be sufficient to raise ten pounds, ten feet in a second,
for ten hours in a day;  or to raise one hundred pounds, which is
the weight of  twelve wine gallons of water, one foot in a second,
or thirty-six thousand feet in a day; or three millions, six hundred
thousand pounds, or four hundred and thirty-two thousand gallons,
one foot in a day. Dr. Desaguliers affirms, that the weakest men,
who are in health, and  not  too  fat, lift about  one hundred  and
twenty-five pounds: and the strongest of ordinary men four  hun-
dred pounds.   Topham, it has been seen, lifted eight hundred.
  The daily work of a horse is estimated as equal to that of five or
six men.
  In the duration of muscular contraction, we  notice considerable
difference  between that of the voluntary and  of the  involuntary
muscles;  the latter being much more rapid and alternating.   The
same  remark applies to the voluntary muscles, when excited by
some other stimulus than that of the will.
  Contraction, excited  by volition, can  be maintained for a con-
siderable time: of this we have examples in bearing a burden, the
act of standing, holding  the arm extended from the body, &c. In
all these cases, the contractility of the muscles is sooner or  later
exhausted, fatigue is experienced, and it becomes necessary to give
them rest; the power of contractility, however, is soon resumed, and
they can be again  put in action.   This law of intermission in  mus-
cular action, appears absolute;—relaxation being followed by con-
traction, in every organ, from the first  infusion of vitality  until
its final  cessation.   The intermission  has, indeed, by many  phy-
siologists,  been held to prevail—to a slight extent only, it is true—
during, what we are in the habit of considering, continuous,  mus-
cular contraction.  In proof of this, they cite  the fact, that when
we put the tip of the finger into the meatus auditorius externus, 
VELOCITY OF MUSCULAR CONTRACTION.         321
 we  hear  a kind of buzzing or huhiming, which does not occur
 when an  inert body is introduced.
   There  are, however, other actions going on  in the finger, be-
 sides this of muscular contraction; and it might, with as much pro-
 priety, be referred to the noise made by the progression  of fluids
 in the vessels, as  to  the oscillations of muscular contraction and
 relaxation.   We know not, in truth, whence  the  sound imme-
 diately proceeds.
   In the velocity  of muscular contraction, much difference also
 exists according to the stimulus, which sets it in action.  If we
 apply galvanism  to a muscle, we find the contractions at  first ex-
 ceedingly rapid; but they become progressively feebler, and require
 a stronger stimulus, until their irritability appears to  be exhausted.
 Irritating the nerve,  in these cases, is found to produce a greater
 effect, than when the stimulus is applied directly to the  muscle.
 The velocity of voluntary contraction is, of course, variable, being
 regulated  entirely by  the will.  We have, in various  classes of the
 animal kingdom, remarkable instances of this velocity.  The mo-
 tions of the racer, of the grayhound, of a practised runner, of the
 fingers, in playing upon musical instruments,—as the violin, flute,
 piano-forte,—and in writing, of the voice in enunciation, and of the
 upper and lower limbs in striking, leaping, and  kicking, convey
 a general  notion of this rapidity of contraction, and how nicely, in
 many of the cases,  it  must be regulated by volition.  The fleetest
 race horse, on record, was capable of going, for a short distance, at
 the rate of a mile per minute;  yet this is trifling, when compared
 with the  velocity of many birds,—which can, with facility, wheel
 round and  round the most rapid  racer in circles of immenso
 diameters,—and with that of numerous  small  insects, which ac-
 company  us, when  we travel with great rapidity—and even against
 the wind—with apparent facility.
  It has frequently excited  surprise, how the migratory birds can
 support themselves so long upon the wing, as to reach the country
 of their migration, and, at the same time, live without food during.
 their aerial voyage.   The difficulties of the subject have impelled
 many to deny the fact of their migration; and have excited others
 to form extravagant theories to  account for the preservation of the
 birds during the winter months; but if we attend to their excessive
 velocity, the difficulties, in a great measure, vanish.   Montagu,
 a celebrated ornithologist, estimates the  rapidity with which a
 hawk and many other birds occasionally fly, to be not less  than
 one hundred and fifty miles an hour; and that one hundred miles
per hour is certainly not beyond a fair computation for the conti-
nuance of their migration.   Major Cartwright, on the coast of
Labrador, found, by repeated observations, that the  flight of the
eider duck is at the rate of  ninety miles  an hour, yet it  has not
been esteemed very remarkable for its swiftness.
  Sir George Cayley computes the rate of flight, even of the
  Vol. I.                   41 
322                  MUSCULAR MOTION.
common crow,  at nearly twenty-five miles an hour.   Spallan-
zani found that of the  swallow about ninety-two miles an hour;
and he conjectures,  that the velocity of the swift is nearly three
times greater.
  A falcon, belonging to Henry IV. of France, escaped fromFon-
tainbleau,  and was,  in twenty-four hours afterwards, at Malta,—a
distance computed to be not less than one thousand three hundred
and fifty miles,  making a velocity  of  nearly fifty-seven miles an
hour, supposing the falcon to  have been on the  wing the whole
time; but  as such birds never fly by night, if we allow the day to
have been at the longest, his flight was perhaps at the rate  of se-
venty-five miles per hour. It is not probable, however, as Montagu
observes, that it either  had so many hours of light in  the twenty-
four hours to perform its journey,  or  that it  was retaken at the
moment of its  arrival.—Again, a  society of pigeon fanciers from
Antwerp,  dispatched ninety pigeons from Paris, the first of which
returned in four hours and a half, at a rate of nearly fifty miles an
hour; and, in a number of the New Monthly Magazine, for
1826, there is an instance of the migratory or passenger pigeon—
the Columba migratoria of Wilson—having been shot in Fife-
shire, in Scotland.  It  was the first ever seen in  Great Britain,
and had been forced over, it was  imagined,  by unusually strong
westerly gales.
  The velocity of the contraction of the muscles of the wings, in
these rapid flights, is  incalculable.  The possible  velocity, in
any  case,  must, indeed,  be greatly dependent upon habit.   No-
thing can be more awkward  than the. first attempts at writing,
drawing,  playing  on  musical  instruments,  or performing  any
mechanical process  in the arts; and what  a contrast is  afforded by
the astonishing celerity, which  practice never fails to confer, in
any  one of those  varieties  of  muscular contraction?  In running,
leaping, wrestling,  dancing, or any other  motion of the body, one
person can execute with facility, what another, with equally fa-
vourable original  powers, cannot effect, because  he has  not  pre-
viously and frequently made the attempt.  Prize-fighting affords
an instance of  this kind of muscular velocity and precision, ac-
quired by habit:—the practised boxer being able to inflict his blow
and  return his arm  to his guard so quickly as almost to elude the
sight.   By considering the muscular motions, employed in trans-
porting the body of the fleetest horse,  Haller  has concluded,
that the elevation of the leg must have  been performed in y^th
part of a second.  He calculates, that the rectus femoris—the
large muscle,  which  is  attached to the knee-pan  and extends
the leg, is shortened three  inches in the ¥|^-th part of a second in
the most  rapid movements of man.  But, he adds, the quickest
motions are executed by the muscles, concerned in the articulation
of the voice.   He himself, in one  experiment, pronounced  fifteen
hundred letters in  a minute; and, as the relaxation  of a muscle 
EXTENT of muscular contraction.
323
occupies as much time as its  contraction :—the contraction of a
muscle, in pronouncing one of these letters, must have been exe-
cuted in -j^V^th Part °f a minute; and in much less time in some
letters, which require repeated contractions of the same muscle or
muscles, as r.  If the tremors, that occur in the pronunciation of
this letter be estimated at ten,  the muscles,  concerned in it, must
have contracted, in  Haller's experiment,  in -jo^o^h  Part of a
minute.
   It has been the opinion of many physiologists and metaphysi-
cians, that, only within certain limits of velocity, is muscular con-
traction directed by volition; and that when it exceeds a certain
velocity, it evidently depends upon habit.   The effects of volition
have, in this respect, been divided into the immediate andremote.
Of the first we have examples in the formation of certain vocal and
articulate sounds, and in certain  motions  of the joints, as  in  the
production of voice, speech, and locomotion.   In the second  are
included those actions, which we conceive to be within our power,
but where we think only of the end to be  obtained, without at-
tending to the mechanical means.
   ■" In learning a language, for example," says Dr.  Bostock, "we
begin by imitating the pronunciation of the  words, and use a direct
effort to put the organs of speech in the proper form. By degrees,
however, we become familiar with this part of the  operation,  and
think only of the words, that are to be employed, or even  the
meaning, that is to be conveyed by them.   In learning music, we
begin by imitating particular motions  of the fingers,  but at length
the fingers are disregarded, and we only consider what sounds  will
follow from certain notes, without thinking of the mechanical way
in which the notes are produced."
   In these, however, and in all other cases  that can  be adduced,
it is difficult  to conceive how the effect can be produced without
the agency of volition;—obscure it is true, but still  in action. The
case of  reading is often assumed, as confirming  the view  that
invokes habit; yet, if a letter be inverted, we immediately  detect
it; and although, by habit, we may have acquired extreme facility
in playing the notes of a rapid  musical movement, no doubt, we
think, ought to exist, that an effort of volition is exerted on each
note composing it,—inasmuch as there is no  natural sequence of
sounds;  and hence there  appears no cogent reason,  why  one
should follow rather than another, unless a controlling effort of the
will were exerted.
   With regard to the extent of muscular contractions, this must
of course be  partly regulated by volition;  but it is  also greatly
owing to the length of the muscular fibres. The greater the length,
of course the greater the  decurtation during contraction.  We shall
see, likewise, that this  depends upon the kind of lever which  the
bone forms, and the distance at which the muscle is inserted from
the joint or fulcrum. 
324                  MUSCULAR MOTION.
  Before passing to the examination of special movements, it will
be necessary to consider  briefly a few  elementary principles of
mechanics, most of which are  materially concerned in every ex-
planation ;  and without some knowledge of which such  explana-
tions would, of course, be obscure  or unintelligible.   Were we,
indeed, as Magendie has remarked, to investigate narrowly every
motion of the body, we should find the applicability to them of al-
most all the laws of mechanics.
  If we take a rod of wqod or metal, of uniform matter  through-
out, and support it at the middle either like the beam of a balance,
or on a pointed  body, we find, that the two ends accurately balance
each other; and if we add weights at corresponding parts of each
arm of the beam, that is, at parts equidistant from the point of sus-
pension, the balance will still be maintained. The point by which
the beam is suspended, or at which  it is equilibrious, is called the
centre of gravity of the beam; and  in every mass of matter, there
is a point of this  kind, about which  all the parts balance or are
equilibrious;  or, in other words, they have all this centre of gra-
vity or of inertia.
  The centre of gravity, in a mass of  regular form and uniform
            substance, as in the parallelograms, Figs. 52 and 53,
  Fig. 52.  is easily determined, inasmuch as it must necessarily
  _________ occupy the centre c; but in bodies, that are irregular,
           1 either as regards density or form, it has to  be deter-
            mined by rules of calculation, to be found in  all works
            on physics,  but  which it  is unnecessary to adduce
            here.
       ........,    The nearer the centre of gravity is to the soil on
       f     which the body rests,  the  more stable is the equili-
            brium.  In order that the figures 52  and 53 shall be
            overturned from  left to right, the whole mass must
            turn upon e as upon a pivot; the centre of gravity
       ■     describing the curve c b, and the whole mass  being
  ----jj---'€ lifted in the  same degree.   In Fig. 52, the  curve is
            nearly  horizontal,  owing  to  the narrowness of the
base and the height of the centre of gravity.  In Fig. 53, on  the
                   other hand, whose base is broad and the centre
     Fig. 53.      of gravity low, the curve rises considerably;
                   the resistance to overturning is consequently
             ~~^\   nearly equal to the  whole weight  of the  body,
          s"   &  and the equilibrium necessarily firm.
       . /'            The  condition of equilibrium, of a body-
                   resting upon  a plane, is such, that a perpendi-
        }           cular, let fall from the centre of gravity, shall
        <£,      e fall within the points by which it touches the
                   plane.  This  perpendicular is called the verti-
cal Hne or line of direction, being that in which it tends naturally
to descend to  the  earth;  and  the space, comprised between  the 
MECHANICAL PRINCIPLES.                325
points, by which the body touches the soil,  is called the  base  of
sustentation.
  We can now understand why a wagon, loaded with heavy goods,
may pass with safety
alonga sloping road;                  Fig.54.
whilst if it be loaded
to a greater height
with a  lighter  sub-
stance,  it  may  be
readily  overturned.
When the wagon is
loaded  with metal,
the centre of gravity
is low as at c;  the
vertical line cp falls
considerably within
the base of sustenta-
tion; and the centre
describes a rising
path;  but  in  the
other case the centre
is thrown higher, to
a;  and  the  vertical
line falls very near
the  wheel,  or   on
the outside of it, and
consequently of the base, whilst the centre describes a falling path.
   Of two hollow columns, formed of an equal quantity of the same
matter and of the same height, that, which  has the largest cavity,
will be  the stronger of the two; and  of two columns of the same
diameter, but of different  heights,  the higher will be the weaker.
   All bodies tend to continue in the state of motion or of rest, so
as to render force necessary to change their state.   This property
is called the inertia of motion or of rest, as the case may be.
  •When a carriage is about to be moved by horses, considerable
effort is necessary to overcome the inertia of rest; but if it move
with velocity, effort is also required  to arrest it, or to overcome
the inertia of motion.
   We can thus  understand why, if a  horse  starts unexpectedly, it
is apt to get rid Of its burden;  and why an unpractised rider is
projected over his horse's head if it stop suddenly.  In the former
case, the inertia of rest is  the cause of his being thrown; in the lat-
ter, the inertia of motion.  The danger of attempting to leap from
a carriage, when  the horses have taken fright, is thus,  likewise,
rendered apparent.  The traveller has acquired the same velocity
as the vehicle;  and if he  leap from it, he is thrown to the ground
with that velocity; thus incurring an almost  certain injury to avoid
one more remotely contingent.
 
326                  MUSCULAR MOTION.
Fig. 55.
  The force, momentum, or quantity of motion  in  a body,
is  measured by the velocity,  multiplied into the  quantity of
matter.
  A cannon ball, for example, may be rolled so gently  against a
man's leg, as not even to bruise it; but if it be projected by means
of gunpowder, it may mow down a dense column of men, or pene-
trate the most solid substances.
  If a man be running, and strike against another, who is stand-
ing, a certain shock is received by both; but if both be running in
opposite directions  with the same velocity, the  shock  will be
doubled.
  The subject of the direction of forces applies  to most cases of
muscular movements.   Where  only one force acts upon a body,
the body proceeds in the direction in which the force is exerted;
as in the case of a bullet fired from a gun;  but if two  or more
forces act upon it, at the same time, the direction of its motion
will be  a middle course between the directions of the separate
                       forces.   This course is called the result-
                       ing direction,  i.  e. resulting from   the
                       composition of the  forces.  Let us sup-
                       pose two forces a T and b T  in  Fig. 55,
                       acting upon  the body T, which may be
                       regarded as the tendon of a muscle, and
                       the two forces as the power developed by
                       muscular fibres holding the same situation;
                       the result will be the same, whether  they
                       act together or in succession.   For exam-
                       ple, if the force a T is sufficient to draw
                       T to a,  and  immediately afterwards the
force b T be exerted upon it, the tendon will be at c,  the place to
                 which it would be drawn  by the simultaneous
                 action of the two forces or fibres. If, therefore,
                 we complete  the figure, by drawing  a c equal
                 and parallel to T b and c b equal and parallel to
                 a T,  we have the parallelogram of forces,*as
                 it is called, of which the diagonal shows the
                 resultant of the forces, and the course of the
                 body on which they act.
                    In the case, assumed in Fig. 55, the forces
                 are equal.  If not so, the parallelogram may re-
                 sult as in Fig. 57; in which T c will,  again, be
                 the resultant of the  forces a T and T b, or we
                 may  have the arrangement in Fig.  56.
                    By these  parallelograms,  we are  enabled,
also, to  resolve the resultant into its component forces.   Suppose,
for example, we are desirous of knowing the quantity of force in
the resultant T c, Fig.  55, which is capable of acting in the direc-
tions T a  and T b; it is only necessary to draw, from the point c,
 
MECHANICAL PRINCIPLES.                327
c d parallel to T b, and c b parallel to T a; and the lines cut offby these
T a and T b, will be the forces
into which it may be resolv-              Fig. 57.
ed. The same applies to Figs.
56 and 57, and to every other.
   Friction is the resistance
necessary to be overcome in
making one body slide over
another; and adhesion  is the
force which unites two po-
lished bodies  when  applied
to each other,—a force which
is   measured  by  the  perpendicular  effort  necessary  for sepa-
rating the two bodies.  The more polished the surfaces in contact,
the greater is the adhesion, and the less the friction; so that where
the object is merely to facilitate the sliding of one surface over an-
other, it will be always advantageous to make the surfaces polish-
ed, or to put a liquid between them.
   A beam or rod of any kind,  resting  at one  part on a prop or
support,  which thus becomes its centre of motion, is a lever. The
ten inch beam,
P W, Fig. 58, is                  Fig. 58.
a lever, of which
F may be consi-
dered the prop
or fulcrum;  P,
the part at which
the power is applied; and W,the point of application of the weight
or resistance. In every lever we distinguish these three points;—
the fulcrum, power, and resistance; and, according  to  the rela-
tive position of these points, the lever is said to be of the first, se-
cond, or third kind.
   In a lever of the first kind, the fulcrum is between the resist-
ance and the power, as in Fig. 58; F being the fulcrum on which
 the beam rests and turns; P,  the power; and W, the weight or re-
sistance.  We have numerous familiar examples of this lever:—the
 crow-bar in elevating a weight;—the handle of a pump;—a pair of
scales;—steelyard, &c.
   A lever of the second kind has the resistance W, Fig. 59, be-
 tween the power
 P  and the  ful-                   Fig. 59.
 crum F; the ful-
 crum and power
occupying each
one  extremity.
The rudder of a
ship, the wheel-
barrow, and nut-crackers, are varieties of this kind of lever.
 
328
MUSCULAR MOTION.
W)
F
iirrmrnmtiiirrfiimiiinmmnnnunnn inmiromnTO^          IU1U1IHI1I1H
   In a lever of the third kind, the power P is between the re-
                                            sistance  W,  and
                   Fig. 60.                  the   fulcrum  F,
                                            Fig. 60; the resist-
                                            ance and the ful-
                                            crum   occupying
                                            each  one  extre-
                                            mity of the lever.
                                            In the  two  last
                                            levers, the weight
                                            and  the  power
                                            change    places.
Tongs and shears are levers of this kind; and  also a  long ladder
raised against a wall by the efforts of a man; here, the fulcrum  is
at the part of the ladder which rests on the ground;  the power
is exerted by the man; and the resistance is the ladder above him.
   In all levers are distinguished,—the arm of the power, and the
arm of the resistance.  The  former  is  the distance comprised be-
tween the power and the fulcrum, P F, Figs. 58, 59, and 60; and
the latter is the distance W F, or that between the weight and the
fulcrum.   When, in the lever of the first kind, the fulcrum occu-
pies the middle, the lever is  said  to have equal arms;  but if it be
nearer the  power or the resistance, it is said to  be a  lever with
unequal arms.
   The length of the arm of the lever gives more or less advantage
to the power or to the resistance, as the case may be.  In a lever of
the first kind, with equal arms, complete equilibrium  would ex-
ist, provided the beam were alike in every  other respect.  But  if
the arm of the power be longer than that of the resistance, the re-
sistance is to the power as the length of the arm of the power  is
to that of the arm of the resistance; so that if the former be double
or triple the latter, the power need only be  one-half or one-third
of the resistance, in order that the  two forces be  in equilibrium.
A reference to the figures'will exhibit this  in a clear light.  The
three levers are all presumed  to be of equal substance throughout,
and to be ten inches or ten feet in length.
   The arm of the power, in Fig. 58, is the  distance P F, equal to
eight of those divisions; whilst that of the resistance is W F, equal
to two of them.   The advantage of the  former over the  latter is,
consequently, in the proportion of eight to two, or as four to one;
in other words, the power  need only be one-fourth of the resist-
ance, in order that the two forces may be equilibrious.
   In the lever of the second kind, again, the proportibn of the arm
P  F of the power, is to that,  W F, of the  resistance, as ten—the
whole length of the lever—to two; or as five to one: whilst, in the
lever of the third  kind, it is as two to ten, or as one to five; in
other words,—to  be equilibrious, the power must be  five times
greater than the resistance. 
           APPLICATION OF MECHANICAL PRINCIPLES.       329

   We see  therefore, that, in the lever of the second kind, the arm
of the power must necessarily be longer than that of the resistance,
since the power and the fulcrum are separated from each other by
the whole length of the lever: hence this kind of lever must al-
ways be advantageous to the power; whilst the lever of the  third
kind, for like reasons, must always be unfavourable to the power,
seeing that the arm of the  resistance is the whole length of the
lever, and, therefore, necessarily greater than that of the power.
   It can now be understood  why a lever of the first  kind should
be the most favourable for equilibrium; one of the second kind for
overcoming resistance; and one of the third kind for rapidity and
extent of motion: for  whilst, in Fig. 60, the power  is  moving
through the minute ark at P, in order that the lever may assume
the position indicated by the dotted lines F W, the weight or re-
sistance is  moving through  the much  more considerable space
Ww.
  The direction in which the power is inserted into the lever, like-
wise demands notice.
  When it is perpendicular  to the  lever, it acts with the greatest
advantage; the whole of the force developed being  employed in
surmounting the resistance;  whilst, if inserted obliquely,  a part of
the force is employed in tending to move the lever in its own di-
rection; and this part of the force is destroyed by the resistance of
the fulcrum.
   Lastly, the general principle of equilibrium in  levers consists in
this;—that whatever may be the direction in which the power and
resistance are acting, they must always be to one another inversely
as the perpendiculars drawn from the fulcrum to their lines of di-
rection.   In Fig. 60, for example, the line of direction of the up-
per weight is W w; that of  the power P p; to keep the  lever in
equilibrium in this position, the forces must be to  one another in-
versely as F w to F p.

   In  applying these mechanical principles to the illustration of
muscular motion, we must, in the first place, regard each  movable
bone  as a lever, whose fulcrum or centre of motion is in its joint;
the power at the insertion of the muscle; and the resistance  in its
own weight and that of the parts, which it supports.
   In  different parts of the  skeleton we find the  three kinds of
levers.  Each of the vertebrae of the back forms, with the one im-
mediately beneath it, a lever of the first kind; the fulcrum being
seated in the middle of the  under surface of the body of the ver-
tebra.   The foot, when we stand  upon  the toe, is a lever of the
second kind; the fulcrum being in the part of the toes resting upon
the soil, the power in  the muscles, inserted into the  heel, and the
resistance in the ancle joint,  on  which  the whole weight of the
body rests: of levers of the third kind we have numerous instances;
of which the deltoid, to be described presently, is  one.  In this,
  Vol. I.                     42 
330
MUSCULAR  MOTION.
as in  other cases, we shall see the applicability of the principle,
laid down regarding the arms of the lever, &c, and we shall find,
that, in the generality of cases, the power is inserted into the lever
so near to the fulcrum, that considerable force must be exerted to
raise  an  inconsiderable  weight;—that so  far, consequently, me-
chanical  disadvantage is occasioned;  but we shall find, that such
disadvantages  enter into the economy of nature, and that they are
attended  with so many valuable concomitants, as to compensate
richly for the expense of power.   Some of these causes, that tend
to diminish the effect of the forces, we will  first consider; and af-
terwards attempt to show the advantages resulting from these and
similar arrangements in effecting the wonderful, the complicate
operations of the muscular system.
  In  elucidation of this subject, let  us  take, with Haller,  the
case of the deltoid—the  large  muscle, which constitutes the fleshy
mass on the top of the arm, and whose office it is to raise the whole
of the upper  extremity.  Let W F, Fig.  61, represent the  os
                              humeri, with a weight W at  the
           Fig. 61.            elbow, to be raised by the deltoid
                              muscle D.  The fulcrum F  is ne-
             s^" J^N.      cessarily,  in  this case, in  the
           j           \     shoulder joint; and the muscle D
          /            I>\§-  is  inserted much nearer to  the
 -----.-i  ....[---------1—"   ^TO    fulcrum than  to the  end  of  the
  *^      \      *       4r^ bone  on which the weight  rests;
          \             /    the arm of the power P F, (sup-
            \.        y^     posing, for  a moment, that it is
                              acting at this part with every ad-
vantage,  which we will  see presently, it is not,) is, consequently,
much shorter  than that  of the resistance W F, which, as  in  all
levers of the third  kind, occupies the whole  length of the  lever.
In estimating the effect from  this cause alone  upon  the power to
be exerted  by the  deltoid; we will suppose, that the arm of the
power is to that of the  resistance as  1 to 3; the deltoid being in-
serted into the humerus  about one-third down.  Now, if we raise
a weight of fifty-five  pounds in this way, and add five pounds for
the weight of the limb, (which may be conceived to act entirely at
the end of the bone,) the power, which the deltoid must exert, to
produce the effect, is not equal to sixty pounds, but to three times
sixty, or one hundred and eighty pounds.
  Many  muscles  have  insertions  much  less  favourable than
this.   The biceps D, for example, in Fig. 62,—the muscle  which
bends the forearm on the  arm,—is attached to the forearm  ten
times nearer the elbow-joint, or the fulcrum, than to the extremity
of the lever;  and  if we apply the argument to it, supposing the
weight of the globe, in the palm of the hand, to be fifty-five pounds,
and the weight of the limb five pounds, it would have to act  with a
force equal to sixty x ten, or six hundred pounds to raise the weight. 
APPLICATION OF  MECHANICAL  PRINCIPLES.


                Fig. 62.
331
  A, the os humeri; B, the ulna; C the radius; D, the biceps; E, insertion of the biceps into the radius.

   Muscles, again, are attached to the bones at unfavourable angles.
 If they were inserted at right angles, in the direction P P, Fig. 61,
 the whole power would be effectually applied in moving the limb.
 On the  other hand, if  the muscle were parallel to the bone, the
 resistance,  it is  obvious,  would  be  infinite, and no effect could
 result.
   In the animal, it rarely happens, that the muscle is inserted at
 the most favourable angle:  it is  generally  much  smaller than  a
 right angle.  Reverting to the deltoid, this muscle is inserted into
 the humerus  at an angle  of about ten degrees.  Now, a power,
 acting obliquely upon a lever, is to one acting perpendicularly, as
 the sine  of inclination, represented by the dotted line F s, Fig. 61,
 is to  the whole sine, P P.  In the case of the deltoid the proportion
 is as  1,736,482 to 10,000,000.  Wherefore, if the muscle had to
 contract with a force of one hundred and eighty pounds, owing to
 the disadvantage of its insertion  near the fulcrum, it will have,
 from  the two causes combined, to exert  a force  equal to 1,058
 pounds.
   Again, the direction, in which the fibres are inserted into  the
 tendon,  has great  influence  on
 the   power  developed by  the
 muscle.    There   are   but  few
 straight  muscles,  in which the
 fibres have  the same direction as
 the tendon.   Fig.  63 will exhi-
 bit the loss of power, that the
fibres must sustain in proportion
to the angle of  insertion.  The
fibre  T t F would, of course, ex-
ert its whole force  upon the ten-
don, whilst the fibre t 90°  would,
by its contraction, merely displace
the tendon.
Fig. 63.
 
332
MUSCULAR  MOTION.
   Now, the force exerted is, in such a case, to the effective force,—
 that is, to that which acts in moving the limb,—as the whole sine
 t F is to the sines of the angles at which the fibres join the tendon,
 represented by the dotted lines.  Borelli  and Sturm have cal-
 culated these  proportions as follows:—At an angle of  30°,  they
 are 100 to 87;  at 45° as 100 to 70;  at 269 as 100 to 89; at 14° as
 100 to  97, and at 8° as 100 to 99.
   The  largest angle, formed by the outer fibres of the deltoid, is
 estimated by Haller at 30°; the smallest about  8°.  If this dis-
 advantage be taken into account, the deltoid will have to contract,
 with a force equal  to 1,284  pounds, to raise fifty-five pounds at
 the elbow.
   It is  farther contended by Borelli, Sturm,  and Haller, that
 the force of the muscle, as estimated in  the preceding calculations,
 must be doubled, seeing that it must exert as much force in resisting
 the bone, that affords a fixed point at one extremity, as in elevating
 the weight at the  other.  This estimate,  if admitted, would ele-
 vate the force, which must be exerted  by the  deltoid in raising
 the fifty pounds, to 2,568 pounds.
   Lastly; much force is  spent when a muscle  passes over many
joints.  Antagonist muscles must, likewise, exert  an influence of this
 kind, consuming a  certain  portion of the  force developed  in the
 contraction of the muscle.
   On the other hand, there are certain  arrangements, which aug-
 ment the power developed by muscles; as the  thick articular ex-
 tremities of the bones; the patella and the sesamoid bones in general;
 all of which enlarge the angle, at which the tendon is inserted into
 the bone or lever.   The projecting processes for muscular attach-
 ments, as the trochanters, the protuberance of  the os calcis, the
 spinous processes of the vertebrae, &c. augment the arm of the lever
 and are, thus, inservient to a like valuable purpose.  The smooth-
 ness of  the articular  surfaces of bones, tipped,  as they  are, with
 cartilage;  and the synovia, which lubricates the  joints, by dimi-
 nishing the friction,  also  augment  the power,  as well  as the
 bursae  mucosae, which are interposed,  wherever  there is  much
 pressure or friction.  The trochleae or pulleys act only in directing
 the force, without augmenting its amount; and  the same may be
 said of the bony canals and tendinous sheaths, by  which the ten-
 dons of the muscles, especially those passing to the fingers and toes
 are kept in their proper course.
   Still, it must be  admitted, that, as regards the  effort to be ex-
 erted by the muscles, it must, in almost all cases, be much greater
 than the resistance it has to overcome.  The very  fact  of the lever
 of the  third  kind being that which prevails in  our movements
 exhibits this.  The mere mechanician has conceived this to be an
 unwise  construction; and  that there is a needless expense of force
 for the  attainment of a determinate end. In all cases we find, that 
APPLICATION OF MECHANICAL PRINCIPLES.
the expense of power has been but little regarded in the con-
struction of the frame; nor is it necessary that it should have
been.  It must be recollected, that the contraction  of the muscle
is under the influence of volition, and that, within certain limits,
the force, to be employed, is regulated  by the  influx sent by it
into the muscles.   The great object, in the formation of the body,
appears to have been;—to unite symmetry and convenience, with
the attainment of great velocity and extent of motion,  so that,
whilst the power is moving throughout a small space, the weight
or resistance shall move rapidly through  one more extensive. We
have seen that, in these respects, the  lever of the third kind is most
fitting.  With any other, indeed, less power  might be required;
but we should have less extent of motion and less velocity, whilst
the symmetry and convenience of the body would  be destroyed.
Suppose, for example, that in Fig. 62, the biceps,—instead of being
inserted at E,—near the elbow,—had passed  on to the wrist, or,
to simplify the matter, to the extremity  of the member;  it would
assuredly have acted with  more force,—the  lever having been
changed into one of the second kind,—but the hand would have lost
that velocity and extent of motion,  which are so important to it;
and the course of the muscle would  have been so  modified, as to
convert the convenient and symmetrical member into a cumbrous,
webbed instrument,  badly adapted for the multitudinous purposes
to which it has to be applied.
   The same effect results, as Sir Charles Bell  has remarked,
from the course of the
tendons and their con-
finement by sheaths,
strengthened by liga-
ment.
   If the  tendon  A,
Fig.   64,   took   the
shortest  course to its
termination at B,  it
would draw up the toe
with more  force;  but
the toe would lose its
velocity of movement.
   To favour this velo-
city, we find that the
majority  of  muscles
are inserted obliquely into their  levers, and the fibres into the ten-
dons. By this arrangement, as we have proved, considerable loss
of power results; but, in the majority of cases,  the motion is
effected by a less degree of decurtation  than if the muscle were
straight.
Fig. 64.
 
334
MUSCULAR MOTION.
Let A B and C D, Figs. 65 and 66, be parts of two ribs,  that
                                              are parallel, and
                 Fig. 65.


■AjiiiiiiiiiiiiuiiiiiniminiiuiiiiiiiiiiiiHiiiiiiiiiiiiiiHiiiiiiimiiiiiimiiHiiiiiiiii

Fig. 66.
                                                will   continue
                                                parallel till they
                                                are brought in
                                                contact by the
                                                action  of  the
                                                straight    mus-
                                                cle E F; or by
                                                that of the ob-
                                                lique  muscles
                                                F  G  and F H.
                                                Now,  it is ob-
                                                vious,     that,
                                                when the point
                                                E  comes   in
                                                contact with F,
                                                the  length  of
                                                the    straight
                                                muscle  E  F
                                                must  be  null;
                                                whilst  that of
                                                the     oblique
                                             ]jj muscles    will
                                                only  have  ex-
                                                perienced a de-
curtation equal to G g and H h, Fig. 65; and to F g and F h, Fig.
66.  It is clear also that, in  these  cases, the straight muscles  can
never so contract as to admit of a close approximation of the ribs;
whilst the oblique muscles will admit of this to a much greater ex-
tent.  We can, therefore, understand why the intercostal muscles
                                   pass obliquely from one rib to
                                   another, as at D and B C, Fig.
                                   67, instead  of in a direction
                                   perpendicular to the two ribs,
                                   as at A.
                                      There are cases, however,
                                   in which  a straight muscle
                                   maypass between two parallel
                                   ribs, and carry them through
a given space, with less decurtation of fibres, than any oblique
muscle which has the same origin,  but is inserted at a greater dis-
tance from the centre of motion, and acts through the medium of
a longer lever.  Moreover, a muscle, with a less degree of obliquity,
may be so situated  as  to carry the bones through" a given  space
with a less decurtation of fibres than any other muscle having the
same origin,  but a much greater degree of obliquity.
Cr
M
II
 
APPLICATION OF  MECHANICAL PRINCIPLES.       335
  Suppose A B and C D, Fig. 68, to be two parallel ribs, of which
A B is movable
about  A,  as  a                   FtS- 68-
centre; and sup-
pose  it  to  be
brought, by the
action  of  the
straight  muscle
E F, and of the
oblique muscles
E G and  E H,
into the position
Afi The points
of insertion of (he muscles will  now be at a, c, and e, after having
traversed the spaces Fa, G c, and H e. If we, now, from the point
E,  as a centre, describe the arcs  c 6 and e d; the spaces d H and
b G will  indicate the degree of decurtation, which the oblique mus-
cles have experienced, and a F that of the straight muscle.
  This figure also shows,  that when the  muscles change the rela-
tive position of any two bones, they, at the same time, change the
direction of their own action, and vary their lever. When the rib
A B  is brought into the position Af, the muscles E G and E H,
by  being brought down to c and e, have assumed the position E c
and E e, and have, consequently, changed their length, situation,
obliquity, and leverage.
  Again, of the muscles, that are attached to ribs that are parallel,
equally movable, and situated at right angles to the spine, those,
that pass perpendicularly from one rib to the other, will act  upon
each with equal leverage, and each will approach the  other  with
the same velocity; whilst those,  that pass obliquely from one to
the other will make them approach  with  different velocities; a
principle, which  is strikingly applicable to the intercostal muscles.
Let us suppose
A  B and C D,                    Fig. 69.
Fig.  69, to be
 two     parallel
 ribs, articulated
 with the spine
at  A and C, and
 that  they  are
 equally  mova-
 ble on these cen-
 tres of motion.
 Let D B repre-
 sent a straight muscle, passing directly from the  one rib  to the
 other; and D E  an oblique muscle.  The levers of D B, according
 to  the mechanical principle laid down, will be A B and C D, per-
pendiculars drawn from the  centres of motion to the line of diree-
 
336
MUSCULAR  MOTION.
tion of the power.   These levers, being parallel, are of course
equal, but the levers of D E will be C F and A G, perpendiculars
drawn from the centres of motion to the line of direction of the
power.   These levers are of different lengths, and,  accordingly,
the muscle must act with different degrees of force on the two ribs;
so that it will cause C D, on which it acts with the longest lever,
to approach  A B  faster  than  it makes the  latter approach the
former,—in the ratio of C F to A C, or with three times the ve-
locity.
  In all muscular motions, the levers of the power and of the re-
sistance are undergoing variation ; so that the degree of power, ne-
cessary  to  be developed in one position of the member, may be
much less than in another. The case of the biceps, already referred
to,  will elucidate this.
  Let E C, Fig. 70, represent the os humeri;  E  A the forearm;
                                          E the elbow joint;
                 Fig. 70.                 W a weight or re-
                                          sistance, hung at the
                                          wrist, and D the bi-
                                          ceps muscle, inserted
                                          at b, a  tenth of the
                                          distance  down the
                                          forearm.  It is mani-
                                          fest, that the force,
                                          necessary for bend-
                                          ing the arm, must be
                                          much greater when
                                          it is in  the  position
                                          A E than in that of
                                          E a.  The lever of
                                          the resistance, in the
former case, is the whole length of the forearm; or, in other words,
the perpendicular drawn from  the fulcrum to the line of direction
of the weight W;  but, when the arm is raised  to a, the  lever of
the resistance is, no longer,  E A, but E H; but  not only is the
lever of the resistance shortened; that of the power is augmented.
The lever  of the biceps, when the forearm is horizontal, is the
dotted perpendicular, drawn from the fulcrum at the elbow to the
line of direction of the muscle ; but when the forearm is bent to
the position E a, the disposition of the muscle is also modified.  It
assumes the position, occupied  by the dotted line, which is farther
distant from the fulcrum, and the lever of the power is consequently
increased.   In this case, then, of the action of the biceps, in pro-
portion as we raise the arm, the mechanical disadvantages become
less and less; the lever of the  power increasing, whilst that of the
resistance diminishes.
   In many of the changes of position of the body, whilst a bone is
turning upon its centre of motion, the centre itself is often describ-
 
ACTION OF SIMPLE AND  COMPOUND MUSCLES.      337
71, let A B represent the

       Fig. 71.
^IC
-^^OrB—
ing, at the same time, a curve.   In Fig.
foot, B C the tibia, C D the thigh bone,
and D E the trunk; and let us suppose it
is required to bring the body to the erect
position B F;  so that B C shall corres-
pond to B G, C D to G I, and  D E to
I F. The point C will describe the curve
C G;  and, whilst it is accomplishing
this, the point D is likewise moving; so
that the latter, instead of describing the
curve D H, which it would do were the
centre of motion C fixed, proceeds along
the curve D  I;  the point E,  again,  is
subjected  to the like influence, and in-
stead of describing the curve E K, which
it would do if  the  centre D were fixed,
it rises along E F.
  The motions, produced by the  mus-
cles, may be either simple or  compound.
The simple muscles admit of  variety;
some being straight, composed of parallel
fasciculi, others reflected in their course,
and others, again,  circular.
  In the straight muscles, each fibre, by its contraction, draws the
tendon in its own  direction;  and the effect of the whole is to bring
it towards the centre of the muscle.  In a long muscle, the whole
contractile effort is concentrated on the tendon, in consequence  of
the course of  the  fibres being parallel to that of the tendon.  In
most of the broad muscles, on the other hand, as the attachments,
at both extremities, are usually at different points, all the fibres do
not concur in one  effort. Different sets of fibres may have a very
different action from others, and they are capable of being thrown
separately into contraction.  The  ordinary direction,  in which a
muscle acts, is from its tendinous, back to its aponeurotic, attach-
ment ; that is, from the movable to the more fixed part; and in a
straight muscle, this direction can be accurately appreciated.   It
must be borne in mind, however, that the muscle can act in an in-
verse direction also.
  When the whole of the fibres, composing  a broad muscle, are
brought to act on the tendon, as in the case of the deltoid, we find,
by  the composition of forces,  that the middle line of direction
must be taken for  the purpose of estimating  their line of action.
A  part, however, may act and  carry the arm upwards and out-
wards; whilst  the  opposite fibres may move it upwards  and in-
wards.
  Where a muscle is reflected,—like the superior  oblique of the
eye, and the peronei muscles,—the line of motion will be from the
  Vol. I.                     43 
338
MUSCULAR  MOTION.
insertion to the point of reflection ; precisely  as  a rope, passing
over a pulley, raises the weight in a line drawn from the weight to
the pulley.
  The circular  muscles, which have no precise origin or insertion,
are inservient to  the contraction of  the apertures around  which
they are placed.  In  executing  the complex  movements  of any
part of the frame, a combination  of the action of the different mus-
cles, attached to the part, generally occurs, rendering  the process
one of a complicated character.  This, if no other cause existed,
would render it extremely difficult to calculate the precise degree
of force, which particular muscles, alone  or in  combination, are
capable  of exerting.   The mathematical physiologists made multi-
farious attempts in this direction; but their conclusions were most
discrepant. When we bear in mind, that the force, capable of being
exerted by any muscle, is dependent upon the proper organization of
the muscle, and likewise upon the degree of energy of the brain, it
will be  apparent, that all attempts of this kind  must be futile. We
can determine,  with  nicety,  the effect of which the parts are capa-
ble, supposing them  inanimate structures.  We can calculate  the
disadvantages, caused by the insertion of the power near the ful-
crum; by the obliquity of the line of action of the power, &c; but
we have not  the slightest data for estimating the  effect, produced
by the nervous influx,—by that  mysterious process, which  gene-
rates a new force, and infuses it  into the muscles, in a manner so
unlike that in which the ordinary mechanical powers are exerted.
The data, necessary for such a calculation, would be the precise in-
flux from the brain,—the irritability of the muscle,—the mechani-
cal influences, dependent on the straight or oblique direction of
the fibres composing the muscle, as regards the tendon,—the per-
pendicular or oblique direction in which the tendon is attached to
the bone,—the  particular variety of lever,—the length of the arm
of the power and of that of the resistance,—the loss sustained from
friction, and  the diminution of such loss caused by the cartilages,
that tip the bones, and by the synovia, &c.—data, which it is im-
possible to acquire ;  and hence the solution of the problem is im-
practicable.
   One great  source of the combination of muscular motions is, the
necessity for rendering  one  of the attachments fixed, in order that
the full force may be developed  on the other.   In but few of the
muscles is the part, whence the muscle originates, steady.   To
these few the muscles of the eye  belong, which arise from the inner
part of  the orbit and pass forward to be inserted into the  organ.
To show how very distant muscles may be concerned in this fixa-
tion of one end of a muscle, when it is excited to the development
of plenary power, we will take the case of the deltoid. This mus-
cle arises from  the scapula and clavicle, and is inserted into the os
humeri; but  the scapula and clavicle, themselves, are  not entirely 
COMRINED MOVEMENTS.
339
fixed;  and, accordingly, if the deltoid were to contract alone, it
would draw down the scapula and clavicle, as well as elevate  the
humerus.  If, therefore, it be important to produce the latter ef-
fect only, the scapula and  clavicle must be fixed by appropriate
muscles; as by  the rhomboidei, trapezius, &c.  These muscles,
however, arise  from various vertebrae of the neck, which  are
themselves movable.   It  becomes necessary,  therefore, that  the
neck should be fixed by its extensors, which arise from the lumbar
and dorsal regions.  By the united action of all these muscles, the
deltoid is able to exert  its  full effect,  in elevating the humerus.
But the deltoid, like other muscles, is capable of acting inversely;
as in the case of a person lying on the ground,  and attempting to
raise himself, by laying hold of any object above him.   The hand
and forearm are thus rendered firm, and the deltoid now contracts
from origin to insertion, and, consequently, elevates the scapula
and clavicle.
   Again, if a person, in the recumbent posture, endeavour to bend
the head forwards, the recti muscles  of the abdomen are firmly
contracted, for the purpose of fixing the sternum, whence  the
sterno-cleido-mastoidei muscles in part arise, which can then exert
their full power in bending the neck forwards.
   These  instances  will be sufficient  to exemplify the mode, in
which the muscular motions are combined.  The same principle
prevails over the whole body; and where a greater number of parts
has to be moved, the case must, necessarily, be still more complex.
   When a part, movable  in various directions, is contracting to-
wards any point, it must be rendered steady and be prevented from
deviating by the muscles on each side; and the extent  of its  mo-
tion, may be partly regulated by the action of the antagonist mus-
cles.  Supposing, for instance, that the head is inclined forwards,
there must be muscles, not only to move it in that direction, but
also to prevent it from inclining to the right or left, and to limit
the motion forwards;  although doubt may arise, whether this be
not entirely effected by the nervous influx, sent by volition to the
flexor of the head.  Hence, some anatomists have considered, that
there must, in these cases, be movers, directors, and moderators.
   In sleep, the muscles are perhaps in the most  complete state of
relaxation; and, hence, this condition has been invoked, as afford-
ing evidence of the comparative preponderance of particular anta-
gonizing muscles,—the flexors and extensors, for example. In per-
fect sleep, when no volition is exercised over the muscles, we find
the body reposing in a state of semiflexion:—seeming to show that
the flexor muscles have slightly the  advantage  of the extensors.
Richerand, in a memoir laid before the Sociiti de Midecine of
Paris, in 1799, assigned the following reasons for this  preponder-
ance.   First.  The number of flexors is greater than that of exten-
sors.   Secondly.  The fibres, composing them, are more numerous
and longer:—take, for examples, the sartorius, gracilis, semi-tendi-
nosus, semi-membranosus, and biceps, which are the flexors of the 
340
MUSCULAR MOTION.
leg, and the rectus and triceps  cruris, which are its extensors.
Thirdly. Their insertion is nearer the resistance and farther from
the centre of motion,  which adds to their force.  Fourthly. Their
insertion into the bones is at a larger angle and nearer to the per-
pendicular;  and Fifthly. Their arrangement is such, that the con-
tinuation of the movement of flexion, renders them perpendicular
to the bones to be moved.
   The explanation, afforded by Richerand, applies, on the whole,
to the case he has selected, but there are many exceptions to it.
   The extensors of the thigh,  foot, and jaw, are decidedly predo-
minant; and,according to Adelon, experiments, instituted by Reg-
nier with his dynamometer, make the extensors some kilogrammes
more powerful than the flexors.
   In our various attitudes, the  movements of flexion certainly pre-
vail largely; but as the power of contraction is regulated by voli-
tion, it  is unnecessary to inquire whether there  be  any physical
predominance in  the  flexors over the  extensors, as  has been at-
tempted by Richerand.  We have already seen, that  we can in no
way attain a knowledge of the  degree of force, which  any one mus-
cle of the body is capable of developing.

                      OF THE  ATTITUDES.

   The attitudes, which man is capable of assuming, are of different
kinds. They may all,  however, be reduced to two—the active and
the passive; the former, including those that require a muscular ef-
fort; and the latter, comprising only one variety,—that in which the
body is extended  horizontally on  the soil, and where no effort is
necessary to maintain  its  position.
   We shall begin with the most ordinary attitude;—that of stand-
ing on both feet.
   This requires considerable muscular effort to preserve equilibrium.
The base of sustentation—being the space comprised  between  the
feet plus that occupied by the feet themselves—is small; whilst  the
centre of gravity is very  high.
   The body, again, does not  consist simply of one  bone,  but of
many; all of which have to be kept steady by muscular effort;  and
it  is necessary that the vertical line shall fall within the base of sus-
tentation, in order that equilibrium may be  preserved.
   That standing is the effect of the action of the different extensors
is  proved by the fact, that if an animal  be killed  suddenly, or
stunned, so that volition is no longer exerted over the extensors, he
immediately falls forward.
   The head, which is intimately united with  the atlas or first ver-
tebra of the neck, forms  with it a lever of  the first kind, the  ful-
crum of which is in the articulation  of the lateral parts of the atlas
and vertebra dentata;  whilst the power and  the resistance occupy
the extremities of the lever; and  are situated—the one at the face,
the other at the occiput. 
ATTITUDES.
Fig. 12.
 
342
MUSCULAR  MOTION.
  The fulcrum being nearer the occiput than it is to the anterior
part of the face, the head has a tendency to fall forwards. This can
be readily decided by supporting a skull on the condyles; yet Mr.
Abernethy affirms, that "the condyles are placed so exactly pa-
rallel in the centre of gravity, that when we sit upright, and go to
sleep in that posture, the weight of the head has a tendency to pre-
ponderate equally in every direction, as we see  in those  who are
dozing in a carriage."
   In the living subject, the preponderance anteriorly is not as great
as it is in the skeleton, because the greater part of the encephalon
is lodged in the posterior portion; but the fact, that when we go to
sleep in the upright position, the head drops forwards, is sufficient
evidence that it still exists;  and that  in the waking state  the head
is kept in equilibrium on the vertebral column by the contraction
of the extensor muscles of the head, which are situated at  the back
part of the neck, and are inserted into the head;—as the splenius,
complexus, trapezius, and posterior recti.  These muscles are insert-
ed perpendicularly into the lever or bone  to be moved, which is an
advantage, and some compensation for the shortness of  the arm of
the lever by which they act.
   In quadrupeds, the head, not being in equilibrium on the spine,
these muscles are very large and strong; the spinous and transverse
processes of the vertebrae and the occipital depressions  are larger;
and, in addition, they have a strong ligament—the posterior cervi-
cal or ligam'entum nuchas,—which extends from the spinous pro-
 cesses of the vertebrae to the occiput, and aids  in supporting the
 head.
   The vertebral column  supports  the  head, and transmits  the
 weight  to  its  lower extremity.  The tendency of the column
 is to bear forwards: the upper  limbs, the soft parts, and the neck;
 the  thorax with its contents; the greater part  of the contents
 of the abdomen; and the head itself, by  reason of its tendency  to
 fall forwards, all either directly or indirectly, exert their weight on
 it. Hence the  necessity of its great firmness and solidity; which are
 readily  appreciated, if we examine  the  mode  of junction of the
 different vertebrae, with the  strong,  ligamentous  bands connecting
 them;—the whole having the form  of a pyramid, whose base rests
 upon the sacrum, with three  curvatures in opposite directions,
 which give it more  resistance than if it were straight, and enable  it,
 in addition to the weight of the organs pressing upon it, to support
 very heavy burdens.
    The tendency of the spine to fall forward is resisted by the ex-
 tensor muscles, which fill the vertebral fossae or gutters,—the sacro-
 lumbal, lohgissimus dorsi, multifidus  spinae, &c.  which  pass from
 the sacrum to the lower vertebrae of the spine, and from the lower
 to the upper.   Each vertebra, in this action, constitutes  a lever  of
 the first kind; the fulcrum of which is in the intervertebral carti-
 lage, the power in the ribs and other parts that draw the body for- 
ERECT ATTITUDE:—ON  BOTH  FEET.           343
wards, and the resistance in the muscles attached to the spinous and
transverse prpcesses.
  The vertebral column, regarded as a whole, may be considered
a lever of the third kind; the fulcrum of
which is in  the  union  between the last
lumbar vertebra and  the  sacrum, the
power in the parts drawing the spine for-
wards, and the resistance in  the muscles
of the back.  It is on the lower part of
the lever that the power acts most forci-
bly; and it is there, that the pyramid is
thicker;  and that the spinous and trans-
verse processes are larger, and more ho-
rizontal.   We can, accordingly, compre-
hend why fatigue should be experienced
in the loins and sacrum, when we have
.      ..     ,      ,.     •   ,i       Lt  a. Body of a dorsal vertebra.
been, for a long  time, in the erect  at- ft. Canal for containing the spinal mar-
...  i                                     row.
lltUue.                                 c. Spinous process.
   It need scarcely be said, that the longer *£ ATSSegpPS;.
and more horizontal  the spinous pro-
cesses, the greater will be the arm of the lever; and the less the
 muscular force necessary to produce a given effect.
   The weight of the whole of the upper part of the body is trans-
 mitted to the  pelvis; which, resting upon the  thigh bones as upon
 pivots, represents a lever of the first kind, the fulcrum of which is
 in  the ileo-femoral  articulations;  the power and  resistance being
 situated before and behind.
   The pelvis supports the weight of a part of the abdominal viscera;
 and the sacrum that of the vertebral column, which, by reason of
 its shape, transmits the weight equally to the ossa femorum, through
 the medium of the ossa ilii.   When the pelvis is, therefore, in equi-
 librium  on the heads of the thigh bones, this  is owing to many
 causes.  The abdominal viscera, pressing upon the anterior part of
 the pelvis, which is naturally inclined forwards, tend to depress the
 os pubis; whilst the vertebral column, by its weight, tends to press
 down the sacrum.  As the weight of the latter is much more con-
 siderable than that of the former, muscles would seem  to be required
 to keep it in equilibrium, and muscles passing from the femur to be
 inserted into the os pubis; by the contraction of which the excess of
 weight of the vertebral column  might be counterbalanced.  Such
 muscles do exist, but, as Magendie remarks, they are not the great
 agents in producing equilibrium of the pelvis on  the thigh bones;
 for the pelvis, instead of having a tendency to be depressed poste-
 riorly, would appear to bear forwards, inasmuch as the muscles, that
 resist the tendency which the spine itself has to bear forwards, have
 their  fixed point on the pelvis;  and, consequently,  exert a consi-
 derable effort to draw it upwards.
   The strong glutaei  muscles, which form the nates, and are in- 
344
MUSCULAR MOTION.
serted into the os femoris, are the great agents of the equipoise; and
as the hip-joint is nearer to the pubis than it is to the.sacrum, these
muscles act with a greater leverage.
   The thigh bones transmit the weight of the trunk to the tibia;
                   and here we see  the advantage of the neck of
     Fig. 73.      the thigh bone, which, as represented in Fig.
                   73, B, joins the shaft of the bone  at a consi-
                   derable angle.  The prominences D and C are
                   for muscular attachments; and are, of course,
                   advantageous to the muscles, that are inserted
                   into  them.  The  cervix femoris  directs  the
                   head of  the bone A obliquely upwards and in-
                   wards, so that, whilst it supports the vertical
                   pressure of the pelvis, it resists the separation
                   of the ilia, which  the pressure of the sacrum,
                   with its  superincumbent weight has a tendency
                   to produce.
                     But another and  important advantage is, that
                   of affording additional strength in adventitious
                   circumstances. When we are standing perfectly
                   erect, the necks  of the  thigh  bones are very
                   oblique, compared with the line of  direction of
                   the body; but if we are thrown forcibly to  one
                   side, the line of direction of gravitation corres-
ponds more nearly with that of the neck of the  thigh bone,  and
fracture is rarely produced  in this manner.   The most common
cause of fracture of the neck of the thigh bone is, slipping off a curb-
stone in towns, or unexpectedly slipping from a slight elevation, with
one foot, upon a firm  substance beneath, and the fracture in such
case, is  generally transverse.
   The advantage of this arrangement of the neck of the thigh bone
has been compared not inaptly to that resulting from  the dishing
of a wheel; or the oblique position of the spokes from the nave out-
ward to the  felly,  which strengthens the  wheel so  essentially,
against  the strains produced by the wheel sinking with force into
a rut or other hollow.
   The femur transmits the weight of the body to the large bone of
the leg—the tibia; but from the mode  in which the pelvis presses
upon it, its lower extremity  has a tendency to  bear forwards. This
is prevented by the action of the extensors of  the leg,—the rectus
and triceps cruris,—whose power is augmented by the presence of
the patella, a  sesamoid bone, seated behind  their tendon.  The
muscles of the posterior part of the leg, which are attached to the
condyles  of  the  thigh bone, aid  also in preserving  this equili-
brium.
   The tibia is the sole agent of the transmission of the superincum-
bent weight to the foot.  Its upper extremity  has, however, a ten-
dency to bear forwards like  the lower part of the os femoris.  This
 
ERECT ATTITUDE:—ON BOTH FEET.
345
is prevented by the contraction of the gastrocnemii, tibialis posticus,
and the other muscles on the posterior part of the leg.
  The foot sustains the whole weight of the body; and its shape and
structure are well adapted for the purpose.   The sole has some ex-
tent, which  contributes to the firmness of the erect attitude.   The
skin and epidermis are  thick; and beneath the skin is a thick, adi-
pous stratum; in greater quantity at the parts of the foot which come
in contact with the soil.  This fat forms a kind of elastic cushion,
adapted for deadening or diminishing the effects of pressure.
  The whole of the sole of the foot does not come into contact with
the ground.  The weight is transmitted by the heel, the outer margin,
the part corresponding to the anterior extremity of  the metatarsal
bones, and the extremities or pulps of the toes.
  The tibia transmits the weight to the astragalus;  and from this
bone it is distributed to  the others, that compose the foot; but the
heel conveys the largest share.
  When the foot rests upon a flat surface, it is entirely passive: but
when it is upon a slippery soil, the flexors of the toes, especially of
the great toe, are firmly contracted, so as to  fix the  shoe, as far as
possible, and render the attitude more stable.   The use of shoes in-
terferes largely with the exercise of the toes, which, in the savage,
are capable of diversified and considerable action.
  The use of the fibula  is, to serve, as its name imports, the purpose
of a clasp.   The tibia  exerts its pressure chiefly towards the inner
part of the foot, and, consequently, were it not for the fibula, which
passes down below the  articulation,  dislocation outwards would  be
constantly menacing us.  The  fibula has no participation  in the
transmission of the weight to the ground.
  The conditions for equilibrium, as applicable to man, have been
already indicated.  If the base of sustentation  be rendered extensive
in any one direction, by widely separating the  feet,  the  attitude is
more firm in one direction, but less so in the other.   It is as firm as
possible in every direction, when the feet are turned forwards in a
parallel manner, and are separated by a space equal to the length of
one of them.
  Whatever diminishes the base of sustentation, diminishes, in like
proportion, the stability of the erect attitude.   Hence the difficulty
of walking on stilts or on wooden legs, on the toes, tight rope, &c.
  It seems, that the inhabitants of Les Landes,  in the south-west of
France, are enabled by  habit to use the stilts with singular facility.
The sandy plains,  that bear this name, afford tolerable pasturage for
sheep; but during one part of the year they are half covered with
water; and during the remainder, they are very unfit walking ground,
on account of the deep, loose sand and thick  furze. The  natives, in
consequence, habituate themselves to the  use  of stilts or wooden
poles,  which are put on and off as regularly as the  other parts  of
their dress.   With these they walk readily  over the loose sand or
through the water, with steps eight or ten feet long.
  Vol. I.                      44 
346                   MUSCULAR MOTION.
  The difficulty,  in this kind of progression, does not arise solely
from the smallness of the base of sustentation, but from the greater
height to which the centre of gravity is thrown, which renders the
equilibrium* unstable.
  Standing on one foot is necessarily more fatiguing, as it requires
the strong and sustained contraction of the muscles, which surround
the hip-joint, to keep the pelvis in equilibrium on the os femoris;
especially as the body has a strong tendency to fall to the side that
is unsupported.  The muscles, that prevent the trunk from falling
in  this direction, are the glutaei, the gemelli, the tensor  vaginae fe-
moris, the pyramidalis,  the  obturators and  the quadratus femoris.
The use of the neck  of  the thigh bone and of  the great  trochanter
is here manifest.
  The base of  sustentation,  in this case, is the space, occupied by
the foot in contact with the soil simply; and it need hardly  be said,
that if this be still farther diminished, by attempting to stand on the
toes, the attitude cannot be sustained.
  In the attitude on the knees, the centre  of gravity  is brought
lower, but the base  of  sustentation is  smaller than  on the feet.
The patella has to bear the chief pressure; and  as it is not pro-
vided with such a fatty cushion as exists at the sole of the foot, the
position becomes painful and the surface soon  abraded.  These re-
marks apply to the case, in which the knees only come in contact
with the soil.  When the feet are  allowed to touch by the points of
the toes, the attitude  is much more easy and firm, as  the base of
sustentation is largely augmented,—comprising the space between
the knees and toes plus the space  occupied by  those parts.
  The sitting posture admits of  variety,  and is easily intelligible.
In every variety in which the back is  unsupported, the weight of
the body is conveyed to the soil by the pelvis; and the broader this
base the firmer the attitude.
  When we sit upon  a  stool without any back, and  with the legs
raised from the ground, the whole of the weight is conveyed by the
parts  in contact with the seat; but if the feet touch the ground,  the
weight of the lower extremities is transmitted to the soil  by the feet,
whilst the pelvis  transmits that of the upper part of the body.   In
both these cases,  if the  attitude be long maintained,  fatigue is  felt
in the back, owing to the  continued action of  the extensor  muscles
in keeping the body  erect.
   Sitting in an ordinary chair differs somewhat, in part of the body
being supported.   Fatigue is then felt in the neck, which is unsup-
ported, and requires  the sustained contraction  of the extensor mus-
cles of the head.
   To support all the parts, as far  as possible, the long-backed chairs
have  been introduced, which sustain the whole body and head; and,
by being provided with rockers, a position approaching to the easiest
of all attitudes can be assumed. To produce a similar effect in a com-
mon  chair, the body  is often thrown back until the chair rests on its 
MOVEMENTS.                       347
 hinder legs only. When the feet of the individual are on the ground,
 this position is stable; the base of sustentation being large, and com-
 prised between the legs of the chair and the feet of the individual,
 added to the space occupied by the parts themselves, that are in con-
 tact with the soil; but as soon as he raises his feet, the equilibrium
 is destroyed from the impracticability of making the vertical line fall
 within the base of sustentation, which  is now reduced to the space
 occupied by the legs of the chair plus the space between  them.
   In all the varieties of the sitting posture, equilibrium is facilitated
 by  the centre of gravity being brought nearer to the ground.
   Lastly. The horizontal posture is the only one, that requires no
 muscular effort.  Hence it is  the attitude of repose and of the sick
 and the feeble.   The base of  sustentation is here extremely large;
 and the centre of gravity very low.  Accordingly, the attitude can
 be maintained for a long  time;  the only  inconvenience being, that
 which results to the skin from prolonged pressure  on those parts,
 that chiefly convey the weight to the bed,—as the back of the pelvis,
 the  region of the great trochanter, &c.—an  inconvenience, which
 attracts the attention of the physician, more or less, in all protracted
 and consuming maladies.
   The reason why we prefer soft,  elastic beds, is not simply to di-
 rectly prevent abrasion of those parts of the body, that are most ex-
 posed to  pressure, but  to  enable a greater portion of the body to
 transmit the weight; and thus to occasion a more equable partition
 of the pressure.
   There  are numerous other attitudes, that may  be  assumed; as
 that upon one knee, on the head, astride, &c.; but they do not merit
 explanation, their physiology being  obvious after what  has been
 said.

                     OF  THE MOVEMENTS.

   The movements, of which the  body is  susceptible, are of two
 kinds—the partial and locomotive; the  former simply  changing
 the  relative situation of parts  of the body; the latter the relation of
 the  whole body to the soil.
  • Many of the partial  movements constitute an inherent part of
 the  different functions, and are considered under those heads.
   In the  erect attitude, whilst the body holds the same correspon-
 dence with the soil, the position of the upper  parts of the body
 may be varied  in  all directions, provided  the  vertical line falls
 within the base of sustentation.   Accordingly, to  produce this ef-
 fect, if the upper part of the body be  inclined in one direction,  the
 lower  part will  have to be thrown more to the opposite.
   The head may be turned forwards, backwards,  or to one side;
 and  it  is capable of a rotatory motion to  the right  and left  The
three first movements occur  in the  articulation of the occipital
bone and atlas, when they are slight; but if to a greater extent, the 
348
MUSCULAR MOTION.
whole of the cervical vertebrae participate in them.   The rotatory
motion is effected essentially in the  articulation between the first
and  second vertebrae;  the latter of which has an arrangement ad-
mirably  adapting  it for  this purpose.   A tooth-like  or odontoid
process rises from  its anterior part, on which the posterior surface
of the anterior part of the atlas or first vertebra turns as on a pivot.
This arrangement has obtained  the second vertebra the name ver-
tebra'dent at a; and its  function, that of axis.  Rotation to the right
is effected by the contraction of the left sterno-mastoid and sple-
nius and of the right complexus, to the  left by the action of the
opposite  muscles of the same name.
  The motions of the head aid the senses of sight, hearing, and
smell; and are useful in the production of the different vocal tones,
by occasioning elongation or decurtation of the trachea and vocal
tube.  They are, likewise, inservient to expression.
  The spine, as a whole, and each of the vertebrae, composing it,
are capable of flexion, extension, lateral inclination, and circumduc-
tion.  These motions occur in the fibro-cartilages between the ver-
tebrae; and they are more easy and extensive, in proportion to the
thickness and width of the cartilages.  This is one cause, why the
motions of the cervical and lumbar  portions of the vertebral column
are freer than those of the dorsal.
  The intervertebral substances or fibro-cartilages possess a re-
markable degree of elasticity.   They yield, however, somewhat
to prolonged pressure; and  hence, after  long continuance  in the
erect attitude, our stature may be sensibly curtailed.  We can thus
understand, that at night we may be shorter than in the morning.
Buffon asserts, that the  son of one of his most zealous collabora-
teurs, M. Gueneau de Montbeillard,—a young man of  tall
stature,—lost an inch  and a half after having danced all  night.
The difference must, however, be partly ascribed to the condensa-
tion  of the adipous tissue beneath the foot.
  During the flexion of the spine, these cartilages are depressed on
the side  of the flexure, but they rise on the other; and, by their
elasticity, they are important agents in the restoration of the body
to the erect p'osition.  Where they are thickest the greatest extent
of motion is permitted, and  this is a cause, why the spine admits
of the greatest motion anteriorly. In rotation, the whole is pressed
upon and undergoes elongation in  the direction of its constituent
laminae.
  In old age, the cartilages  become shrivelled; and this, with the
loss of muscular power, is one of the causes why old people bend
forwards.
  When we assume different positions with the trunk, the centre
of motion of the vertebrae becomes  modified. If we bend forwards,
it is  thrown to the anterior part of the body of the vertebrae; if to
one side, to the articulating processes, &c.  Each vertebra, we have
seen, is a lever of the first  kind; and  as the centre of motion  be- 
LOCOMOTIVE MOVEMENTS.                349
comes altered the leverage must be so likewise.   It is when the
body has been bent forwards, and the object is to restore it to the
erect position, that the power acts with the greatest advantage:—
the fulcrum being thrown to  the anterior part of the body  of the
vertebra, and the arm of the power being the distance between this
point  and the extremity of the spinous process, into  which the
power is inserted.
   Each vertebra has but a slight degree of motion; but the sum of
all their motions is considerable; and is estimated by multiplying
the single motion by the number of vertebrae.  The result, how-
ever, can only be regarded as approximate, as the extent of motion,
of which the different vertebrae  are capable, is necessarily various.
   The arrangement of the spinous processes of the vertebrae—es-
pecially of the dorsal—prevents any considerable flexion  of the
body backwards: and when we find the tumbler bending his body
back until his  head touches his  heels, it is  owing to  the arrange-
ment of the  spines having been modified, in early life, by constant
efforts of this kind, until they are no longer obstacles to the move-
ment.
   The motions of the vertebrae are  frequently united to  those of
the pelvis on the thigh bones, when they seem to be more exten-
sive than they really are. This is the case, when we make a low bow.
   The motions of the spine are inservient to those of the head, and
of the superior and inferior extremities.
   The upper limbs are capable  of various motions: some of which
have been already described and others will be, hereafter.   They
are useful in the different attitudes; and at  times, by transmitting
to the soil a part of the weight of the body, and thus enlarging the
base of sustentation; as when  we employ a stick, rest on the hands
and knees; or support the head on one or both elbows.  They are
of great use, likewise, in preserving equilibrium when we walk
on a very narrow base; serving in part the purpose of  the pole,
employed by the dancer on the tight rope.
   The lower  extremities are, of course, locomotive organs; but
they  are susceptible  of partial  movements, likewise; as when we
kick  with one foot, try the  consistence of the  ground, cross the
legs, tread the foot-board of the lathe, &c.
   So much for the attitudes.  We shall now consider the mode in
which the relation of the body to the soil is altered, comprising the
physiology  of walking, leaping, running, swimming, flying,  &c.
which constitute the differentvarieties of locomotion or progression.

                  LOCOMOTIVE MOVEMENTS.

                          Walking.

   Walking is a motion on  a  fixed surface, the centre of gravity
being alternately moved by one  of the extremities and sustained by 
350                   muscular motion.
 the other, without the latter being, at any time, completely off the
 ground.  It consists of a succession of steps, which are effected—in
 the erect attitude and on a horizontal surface—by bending one of
 the thighs upon the pelvis and the leg upon the thigh, so as to de-
 tach the foot from the ground by the general decurtation of the
 limb. The flexion of the limb is succeeded by its  being carried for-
 ward; the heel is then  brought  to  the  ground, and, successively,
 the whole of the inferior surface of the foot. If  the bones of the
                                leg were perpendicular to the
            Fig. 74.             part  which  first   touches the
                                ground, we should experience a
                                considerable jolt, but, instead of
                                that, the foot descends in an arc
                                of a circle, the centre of which is
                                the point of the  heel.
                                  In order that  the limb shall be
                                thus carried forward,  the pelvis
                                must have described a movement
                                of rotation, on  the head of the
 thigh bone of the limb, which has not been moved; and have car-
 ried forward the corresponding side of the body.   As yet, only one
 limb has advanced. The  base, of sustentation has been modified,
 but there has been no  progression.  The limb, remaining behind,
 has now to be raised and brought forward, so as to pass  the other,
 or to be on the  same line with  it, as the case  may be; and this
 finishes the step.   In order to bring up the limb, which is behind,
 the foot must be successively detached from the soil, from the heel
 to the toe.  In  this way, an elongation  of the limb  is  produced,
 which assists in advancing the corresponding side of the trunk, and
 excites the rotation of  the pelvis on the head of  the  thigh bone,
 first carried forward. A succession of these movements constitutes
 walking; the essence of which consists in the heads of the thigh
 bones forming fixed points, on which the pelvis turns alternately,
 as upon a pivot, describing arcs of circles, which are more extensive
 in proportion to the size of the steps.
  Walking in a straight line requires, that the arcs of circles, de-
 scribed  by the pelvis, and the extension of the limbs, when carried
 forward, shall be equal;  otherwise the body will  be directed to-
 wards the side opposite to that of the limb, whose movements are
 more extensive.   Without the aid of vision, it would be impracti-
 cable for us to make the arcs  equal; or, in  other words, to walk
 straight forward.
  Walking backwards  differs  somewhat from this.  The step is
 commenced by bending the thigh upon the pelvis, and, at the same
time, the leg upon the thigh.   The extension of the thigh on the
pelvis succeeds, and the whole limb is carried backwards, the leg is
afterwards extended upon the thigh, the point of the foot is brought
to the ground, and the remainder of its under surface in succession.
 
walking.
351
The other foot is then raised on its point, by which the correspond-
ing limb is elongated; the pelvis, being pushed backwards, makes
a rotation on the limb which is behind, and is, by the action of ap-
propriate muscles, carried on a level with, or behind the other, to
afford a new pivot in its turn.
  Walking  laterally is different from the two  last in  no arcs
being described. In this case, one of the thighs is  first slightly bent
upon the pelvis, in order to detach the foot from  the ground; the
whole limb  is then moved away by the action of the abductors, and
is brought down to the ground.  The other limb follows.
  If we walk up hill, the fatigue is much augmented; because the
flexion of the limb, first carried forward, has to be more considera-
ble; and the limb, that remains behind, has not only to cause the
pelvis to execute the movement of rotation, but it has to raise the
whole weight of the body, in order  to transport it upon the limb,
which is in advance.  To aid in throwing the weight  anteriorly,
the body is bent forward, so that the  centre of gravity  may be as
favourably disposed as possible; and  the extensor muscles  of the
leg carried forward, are powerfully contracted to  raise the  trunk;
hence, the feeling of fatigue,  which we experience in the knee and
anterior part of the thigh, on ascending a long flight  of stairs.  Fa-
tigue is likewise felt in the calf of the leg, on account of the strong
efforts developed in  extending the foot, and projecting the body
forwards.
   Walking down hill is, also, more fatiguing than on the level
ground.  In this case, there is a tendency in the  body to fall for-
wards;  great effort is, consequently, required to keep the vertical
line within  the  base of sustentation, and, accordingly, the muscles,
employed in the extension of the head and vertebral column, expe-
rience fatigue.
   In all these kinds of progression,  the character of the soil is  a
matter  of importance.  It must be firm enough to afford a support
to the limb, that presses upon it, otherwise fatigue is experienced,
and progression is slow and laborious.  This occurs, whenever the
soil is too soft or too smooth: the former yielding to the foot, and
the latter presenting no inequalities, by which the  foot can attach
itself.  The soil, too, has  some  influence, in particular  cases, by
virtue of its elasticity.   Such, at least, is the opinion of Borelli;
but Barthez thinks, that the influence of the soil is limited to the
 degree in which it furnishes a firm support.   If  the soil, again, be
 movable, as the deck of a vessel, the line of gravity is apt to fall
 outside the base of sustentation; and, to avoid this, the  base of sus-
 tentation is enlarged by separating the legs;—so as to give a charac-
 teristic air to the gait of the mariner;—and, lastly,  if the base be
very narrow, as on the tight rope, the steps are obliged to be rapid,
 and the arms are aided—in modifying  the centre of gravity, as
 may be required—by the use of a long and heavy pole. 
352                   muscular motion.
                          Leaping.

  In the action of leaping, the whole body is raised from the ground;
and is, for a short period, suspended in the air.   It consists, essen-
tially, in the sudden extension of the limbs, after they have under-
gone an unusual degree of flexion.   Leaping may be  effected di-
rectly upwards, forwards, backwards, or laterally.
  In the ordinary case of the  vertical leap, the head is slightly bent
on the neck;  the vertebral column  is curved  forwards; the pelvis
is bent upon the thigh ;  the thigh upon the leg; and the  leg upon
the foot; the  heel generally pressing but lightly on the soil, or not
touching it at all. This state of general flexion is suddenly succeeded
by a quick extension of all the bent joints;  so  that the  different
parts of the body are rapidly elevated, with a force surpassing their
own gravity,  and  to an extent dependent upon the force developed.
  In this general  muscular movement, the muscles, that form the
calf of the leg, and are inserted into the heel, have to develope the
greatest force, inasmuch as they have to raise the whole body, and
to give it the impulse, that surmounts its gravity.  They are, how-
ever, favourably circumstanced for the purpose; being remarkably
strong; inserted perpendicularly into the heel;  and having the ad-
vantage of a long arm of a lever.
  Figure 71 will show, that whenever the body is bent in the po-
sition it assumes preliminary  to a leap, opposite impulses must be
communicated, by the restoration of the different parts to the verti-
cal line B  F.   The leg B will tend to  impel  the body backwards,
by following  the curved line C G.   CD, on the  other hand, by de-
scribing the curve D I, will tend to impel it forward;  whilst the
head and trunk, represented by the line D E, will describe the curve
E F, and give an impulse backwards.   Every vertical leap must,
therefore,  be  a mean between  these different impulses, or rather the
backward  and forward  impulses must destroy  or neutralize  each
other; and that which is concerned in the elevation of the trunk be
alone effective.
  In the forward leap, the movement of rotation of  the thigh pre-
dominates over the impulses backward, and the body is projected
forward. On  the other hand,  the impulses  of the vertebral column,
and of the leg on the foot prevail, in the backward leap. The length
of the lower limbs is favourable to the extent of the leap.  The for-
ward leap, in particular, is greatly dependent upon the length of the
femur, the part in which the forward impulse is situated.
  It does  not appear, that any kind of impulse is communicated to
the body by the surface on which we rest, at the moment of leaping,
unless it be very elastic.  In  this last case, however, its reaction is
added to the effort of the muscles, that occasion the elevation of the
body;  hence, the  wonderful leaps of the performers in our circuses
and on the tight rope.   On the other hand, if the soil do not afford 
RUNNING.                       353
the necessary resistance, and yields to the feet, leaping is almost or
wholly impracticable.
  The upper extremities are not without their use in leaping. They
are brought close to the body, whilst the joints are bent, and are
separated from it, at the moment when the body leaves the soil.  By
being held firmly in this manner, they allow the muscles, that pass
from the os humeri to the trunk, to exert a degree of  traction up-
wards, and thus to assist the extensors of the foot  in the projection
of the body.   It is with this view that the ancients employed their
halteres or poisers in leaping; and the moderns use bricks, stones,
or other solid, heavy bodies, with a like  intent.   It  is, likewise,
manifest, that by steadying  the  arms,  and then moving them ra-
pidly backwards, a backward impulse may be given to the upper
part of the trunk.
  The effect of a run, before we leap, is to add to the force, deve-
loped by muscular contraction, that of the impulse acquired by the
body whilst running.   The  leap is, under such circumstances, ne-
cessarily more extensive.
  Some of the smaller animals surprise us by  the extent of their
leap. The jumping maggot, found in cheese, erects itself upon its
anus, forms its body into a circle, by bringing its head  and tail into
contact, and, having  contracted every part as much as possible, it
unbends with a sudden jerk, and darts  forward to an astonishing
distance. Small animals, indeed, leap much farther than the larger,
in proportion to their size; and we perhaps know of  none, whose
muscular strength, in this way, can be put in competition with that
of the  flea, which, on a moderate computation, leaps  to a distance
of at least two hundred times its own length.

                           Running.

   This variety of progression consists of a series of low leaps,  per-
formed by each leg in alternation.  It  differs from walking in the
body being projected forward at each step, and in  the hind foot be-
ing raised before the fore-foot touches the ground. It is more rapid
than the quickest walk, because the acquired velocity is preserved
and increased, at each bound, by a new velocity.  Running, there-
fore, cannot be instantaneously suspended, although a stop may be
put to walking at any moment.
   In running, the body is inclined forward, in order that the centre
of gravity may be in a proper position for receiving an impulse, in
that direction, from the hind leg; and the fore leg is rapidly advanced,
to keep the vertical line within the base of sustentation; and thus to
prevent the body from falling.  There is, consequently, in running,
a moment in which the body is suspended in the air.
Vol.  I.
45 
354
MUSCULAR MOTION.
                         Swimming.

  Although Magendie affirms that the human body is, in general,
specifically heavier than water, and that, consequently, if left to it-
self in a considerable quantity of that fluid, it would tend to sink to
its lowest portion, the question respecting the specific  gravity of
the human body has not been rigorously determined;  and many
eminent practical philosophers have even held an opinion the reverse
of that of Magendie.  Borelli accords with him; and a writer of
a later period—Mr. Robertson; who details a set of experiments,
on this subject, in the fiftieth volume of the Philosophical Trans-
actions,—seems to  have originally coincided with  him also.   He
weighed, however,  ten different individuals in water, comparing
their weight with that of  the fluid, displaced by their bodies; and
he affirms, that, with the exception of two, every man was lighter
than his equal bulk of fresh water, and much more so than his equal
bulk of sea water;—" consequently," he says, " could persons, who
fall into water, have presence of mind enough to avoid the fright,
usual on such accidents, many might be preserved from drowning."
In corroboration of this inference, Mr. Robertson relates a circum-
stance connected with his own personal knowledge. A young gen-
tleman thirteen years of age, little acquainted with swimming, fell
overboard from a vessel in a stormy sea; but having had presence
of mind enough to turn immediately upon his back, he remained a
full half hour, quietly floating on the surface of the water,  until a
boat was lowered from the vessel.  He had used the precaution to
retain his breath, whenever a wave broke over him, until he again
emerged.
  A case  is given in the Rev. Mr. Maude's  Visit  to Niagara3
in 1800, which is strikingly corroborative of  Mr. Robertson's
view of this matter.  The author  was on  board a sloop on Lake
Champlain, when a boy, named Catlin, who was on deck  cutting
bread and cheese with a knife, was knocked overboard by the cap-
tain jibbing the boom. He missed  catching hold of the canoe, which
was dragging astern, and an attempt  of Mr. Maude's  servant to
untie or cut the rope, which fastened it, that  it  might drift to his
assistance, also failed.  Catlin was known to be unable to swim.
It was in the night and very dark, and it  was with difficulty, that
the captain, who considered that there was no  hope of saving his
life, was at last prevailed upon to  go in the canoe to attempt it.  He
succeeded, however, in picking the boy up, and brought  him on
board again in about a quarter of  an  hour.  "Catlin's relation,"
proceeds Mr. Maude, "almost exceeds probability. He had heard
my exclamation to seize the canoe, which he was on the  point of
doing, when it gave a sudden swing and baffled him ; but, finding
he could support  his head above  water, he dismissed all fear, ex-
pecting that the canoe would come every moment to his assistance. 
SWIMMING.
355
When he no longer heard our cheers from the sloop, hope began to
fail him, and he was on the point of resigning himself to a watery
grave, when he heard the captain's life-restoring voice.  On telling
Catlin that we despaired of his  safety, as we understood that he
could not swim, he replied, • nor can I.  I was never before out of
my depth ; but I am fond of bathing, and have often seen lads what
they call tread the water, and that's what I did.'  The truth of this
account was made  manifest, by the boy not  only retaining his hat
on his head, but its  being perfectly dry ; and what adds to the
singularity of this  event, the  boy never quitted his grasp of the
knife, that he was  eating his bread and cheese with."
  Knight Spencer found, that he was buoyant on  the surface of
the sea, when he held  stones, weighing six pounds avoirdupois in
his hands.  In the  water, however, the stones lost two pounds five
ounces in weight, so that he was really freighted with no more than
three pounds eleven ounces.  He himself weighed one hundred and
thirty pounds.
  Dr. Franklin, again, whilst he considers the detached members
of the body, and particular^ the head, as of greater weight than
their bulk of water, acknowledges the body, in the aggregate, to be
of less specific gravity, by reason of the hollowness of the trunk.
He thinks, that a body, immersed in water, would sink up to the
eyes, but that if the head were inclined back, so as to be supported
by the water, the mouth and nostrils would remain above;  the body
rising one inch at  every inspiration, arid sinking one inch at every
expiration ; and also, that clothes give little additional weight in the
water, although, in stepping out of it, the case is  quite otherwise.
If a person, therefore, could avoid struggling and plunging, he con-
cludes, that he might remain in the posture described with safety.
That the body is to a certain degree buoyant he refers to the expe-
rience of every one, who has ever attempted to reach the bottom of
deep water, the effort required sufficiently proving,  that something
resists our sinking.
  The truth would appear to be, that there is only a slight differ-
ence between the specific  gravity of the human body and that of
water; but that  the  former is something  greater, otherwise  there
would be no reason, why the dead body should sink to the bottom,
as it is known to do.   The old notion was, that, in the living state,
the specific gravity of the body is decidedly less; but that, in death
from  drowning, a  quantity of water always enters  the  lungs and
stomach, and that thus, these cavities, being no longer occupied with
air, the buoyancy  is lost and the body sinks. Nothing is now better
established than that no water gets into the stomach, except what is
accidentally swallowed during the struggling, and, that  no  water
must be looked for in the lungs; a quantity of frothy mucus being all
that is generally perceptible there.  Yet, in courts of justice, the ab-
sence of water, in  these situations, has been looked upon as  evi-
dence,—where a  body has  been found in  the water,—that  death
has not occurred from drowning; and attention has, consequently, 
356                 MUSCULAR MOTION.
been  directed to  other causes, which could have produced it; the
presumption being, that the person had been first killed and then
thrown into the water for the purpose of averting suspicion.
  Another erroneous opinion, at one time prevalent, was, that if a
person goes alive into water he will sink, if dead he will swim; and
that, therefore, it is necessary, that some weight should be attached
to a body, when committed to the deep, to make it sink.
  All these fallacious notions are dwelt upon in a case, deeply in-
teresting to all jurists, medical and  others;—that of Spencer Cow-
per, Esq. a member of the English bar, who, with three other in-
dividuals, was tried at the Hertford Assizes, in 1699, for the murder
of Mrs. Sarah Stout.   The speeches of the counsel, with the evi-
dence of many of the medical witnesses, sufficiently testify the low
condition of medico-legal knowledge at that period.
  Mr. Jones,—the counsel for the prosecution—affirmed, that" when
her (Mrs. Stout's) body came to be viewed, it was very much wonder-
ed at; for, in the first place, it is contrary to nature, that any persons,
that drown themselves, should float upon the water.  We have suf-
ficient evidence,"  he adds, " that it is a thing that never was; if
persons go  alive into the water, then they sink;  if dead, then they
swim."  In confirmation of this strange opinion, two seamen were
examined, one of whom deposed as follows:—" In the  year  89 or
90,  in Beachy fight, I saw several thrown  overboard, during the
engagement, but one particularly I took notice of, that was my friend
and killed by my  side.  I saw him  swim for a considerable distance
from the ship, &c.  Likewise in another engagement where a man
had both his legs shot off and died instantly, they threw over his
legs; though they sunk, I saw his body float; likewise I have seen
several men, who  have  died natural deaths at sea; they have, when
they have been dead, had a considerable weight of ballast made fast
to them and so were thrown overboard; because we hold it for a
general rule,  that all men swim if they be dead before they come
into the water; and, on the contrary, I have seen men  when they
have been drowned, that they have sunk as  soon as the breath is
out of their bodies," &c.   The weights are, however,  attached to
the dead, when they are thrown into the sea, not for the purpose of
facilitating  their descent, but to prevent  them from rising, when
putrefaction renders them buoyant, by the disengagement  of air
into the splanchnic cavities.
  On the same trial, Drs. Coatsworth, Burnet, Nailor, and
Woodhouse  deposed, that when a person is drowned, water  will
be taken into the stomach and lungs, and as none was found, in the
case of Mrs.  Stout, they were of opinion, that she came to her
death by other means.
  From all that has been  said, it would appear, that the great re-
quisite for  safety to the inexperienced, who may fall accidentally
into the water, is a firm and sufficient conviction of the fact, that
the living body naturally floats, or that it can be easily made to do
so.   This conviction being acquired, no more than a common share 
flying.                        357
of presence of mind would seem to be necessary to insure that that
portion of the body, which  is the great outlet of the respiratory
organs, shall be above the surface.
  The movements, adapted  to the progression of the body, are to
be acquired in the same manner  as a child learns to walk;—profi-
ciency in this, as in every thing else, being the result of practice.
  Swimming nearly resembles leaping, except that  the leap in it
does not take place from a fixed surface.  Both the upper and lower
extremities participate  in it.  Whilst the former are brought to a
point anterior to the head, and form a kind of cut-water, the lower
extremities are  drawn .up  and suddenly extended, as in  leaping.
The water, of course, yields to their impulse, but not as rapidly as
it is struck, and hence the body is projected forwards.  The upper
limbs are now separated, and carried circularly and forcibly round
to the sides of the body; by  which the impulse is maintained: the
legs are, in the mean time, drawn up; and, by a succession of these
movements, progression is effected;  in all of which, the hands and
feet are turned outwards to  present as large a resisting surface as
possible.   The chest is, at the same time, kept dilated, to augment
the bulk of the body, arid, of course, to render it specifically lighter;
and the head is  raised above the surface to admit of respiration.
This action is analogous to that of the propulsion of a boat by oars.
The body resembles the boat; and the upper and lower extremi-
ties are the oars or sculls.
  The practised swimmer can execute almost as many movements
in the water as he can on land.

                           Flying.

  If the human body sinks in water, how little can it be susceptible
of suspension in the air by its own unassisted  muscular powers.  It
is a mode of progression, which is denied to man; and, accordingly,
most of the attempts at flying, since the mythical exploits of D^jdalus
and Icarus, have been confined to enabling the body to move from
one place to another, by means of ropes and appropriate adjuncts.
Not many years ago, a native of this country exhibited a curious
variety of progression, at Dover, England.   He was called the
"flying phenomenon:" and his plan, so far as we can recollect,
was to have a rope extending from the heights to the beach beneath,
along which he  descended, by means  of rings, attached  to differ-
ent parts  of his  person, and which had the rope passing through
them.
  The sources of difficulty, in this mode of progression, are;—the
great weight of  the  body,  and the insufficient force, which the
muscles are capable of exerting.  It is by no means impossible, how-
ever, that by some contrivance, of which the lightest gases might
form a part; and by an imponderous apparatus, which would enlarge
the surface of the upper extremities, progression, in this  manner,
might be effected;—but to a limited and unmanageable extent, only. 
358                   MUSCULAR  MOTION.
  Connected with this subject, we may refer, briefly, to some va-
rieties of muscular action, the nature of which will be easily intel-
ligible.
  In  bearing a load, we have simply a variety of walking in the
erect  attitude, with this addition, that the extensor muscles of the
head, neck, or back,—according to the part on which  the  burden
may be placed,—have to contract forcibly to support it.
  The position of the individual has, also, to be so regulated, that
the centre of gravity shall be always over the base of sustentation.
Hence, if the load be on his back, he leans forward; if borne before
him, he leans backward; and this is the causae of the portly and con-
sequential appearance of the corpulent.   If the load be on his head,
he stands as upright as possible, for a like reason.
  In propelling a body forwards, either by the hands or shoulders,
the feet are  firmly fixed on  the ground;  the limbs are in a state
of semi-flexion, and the centre of gravity is directed forwards, so
as to aid the force that has  to be developed  by the muscles.  The
limbs are then suddenly extended, the body is thrown forward, and
the whole power exerted on the obstacle which has to be moved.
  On the other hand,  when we drag a weight after us, or attempt
to dislodge a stake, for example, from the earth; the feet are equally
fixed firmly  on the ground: but the body is in a state of extension,
and is directed as  far as practicable  backwards, in order that the
tendency to fall, owing to the centre  of gravity overhanging the
base of sustentation, may aid the force that has to be  developed by
the muscles of the arms, which embrace the substance to be moved,
or are attached  to it  indirectly.  The flexor  muscles are, then,
powerfully contracted, and the whole force is exerted upon the object.
  As, in both these cases, there is danger of falling should the body
yield  suddenly, the feet are so placed as to obviate  this, as far as
possible; by being separated in the direction in which the force is
exerted.
  Squeezing consists in laying hold of the object, either between
the arms and body, or by the fingers; and then forcibly contracting
the flexor muscles.
  In all these, and  other varieties of strong muscular contraction,
the respiration is interrupted, in order that the thorax may be ren-
dered  fixed, and serve  as  an immovable point of origin  for the
muscles of the head, shoulders, and arms.  This is effected by taking
in a full inspiration; strongly contracting the respiratory muscles;
and, at the same time, clpsing the glottis  to prevent the  exit of
the air.
  Lastly, as organs of prehension, the upper extremities are of ad-
mirable organization; possessing great mobility;  and, at the same
time,  solidity.  The joint at  the  shoulder allows of extensive mo-
tion ;  and the bones,  to which the arm is attached at this joint,—
as the scapula and clavicle—are themselves movable.   The  fore-
arm is, likewise, susceptible  of various movements on the  arm,
of which those of pronation and supination are not the least impor- 
EXPRESSION.                      359.
tant; whilst the hand possesses every requisite for an organ of pre-
hension.   It is composed of numerous bones, and is capable of being
applied to the most irregular surfaces.   The great superiority of
the human hand arises, however, from the size and strength of the
thumb, which can be brought into a state of opposition to the fingers;
and is, therefore, of the highest use in enabling us to seize hold of,
and grasp spherical  bodies;  to take  up any object; to take a firm
hold of whatever we seize, and to execute  the various useful, and
ornamental processes of the arts.  These processes require the most
accurate, quick, and combined movements  of the muscles.   How
quick, for  example, is  the motion of the hand  in writing, and in
executing the  most rapid movements on the piano-forte!  How ac-
curate the muscular contraction, which stops the precise part of
the violin-string to  bring out the note or  semi-tone  in the most
allegro movements; and what a multitude of combinations must be
invoked in all these cases!
   As an organ of touch, the advantages of the upper extremity have
already been depicted;  and  much, of what was then  said, applies
to it as an organ of prehension.
   " In this double  respect," observes Adelon, " man is the  best
provided  of all animals. How much, in fact, does he stand in need of
an ingenious instrument of prehension!  As we have several times re-
marked, he has, in his organization, neither the offensive nor de-
fensive arms, that are  bestowed on other  animals.   Naked  from
birth, and exposed to the inclemencies of the atmosphere, without
means of attack or defence against animals, he must incessantly la-
bour  to  procure what  he  requires.  It was not, consequently,
enough that he should possess an intellect,  capable of making him
acquainted with, and of appropriating to  himself, the universe. He
must have an  instrument adapted for the execution of all  that his
intellect conceives.  Such instrument is his upper extremity.  In
short, whilst other animals find every thing in nature—necessary for
their different wants—more or less prepared, man, alone, is obliged
 to labour to  procure  what his  require.   He must make himself
 clothes, construct his habitations, and prepare his food.  He is the
 labouring and producing  animal,par  excellence; and hence he
 needs not only an intellect to conceive, but an  instrument to  exe-
 cute."

       OF THE FUNCTION OF EXPRESSION OR OF  LANGUAGE.

   Under this head will be included those varieties of muscular con-
 traction,  by which man and animals exhibit the feelings that im-
 press them, and communicate the  knowledge  of such feelings to
 each other.
   It comprises two different sets  of actions:—those that  are ad-
 dressed to the ear,  or  the phenomena of voice: and those that are
 appreciated by the senses of sight and touch, or the gestures.  Of
 these we shall treat consecutively. 
360
MUSCULAR MOTION.—EXPRESSION.
                        OF THE VOICE.

   By the term voice—or by phonation, which has been proposed by
Chaussier,—is meant the sound produced in the larynx, whilst the
air is  passing  through  it, either  to  enter,  or issue  from, the
trachea.

              Anatomy of the Vocal Apparatus.

   The apparatus concerned in the production of the voice, is com-
posed, in man, of the muscles concerned in respiration; of the larynx;
and of the mouth and nasal fossae.   The first are merely agents  for
propelling the air through the instrument of voice.  They will fall
under  consideration when we are  on the subject of respiration;
whilst the anatomy of the mouth and nasal fossae have been, or will
have to be, described in other places.  The larynx, and its primary
dependencies, which are immediately concerned in the production
of voice, will, therefore, alone engage us at present
   The larynx is situated at the anterior part of the neck, and forms
the projection so perceptible in that of the adult male, calledpomum
Adami.
   An attentive examination of the various parts that compose it, so
far as they concern its physiological relations, will be  necessary;
and it will exhibit the imperfect knowledge of several writers  on
the voice, and the false and insufficient views that have been en-
tertained on this subject.
   If we look along the larynx from the trachea, of which it is a
continuation, we  find  that the tube becomes gradually  narrower
from side to side; and, at length, presents an oblong cleft, called the
glottis, the sides  of which are the essential organ of voice.
   The larynx is composed of four cartilages—the cricoid, thyroid,
and two arytenoid.  The cricoid is  the lowest of these,  and  is the
inferior part of the organ;—that by which it joins the trachea.  It
is shaped like a ring, whence its name, but is  much deeper behind
than before. The thyroid is situated above the cricoid, with which
it is articulated in a movable manner, by means of its inferior cor-
nua.  It is the large cartilage that occupies the anterior, prominent,
and lateral part of the larynx.
   The arytenoid cartilages are two in number.  They are  much
smaller than the others, and are  articulated with the posterior part
of the cricoid;—also, in a movable manner.   Around this articula-
tion is a synovial capsule,—close  before and behind, but loose within
and without.  Before it, is the  thyro-arytenoid ligament; and, be-
hind, a strong, ligamentous fascia, called, by Magendie, from  its
attachments—crico-ary tenoid.   The arrangement of this articula-
tion would appear to permit only of lateral movements of the ary-
tenoid  cartilages on the cricoid; all motion anteriorly or posteriorly,
or in any other direction, being  impracticable.  The joint, conse-
quently, must be a lateral ginglymus. 
VOCAL APPARATUS.                   361
  Three fibro-cartilages, likewise, form part of the constituents  of
the larynx.   These are the epi-
glottis,  and two small bodies,             FlS-  '5-
that tip the arytenoid cartilages,
and are met with only in man—
the capitula Santorini, or the
supra-arytenoid cartilages, or
the capitula cartilaginum ary-
tenoidarum.
  On examining the interior of
the larynx, wediscover that there
are two  clefts,—one above the
other;  the   uppermost  being
usually  oblong-shaped,  ten or
eleven lines long, and two or
three  broad, having the shape of
a triangle, the base of which is
forwards.  It is circumscribed,
anteriorly, by the thyroid car-
tilage and epiglottis; posteriorly,
by the arytenoid cartilages; and,
laterally, by two  folds of the
mucous  membrane,  C  C, Fig.
77, which pass from  the epi-
glottis to each arytenoid carti-
lage,  and are called the superior
ligaments of  the glottis, and
the superior vocal cords.  A
few lines below this is a second
cleft, also oblong from before to
behind, (No. 4, Fig. 76,) and of
a triangular  shape,  the  base
of which  is  behind.   It is
bounded,  anteriorly,  by  the
thyroid  cartilage;  posteriorly,
by a  muscle extending from one
arytenoid cartilage to the other
—the arytenoideus;  and, late-
rally, by two  folds,  formed of
the  thyro-arytenoid   ligament,
passing  from the anterior part
of the arytenoid cartilage to the
posterior part  of the  thyroid,
and  of  a muscle  of the  same
name.   These  folds are called  the inferior ligaments or lips of
the glottis, or  the inferior vocal cords.   They are represented by
Nos.  3, 3, in Fig. 76; and by B B,  Fig. 77.
   Vol. I.                      46
 
362            MUSCULAR MOTION.—EXPRESSION-
  Between these two clefts are the sinuses or ventricles of the la-
                    rynx, V V, Fig. 77.  The inferior, exterior
                    and superior sides of these are formed by the
                    thyro-arytenoid muscle. By means  of these
                    ligaments—superior and inferior,—the lips of
                    the superior and inferior apertures  are per-
                    fectly free, and unencumbered in their action.
                       Anatomical descriptions will  be found to
                    give different significations to the word glot-
                    tis.  Some have applied it to the upper cleft,
                    some to the lower; some, again, to the ven-
                    tricles of the larynx; and others  to the whole
                    space, comprised between the inferior  liga-
                    ments and the top of the larynx.  It is now,
                    generally perhaps, restricted to the part of the
                    larynx engaged in the production of voice,
                    or usually considered to be so engaged—the
                  W\ space between the inferior ligaments with the
                  1= ligaments themselves—and  in this significa-
                    tion it will be employed by us.
  The mucous membrane,  which  lines the larynx, is continuous,
above, with that of the mouth; below, with that of the trachea.  It
contains several mucous follicles, some of which are agglomerated
near the superior ligaments of the  glottis and the environs of the
ventricles of the larynx, seeming to constitute distinct organs, which
have been called arytenoid glands. A similar groupe exists between
the epiglottis behind, and the os hyoides and thyroid  cartilage be-
fore, which has been termed the epiglottic gland. The uses of this
body are not clear.  Magendie conceives, that it favours  the fre-
quent slidings of the thyroid cartilage over the posterior surface of
the os hyoides; that it  keeps the epiglottis separated above from
this  bone;  and, at  the  same  time, furnishes it a very elastic sup-
port, which may aid it in the functions it has to execute, connected
with voice and deglutition.
  The larynx is capable of being  moved  as a whole,  as well as in
its component cartilages.   It may be  raised,  depressed, or carried
forwards or backwards.   The movements, however, which are the
most concerned in the production of the voice, are such as are effect-
ed by the action  of the intrinsic muscles, as they have been termed.
These are, 1st.  The crico-thyroid, a thin,  quadrilateral  muscle,
which, as its name imports, passes obliquely from the upper margin
of the cricoid cartilage to the lower one of the thyroid. Magendie
affirms, that its use is not, as generally imagined, to depress the thy-
roid on the cricoid, but to elevate the cricoid and approximate it to
the thyroid, and even to  make it  pass slightly under its  inferior
margin.  2dly. The crico-arytenoidei postici and the crico-aryte-
noidei laterales; the former of which pass from the posterior surface
of the cricoid to the base of the arytenoid; and the latter from the side 
VOICE.                         363
of the cricoid to the base of the arytenoid cartilage.  The use of these
muscles is to carry the arytenoid cartilages backwards, separating
them at the same time from each other.( 3dly. The arytenoid muscle
—of which there is one only.  It extends across from one arytenoid
cartilage to the other; and, by its contraction, brings them towards
each other.  4thly. The thyro-arytenoid muscle, which, according
to Magendie, is the most important to be known of all  the mus-
cles of the larynx, as  its vibrations produce the vocal sound.   It
forms the lips of the glottis, and Magendie describes it as  consti-
tuting, also, "the inferior, superior, and lateral parietes of the ven-
tricles of the larynx."  Generally, it is considered to arise from the
posterior surface of the thyroid cartilage, and the ligament connect-
ing it with the cricoid, and to  be inserted into the anterior edge of
the arytenoid cartilage. Lastly.  The muscles of the epiglottis—the
thyro-epiglotticus and aryteno-epiglotticus, and  some fibres that
may be looked upon as the vestige of the glotto-epiglotticus, which
exists in many animals.  These muscles,—the position of which is
indicated by the name,—by their contraction, modify the situation
of the epiglottis.
   The intrinsic muscles  of the larynx receive their nervous influ-
ence from the eighth pair.  Shortly after this nerve has issued from
the cranium  it gives off a branch  called the superior laryngeal,
which is distributed exclusively to the arytenoid  and crico-thyroid
muscles; and, after its entrance into the thorax, it furnishes a second,
which ascends towards the larynx,  and is, on  that account, called
the recurrent or inferior laryngeal. It is distributed, exclusively,
to the crico-arytenoidei postici and crico-arytenoidei laterales,  and
to the thyro-arytenoid muscles.
   In each animal species, the glottis has a construction, correspond-
ing to the kind of voice, that has to be elicited; and, when it is ex-
amined on a living animal—on  dogs  for example—it enlarges and
contracts alternately, the arytenoid cartilages separating  when the
air enters the lungs, and  approximating during expiration.
   To the trachea the larynx  is attached by a fibrous membrane,
which unites the cricoid with the first ring of the trachea; and, above,
it is connected with the  os hyoides by a similar membrane—the
hyo-thyroid, No. 5, Fig. 75, as well as by the thyro-hyoid muscle.

                    Physiology of the  Voice.

   The production of the voice requires, that air shall be sent from'
the  lungs, which, in passing  through the glottis, throws  certain
parts into vibration, and  afterwards makes its exit by the vocal tube,
—that is, by the mouth and nasal fossae.
   Simple expiration does not, however,  produce it, otherwise we
should have the vocal sound accompanying each contraction of the
chest.   Volition  is necessary  to excite the requisite action of the
muscles of the larynx; as well as of those of respiration; and by it
the tone  and intensity of the voice are variously modified. 
364
MUSCULAR  MOTION.—EXPRESSION.
  That the voice is produced  in the larynx, we have both direct
and indirect testimony.  An aperture, made in the trachea, beneath
the larynx, deprives both man and animals of voice.  This occurs
also, if the aperture be made in the larynx  beneath the inferior li-
gaments;  but if made above the  glottis, so  as to implicate the epi-
glottis and its muscles,  the superior  ligaments of  the glottis, and
even the upper portions of the arytenoid cartilages, the voice con-
tinues.  Magendie and J. Cloquet refer to the cases of  two men,
who had fistulae  in the trachea; and who were unable  to speak un-
less the fistulous openings were accurately stopped  by  some mecha-
nical means.
  If, again, we take the  trachea and larynx  of an animal or of man,
and blow air forcibly into the tracheal extremity towards the larynx,
no sound is produced, except what results from the friction of the
air against the sides  of the larynx.   But  if we approximate the
arytenoid cartilages, so  that they  touch at their inner surfaces, a
sound will be elicited, bearing some resemblance to the voice of the
animal to which the larynx belongs; the sound being acute or grave
according as the cartilages are pressed against each other with more
or less force; and varying in  intensity, according to the  degree of
force with which the air is sent through it.  In this  experiment, the
inferior ligaments can be seen  to vibrate. Paralysis of the intrinsic
muscles of the larynx likewise produces dumbness; and this can be
effected artificially.   Much discussion, at one time, prevailed re-
garding the effect of tying or cutting the nerves distributed to these
muscles.  The experiments of Haighton induced him to think,
that the recurrent branches of the  par vagum supply  parts, which
are essentially necessary to  the formation  of the voice; whilst the
laryngeal branches seemed to him to affect only its modulation or tone.
Subsequent experiments have sufficiently shown,  that if both the
recurrent nerves and the superior laryngeal are divided, complete
aphonia must result.  Magendie found,  indeed, that when both re-
currents,—which, as has been remarked,  are  distributed to the thyro-
arytenoid muscles,—are cut, the voice is usually lost;  whilst if one
only be divided, the voice is but half destroyed.  He noticed, how-
ever, that several animals, in  which the recurrents had  been cut,
were still capable of eliciting acute sounds, when  labouring under
violent pain: sounds, which  were very analogous to  those, that could
be produced mechanically with the larynx  of the dead animal, by
blowing into the trachea and approximating-the arytenoid cartilages;
and this he properly explains  by the distribution  of the  nerves of
the larynx. The recurrents being divided, the thyro-arytenoid mus-
cles are  no  longer capable of contracting, and hence aphonia re-
sults; but the arytenoid muscle which receives  its  nerves  from
the superior laryngeal, still  contracts, and,  during  a strong expira-
tion, brings the arytenoid cartilages together, so that  the chink or
cleft of the glottis is sufficiently narrow for the air to cause vibration
in the thyro-arytenoid muscles, although they may not be in a state
of contraction. 
VOICE.
365
  Again, every part of the larynx, with the exception of the inferior
ligaments, may be  destroyed, and  yet  the  voice may continue.
Bichat split the upper edge of the superior ligaments of the glottis,
without the  voice being destroyed; and the excision of the tops  of
the arytenoid cartilages  had no  more effect.  Magendie divided,
with impunity, the epiglottis and its muscles, and voice was accom-
plished,  until he cut the  middle of the  arytenoid cartilages  or
split the thyroid cartilages longitudinally, when he,-of course, des-
troyed the glottis.   Lastly, when the larynx  is exposed in a living
animal, so that the different parts can be readily seen, at the time
when voice  is accomplished, the superior ligaments, according  to
Bichat and Magendie, who have performed the experiment, are
manifestly unconcerned in the function, whilst the inferior ligaments
distinctly vibrate.  These ligaments must, therefore, be regarded  as
the essential organs  of voice.
  The deeply interesting, but difficult problem  now presents itself;
—to determine the precise mechanism of the vibration of those li-
gaments; and what kind of instrument the vocal organ must be re-
garded.  The latter question, on which, it might  be conceived,  so
much physical evidence  must exist, has been  the topic of much dis-
sension, and is by no means settled at this day.
  Aristotle, Galen, and the older writers in general, looked upon
the larynx as a wind instrument of the  flute* kind, in  which the
interior column of air is the sonorous body;  the trachea the body
of the flute, and the glottis the beak. The air, they conceived, when
forced from  the lungs,  in  passing through  the glottis or beak is
broken by  the inferior  ligaments of the larynx; vibrations are,
consequently, produced, and these vibrations  give rise to the sound.
  Fabricius, of Acquapendente, was one of the first to object to
this view of the subject.  He properly remarked, that the trachea
cannot be regarded  as the body of the flute,  but as a porte-vent to
convey the air to  the glottis.   He was of opinion, that  the glottis
corresponds to the beak of the flute, and that the vocal tube or  all
that part above the glottis  resembles the body of the  instrument.
Similar opinions, with more or less modification, have been adopted
by  Blumenbach, Soemmering, Savart, &c.
  About the commencement of the last century  DoDARTlaid before
the Acadimie des Sciences of Paris, three memoirs on the theory
of the  voice, in which he considered the larynx to be a wind in-
strument of the horn, and  not of the flute, kind; the inferior liga-
ments  of the glottis being  to the larynx what  the lips are to the
performer on the horn.
  In 1741, Ferrein, in a communication, also made to the Aca-
dimie des Sciences, maintained that the  larynx  is a stringed instru-
ment:—the sound resulting from the oscillation caused  in what  he

  • The flute, here alluded  to, is the common flute or flute d bee, in which the
embouchure is at one extremity. 
366
MUSCULAR  MOTION.--EXPRESSION.
called the cordae vocales, or the inferior ligaments of the larynx, by
the air in expiration; and a modification of this view was professed
by Dr. Young.
  At the present day, the majority of physiologists and natural
philosophers regard the larynx as a wind instrument, but of the reed
kind; such as  the clarionet, hautboy, &c. and they differ chiefly from
each other, in explaining the various modifications of the tone and
quality of the voice: for all are agreed, that it  is produced  by the
vibrations of the inferior ligaments of the glottis.  Piorry, indeed,
considers the glottis to  be an instrument sui generis, eminently
vital, and which, of itself, executes the movements necessary for the
production of vocal sounds.  All that we know, of the physiology
of the production of the voice, is this,—that the expired  air is sent
into the larynx by the muscles of expiration; that the intrinsic mus-
cles of the larynx give to the inferior ligaments sufficient tension to
divide the air, and that the  air receives the vibrations, whence sound
results, which escapes by the vocal tube.
  Intensity or strength of the voice.—The  strength of a  sound
depends  upon the extent  of the vibrations of the body producing
it.   In the case of the voice, it is partly dependent upon the force
with which the air is sent  from the lungs, and partly on the size of
the larynx.   A strong, active person, with a  capacious  chest  and
prominent pomum adami, in other words, with  a large larynx, is of
an organization the most favourable for a strong voice. But if this
same individual, thus favourably organized, be reduced in strength
by  sickness, his voice is enfeebled; because, although the formation
of his  larynx may be favourable, he  is incapable of sending the air
through it, with sufficient  force to excite extensive vibrations of
the vocal ligaments.
  The voice  of the male is much stronger than that of the female,
of the eunuch, or of the child. This is greatly owing to his larynx
being more developed.  The change of the voice  in the male at
puberty is owing to the same cause;  the prominence of the pomum
adami, which is first observed  at this age, indicating the elongation,
that has supervened in the lips of the glottis. As voice is commonly
produced, both ligaments of the glottis participate; but if one should
lose its power of  vibrating, from any cause, as from paralysis of
one-half the  body, the voice loses, caeteris paribus, one-half its
intensity.  Magendie affirms, that  this  is manifested  by cutting
one of the recurrents of a dog.
   Tone of the voice.—Nothing can exceed  the human organ of
voice in variety and execution.  Dr. Barclay has endeavoured to cal-
culate  the different changes of which it is susceptible, proceeding on
the principle, that where a number of movable parts constitute an
organ, destined to some particular function; and where this func-
tion is varied and  modified by every change in  the relative situa-
tion of the movable parts, the number of changes, producible in the
organ, must at  least equal the number of muscles employed, to- 
VOICE.
367
gelher with all the combinations of which  they are capable.   The
muscles, proper  to the five  cartilages of the larynx, are, at least,
seven pairs; and fourteen muscles, that can  act separately  or  in
pairs, in combination with the  whole or with any two or more of
the rest, are capable of producing upwards of sixteen thousand dif-
ferent movements,—not reckoning as changes  the various degrees
of force and velocity, with which they are occasionally brought into
action.  These muscles, too, are only the proper muscles of the la-
rynx, or the muscles, restricted in their attachments to its five car-
tilages.  They are but a few of the muscles of voice.   In speaking,
we use a great many more.  Fifteen pairs of  different muscles, at-
tached to the cartilages, or to the os hyoides, and acting as agents,
antagonists, or directors, are constantly employed in  keeping the
cartilages steady, in regulating their situation, and moving them as
occasion requires,—upwards and downwards, backwards and for-
wards, and in every intermediate direction, according to the course
of the muscular  fibres or in the diagonal between different fibres.
These muscles, independently of the former, are susceptible of up-
wards of 1073,841,800 different combinations; and,  when they co-
operate with the seven pairs of the larynx, of 17592186.044,415;
exclusive of the  changes, which must arise from the  different de-
gress of force, velocity, &c. with which they may be brought into
action.
   But these muscles are not the  whole, that cooperate with the
larynx, in  the  production of the  voice.  The diaphragm, the
abdominal muscles, the  intercostals, and all  that directly or in-
directly act on the air or on the parts to which the muscles of the
glottis or os hyoides are attached,—in short, all the muscles, that re-
ceive nerves from the respiratory system of Sir Charles Bell,—
contribute  their  share. The  numerical estimate would consequently
require to be largely augmented.   Such calculations are, of course,
only approximate,  but they  show  the inconceivable variety of
movement of which  the vocal apparatus is directly or indirectly
susceptible.
   The tone of the voice has been the great stumbling block to the
physiologist and natural philosopher.   The  mode, in which it is
produced, and the parts, more immediately concerned in the func-
tion, have  been  the object  of  the various theories or hypotheses,
from time  to time enunciated, regarding the voice.
   Galen, under his theory, that the larynx is a wind instrument
of the  flute kind, of which the glottis is the beak and the trachea
the body of the  flute, ascribed the  variety of tones to two causes—
to variation in the length of the musical instrument and in the em-
bouchure.   Now, the trachea is susceptible of change in its length,
when the larynx rises or descends, and the aperture of the  glottis,
we have seen, admits of a change in size, according to the action of
its proper muscles.   Accordingly, Galen ascribed  the acute tone
to the contraction of the embouchure—the glottis—and to the de- 
368            MUSCULAR  MOTION.--EXPRESSION.

scent or depression of the larynx, which shortened the body of the
instrument,  the  trachea; whilst  the grave tone, he thought, was
owing  to the greater dilatation  of the glottis, and to the larynx,
rising and elongating the trachea, and, consequently, lengthening
the instrument.
  The first part  of the theory of Galen is  correct.   The glottis
does contract for the production of acute tones; but, instead of de-
scending in the case of acute tones and rising in that of the grave,
the reverse is the fact; and, accordingly, what Galen calls the mu-
sical tube, in man, is elongated in the formation of acute tones, and
shortened in the case of the grave.  This, every flute-player knows,
is not the case in the artificial instrument.
  This objection to the theory of Galen was obviated by that  of
Fabricius, of Acquapendente, who regarded the vocal tube or the
whole of the space above the glottis as corresponding to the body
of the flute;  and, as the larynx ascends at the time of  the  produc-
tion of acute sounds, and descends during that of grave, the length
of the vocal tube or of the body of the  instrument, will be dimi-
nished in the former case and augmented in the latter, as in the ar-
tificial  instrument.
  In the theory of Dodart, to which allusion has been made, the
human vocal instrument was likened to a horn; the inferior liga-
ments of the glottis being compared to the lips of the performer.
He attached no importance to  variation in the length of the instru-
ment, but attributed the variety of tones to simple alteration in the
embouchure or mouthpiece; in other words, to changes in the size
of the glottis, by the action of its appropriate muscles.
  The rising and falling of the larynx, he regarded, as serving  no
other purpose than that of influencing, mechanically, the size of the
aperture of the glottis.
   Upwards  of thirty years after this, Ferrein promulgated his be-
lief, that the larynx is a stringed instrument; and he accounted for
the variety of tones by the different degrees of tension and length
of the inferior ligaments of the glottis  or of the vocal cords.  In the
production of acute tones, these cords were stretched and shortened.
For grave tones, they were relaxed, and, consequently, longer. He
was of opinion, that the length  of the vocal tube had no influence
on the tone.   Ferrein  supported his  theory, by experiments per-
formed before commissioners,  appointed  by  the Acadimie des
Sciences.  These experiments consisted in  forcing air  from the
trachea into the larynx of the  human subject, as well as of animals,
so as to produce vocal sounds, and to vary these by giving  the vocal
cords different degrees of tension.   From  these experiments he
drew the conclusion, that  he had succeeded in producing vocal
sounds, which could be  recognised,—that, at the time of  the pro-
duction of this artificial voice  he had distinctly seen the vocal cords
vibrating; and that the different  tones had been produced,  not by a
change in the aperture of the glottis,  but by a variation in the ten- 
voice.                        369
sion and length of the vocal cords; and according as one-half, two-
thirds, or four-fifths of each cord was made to vibrate, the octave
above, the fifth, or the third of the fundamental note was obtained.
The result was the same, whether the  two cords vibrated or only
one;  and if both cords were compressed, in their whole length, so
that they could not vibrate, no sound was produced.
   To this theory, however, it was judiciously objected, that  the
" vocal cords" are not sufficiently dry, tense, or insulated, to execute
vibrations, similar to those of musical cords; that, in many animals,
possessed of voice, they are not apparent; and that,  in birds, the
tones of whose voices are various, they are replaced by cartilages,
which can merely approach or recede from each other so as to mo-
dify the aperture of the glottis, but cannot be conceived susceptible
of different degrees of tension; and, lastly, that these cords cannot,
at the farthest, be shortened more than three  lines, which would
not be sufficient for the production of all the different tones of the
human voice.  It was farther asked—what use Ferrein assigned,
in his theory, to the  arytenoid muscle,  and how he explained why
the larynx rises or descends at each change of tone.
   It would appear, likewise, that the different academicians, who
were present at his experiments, did not unanimously accord with
Ferrein as to the results. Several of them asserted, that the sounds
produced were rather a simple rustling  of the air  than real vocal
sounds; and that, in the production of these sounds, the vocal cords
acted like the reed.
   Of late years, several new views have been propounded on this
subject,  and  chiefly by Cuvier,  Dutrochet, Magendie,  Biot,
Savart, &c.—men of the highest eminence in various departments
of physical science.
   Cuvier attributes  the variety of tones, in the first place,  to the
varied length of the vocal tube, and to differences in the size of the
aperture of the glottis; and, secondly, to the shape and condition of
the external aperture of the tube—that is, of the lips and nose. The
larynx he regards as a wind instrument, in which the inferior liga-
ments act, not as cords, but like the reed of a clarionet, or the lame
of an organ pipe.  The lungs and their external muscular apparatus
constitute the reservoir of air and the bellows;  the trachea conducts
this air, and the glottis is the embouchure with its reed; the mouth
and the whole of the space, comprised  between the glottis and the
opening of the lips,  being the body of  the  instrument; whilst the
openings of the nostrils are lateral holes, which  permit the size of
the instrument to be varied.
   The tones are changed by three causes, of a similar character to
those, that modify them in musical instruments;—the length of the
body of the instrument, the variableness of the embouchure, and of
the aperture at the lower extremity of the instrument.
  The condition of  the  external aperture  of the vocal tube has,
doubtless, much to do with the character of the  tone produced by
  Vol.  I.                    47 
370
MUSCULAR MOTION.—EXPRESSION.
the glottis; but its influence appears to be greatly limited to giving
it rotundity, volume, or the contrary, as will  be shown hereafter;
although analogy would seem to show that the tone may be varied
by more or less closure of the aperture.   Many different notes can
be produced in the first joint of a flute, if we modify the size of the
opening at its  extremity by passing the thumb more or less within
it.  It is doubtful, however, whether in man the altered size of the
external aperture or the elongation or decurtation of the tube exerts
as much influence on  the production of  acute  or grave sounds as
Cuvier imagines.
  Dutrochet, again, believes,  that, the vocal  tube has no influence
in the production of tones, and that the larynx is a simple vibrating
instrument, uncomplicated with  a tube, the vocal sound being caused
by the vibrations  into  which the vocal cords are thrown, by the im-
pulse of the expired air.  Dutrochet repeated the experiments of
Ferrein, but  without obtaining the same results.  He was unable,
for instance, to produce grave tones; those, which he succeeded  in
producing, comprised  only one octave; and even in the case of such
of these as were the most acute, the inferior ligaments of the glottis
were  so tense, that the strongest rush  of air could scarcely throw
them  into vibration, and the arytenoid cartilages were carried back
much beyond the point to which the posterior crico-ary tenoid muscles
naturally draw them;  and he pronounces the remark of Ferrein—
that the most acute sound was produced at the moment of greatest
dilatation  of the glottis—to be incorrect.
  In these experiments, he saw the inferior ligaments vibrate; and he
concludes, that the tone of the voice depends upon the number  of
vibrations of these ligaments in a  given time,and that the number will
necessarily vary considerably,—as the dimensionsof the ligaments,—
that is, their length, thickness, and elasticity, are susceptible of in-
cessant changes, by the contraction of the  thyro-arytenoid muscle
of which they are essentially composed,—the  ligament, covering
the muscle, serving only " to prevent the collisions of the muscle
at the time of vibration,"—as well as by that of the other  intrinsic
muscles of the larynx.
  MM. Biot and Magendie dissent from  Dutrochet  in  some
important points.   Like him, they do not consider the human la-
rynx  to constitute a stringed  instrument.  They regard it as a va-
riety  of reed instrument, but they consider the vocal tube to  be  of
moment in the production of the voice.  The objections they urge
against the view of its resembling the stringed instrument, are,—not
only the kind  of articulation between the arytenoid and cricoid car-
tilages, which admits of motion inwards and outwards only, but they
ask how the vocal cords can attain the length, they would  require
for the production of grave tones;  and how these cords could elicit
sounds of a volume so considerable as those  of the human voice.
They efteem it, consequently, as a reed instrument, of such nature
as to be capable of affording very grave tones, with a  pipe of little 
VOICE.
371
length; and such that the same tube, almost  without varying its
length, is susceptible, not only of furnishing a certain series of
sounds in harmonic progression, but all the imaginable sounds and
shades of sounds in the compass of the musical scale, which each
voice embraces.
   In the reed  instrument,  comprising the clarionet, hautboy,
bassoon, &c. two  parts  are distinguished,—the  reed, and the
tube  or body of the instrument.  A reed is  generally formed of
one and sometimes of two thin laminae, capable of moving rapidly,
and the vibrations  of which alternately intercept and permit the
passage of a current of air.  In this instrument, the  reed alone pro-
duces^and modifies the sound.  If the lamina be long, the  move-
ments are extensive, slow, and, consequently, give rise to grave
sounds; a short lamina, on the contrary, produces acute sounds, be-
cause the movements are  less extensive and  more rapid.  To vary
the tones, it is, therefore, only necessary to  vary the length of the
reed.  It is proper, however, to add, that the  tone, according to
Biot, is partly  also  dependent upon the elasticity, weight, and
shape of the tongue or lamina, and on the intensity of the current of
air;  for if these elements vary,—the length continuing the same,—
the tone changes. In a reed instrument, the reed is never employed
alone.  It is always adapted  to a tube, through which  the wind
passes, after it has  thrown the reed into vibration.   The tube, how-
ever, has no influence upon the tone of the sound.  It affects only
its intensity and timbre,  and the practicability of making the reed
speak.  Those, that occasion the shrillest sounds are such as are
conical, with the expanded base outwards.  If the cone be inverted,
the sound becomes dull; but if two similar cones are applied, base to
base, and  adjusted to a conical tube, the sound  assumes rotundity
and force, an effect, which has not been accounted for by the natu-
ral philosopher.
   A column of air, vibrating in a tube, can  only produce a  certain
number of sounds; and,  consequently, the tube of a  reed  instru-
ment, when long, transmits only those sounds readily, which it is
apt to produce ;  hence it generally becomes necessary to establish,
beforehand, an accordance between the reed  and the body of the
instrument; and, therefore, when we are desirous of obtaining dif-
ferent sounds in succession from the same reed instrument, we have
not only to  modify the length of the reed, but, in a corresponding
manner, that of the  tube; and this is the use of the  holes in the
sides of the clarionet, bassoon, &c.   By closing or opening these,
the tube is placed in the  proper relation with the reed.  This ac-
cordance has the additional advantage of facilitating the production
of any desired note from the reed, by means of the lips.  The in-
fluence of the tube is very evident in  the narrow  instruments, as
the clarionet and hautboy, in which it is extremely difficult to make
the reed speak, unless the tube be previously adapted to its  tone.
   This theory of the reed instrument MM. Biot and Magendie 
372     '       MUSCULAR  MOTION.--EXPRESSION.

apply to the human vocal apparatus.  The lips of the glottis are the
reed and the thyro-arytenoid muscles render them fit for vibrating.
In his experiments, made on  living dogs, Magendie  saw, that
when grave sounds were produced, the ligaments of the glottis  vi-
brated in their whole extent, and the  expired air issued through the
whole of the glottis.  In acute sounds, on the other  hand, they  vi-
brated only at their posterior part, and the air passed out through
the part only that vibrated, the aperture being, consequently, dimi-
nished; and, when the sounds became very acute, the ligaments vi-
brated only at their arytenoid extremity, and scarcely any air issued;
so that tones, beyond a certain degree of acuteness, cannot be pro-
duced in consequence of the  complete closure of the glottis.  The
arytenoid muscle, whose chief use is to close the glottis by its pos-
terior extremity, he conceives to  be the principal agent in the pro-
duction of acute sounds, and this idea was confirmed by the section
of the two laryngeal nerves, that give motion to this muscle,  which
was followed by the loss of the powTer of producing almost all the
acute tones ; the voice, at the same time, acquiring a degree of ha-
bitual graveness, which it did not previously possess.
   The influence of contraction of the thyro-arytenoid  muscles  on
the tones he considers to be exerted  in  increasing or  diminishing
the elasticity of the ligaments, and, thus, in modifying the rapidity
of the vibrations, so as to  favour the production of acute or grave
tones.   He thinks, too, that the contraction of these muscles con-
curs greatly in closing, in part, the glottis, particularly its anterior
half; although the course of its fibres, it appears to us, ought rather
to widen the aperture.
   The trachea  or porte-vent has  usually been considered to exert
no influence on the nature of the sound produced. It has been con-
ceived, however, by Grenie and  others that  its elongation or de-
curtation may occasion some  modification.
   So much for  the reed; but  MM. Biot and Magendie include,
in their theory  of the voice, the action of the vocal  tube, likewise.
This  tube, being capable of  elongation and decurtation, of being
dilated or contracted, and susceptible of assuming an infinite number
of shapes, they think it well  adapted for fulfilling the  functions of
the body of a reed instrument,—that is, if placed in harmonic relation
with the larynx,—and thus of favouring the production of  the nume-
rous tones of which the voice  is capable; of augmenting the intensity
of the vocal sound by assuming a conical shape with a wide external
aperture; of giving rotundity and  sweetness by the proper arrange-
ment of its external outlet, or by entirely subduing it, by the closure
of the outlet.  The larynx  rises in the production of acute sounds;
and falls in that of grave. The vocal  tube is, consequently, shorten-
ed in the former case; elongated in the latter.   It experiences also
a simultaneous  change in its width.   When the larynx  descends;
in other words, when the vocal tube is elongated, the  thyroid car-
tilage is depressed  and separated from the os hyoides by the whole 
voice.                        373
height of the thyro-hyoid membrane.   By this separation, the epi-
glottic gland is carried forwards, and lodged in the concavity at the
posterior surface of the os hyoides.  The gland drags after it the epi-
glottis; and a considerable enlargement in width  occurs at the in-
ferior part of the vocal tube.  The opposite effect results, when the
larynx rises.  The use of the ventricles of the larynx, Magendie
considers to be, to isolate the inferior ligaments, so that they may
vibrate freely in the air.  Lastly, in this theory the epiglottis has a
use assigned to it which is novel. In certain experiments, instituted
by Grenie for the improvement of reed instruments; being  desirous
of increasing the intensity of a sound without changing the reed in
any respect; he found that to succeed in it he was compelled to aug-
ment gradually the strength of the  current of  air:  but this augmen-
tation, by rendering the  sounds stronger, made them rise.   To re-
medy this  inconvenience, Grenie  found  no other means  answer,
except that of placing obliquely in  the tube, immediately below the
reed, a supple, elastic tongue, nearly as we see the epiglottis above
the glottis.  From this, Magendie infers, that the epiglottis may
assist in  giving  to man  the faculty of increasing or inflating the
vocal sound, without its mounting.
   Such are the main propositions of the theory of the voice by Biot
and Magendie. The larynx represents a reed with a double tongue;
the tones of which are acute, in proportion to  the decurtation of the
laminae;  and grave in proportion to their length. They admit, how-
ever, that,  although the analogy between the organ of voice and the
reed is just, the identity  is not  complete.   The ordinary reeds are
composed of rectangular  laminae; fixed at one  side, but loose on the
three others; whilst in the larynx the vibrating laminae, which are
likewise  nearly rectangular, are fixed by three sides and free by one
only. Moreover, the tones of the ordinary reed can be made to rise
or to  descend by varying their  length, whilst in the laminae of the
larynx the width varies.   Lastly, say they, in musical instruments
reeds are never employed, whose movable laminae can vary in thick-
ness and elasticity, every moment, as is the case with the ligaments
of the glottis: so that although  we may conceive, that the larynx
can produce the voice and vary its tones, in the manner of a reed
instrument, we  are  unable to  demonstrate the particulars  of its
mode of action.
   All the more  modern  theories, which we have detailed  at more
or less length, agree, then, in considering  the larynx to be a wind
instrument and of the reed  kind: they differ, chiefly, in the part,
which they assign to the vocal tube in causing  the variation of tones.
   More  recently, in 1825, M. Savart has propounded a theory of
the human  voice in which he differs from Cuvier, Dutrochet and
Magendie;—denying, that the mechanism of the  voice resembles
that of the reed instrument, and returning to  the old idea, which
referred the vocal organs to  an instrument of the flute kind. 
 374            MUSCULAR  MOTION.—EXPRESSION.

    The objections, which he makes to the doctrine, that assimulates
 it to a reed instrument, are the following.
    In order, that a reed shall produce a sound, it must be almost in
 contact with the sides of the gutter or depression in which it moves;
 so that the current of air may take place only periodically; but, ac-
 cording to this principle, the larynx would be unable  to render any
 sound, whenever the inferior vocal ligaments  are  separated from
 each other.
    Again, according to the theory  of the reed, great efforts ought to
 be required to produce vocal sounds; for the thyro-arytenoid mus-
 cles  being very  strong and thick, it would seem, that they could
 not vibrate without a strong impulse: yet the voice is  produced by
 the most feeble jet  of air, and even when the breath is partly with-
 held.
   Again, there is nothing in the sound  of the voice, which resem-
 bles that of a reed,  even of the best formation; and,  lastly, he re-
 marks, in the theory of the reed, no use  is assigned to the ventricles
 of the larynx, and to the two superior ligaments of the glottis; which,
 with the epiglottis, form a membranous tube  situated above the
 glottis;  and yet it cannot  be doubted, that these parts  are im-
 portant in the production of  the  voice;  for, if we blow through
 the trachea into the larynx  of a dead body, from which all but the
 inferior  ligaments have  been removed, vocal sounds  can  only be
 elicited by great exertion; whilst they can  be easily produced in a
 perfect larynx,—even although the  thyro-arytenoid muscles may not
 be contracted,—by  merely approximating the arytenoid cartilages.
   These objections  led Savart to  discard the doctrine, that the la-
 rynx is a reed instrument.   The sounds of the  human voice have,
 indeed, he remarks, a peculiar character, which  no musical instru-
 ment can imitate; and this must necessarily be the case, as they are
 produced by a mechanism  founded  on principles  which  do not
 serve as a basis for any of our instruments.  He conceives, that the
 production of the voice is analogous to that of the sound in the tube
 of a flute, and that the small column of air, contained in the larynx
and mouth, by the nature of the elastic parietes which bound them,
as  well as by the mode in which it  is thrown into vibrations, is sus-
ceptible of rendering sounds of a particular nature, and, at the same
 time, of a much  more grave character than  the dimensions would
 seem to admit of.
   In the tube of a flute the column of air, within it, is  the sonorous
 body.  A sound is first produced at the embouchure of the instru-
 ment,  by the division which  the air experiences when blown into it;
and this sound excites similar sonorous undulations in the column of
air which fills the tube.  The sound,  resulting in this way, is more
grave in proportion  to the length of the tube; and it is in order to
vary its tones,  that the  instrument  has apertures in  its side, by
means of which the  length may be  modified. 
voice.                         375
  In  assimilating the human vocal apparatus to a flute, the great
difficulty  has been to explain  how, with so short a tube as the
vocal tube in man;  and so little variable in length, tones, so differ-
ent, and especially so grave, can be produced.
  To explain this, Savart establishes the existence of a number of
physical facts, previously unknown or unnoticed.
  In  organ pipes of great length the velocity of the current of air,
which acts as a motor, has but little influence on the  number of os-
cillations.  When  the length of the pipe  is, for instance, twelve or
fifteen times greater than its diameter,  it is difficult to vary the
sound a semitone.   When the air  is forcibly driven  in,  it rises an
octave; and when the velocity is diminished, the sound merely be-
comes more feeble; but is depressed an almost imperceptible quan-
tity.  In short pipes, on the contrary, the influence of the velocity
of the current of  air is much greater, and  several  tones can be
elicited.
  The bird-call, used by sportsmen, is illustrative of  this principle.
It is a small instrument used  for imitating the notes
of certain birds; consisting of a cylindrical tube, about   Fig. 78.
three-fourths of an inch in diameter, and a  third of isnan
an inch high; closed at each end by a thin, flat plate,
which is pierced, at its centre, by a'hole about the
sixth  of an  inch  in diameter.    Sometimes, it
has the shape represented in the  lower of the
marginal  figures.   By placing this instrument
between  the  teeth and lips,  and forcing  air,
with  more  or  less strength through  the   two
apertures, different  sounds can be produced.  This
is more certainly effected, by attaching a porte-
vent to the whistle, as A A,  Fig. 79, when  it is
capable of producing all the sounds comprised in
an extent of from an octave and a half to two oc-
taves.  M. Savart found, that, other things be-
ing equal, the diameter of the apertures  has an
appreciable influence on the  acuteness or grave-
ness of the sounds; which are more grave when the orifices  are
larger. The nature of the parietes of the instrument appeared, also,
to exert some effect on the number of oscillations, and on the qua-
lity of the sounds; and if, in the hemispherical whistle, Fig. 79, the
plain  plate was replaced by a thin leaf of some extensible substance,
as parchment, the  sounds issued  more readily, and  were, usually,
more grave, full, and agreeable, than when they were formed of a
more solid substance.
  It is  an opinion, generally admitted, that the  material, which
composes an  organ pipe, has  no influence on the number of vibra-
tions, which  the column of air, contained in it, is capable  of exe-
cuting. This  is true as regards long pipes; but, according to Savart,
Fig. 79.
      HIIIIIHIIIII".!!
iA 
  376            muscular motion.—expression.

  it is not so with the short, and the nature of the biseau,* he con-
  ceives, may have a great influence, even on the sound of long pipes.
  For instance, if we substitute, for the stiff lamina, which forms the
  biseau of an organ pipe, two feet long and two inches on the side,
  a lamina,  formed of some elastic substance, as skin or parchment,
  and so arranged as to admit of being stretched at pleasure; by gra-
  dually increasing the tension of the membrane, at the same time
  that we increase the velocity of the current of air, the tone may be
  made to vary a fourth, and even a fifth.  In still  shorter tubes, the
  much greater influence of the velocity of the current of air being
  united to that of the tension of the biseau, the result is still more
  evident.  Thus, the sound of a cubical tube may  easily be lowered
  an  octave, when the parietes of the biseau are susceptible of differ-
  ent degrees  of tension; but when all the parietes,  which compose a
  short pipe, are of a nature to enter into vibration  along with the air
  they contain; and when their degree of tension can be, moreover,
  varied;  they have such an influence on the number of vibrations,
  that it seems the sound may be depressed indefinitely.
    Short tubes, open at both extremities, and formed of elastic pa-
  rietes, are also susceptible of producing a great number of sounds,
  even when  they are only partly membranous.
    The quality of the sound of membranous tubes is said to be some-
  what peculiar.  It partakes of that of the flute, and of the free reed.
    Again,  in order that a mass of air  shall enter into vibration, a
  sound must  be produced in some part of it.  In an organ pipe, for
  example,  a  sound  is  first excited at the embouchure, and this
  throws  the  column of air, within the instrument, into vibration.
  Every sound, indeed, produced at the orifice of a column of air,
  throws  it  into vibration, provided its dimensions are adapted to the
  length of the waves produced directly. Hence, the utility of a mu-
  sical pipe, having parietes susceptible of varying  in dimension and
  in tension, whatever may be the character of its embouchure.
    Lastly. The  fundamental note of a tube, closed at  one end, and
  whose diameter is every where the same, is an  octave lower than
  the sound of the same tube, when open at both extremities.   But
  this is not the case with tubes that are of unequal diameter, conical,
• pyramidal, &c.  when made to vibrate at their narrowest part.  The
  tone, produced in such  case, will increase in graveness, according
  to the difference between its narrow and expanded portions.
    These  different physical conditions Savart invokes to account
  for the  different tones of the human voice,—under the theory, that
  the vocal organ, composed of the larynx, pharynx, and mouth, forms
  a conical tube, in which the air is set  in vibration by a movement
  similar  to that which prevails in organ pipes.

   * The  biseau or languette is the diaphragm, placed between the body of an or-
  gan pipe and its foot. 
voice.                        377
  The trachea is terminated above by a cleft,—the glottis,—which
is the inferior aperture of the vocal instrument.  This cleft, which
is capable of being rendered  more or less narrow, plays the same
part as  the lumiere des tuyaux a bouche, or the narrow space in
the organ pipe, at the edge of the biseau or languette, along which
the air  passes.   The  air clears it, traverses the ventricles of the
larynx,  or the cavity of the instrument,  and strikes the  superior
ligaments.   These surround the upper aperture of the instrument,
and fulfil the same function as the  biseau of the organ pipe.   The
air, contained in the interior of the larynx, now vibrates, and sound
is produced.  This sound acquires intensity, because the waves that
constitute it are extended into the vocal tube, situated above the
larynx, and excite, in the column of air filling it, a movement similar
to that occasioned in the tube of a flute; except that the tone can be
much varied, because the larynx, being a short tube, can give rise
to various tones by simple modification  in the velocity of the air
sent through it; and, moreover, the vocal  tube has the same power,
its parietes being  membranous, of a vibratory nature, and capable
of different degrees of  tension.  The  inferior or  outer part of the
vocal tube is equally constituted of elastic parietes, susceptible of
varied tension; and the mouth,by modifying the dimensions of the co-
lumn of air within the vocal tube, exerts an influence on the number
of vibrations, which the column is capable of experiencing; whilst
the lips can convert the channel at pleasure into an open or closed
conical tube.  Certain  sounds, Savart affirms, are produced alto-
gether in  the ventricles of the larynx,—those of pain and the fal-
setto voice,  for example. They can be elicited, even when the vocal
tube has been removed; and there  are animals, in which the vocal
organ is reduced to the ventricles of the larynx—frogs for instance.
Savart, consequently, considers, that the human vocal organ has, in
its essential  parts, C C, B B, Fig. 77, a  striking analogy to the action
of the bird-call;  and, in this way, he explains the use of the superior
ligamepts C C, which are entirely overlooked in the different theo-
ries of the voice previously propounded.
  We have given Savart's view at  some length, in  consequence
of its ingenuity, and of its seeming to explain better than any other
theory the varied  tones of which  the  human voice is susceptible.
It cannot, however,  be esteemed established,  inasmuch as it  is
diametrically opposed, in many of its points, to the observations and
vivisections of other  distinguished physiologists; who, it has been
seen, affirm, that voice is produced solely by the inferior ligaments;
that all  the parts above these may be destroyed, and yet voice may
continue; and that, a wound in the ventricles, which permits the exit
of air through the parietes of the larynx, does not destroy the func-
tion.  Our notions on this point must not, therefore, be  considered
definite.  Farther experiments are necessary; and, in all the de-
ductions from them, great importance will have to be attached to
the vital action of the parts; especially  of  the  intrinsic  muscles,
  Vol. I.                     48 
378
MUSCULAR  MOTION.—EXPRESSION.
which are capable of modifying the situation of parts, and the cha-
racter of the function in myriads of inappreciable ways.

               Timbre, or Quality of the Voice.

  In the preliminary essay on sound, attached to  the physiology of
audition, it was remarked, that the cause of the different timbres of
sound, in  the various musical  instruments, had hitherto remained
unexplained.  The same remark is applicable to the timbre of the
voice.   Each individual has his own, by which he is distinguished
from those around  him; and it is the same with each sex and period
of life.   In  this, the larynx  is, doubtless, concerned; but in  what
manner is not clear.   The feminine timbre or stamp, which charac-
terizes the voice of the child and of the eunuch, would appear  to be
generally connected with the cartilaginous  condition  of  the larynx;
whilst the masculine voice, which is sometimes met with in the fe-
male, is connected  with the osseous condition of these parts, and es-
pecially of the thyroid cartilage.  An infinity of modifications may
also be produced by  changes in the thickness, elasticity, and size of
the lips of the glottis.
  The vocal tube  probably exerts great influence, in this respect,
by  its shape as well  as by the  nature of the material composing it.
Such conditions, at least, appear to modify the timbre of our wind
instruments.  The timbre of a flute, made of glass or brass, is very
different from that of one formed of wood, although the instruments
may resemble each other in  every other respect.
  The form of the  body of the  instrument has, also, considerable
effect.  If it be  conical, and wider towards its outlet, as in the cla-
rionet, or hautboy, the quality of the sound is shrill. If it be entirely
cylindrical,  as in the flute, we have the soft  quality, which charac-
terizes that  instrument; and, on the other hand,  if the  tube be ex-
panded at its middle portion, the quality of the sound is raucous and
dull.   It is probable, therefore, that  we must reckon, amongst the
elements of the varying character of the timbre, or stamp of the
voice, the different conditions of  the vocal tube as to length, width,
and form; and that we must likewise include the position and shape
of the tongue, of the velum  palati, and of the mouth and nose; the
presence or want of teeth, &c. all of which  circumstances modify the
voice considerably.
   By the generality of physiologists, it is conceived, that the voice
enters the different nasal fossae, and by resounding in them, a timbre
or  character is given to it, which it  would  not  otherwise possess.
According to this  belief, when the voice is prevented from passing
through the nose, from any cause, it acquires the nasal twang;  or
by a singular inaccuracy of language, we are said " to talk through
the nose."   Magendie, however,  considers that, whenever the
sound passes through the nasal fossae, the  vocal sound becomes dis-
agreeable and nasal.  Simple experiment, by holding the nose, ex- 
TIMBRE of the voice.
379
hibits, that, in the enunciation of the true vocal sound, unmodified
by the action of the organs of articulation, the timbre or quality is
materially altered; and we shall see, hereafter, that there are cer-
tain letters, which do not admit of enunciation, unless the nasal
fossae be pervious—the m and the n, for example.  It would seem
that, under ordinary circumstances, the sound, after it is produced in
the larynx, flows out by both channels; and that, if we either shut off
the passage through the nose altogether, or attempt to pass the sound
more than usually through the nasal fossae, the voice becomes nasal.
  Not only does the voice, when produced in the larynx, pass out
by the vocal tube, but it resounds along  the trachea and bronchial
tubes; and, when cavities exist in the lungs, in persons labouring
under pulmonary consumption, if the ear be placed upon the chest,
immediately over one  of those cavities, the voice will  appear to
come directly up to the ear. The same thing happens, if the  stetho-
scope of Laennec be used, which  is nothing more than a hollow,
wooden cylinder, of particular construction.  In this case, the voice
will appear to pass directly through the tube to the ear, when the
extremity of the instrument is applied over the vomica, giving rise
to what Laennec terms pectoriloquy. Adelon conceives, that this
distribution of the sound, along the trachea or porte vent and the
lungs, may induce a belief, that  the condition of these organs has
some effect on the timbre of the voice.

  In speaking of the  timbre  of the voice in different individuals,
we have had in view the natural quality,  not that which is the result
of imitative action, and  which can be  maintained for a time only.
Many of the conditions, that have been described, as regulating the
timbre, are voluntary, especially that of the shape of the vocal tube.
In this way, we can modify  the timbre and imitate voices, very
different from our own.  The table d'hote of many of the hotels of
continental Europe is enlivened by the presence of individuals, ca-
pable of not only imitating various kinds of birds,  but the timbres
of different musical instruments; and the success, that  has attended
the personation of the different voices of public speakers, by Ma-
thews, Yates, and others, is sufficient evidence of the fidelity of
their representations.
  We see the  difference between the  natural  and imitative voice
strongly exemplified in one of the feathered songsters of our  forests,
the turdus poly glottis or mocking bird; which is capable of imi-
tating, not only the voices of other birds, but sounds of other cha-
racter, which cannot be regarded in the light of accomplishments.
  There is a singular variety of the imitative voice, now employed
only for purposes of amusement; but, of old,  perhaps, used in the
Pagan temples, by the priests,  to infuse confidence in the oracular
dicta  of the  gods, which requires some  notice;—it  is engastri-
mism or ventriloquism.   Both  these  terms,  by their derivation,
indicate the views, at one time entertained, of its physiology, viz. 
380            MUSCULAR  MOTION.—EXPRESSION.

that the voice of the ventriloquist is made to resound in the abdo-
men, in some inexplicable manner, so as to give rise to the pecu-
liarity it possesses.
  This  singular view seems to have been  once embraced by M.
Richerand.   " At first," says he, " I had conjectured, that a great
part of the air expelled by expiration  did not pass out by the mouth
and nostrils, but was swallowed and carried into the stomach;  and
being reflected in some part of the digestive canal, gave rise  to a
real echo; but  having afterwards  more attentively  observed  this
curious phenomenon on Mr. Fitzjames,  who exhibits it in its
greatest perfection, I was soon convinced, that the name of ventri-
loquism is by no means applicable."  M. Richerand was probably
the last remnant of the ancient vague hypothesis, and his views soon
underwent a conversion.
  Another, equally unfounded notion, at one time entertained, was,
that the ventriloquist possesses a double or triple larynx.  But  it is
now universally admitted, that the voice is produced at the ordinary
place, and that it is modified in its  intensity and quality by actions
of the larynx and of the vocal tube, so as to give rise to the decep-
tions we experience.
  It is known, that our appreciation  of the  distance and nature  of a
sonorous body is formed from the intensity and quality of the sound
proceeding from it.  We instinctively believe,  that  a loud sound
proceeds from a near object, and a feeble sound from one more re-
mote; accordingly, if the intensity and quality of the sound, from a
known body, be such as to impress us with the idea, that it is more
remote than it really is, we incur an  acoustic illusion.  The ventri-
loquist takes advantage  of  this source of illusion; and, by skilfully
regulating the  force and  timbre of  his voice,  irresistibly leads us
into error.  It is to account for the mode in which this is  effected,
that different hypotheses have been, from time to time, entertained.
Haller,  Nollet,  and others, believed, that  the voice is formed
during inspiration; but this does not  seem to be the case. Voice can
certainly be effected during inspiration, but it is raucous, unequal,and
of trifling extent only.  Dumas and Lauth consider it a kind of
rumination of sounds; the voice, formed in the larynx, being  sent
into the interior of the chest, attaining there a peculiar timbre, and
issuing of a dull character.
  Richerand is of opinion,  that the whole mechanism consists in
a slow, gradual expiration, which is always preceded by a deep inspi-
ration.  By means of this,the ventriloquist introduces into his lungs a
considerable quantity of air, the exit of which he carefully regulates.
  In the Manchester Memoirs, Mr. Gough attempts to explain the
whole phenomenon upon the principle of echoes;—the ventriloquist,
he conceives, confining himself to  a room, well disposed for echoes
in various parts of it, and producing false  voices, by directing his
natural voice, in a straight line, towards such echoing parts, instead
of in a straight line towards the audience, who are supposed, by Mr. 
VOICE.—ventriloquism.
381
Gough, to be placed designedly by the ventriloquist on one or both
sides of him.
  A sufficient answer to  this is, that the practised ventriloquist is
careless about the room, selected for his exhibitions; and that he
habitually performs in rooms, where this system of echoes would
be totally impracticable.
  But let us see what the ventriloquists themselves have said of the
mechanism of their art.
  We pass over the explanation of Baron von Mengen, an Aus-
trian colonel, who forms a kind of vocal organ between his tongue
and his left cheek, if we understand his description correctly; and
keeps a reservoir of air in his throat to throw this organ into vibra-
tion.   His object must evidently have been to mislead.
  In 1S11,M. Lespagnol, a young physician, maintained a thesis
on this subject before the Faculti de Medecine of Paris, which may
be regarded, at least, as an honest exposition of his belief, regarding
the mode in which the phenomenon was effected in his own person.
  According to him, the whole is dependent upon the action of the
velum pendulum  palati.  In the ordinary voice, he remarks, a part
of the sound passes directly through the mouth, whilst another re-
sounds in the nasal fossae.  If we are near the person  who is speak-
ing, these two sounds strike equally and  almost synchronously upon
the ear; but. if we are at a distance, we hear only the first of the two
sounds, when the voice  appears more  feeble;  and especially has
another timbre, which experience makes us judge to  be that of the
voice at a distance.
   The whole of the difference, says Lespagnol, between the voice
that proceeds from  a near, and that from  a  more  distant object
is, that in the former, we  hear the  mixture of the two sounds;
whilst in the latter we hear  that sound only, which issues directly
from the mouth.   Now,  the  secret of the ventriloquist  is, only to
permit this direct sound to pass to the ear, to prevent the nasal sound
from being  produced, or  at least from being heard; and  this is done
by the elevation  of the velum pendulum palati.  The vocal sound
does not then resound in the nasal fossae; the direct sound is alone
produced; the voice  has the feebleness and timbre that belong to
the distant voice; and is judged to proceed from a distance; and if,
during the performance, the  voice seems to come  from any deter-
minate place, it is owing to the ventriloquist attracting our attention
to it; but the voice, of itself, need only appear to proceed from a dis-
tance; and this it does more or less, according as the pendulous veil
has prevented,  more or less completely, the vocal sound from issuing
by the nasal fossae.   The ventriloquist  thus, according to M. Les-
pagnol, makes the voice nearer or more remote at pleasure, by
raising or depressing the velum palati.  He denies  that  the ven-
triloquist speaks with his mouth closed; and affirms,  that he articu-
lates, but to a trifling extent only.
   Mr. Comte, another ventriloquist, and  of some celebrity, who 
382
MUSCULAR MOTION.--EXPRESSION.
has endeavoured to explain the physiology of his art, affirms, that
the voice takes place as usual in the larynx; but that it is modified by
theaction of other parts of the apparatus; inspiration directing it into
the thorax where it resounds; and that both strength and flexibility
are required in the organ to produce this effect.   This, however, is
no  explanation.  It is now universally admitted, that the voice of
the ventriloquist is produced in the larynx; and that  its character
and intensity are modified by the action of other parts of the appa-
ratus, but  the particular action  producing  it, is  not elucidated by
any of these attempted explanations of the ventriloquist.
  About twenty years ago,  Dr. John Mason Good, in some  lec-
tures delivered before the Surrey Institution of London, suggested
that the larynx alone, by long and dexterous practice, and,perhaps,
by  a peculiar modification in some of its muscles or cartilages, may
be capable of answering the purpose, and of supplying the place of
the associate organs of the mouth.
   In  confirmation of this view, he remarks, that in singing, the
glottis is the only  organ made  use of, except where the  notes are
articulated;  and  it  is apparently the sole  organ employed in the
mock articulations of the parrot and other  imitative  birds; some of
which have exhibited unusual powers of  articulation.   A parrot,
belonging to a Colonel O'Kelly, could repeat twenty of the most
popular English songs, and sing them to their proper tunes.
   The larynx, too, is the sole  organ of all the  natural cries;  and
hence it has been imagined  by Lord Monboddo, to have been the
chief organ of articulate language in its rudest and  most barbarous
state. "As all natural cries,"he observes,"even though modulated
by music, are from the throat and larynx, or knot of the throat, with
little or no operation of the organs of the mouth, it  is natural to
suppose, that the first languages were, for the greater part, spoken
from the throat; and that what consonants were used to vary the
cries, were mostly gutterals; and that the organs of the mouth would
at first be but very little employed."  Certain it is, that the priva-
tion of tongue does not necessarily induce incapacity of articulation;
whether the defect be congenital, or  caused after speech has been
acquired.   Under  the sense of taste, several authentic  cases were
stated of individuals, who were deprived of this organ, still posses-
sing the faculty of speech.  To these we may add one other, which
excited unusual  interest at the  time, and was examined  under cir-
cumstances, that could admit of no deception.   The case forms the
subject of various papers, by  Dr.  Parsons, in  the Philosophical
 Transactions, between 1742 and 1747.
   A young woman, of the name of Margaret Cutting, of Wick-
ham market,  near Ipswich, in  Suffolk, when only four years  old,
lost the whole of her tongue, together with the uvula, from a can-
cerous affection; but still retained  the powers of speech, taste, and
deglutition, without any imperfection; articulating as fluently and
correctly  as other persons; and  even those syllables  that commonly 
VOICE.—VENTRILOQUISM.
383
 require the aid of the tip of  the tongue for accurate enunciation.
 She also sang admirably; articulating her words whilst singing; and
 could form no conception of  the use of a tongue in other people.
 Her teeth were few, and rose scarcely higher than the surface of
 the gums, owing to the  injury to the sockets from the disease that
 had destroyed  the  tongue.   The case, when first  laid before the
 Royal Society, was attested  by the minister of  the parish;  by a
 medical practitioner of repute, and by  another respectable indivi-
 dual.  The society, however, were not satisfied, and they appointed
 commissioners to inquire into the case,  whose report coincided mi-
 nutely with the first;  and, to  set the matter completely at rest, the
 young woman was shortly afterwards conveyed to London, and
 examined, in person, before the Royal  Society.
   These cases are not so extraordinary as they appear at first sight to be;
 when we  consider that the tongue is not the sole organ of articula-
 tion,  but that it shares the function with the various parts that com-
 pose the vocal tube.  In reality, out of the twenty-four articulate
 sounds, which our common alphabet comprises, there are but few in
 which the tongue takes a distinct lead, as in the /, d, t, r, &c. though
 it is auxiliary to several others; but the guttural or palatine,g-,h, k, q;
 the nasal, as m and n; the labial, as b, p,f, v; and most of the dental,
 together with all the vowels, are but  little indebted to its assistance.
   From these, and other concurrent facts, Dr. Good  concludes, that
 ventriloquism appears to be an imitative art, founded on a close at-
 tention to the almost infinite variety of tones, articulations, and in-
 flexions, which the glottis is capable of producing in  its own region
 alone, when long and  dexterously practised upon; and in a skilful
 modification of these  vocal sounds, thus limited to the glottis, into
 mimic speech,  passed, for the most  part, and whenever necessary,
 through the cavity of the nostrils, instead of through the mouth. It
 is possible, however, he  adds, though no opportunity has hitherto
 occurred of proving the fact by dissection, that those who learn this
 art with facility, and carry it to perfection, possess  some peculiarity
 in the structure of the glottis,  and particularly in respect to  its mus-
 cles or cartilages.
   Magendie and Rullier, however, affirm, that the quiescence of
 the lips, observed  in the practised ventriloquist when  enunciating,
 is more apparent than real; and that, if he is capable of pronouncing
 without moving his lips, it is  because he is careful to  make use of
 words in which there are no labial consonants, or which do not ab-
 solutely require the movement of the lips in their  formation. Rul-
 lier, indeed, denies positively, that the ventriloquist can speak with-
 out opening his mouth and moving his lips; but he affirms that he
 uses his jaws, mouth, and lips, as little as possible in articulation; and
 he ascribes the common  belief in  their perfect quiescence to  the
habit, acquired by the ventriloquist, of restraining their movements,
united to the care he takes in  concealing them; and of giving to his 
384
MUSCULAR MOTION.--EXPRESSION.
face an impassive expression; or one very foreign to the verbal ex-
pression to which he is giving utterance.
  On the whole, the explanation of Dr. Good appears most  satis-
factory. The larynx or glottis affording to some individuals a facility
in acquiring the art, which others do not possess; in the same man-
ner as it makes some capable of singing, whilst others are ever in-
capacitated.   It is probable, however, that there  may be a greater
degree of obscure action about the  parts composing the vocal  tube,
than Dr. Good  is disposed to admit; and that this may be materially
concerned in giving the voice its peculiar  quality and  intensity;
and in eliciting some of the sounds which might not  be so easily
produced by the action of the glottis alone.
  Such is a  history of the  simple voice, as effected in the larynx.
Articulate sounds  may, however,  be produced in the vocal tube
alone.  Whistling, for example, is  caused by the expired air being
broken or divided  by the lips; which act the part of the lips of the
larynx in the production of voice.
  Whispering consists in the articulation of the air of expiration.
It is wholly accomplished  in the vocal  tube; and, hence, the im-
practicability of singing in a whisper; singing being produced in the
glottis.
  The sound of sighing is produced by the rushing of the air along
the air passages, and especially along the vocal tube  In laughing,
crying, and yawning,  the voice  is likewise concerned; but the
physiology of these functions of expression will  fall more appro-
priately under  that of respiration.
  Having described the different views, that have been entertained,
with regard to  the production of voice,  we shall  now inquire into
the function in connexion with expression.  In this respect it ad-
mits of division into the natural or inarticulate voice, and into
the artificial or articulate.

            Of Natural or Inarticulate Language.

  This, which  is sometimes termed the cry  or  native voice, is an
inappreciable  sound,  entirely produced in  the larynx, requiring
none of the  organs of articulation to aid in its formation.  As, how-
ever, it is caused by different degrees of contraction of the intrinsic
muscles of the larynx, it is susceptible of a thousand different tones.
It is elicited independently of all  experience or education; seems
to be inseparably  allied to  organization;  and, consequently, occurs
in the new-born infant, in the idiot, in the deaf from  birth, and in
the wild man, if any such there be, as well as in the  civilized  in-
dividual.
  The natural voice differs as much as the sentiments  it is employ-
ed to express.  Each moral affection has its appropriate cry;—the
cry of joy is very distinct from that of grief;—of surprise  from that 
VOICE.—NATURAL  LANGUAGE.
385
 of fear, &c; and the pathologist finds, in  the diseases of children
 more especially, that he can occasionally judge of the seat of a dis-
 ease by the character of the cry, to which the little sufferer gives
 utterance; in other words, that there is, in the language of Broussais,
 a  cry peculiar to the suffering organ.
   By the cry, our vivid sensations are expressed, whether they are
 of the external or internal kind; or are agreeable or painful: and, by
 it we exhibit all our natural passions, and most simple instinctive
 desires.
   Generally, the most  intense  sounds to which the organ of voice
 can  give  utterance, are embraced  in  the  natural cry; and, in its
 character, there  is frequently something, which annoys the ear and
 produces more or less effect on  those within its sphere.
   It is, indeed, by its agency, that sympathetic relations are estab-
 lished between man and his fellows;  and  between animals of the
 same kind.
   The language, possessed by the greater  part of animals, is, as we
 have  already remarked, this natural  voice, differing according to
 varying organization; and, therefore, instinctive; hence the various
 notes of birds; and the different ranges which we find the voice to
 possess in the different species.  Yet each species has one, by which
 it is distinguished, and which it possesses, even when brought up in
 the same cage with one of another species; or hatched, and attended
 to, by a foster mother,  endowed with very different  vocal powers.
 In the case of a goldfinch and chaffinch, this has been put directly to
 the proof: and it is well known, that  the cuckoo, which is never
 hatched or nurtured by its own parent, still retains the note, which
 has acquired it its  name in almost every language of  the globe. It
 is, probably, by this natural cry, and  not from any signs addressed
 to the eye, that the process of pairing is effected, and that the female
 is induced to select her mate.
   The vocabulary of the  common cock and hen is quoted  as per-
 haps the most extensive of that of any tribe of birds, with which
 we are  acquainted: or  rather as Dr. Good remarks,  we are better
 acquainted with the extent of its range than with that of any other.
   The cock has his watch-word for announcing the  morning; his
 love speech and his terms of defiance.  The voice of the  hen, when
 leaving her nest, after  laying, is far different from that  which she
 assumes, when the brood  is hatched, and both  are very different
 from  her cries, when her  young are placed in jeopardy.   Even the
 chick exhibits a variety in its voice, according to the precise emotion
 it  experiences.
   All these sounds are such as the larynx of the animal permits
 alone to be  produced:  and  hence we  can understand why, so far,
 they should be  mere modifications of the natural voice; but it is
more than probable, that the chick learns the  adoption  of a  parti-
cular sound, by the parent to express a  particular emotion, asan affair
   Vol.  I.  "                 49 
386            MUSCULAR  MOTION.--EXPRESSION.

of education. It can scarcely, indeed, be conceived, that the cluck-
ing of the hen, when she meets with food proper for her offspring,
can be understood at first by the chick.   But as soon as it traces
the connection between the sound produced and the object of such
sound, it comprehends the signification ever afterwards.
   There are sounds which  from their discordant and harsh cha-
racter affect  most animals perhaps, independently of all experi-
ence.  The cry of terror, for example, or of pain appears to occa-
sion, sympathetically, disagreeable effects in all that are within its
sphere.

             Of Artificial or Articulate Language.

   Speech is, likewise, a vocal sound; but it is articulated, in its pas-
sage through  the vocal tube; and  is always employed to convey
ideas, which have been attached to it by the mind. It is a succession
of articulate sounds, duly regulated by volition, and having deter-
minate significations attached to them.
   The faculty of speech has been assigned, by some philosophers,
chiefly to the organ of hearing.   It is manifest, however, that this,
like the musical ear, is referable to a higher organ.  The brain must
attach an idea to the impression, made upon it by the sound, received
through the organ of hearing; the sound,  thus, becomes the sign of
such idea; and is reproduced in the larynx, at the will of the indi-
vidual.
   Of the intellectual character of the process we  have the most de-
cisive evidence. The infant, of tender age, has the ear and the voice
well developed, yet it is long before he is capable of  speech; and
this does not happen until he discovers the meaning of the  sounds
addressed to him, and finds his own larynx capable of producing
similar sounds, which can be made subservient to his wishes.  It is
thus, by imitation, that he acquires the faculty of speech.  Again,
the idiot, notwithstanding his hearing may be acute, and his voice
strong, is  incapable of speech; whilst, in the maniacal and delirious,
the language participates in the derangement and irregularity of the
ideas.  The brain must, therefore, be regarded as the organ of the
faculty of language, and the ear, larynx, and vocal tube as its instru-
ments. Man, who is endowed with the most commanding intellect,
has the vocal apparatus most happily organized  for expressing its
various combinations; and, according to Gall, if the ourang-outang
and other animals are incapable of  speech, it is  because they have
not the intellectual faculty of language. In proof that it is not to the
vocal organ that this deficiency must be ascribed, he remarks, that
animals may be made to enunciate several of the words of human
speech, and to repeat them to music.   The  case of the far-famed
parrot of Colonel O'KELLYhas already been referred to; and Gall,
amongst other cases, refers to that of Leibnitz's dog, which could ar- 
VOICE.—ARTIFICIAL LANGUAGE.             387
ticulate some German and French words. There is no doubt, how-
ever, that,  in numerous animals, speech  would be impracticable,
owing to defective vocal organization, even were they gifted with
adequate intellect.
  It is difficult, perhaps impossible, to say, how man came to select
certain sounds as the types of certain intellectual acts; nor is  it a
matter which strictly concerns the physiologist.  We may remark,
however, that whilst some contend, that speech is  a science  that
was  determined upon, and inculcated, at an  early period of the
world, by one or more superior persons, acting in concert and in-
ducing those around them to adopt  their articulate  and arbitrary
sounds; others affirm, that it  has grown  progressively out of the
natural language, as the increasing knowledge and increasing wants
of mankind hare demanded a more extensive vocabulary.
  The first view is that of Pythagoras  and  Plato; but it  was
opposed by Lucretius, and the Epicureans, on the ground, that it
must have been impossible for any one person or synod of persons
to invent the most difficult and abstruse of all human sciences, with
the paucity of ideas, and of the means of communicating them, which
they mu%t have possessed; and that even allowing they could have
invented such a science, it must still have been utterly impossible
for them to teach it to the barbarians around them.
  The opinions of those philosophers, who confine  themselves  to
the phenomena of nature and hold themselves uncontrolled by other
authority, accord with those of the Epicureans.
  In the  origin of language, it  is probable, that words were  sug-
gested to mankind by the sounds, which were heard around them:
—by the cries of quadrupeds:—the notes of the birds of the forest:
—the noises emitted by the insect tribe:—the audible indications
from the elements, &c.  These, being various, probably first of all
suggested discriminative names, deduced from the sounds heard.  It
is this imitation of the noise, made by objects, that constitutes the
figure of speech, called onomatopoeia,—the " vox repercussa na-
turae," or " echo of nature," as Wachler has defined it.
  Daily experience shows us, that this source  of words is strictly
physiological.   Children always designate a sonorous object by an
imitation of the sounds given off by it; and the greater number  of
sonorous bodies have had names, radically similar, given to them in
languages differing most from each  other.  We say the serpents
"hiss," the bees " hum," the storm " blusters" the wind " whis-
tles," the hogs " grunt," the hen " cackles," the man " snores,"
&c.  words used, originally, not perhaps in these very shapes, but
varying, according to the varying idiom of the language, to imitate
the sounds elicited from these objects.
  Such words are numerous in all languages, and have been adopted
to depict both the sound emitted, and the sonorous body itself; but,
in some cases, the word, imitating the sound, has survived its trans- 
368
MUSCULAR MOTION.—EXPRESSION.
 mission from language to language to the most modern times, whilst
 the name of the object, whence it proceeded, has experienced con-
 siderable mutation.
   The Sanskrit, the antiquity of which will not be contested, has a
 number of such words, as wilala, the cat,—kukada, the hen,—and
 waihu, the wind;  in the last of which the sound of the  w,  (oo,)
 imitates that of the passage of the air, and is found in the word corres-
 ponding to wind, (ooind,) in many languages.  The Hebrew and
 the Greek have numerous phonetic words, but no language is richer,
 in this respect, than the Teutonic, in all its ramifications, including
 the English.
   The animal kingdom affords us many examples, of which the fol-
 lowing is one.
   Cuckoo.—This word is nearly the same in almost all languages.
 Greek, xox*f|; Latin, cucullus; Irish, cuach; Bask, cucua;  Scla-
 vonic, kukulka, kukuscka, &c;  Hungarian, kukuk; Hebrew, ca-
 catha; Syriac, coco; Arabic,  cuchem;  Persiac, kuku;   I£oriak,
 kaikuk;  Kamtschadale,  koakutschith;  Kurile, kakkok;  Tartar,
 kauk; German, kuckucks, or guckguck; Dutch, koekoek;  whence
 our word cuckoo, and the Scottish gouckoo, gowk or golk;  French,
 oocu, &c.
   In the greater part of  languages, words, expressive of the cries
 of animals, are accurate imitations.  Of this the following area few
 examples.
   Bleating of sheep.—Greek, fi^xxo^xii Latin, balare; Italian,
 belare; Spanish, belar;  French, biler;  German, blbken; Dutch,
 bleeten;  Saxon, blaetan, &c.
   Howling of wolves.—Greek, ouxvgu; Latin, ululare; German,
 heulen;  Dutch, huilen;  Spanish, aullar;  French, hurler, &c.
 Hence the word owl.
   Neighing of the horse.—Latin, hinnire;  French, hennir; Ger-
 man, wiehern; Saxon, hnasgan, &c.
   Clocking, or clucking of hens.—Latin, glocire; French, glous-
ser; Greek, *«**«£«/»j German, glucken; Dutch, klokken; Saxon,
cloccan, &c.
   Crow, like  a cock.—Greek, *p*€»}  German, krdhen; Dutch,
 kraayen; Saxon, craw, &c.  whence the  word crow, the bird.
  The Latin words tinnimentum,  tinnitus, tintinnabulum, &c.
from tinnio, I ring, are all from the radical tin; imitating the sound
rendered on striking a metallic vessel. The gurgling of water, the
clanging of arms, the  crash  of falling ruins, are  of the same  cha-
racter; and the game trictrac, formerly tictac, seems to have been
so called, from the  noise made in putting down the men or dice.
  In whatever manner language was first  formed, it is manifest,
that the different sounds  could make but a transient impression,
until they were reduced  to legible characters, which could bring
tbem back to the mind.  In our continent, the fact has  often  been 
               VOICE.—ARTIFICIAL LANGUAGE.             389

noticed of a tribe of Indians, separating themselves into two parties,
and remaining distinct for years. In all cases, the language has be-
come so much modified, that after the lapse of a considerable period
they have scarcely been able to comprehend each other.   Hence,
the importance of the art of writing, certainly the most valuable of
human inventions.  Of this, there have been two kinds,—the imi-
tative or alphabetic,—and the symbolical, allegorical, or emble-
matic,  which latter consists of hieroglyphics or designs, repre-
senting external objects, or of symbolical allegories.
   The former or the written representation of spoken sounds alone
concerns us. To attain this, every compound sound has been reduced
to certain elementary sounds, which are represented by signs, called
letters.  These elementary sounds, by combination, form syllables;
and the syllables, by combination, words.  The number of elemen-
tary sounds, admitted in each language, constitutes  its alphabet,
which differs more or less in certain languages; but as it is entirely
a matter of human invention, and as the elementary sounds,  of which
the human  voice is capable, are alike in the different races of ipan-
kind, we see readily,  that the alphabets of the different languages
must strikingly correspond, although the combinations of the letters
constituting syllables and words, may vary essentially.
   Into the  origin of the written legible language, it is  not necessary
for us to inquire.   We may remark, however, that  the invention
has been considered so signally wonderful as to transcend the human
powers; and  hence St. Cyril, Clement of Alexandria, Eusebius,
Isidore, and, in  more modern times, Messrs. Bryant, Costard,
&c. have been of opinion, that  the  knowledge of letters  was first
communicated to Moses by the Almighty himself, and that the de-
calogue was the earliest specimen of alphabetic writing.  Many
passages, however, in the writings of Moses, show unequivocally,
that written records must have existed prior to his time.  In the
passage in which writing is first mentioned  in the sacred volume,
the art is alluded to as one of standing:—" And the Lord  said  unto
Moses, * Write this for a memorial in a book or table;"'  and in a
subsequent chapter—" And thou shalt make  a plate of pure gold,
and grave upon it, like the engravings of a signet, Holiness to the
Lord."
   The English alphabet is considered to consist of twenty-six letters.
It  may, however, by ultimate analysis, be reduced to twenty-four
simple sounds—A, B, D, E, F, G, H, I, J, K, L, M, N, 0, P, R, S,
T, U, V, Z, Ch, Sh, and Th. To these letters arbitrary names have
been assigned, as Bee, (B,) See, (C,) Dee, (D,) &c. which express very
different sounds from those that belong to the letter when it forms
part of a word or syllable. The word bad is  not pronounced bee-a-
dee; as  the child, just escaped  from learning his  alphabet, must
imagine; hence, he has to unlearn all that he has acquired, or to ima-
gine, that the different letters have very different sounds, according 
390
MUSCULAR  MOTION.—EXPRESSION.
to the situation in which they may be found. To obviate this incon-
venience, many individuals are in the habit of successfully teaching
their children syllabically from the very first, by which they ac-
quire the true sound, attached to each letter of the alphabet.
   In the preceding enumeration of the simple sounds, constituting
the alphabet, C, Q, W, X and Y, have  been excluded, for the fol-
lowing reasons.  C  has  always the sound of either S or K, as in
cistern or consonant. Q has the sound of koo, as in quart, (kooart;)
W of oo, as in word, (oourd;) X of ks,  or Z, as in vex, (vecks,) or
Xerxes, (zerkses;) whilst Y has the sound of I or  E, as in  wry or
yard, (wri or eeard.)  Ch, Sh, and Th, have been added, as being
true alphabetic or simple sounds.
   Letters have been usually divided into two classes,—vowels and
consonants.
   The vowels or vocal sounds are so called, because they appear to
be simple modifications of the voice, formed in the larynx, uninter-
rupted by the tongue and lips, and passing entirely through the
mouth.  Such at least is the case with those that are reckoned pure
vowels.  These, in the English alphabet, are five in  number,—A, E,
I, 0, and U.  W and Y are, likewise, vowel sounds in all situations.
   In enunciating A, as  in fate, the tongue is drawn  backwards
and slightly upwards, so as to contract the passage immediately
above the larynx.  In sounding E, the tongue and lips are in their
most natural position, without exertion.   I is formed by bringing
the tongue nearly into contact with the bony palate. 0, by the con-
traction of the mouth being greatest immediately under the uvula,
the lips being also somewhat contracted; and, in the production of
U, the contraction is prolonged beneath the whole of the soft palate.
   From these principal vowels, all the other vowel sounds of the
language may be formed, by considering  them as partaking  more
or less of the nature of each.  These are, in our language, thirteen
in number; besides  compound sounds,  as in oil and pound.  Of
these thirteen, three belong to A;  two to  E;  two to I; three  to 0;
and three to U.
A, as in
E, as in

I, as in
C Fate.		CNo.
^Fat.	0, as in -	•2 Move
(Fall.		(Not.
CMe. 2 Met.		CTune.
	U, as in -	«>Tub.
CPine. £Pin.		(Bull.
		
  The vowels are more easy of pronunciation than the consonants.
They merely require the mouth to be opened; and, however it may
be arranged  in the  enunciation of the  different vowels, the  vocal
tube is simply modified to vary the impression, which has to be
made on the organ of hearing.  The shape of the cavity is altered, 
VOICE.—ARTIFICIAL LANGUAGE.
391
 but the passage of the air continues free, and the voice, consequently,
 issues in an unrestrained manner.  Hence, perhaps, the physiologi-
 cal origin  of the Danish word Aa, "a river"—a generic  term,
 which became afterwards applied to three rivers in the Low Coun-
 tries, three  in Switzerland, and  five  in Westphalia—the sound of
 the two broad As flowing without obstacle, like a river. Time passes
 away in a similar manner; hence, for a like reason, the Greek uei,
 which signifies "always, perpetually;" and the  German je, which
 has the same signification.
   The consonants are more difficult of enunciation than the vowels;
 as they  require different, and sometimes complex,  and  delicate
 movements of the vocal tube; and, on this account, are not acquired
 so early by children.
   The term consonant is  derived from  one of its uses,—that of
 binding together the vowels, and being sounded with  them;  but it
 may be defined,—an  interruption to  the sound, effected  in the
 larynx, by  the application of  the organs of  articulation to each
 other.
   By most, and  according to Mr. Walker, by the best, gramma-
 rians, w andy are consonants,when they begin a word; and vowels
 when they end one.  Dr. Lowth, however, a man of learning and
judgment,  who  certainly would  not  suffer in  a  comparison with
 any  of his  opponents, regards them,  as we  have,  to  be always
 vowels.  Physiologically it is impossible to look upon them in any
 other  light.  Yet Mr. Walker  exclaims,—" how so  accurate a
 grammarian as Dr.  Lowth  could pronounce so definitely on the
 nature of y, and insist on its being always a vowel, can only be ac-
 counted for by considering the small attention which is generally
paid to this part  of grammar."  No stronger  argument, however,
could be used against the useless expenditure of time on this sub-
ject, than  the conclusion to which Mr. Walker himself, has ar-
rived; and  for which he can find no stronger reasons, than  that if
w, and y have every property of a vowel, and  not one of a conso-
nant; why, when they  begin a word, do they not admit of the en-
phonick article an before them?
   The consonants are usually divided into mutes, semi-vowels, and
 liquids.
  The mutes are such as emit  no sound without a vowel; as b,p,
t, d, k, and c and g  hard.
  The semi-vowels are such as emit a sound,  without the concur-
rence of a vowel, asf, v, s, z, x, g soft  or^'.
  The liquids are such as flow into, or unite easily with, the mutes,
as /, m, n, r. These letters issue without much  obstacle; and hence
perhaps their name.
  In tracing the mode in which the different consonants are ar-
ticulated, we find, that certain of them  are produced  by an  analo-
gous action of the vocal tube;  so that  the physiology of one will 
 392            MUSCULAR MOTION.--EXPRESSION.

 suffice for the other also.   For instance, the  following nearly cor-
 respond;—
                 p    f    t    s    k     ch
                 &    &    &    &    &     &
                 b    v     d    z    g     j.
 B and P are produced when the lips, previously  closed, are sud-
 denly opened.   B differs from P in the absence, in the latter, of an
 accompanying  vocal sound.   F and V are formed by pressing the
 upper incisor teeth  upon the  lower lip.  They are, consequently,
 not well enunciated  by the  aged, who have lost their teeth. F differs
 from V only in the absence of an accompanying vocal sound. Tand
 D are formed  by pressing the tip of the tongue against the gums
 behind the upper incisor teeth: D is accompanied by a vocal sound;
 T not.   S and  Z are produced by bringing the point of the tongue
 nearly in contact with the  upper teeth, and forcing the air against
 the edges of the teeth with violence.  S differs from Z in  the ab-
 sence of the vocal  sound.  K and G are formed  by pressing the
 middle of the tongue against the roof of the mouth, near the throat;
 and separating  the parts a little more rapidly to form the  first, and
 more gently to form the last of those letters.  In K, the accompanying
 vocal sound is  absent.  Ch and J are formed by pressing / to sh;
 and d to zh.  In Ch, there is  no accompanying vocal sound.
   SH and ZH  are formed in the same part of the tube as s and z.
   TH is formed by protruding the tongue between the  incisor teeth,
 and pressing it  against the  upper incisors to produce its sound in
 think.   Its sound in that, is effected  by pressing the tongue behind
 the upper incisor teeth.  In the former case, it is unaccompanied
 by a vocal sound.
   In M, the lips are closed, as in B and P, and the voice issues by
 the nose.
   N is formed by  resting  the tongue against the  gums, as in  the
 enunciation of  t and d; and breathing through the nose with  the
 mouth open.
   In L, the tip of the tongue is pressed against the palate, the sound
 escaping laterally.
   K:—in forming this letter, the" middle and point of the tongue
strike the palate with a vibratory motion; the tip being drawn back.
   Lastly, in  the formation of H the  breath is forced through  the
mouth, which is  every where a little contracted.   It  need  hardly
be said, that the enunciation of these letters requires, that the vocal
tube, or the parts concerned in the function,  shall  be in a sound
condition.
  Wolfgang von  Kempelen in a work on the mechanism of
human speech, &c. which is considered classical in Germany, divides
the consonants into four classes.  1. Mutes, (g a n z  s t u m m e,) as
K, P, T.  2. Explosives, (w i n d m i 11 a u t e r,) as the F, H, Ch,
S,andSh. 3.  Vocal consonants, (sti m m m i tlauter,) as B, D,G, 
VOICE.—ARTIFICIAL LANGUAGE.
393
L,M,andN:and,4.  Vocal explosives, (wind und stimmlauter,)
as R, I, W, V, Z.
  Dr. Thomas Young has, likewise, divided the English consonants
into classes; of which he enumerates five.  1. Pure semi-vowels,
as L, R, V, Z, and J.  2. Nasal semi-vowels, as M and N.   3.
Explosive letters, as B, D, and G.   4.  Susurrant letters, as H, F,
X, and S: and, 5. Mutes, as P, T, K.
  The most satisfactory classification, in a physiological, as well as
philological point of view, is according to the parts of the vocal tube,
more immediately concerned in their articulation.
Labial.	Dento-labial.	Linguo-dental.	Linguo-palatal.	Guttural.
B M P	F V	Th	D JJLN RS T Z ChSh	G K
  That this physiological arrangement has had much to do, with the
formation of congenerous tongues more especially, is  exhibited by
the facts, connected with the permutation or  change of letters;
when a word passes, for example, from one of the Teutonic or Ro-
manic languages to another.
  " The changes of vowels," says Mr. Lhutd, " whether by chance
or affectation, are so very  easy and so common in all languages, that
in etymological observations, they need  not, indeed, be much re-
garded; the consonants being the sinews of words, and their alter-
ations therefore the most perceptible.  The changes  of consonants
also into  others of the same class, (especially labials,palatals, and
Unguals,) are such obvious mistakes, that there is no nation where
the common people in one part or other  of their country, do  not
fall into some of them."
  A few examples will show to what extent this permutation  oc-
curs between letters of the same class in different languages.  In
this view, we may regard the labials and  dento-Iabials as belonging
to the same class.
  P into B.—Greek, 4>a«4<; Latin, phlebs.   Latin, (and  Greek,)
episcopus; English, bishop; Anglo-saxon,owfcop; German, b i s c h o f.
  P into F and V.—Latin,pater; German, vater; Dutch, vader;
English, father.
  Tinto  S.—Germatljbesser; English,better.  German,wasser;
English,  water.
  D into Th.—German, das; Dutch, dat; English, that.
  T  into Z.—German, zung; Dutch,  tong;   English,  tongue.
German,  zweig; English, twig.
  L into R.—Spanish, Gil Bias; Portuguese,  Gil Bras. Latin,
arbor; Spanish, albero.
  C or K into G.—Latin, hemicranium; French, migraine.  La-
tin, cibarium; French, gibier.  Latin, acer; Italian, agro.  Latin,
alacer; Italian, allegro. Greek, *t;*v«?; Latin, cygnus.
  Vol. I.                     50 
394            MUSCULAR  MOTION.--EXPRESSION.

  The most harmonious languages are such as have but few conso-
nants, compared with the vowels, in their words;  hence the musi-
cal superiority of the Greek and  Italian, over the English, Ger-
man, &c.       *
  " Among certain northern nations," says Richerand, " all arti-
culated sounds appear to issue from the nose or the throat, and make
a disagreeable pronunciation, doubtless because it  requires  greater
effort;  and he  who  listens, sympathizes  in the difficulty, which
seems to be felt by him that speaks;"  and he concludes,—" would
it not seem, that the  inhabitants of cold countries have been led to
use consonants rather  than vowels, because as the pronunciation
does not require the  same opening of the mouth, it does not afford
the same space for  the continual admission of cold air into the
lungs?"  The whole of Richerand's remarks on  this topic are
singularly  fantastic and feeble,  and  unworthy of serious  discus-
sion.
  In regard to the consonants it  has been presumed, that some com-
mon imitative principle must have existed with all nations,  so as to
cause them to conform  in adopting such as produce a certain sound
to convey the same effect to the ear.
  Dr. John  VVallis,  in his Grammatica Linguae Anglicanae,
published in the seventeenth century,  turned  his attention  to  this
matter, chiefly as regards the English language, and he has collected
a multitude of examples to show, that a certain collocation  of con-
sonants, at the commencement of a word, generally designates the
dass of ideas, intended to be conveyed by it.   For instance, he re-
marks that:—
  Str, always carries with it the idea  of great force and effort:—
as strong, strike, stripe, strife, struggle, stretch, strain, &c.
  St, the idea of strength  but less in  degree—the  vis inertias, as
it were:—as stand, stay,  stop, stick,  stutter, stammer, stumble,
stalk, steady, still, stone, &c.
  Thr, the idea of violent motion:—as throw, thrust, throb, threat,
throng, &c.
   Wr, the idea of obliquity or distortion:—as wry, wreathe, wrest,
wring, wrestle, wrench, wriggle, wrangle, wrinkle, &c.
  Br, the idea of violent,—chiefly sonorous,—fracture or rupture:
—as break, brittle, brust or burst, brunt, bruise, broil, &c.
  Cr, the  idea  of straining or  dislocation, chiefly sonorous:—as
crack, creak, crackle, cry,  crow, crisp, crash.
  Other words, beginning with those consonants,  communicate the
idea of curvature, as if from curvus:—as crook, cringe,  crouch,
creep, crawl, cripple, crumple, crotchet, &c.
  Others, again, denote decussation,  as  if from crux:—as cross,
cruise, crutch, crosier.
  Shr,  the idea of forcible contraction:—as shrink, shrivel, shrug,
shrill, &c.
   Gr, the  idea of the rough, hard, onerous and disagreeable, (either 
VOICE.—ARTIFICIAL language.
395
owing to  the  letter of roughness, r, or  from gravis,)—as grate,
grind, gripe, grapple, grieve, grunt, grave, &c.
   Sw, the idea of silent agitation or of gentle lateral motion:—as
sway, swag, swerve, sweat, swim, swing, swift, &c.
   Sm, a very  similar idea to  the  last:—as smooth, smile, smirk,
small, &c.
   CI, the idea of some adhesion or tenacity:—as cleave, clay,cling,
climb, cloy, cluster, close, &c.
   Sp, the idea  of some dispersion or expansion, generally quick,
(especially with the addition of the  letter r,)—as spread, spring,
sprig, sprinkle, split, splinter, spill, &c.
   SI, the idea  of a gentty gliding or slightly perceptible motion:—
as slide, slip, slippery, slime, sly, slow, sling, &c.
   Lastly, Sq, Sk, Scr, denote violent compression:—as squeeze,
squirt, squeak, squeal, skreek, screw, &c.
   Some other interesting observations on the collocation  of conso-
nants, at the termination, and in the  body, of words, are  contained
in the grammar of Wallis.  His remarks, however, are chiefly
confined to his own tongue.   The president De BROssEshas taken
a wider range, with a similar object, and endeavoured to discover,
why certain consonants, or a certain arrangement of consonants in
a word, should designate certain sensible properties, in all languages.
Why, for instance, the st should enter into most  words  signifying
firmness and stability:—as in the  Sanskrit, stabatu, to stand, sta-
nia, a town, &c; in the Greek, g-t»>a?>, a column, o-T£^eo«f solid,im-
movable,  e-reipx,  sterile, remaining  constantly  without   fruit;
o-Ttipt^u, I fix firmly, &c; in  the Latin, stare, to  stand, stirps, a
stem, slupere, to be astonished, stagnum, stagnant water, &c. and
he might have added in  the German, still-stehend, stagnant,
stad t, a town, stand, condition, sterben,to die, still-stand,
cessation, &c,  besides the English words, commencing with st, al-
ready quoted from Wallis.
   He farther  inquires, why words, commencing with  sc, denote
hoUowness,  as c-^ata-™, I dig; 0-**^, a skiff or boat, in the Greek;
scutum, a  shield;  scyphus, a large jug;  sculpere, to engrave;
scrofo, a ditch, in the Latin; ecuelle,former\y escuelle,a dish; scarifier,
to scarify; scabreux, scabrous; sculpture,&.c, in the French; and simi-
lar words might be added from our own language. Ecrire, formerly
escrire, the French for " to write," is from the Latin scribere; and,
anciently, a kind of style was used for tracing the letters in wax;
which instrument, by a like analogy, was called, by the Greeks,
c-x.ctpiQo$.
   M. de Brosses accounts for these, by supposing, that  the teeth,
being the most immovable of the organic apparatus of the voice, the
firmest of what he calls the dental letters T has been mechanically
employed to denote stability; and that, to denote hoUowness, the
K or C has been adopted, which are produced in the throat,—-the
most hollow of the vocal  organs.  The letter S serves, he conceives,
merely as an augmentative; as the  sound can, by its addition, be 
396
MUSCULAR MOTION.--EXPRESSION.
made continuous.  It is itself, however, a letter expressive of soft-
ness, when combined, as we have seen, with  certain other conso-
nants; or when employed alone at the commencement of a word.
   In the same manner the letters,/?are used to designate the motion of
fluids more especially,—as in the Greek, dueg, flame; <P*f^, a vein;
<pxeye6uv} a burning  river in the infernal regions:—in the Latin,
flamma, flame; fluo, I flow; flatus, wind; fluctus, wave, &c:—in
the German,  flossen, to float;  floten, to play on the flute; fluss,
a river; f 1 u g, flight, &c; and the French and English words of the
same meaning.
   Lastly, the idea of roughness and  asperity is  conveyed by the
letter r, as in the words, rude,  rough, rock, romp, Sac.  How dif-
ferent, for example, in smoothness are the two following lines, in
which the S predominates;  from those that succeed them, where
the R frequently, and perhaps designedly, occurs.

                " Softly sweet in  Lydian measures,
                Soon he sooth'd his soul to pleasures;"

   And—
                " Now strike the  golden lyre again,
                A louder yet, and yet a louder strain;
                Break his bands of sleep asunder;
                And rouse him like a rattling peal of thunder."

   The remarks that have been  made, suggested by those of Wal-
lis and of President De Brosses, must not be received too abso-
lutely. In the condition in which we find languages at the present
day, it would be impossible that they should hold  good universally;
but they will tend to show, that the physiology of the voice is in-
timately connected with this part of philology; and that the sounds
emitted by the agency of particular  parts of the vocal tube, may
have led to the first employment of those sounds, according to the
precise  idea  it may  nave been desired to convey;—gutturals,
for example, for sounds conveying the notion of hoUowness:—
resisting dentals, that of obstacles, &c.   The words mama and
papa are composed of a  vowel and consonant, which are  the
easiest of enunciation,  and which the child, consequently,  pro-
nounces and unites earlier than any other.   Hence they have be-
come the infantile appellations  for mother and father in many na-
tions; but, it is scarcely necessary to  say, the child, when it first
pronounces the combinations, attaches no  such meaning to them,
as the parent fondly imagines.
   Lastly, there is a rhetorical variety of the onomatopoeia,  fre-
quently considered under the head of alliteration, but by no means
deriving its chief beauties  from that  source.   It happens when a
repetition of the same letter concurs  with the sonorous imitations
already described; as in the following line in one of  the books of
the ^Ineid of Virgil:—
" Luciantes ventos tempestatesque sonoraa," 
                VOICE.—ARTIFICIAL LANGUAGE.             397

in which the frequent occurrence of the letter of firmness and sta-
bility, T, communicates the idea of the striking of the winds on
objects.
   In the " Andromaque" of Racine, a line of this character oc-
curs:—

            " Pour qui sont ces serpens qui sifflent.sur vos tetes"*

in which the sound impressed on the ear has some similarity to
the hissing of serpents: and in the " Poeme des Jardins" of the
Abbe De Lille, there is the following example:—

           " Soit que sur le limon une riviere lente,
           Deroule en paix les plis de son onde indolente:
           Soit qu'a travers les rocs un torrent en courroux
           Se brise avec fracas."f

   In the first two lines the liquid L denotes the tranquil flow of
the river; whilst in  the  two last, the letter of roughness and as-
perity, R, resembles the rushing of the stream like a torrent. The
remarks already made will have exhibited the radical difference in
the  ideas communicated by  the sound of  those  letters, by the
common consent of languages.
   In the German language, this variety of expression is often had
recourse  to; and  by  none more frequently than  by their poet
Buerger.
   The English language affords a few specimens, but not as many
as might be imagined.   Of  simple alliteration, there are  many;
some that give delight;  others  that do violence to the suggestive
principle; but  there are comparatively few, where the words are
selected,  which, by their sound, convey to the mind  the idea to
be communicated.
   The galloping of  horses may be assimilated by  a frequent  suc-
cession of short syllables; slow,  laborious progression by the choice
of long;  but, in the  onomatopoeia in  question, the words them-
selves must consist of such a collocation  of one consonant, or of
particular consonants,  as adds force to the idea communicated by
the words collectively.   Of this, the following example may be
cited, in which the repetition of the letter R, in the various pho-
netic words especially, adds considerable force to the idea intend-
ed to be conveyed by  the passage.

          "Loud sounds the axe, redoubling strokes on strokes;
         On all sides round the forest hurls her oaks
         Headlong.  Deep echoing groan the thickets brown,
         Then rustling, crackling, crashing, thunder down."

  * " For whom are those serpents that hiss o'er your heads."
  j- Which may be translated as follows:—
                " If o'er deep slime a river laves,
                In peace the folds of its sluggish waves;
                Or o'er the rocks  a torrent breaks
                In wrath obstrep'rous." 
398
MUSCULAR  MOTION.--EXPRESSION.
                         Of Singing.

  The singing voice differs from the other sounds produced by the
glottis, in consisting of appreciable sounds, the intervals of which
can be distinguished by the ear, and which admit of unison.
  Under the sense of  hearing we endeavoured to  show, that the
musical ear is an intellectual faculty; and  that  the ear is only the
instrument for attaining a knowledge of sounds, which are subse-
quently reproduced by the larynx, under  the  guidance of the in-
tellect.  In this respect, therefore, there is a striking resemblance
between the faculty of music and  that of spoken language.
  Like the spoken language, singing admits of considerable differ-
ence as regards intensity, timbre,  &c.
  An ordinary voice  has, between  the lowest  tone and the most
acute, about nine tones; and the voices of greatest compass scarcely
exceed  two octaves in accurate and full  tones.  The celebrated
Madame Catalani, it is said, could sound D alt. distinctly, which
is some notes higher than the ordinary  female voice can attain.
  Voices are sometimes divided into the grave and the acute; the
difference between them  amounting to  about an octave.   The for-
mer is the voice of the adult male; but it  is capable of producing
acute sounds, by assuming the falsetto, which Savart  conceives
to be produced in the ventricles of the  larynx.
  The acute voice is  that of the grown  female, of children, and
of eunuchs.
  By adding all the tones of an acute  to  those of a grave voice,
they are found to embrace nearly three octaves; but, according to
Magendie, it does not appear that such a compass of  voice,  in
pure and agreeable tones, has ever existed in the same individual.
  The musician establishes certain distinctions  in the  voice; such
as counter, tenor, treble, &c. We find it,  also,  differing consider-
ably in strength, sweetness, flexibility, &c.
  It has been already remarked, that the  natural  voice or cry is
allied to the organization of the larynx. So far as  it can be modi-
fied into tones independently of the participation of the intellect,
a natural singing voice may be said to exist. To repeat, however,
any song, requires both ear and intelligence; and,  therefore, sing-
ing may be said to have originated in social life. It can be employ-
ed, as  it is in many of our operas, to depict the different intellec-
tual and moral conditions,

              " And bid alternate passions  fall  and rise."

   When the air is accompanied by the  words,  or is articulated, we
are capable of expressing, by singing, any of the thoughts or feel-
ings, that can  be communicated by ordinary artificial  language.
   Declamation is a kind of singing, except that the  intervals be-
tween the tones are  not entirely harmonic, and  the tones them-
selves are not wholly appreciable.   With  the ancients, it has been 
VOICE.—SINGING.
399
imagined, declamation differed much less  from singing than with
the moderns, and that it probably resembled the recitative of the
operas.*
                      OF THE GESTURES.

   Under this appellation, and that of muteosis, are comprised all
those functions of expression, which are addressed to the sight and
the touch.   It comprises  not  only the partial  movements of the
face, but also those of the upper extremities; besides the innumera-
ble outward signs characterizing the various emotions.  In many
tribes of animals, the conventional language appears to be almost,
if not entirely, confined to the gestures; and even in man,—favour-
ed, beyond all animals, in the facility of communicating his senti-
ments by the voice,—the language of gestures is rich and  compre-
hensive.
   It is in the gestures of the face chiefly, that man  far exceeds
other animals. This  is, indeed, in him, the great groupe of organs
of expression.   In  animals the function  is distributed over  dif-
ferent parts of the body,  the face assuming but little  expression,
whilst the animal is  labouring under any emotion, if we make ex-
ception of the  brute passion  of anger  and of one or  two others.
Hence it is, that, by some naturalists, man has been  defined, by
way of distinction, "a laughing and crying animal."   In  animals,
almost all the facial expression of internal feeling is confined to the
eye and the mouth,  whilst the  attitude of the body  is variously
modified, and the hair  is raised by the panniculus carnosus,—as
we see on  the back of the dog, when the animal is enraged.
   In  the  human countenance, alone,  in  the state  of  society,
can  the  passions be read, the  rest  of the  body being  covered
by clothing; and even were it not, the  absence of a coat  of  hair,
and of a  panniculus carnosus,  would  enable it to minister but
little to  expression.   The  skin of the  face  is very fine, and in
certain parts, as on  the lips and  cheeks, is habitually more or less
florid, and admits of considerable  and expressive variations in its
degree of colour. The union of the different parts, composing the
face,  gives occasion to numerous  reliefs, which are called traits
or features; and, beneath the skin, are  many muscles, capable, by
their contraction, of modifying the features in a thousand  ways.
   To comprehend fully the physiology of the facial expression of
the passions, a few observations will be necessary, regarding these
muscles of the human face.
   The eyebrow is a  part greatly concerned in expression;  and cer-
tain muscles are attached to it for  the purpose of moving  it.
   The fasciculus of fibres, which descends from the frontal mus-
cle A, Fig. 31, and  is attached to the side of the nose, has  been
esteemed,  by some,  to  be a distinct muscle, and to have a distinct
operation.   It  draws the inner extremity of the eyebrow down-
   • The ingenious work of Dr. James Rush, of  Philadelphia, on the Philosophy:
of the Human Voice, may be consulted, on this subject, with great advantage. 
400            MUSCULAR MOTION.--EXPRESSION.

wards.  When the orbicularis palpebrarum, C C, and the last
muscle  act, there is a  heavy lowering expression.   If they  yield
to the action of the frontal muscle, the eyebrow is arched, and  there
is a cheerful, inquiring expression.  If the corrugator supercilii
acts, there is more or less of mental anguish, or of painful exercise
of thought.   If it combines with the frontalis, the forehead is fur-
rowed, and there is an  upward inflection of the inner extremity of
the eyebrow, which indicates more of querulous and weak anxiety.
   " The arched and polished forehead," says Sir Charles Bell, of
whose elegant and accurate Essays on the Anatomy and Philoso-
phy of Expression we shall occasionally avail ourselves on this branch
of our subject, " terminated by the distinct line of the eyebrow, is
a table, on  which we  may see written, in perishable characters,
but distinct while they continue, the  prevailing cast of thought;
and by the indications here, often the mere animal activity dis-
played in the motions of the lower part of the face, has a meaning
and a force given to it.   Independent of the actions of the muscles,
their mere  fleshiness gives character to this part of the face.  The
brow of Hercules wants the elevation  and form of intelligence;
but there may be  observed  a fleshy fulness on the forehead, and
around the eyes, which  conveys an idea of dull brutal strength,
with a lowering and gloomy expression, which  accords with the
description in the Iliad."
   The orbicularis palpebrarum, Sir Charles Bell separates
into two muscles;—the outer, fleshy, circular band, which  runs
round the margin of the orbit; and the lesser band of pale fibres,
which lies  upon the eyelids.  These last are employed in the act
of closing the eyelids,  but the former is only  drawn into action in
combination with the other muscles of the face in expressing pas-
sion, or in some convulsive excitement of the organ.  In laughing
and  crying, the outer and  more  powerful  muscle is  in  action,
gathering up the skin about  the eye, and forcing back the eyeball
itself.   In drunkenness, the power of volition over this muscle is
diminished; and there  is an attempt to raise the upper eyelid by a
forcible elevation of the eyebrow.
   The muscles of the  nostrils are;—first, the levator labii supe-
rioris alaeque nasi, D, Fig.  31, which, as its name imports, raises
the upper lip and nostril; 2dly, the compressor  nasi, E, a set of
fibres, which  compress the  nostril; and 3dly, the  depressor alse
nasi, which lies under the orbicularis oris, and whose function is
indicated by its name.
   These three muscles serve to expand and contract the opening
or canal of the nostril; moving in consent with the muscles of re-
spiration;  and thus  the  inflation of the nostrils  indicates general
excitement, and animal activity.
   The muscles of the  lips are; 1, the levator labii proprius, F,
which raises the upper  lip; 2dly, the levator anguli oris, G, which
raises the angle of the  mouth; and 3dly, the zygomatic muscle,
H, which is inserted into the angle of the  mouth.   Sometimes 
              GESTURES.—MUSCLES OF  THE  FACE.         401

an  additional muscle  of  this name  exists;—the zygomaticus
minor.
  These last muscles raise the upper lip and the angle of the mouth,
so as to expose the canine teeth.   If they be in action, contrary to
the orbicularis oris, there is a painful and bitter expression;  but if
they are influenced along with the orbicularis oris and orbicularis
palpebrarum,—if the former of these muscles be relaxed, and the
latter contracted,—there is a fulness of the upper part of the face,and
a cheerful, smiling expression of countenance.
  The orbicularis oris, K, closes the  mouth; and, when allowed
to act fully, it purses the lips. The nasalis labiisuperioris,X, draws
down the septum of the nose. The triangularis oris, or depressor
labiorum, N, indicates, by its name, its function. The quadratus
menti, 0, is a depressor of the lower lip. The levatores menti, P,
by their action, draw up the chin, and project the lower lip; and
the buccinator, R, is  chiefly for turning the  alimentary bolus in
the mouth; and, in broad laughter, it retracts the lips.
  The orbicularis muscle is affected in the various emotions of the
mind;  trembling and relaxing in both grief and  joy.   It relaxes
pleasantly in smiling.
  The union of these various muscles at the angle of the mouth,
produces  the fleshy prominence, noticed in those who  have thin
faces; and who are, at the same time, muscular.  When the cheeks are
fat and full, the action of these muscles produces the dimpled cheek.
  The angle of the mouth is full of expression, according as the
orbicularis, or Ihe superior, or inferior muscles, inserted into  it,
have the preponderance.
  Lastly, the temporal muscle is a strong muscle, which raises
the lower jaw.  It is assisted by the masseter, which lies on the
outside of the lower jaw, arises from the jugum, and is inserted
into the angle of the jaw.
  Two different nerves are distributed to these muscles;—the fifth
pair; and the portio dura or facial of the  seventh.  Whilst the first
of these conveys to them the volition, necessary for their ordinary
movements  of mastication, &c,  the  latter  is concerned in  the
movements of expression.  This the experiments of Sir Charles
Bell  has satisfactorily demonstrated; and comparative anatomy
exhibits, that the  number and intricacy of these nerves vary in
proportion to the animal's power of expression.
  The nerves of the face and neck of the monkey are  numerous,
and have frequent connexions; but on cutting the seventh pair, or
respiratory nerve of the face, of Sir Charles Bell's system,
the features are  no longer influenced by the passions.   Yet the
skin continues sensible, and the muscles of the jaws and  tongue are
capable of the actions of chewing and swallowing.  If the respira-
tory nerve of one side be cut, the expression of that side  is de-
stroyed; whilst the chattering, grinning, and  other movements of
expression continue in the other.  In a dog, too,  if the respira-
  Vol. I.                    51 
402
MUSCULAR MOTION.—EXPRESSION.
 tory nerve  of the face be cut, he will  fight as  bitterly, but with
 no retraction of his lips, sparkling of his eye, or drawing back of
 the ears.  The face is inanimate, though the muscles of the face
 and jaws, so  far  as they are  liable to influence  through other
 nerves, continue their offices.
   The game  cock, in the position  of  fighting, spreads a ruff of
 feathers around  his head.   The position of his head and the raised
 feathers are the  expressions of hostile excitement, but, on the di-
 vision of the respiratory nerve, the feathers are no longer raised,
 although the pugnacious disposition continues.
   It has been, moreover, found,  that if the galvanic influence be
 passed from one divided extremity of the respiratory nerve to the
 other, the facial expression returns; and, in certain cases of incom-
 plete hemiplegia, in which the expressive movements  of the face
 were alone rendered impracticable, the disease was found to have
 implicated only  the respiratory or facial nerve.
   Independently of the  various  muscular actions, which modify
 the expression of the human countenance, there are certain other
 indications which mark the different mental emotions.  The skin,
 for example, varies in  colour, becoming pale or suffused;  and  fre-
 quently alternating rapidly between these two conditions.  These
 changes are more especially witnessed on the forehead, cheeks, and
 lips; and  arise  from an augmented  or diminished flow of blood
 into the capillaries of the part, under the influence of the existing
 emotion: under  such circumstances the eye may participate in  the
 suffusion. The skin may also vary in its degree ofmofsture or of heat.
 It may be dry, or bathed  in perspiration; and the perspiration may
 be warm or cold;—the  two  conditions occasionally alternating
 frequently.  Particular parts of the face,  again,  are more suscepti-
 ble of this " sweat of  expression," as it has been termed:—the
 forehead and temples, for example.   The heat of the head is also
 occasionally modified;  a  sudden glow will be felt in the counte-
 nance; and this will be sometimes evident to a second person.
   The expression of the human eye, connected  with the action of
 the oblique muscles, has been  referred to under vision.   It was
 there asserted, that, in insensibility, the eye is given up to the ac-
 tion of the oblique muscles, and is drawn up under the upper eye-
 lid. The eye itself is, however, capable of various expressions,  de-
 pending upon varied position of its tutamina;  and especially of
 the secretion  from its mucous covering—the conjunctiva—and
 from the lachrymal gland; so that the eye may be  swimming, or
 the tears may flow over the cheeks and constitute weeping.
   In addition to these, which may be regarded as the  sources of
 expression in the human  countenance, we may add the action  of
 osculation or kissing, which, wherever practised, is employed as
 an expression of love and friendship; confined with us to those of
 the female sex, or of opposite sexes;  but, in some countries, em-
ployed as an expression of regard between males also. 
GESTURES. —LAUGHTER.
403
   It is impossible for us to describe all the facial expressions of
which the human countenance is susceptible.  They are commonly
classed under two heads:—the exhilarating, in which the face is
flushed, and  the countenance  expanded; the muscles being  con-
tracted from  within to without; and the depressing, in which, on
the contrary, the face is pale, and the features are  drawn inwards
and sunken.
   Let us inquire  into the physiology of a few of these  expres-
sions; beginning with  the play of  the features in broad laughter,
as being, perhaps, the  most easy of explanation.   In laughing, it
is in vain that we endeavour to confine  the lips; a  complete re-
laxation of the orbicularis oris gives uncontrolled power to the op-
ponent muscles inserted into the angles  of the mouth and upper
lip.  Hence the lateral retraction of the angles of the mouth; the
elevation of the upper lips disclosing the teeth; the peculiar eleva-
tion of the nostrils without their being expanded, and  the dimple of
the cheek, where the acting muscles congregate; and hence, also, the
fulness of the cheeks, rising so  as to conceal  the eye, and throw
wrinkles about the lower eyelids and the temples.  In this  expres-
sion, the whole of the movable features are raised upwards.   The
orbicularis palpebrarum does not partake of the relaxation of the
orbicularis oris.   It is  excited, so as to contract the eyelids, and
sink the eye, whilst the struggle of a voluntary effort of the mus-
cles to open the eyelids, and raise the eyebrow, gives a twinkle to
the eye, and  a peculiar obliquity to the eyebrow; the outer part of
which is most elevated.

                           Fig. SO.
 
404
MUSCULAR MOTION.--EXPRESSION.
  In this movement of expression we have a striking instance of the
associated action of the  different parts of the respiratory system of
nerves of Sir Charles  Bell.  The facial expression is under the
direction of the portio  dura or respiratory nerve of the face.   At
the same time, the individual holds his sides to control the  con-
tractions of the  muscles of the ribs.  The diaphragm is violently
agitated. The same influence spreads to the throat, and the sound
of laughter is as distinct as the signs in the face.
  In the face of a Faun, Fig. 81, sketched by Sir Charles Bell,
we have the expression of weeping from pain.

                          Fig. 81.
  In the violence of weeping, accompanied with lamentation and
outcry,  the face is flushed or suffused from the stagnation of blood
in the vessels.  The muscles of respiration are here affected from
the commencement, and the return of the blood from the head is
somewhat impeded.   The muscles  of the cheeks, are in action.
Those that depress the angles of the mouth are powerfully con-
tracted, and the orbicularis oris is not relaxed, but drawn open by
the predominant action of its opponents.
  A convulsive action in the muscles about the eyes attends; the
eyebrow is drawn down; the eyes are compressed by the eyelids; 
GESTURES.—WEEPING.                405
the cheek is raised; the nostril drawn out, and the mouth stretched
laterally.   In weeping, also, unless the convulsive  action of the
muscles be very strong, the expression of grief affects that part of
the eyebrows which is next the nose.  It  is turned  up with  a
peevish expression, which corresponds with  the depression of the
corners of the mouth.
   This depression of the angle of the mouth gives  an air of des-
pondency and languor to the  countenance, when accompanied by
general relaxation of the muscles. When the corrugator co-operates
there is mingled in the expression something of mental energy, of
moroseness, or pain.  If  the  frontal muscle unites  its action, an
acute turn upwards is given to the inner part of the eyebrow, very
different from the effeet of the general action of  the frontal mus-
cle, and  characteristic  of aguish, debilitating pain,  or  of discon-
tent, according to the prevailing  cast of the rest  of the coun-
tenance.
   The depression, however, of the angle of the mouth, that indi-
cates  languor and despondency, must be slight; as  the depressor
anguli oris, (Fig. 31, N.) cannot act forcibly, without the action
of the superbus being induced,—a muscle, which quickly produces
a revolution in the expression and makes the under lip pout con-
temptuously.
   The expression at the angles of the mouth demands  the careful
study of the painter; the most opposite characters being communi-
cated to  the countenance by their elevation or depression. When
Peter of Cortona was engaged on a picture of the iron age for the
royal Palace of Pitti, Ferdinand II. who often  visited him, and
witnessed the progress of the piece, was particularly struck with
the exact representation of a child in  the act of crying.   "Has
your  majesty" said the painter "a mind to  see how easy it is to
make this very child laugh?"   The king assented: and the artist,
by merely depressing the corner of the lips and inner extremity
of the eyebrows, made the child, which  at first seemed breaking
its heart with weeping, seem equally in danger of bursting its sides
with  immoderate laughter.  After which, with the  same ease, he
restored the figure to its proper expression of sorrow.
   It is at the angle of the mouth and the inner  extremity of the
eyebrow, that the expression, which is peculiarly human, is situ-
ated.   They are  the  most movable parts of the face.  In them
the muscles are concentrated, and it is upon their changes, that ex-
pression is acknowledged chiefly to depend.   All the parts, how-
ever, of an impassioned countenance have an accordance with each
other.  When the angles of the mouth are depressed in grief, the
eyebrows are not elevated at the outer angles as in laughter.  When
a smile plays around the mouth, or when the cheek is elevated in
laughter,  the eyebrows are not ruffled as in grief.  In real emo-
tion, these opposite actions cannot be  combined; and when  they
are united by the mimic the expression is farcical and ridiculous. 
406
MUSCULAR  MOTION.--EXPRESSION.
   In bodily pain, the jaws are pressed together and there is grinding
 of the teeth.  The lips are drawn laterally, so as to expose the teeth
 and gums; the nostrils are distended to the utmost, and, at the same
 time, drawn  up;  the eyes are largely uncovered, and the eyebrows
 elevated; the face is turgid with blood, and the veins of the temple
 and forehead are distended; the breath  being  suspended,  and the
 descent of the blood from the head impeded.
   In  anguish, conjoined with bodily suffering, the jaw falls; the
 tongue is seen; and, in place of the lateral retraction of the lips, the
 lower lip falls, the eyebrows are knit, whilst their inner extremi-
 ties are elevated; the pupils  of the eyes  are in part concealed by
 the upper eyelids and the nostrils are agitated.  Agony of mind is
 here added to the bodily suffering, which is particularly indicated
 by the change in  the eyebrow and forehead.
   In  rage, the features are unsteady: the eyeballs are largely seen,
 roll, and are inflamed.  The'forehead is alternately knit and raised
 in furrows, by the  motion of  the eyebrows; and the nostrils are
 inflated to the utmost; the lips are swelled, and, being drawn, open
 the corners of the mouth.  The action of the muscles is strongly
 marked.   The  whole countenance  is sometimes  pale, and some-
 times inflated, dark, and almost livid; the words are passed forcibly
 through the fixed teeth and the hair is on end.
   Fear has  different degrees.   Mere bodily fear resembles the
 mean anticipation of pain.  The eyeball is largely uncovered; the
 eyes are staring, and the eyebrows elevated to the utmost stretch.
 To these are added a spasmodic affection  of the diaphragm and
 muscles of the chest, which affects the breathing, and produces a
 gasping in the throat, with an inflation  of the  nostril, convulsive
 ope^ngofthe mouth and dropping of the jaw;—the lips nearly
 concealing the teeth, yet allowing the  tongue to  be seen;—the
 space between the nostril and lip  being  full.   There is  a hoUow-
 ness and convulsive motion of the cheeks, and a  trembling of the
 lips and muscles on the sides of the neck.  The lungs are kept dis-
 tended; and the breathing is short and rapid.   The surface is pale
 from the recession of the blood; and the hair  is  lifted  up  by the
 creeping of the skin.
   In  fear, where  the apprehended danger is more remote, but is
 approaching,  the  person trembles and looks pale; a cold sweat is
 on his face;  the scream of fear is heard; the  eyes start forward;
 the lips are drawn wide; the hands are clenched, and the expression
 becomes  more  strictly animal, and indicative of such  fear as is
 common to brutes.
   In terror,or that kind of fear,in which the mind participates more,
 there  is a more varying depression in the features, and  an action
 of those muscles,  that are peculiar to man, and which  seem to in-
dicate  his superior intelligence and mental feeling.   The eye is
 bewildered, the inner extremity of the  eyebrows turned  up and
strongly knit, by the action of the corrugator and orbicular muscles; 
GESTURES. —PHYSIOGNOMY.
407
and distracting thoughts, anxiety and alarm are strongly indicated
by this expression, which does not belong to animals.  The cheek
is slightly elevated, and all the muscles, that concentrate about the
mouth are in action.
  In admiration, the forehead is expanded  and unruffled; the eye-
brow gently raised; the  eyelid lifted so as to expose the coloured
circle of the eye, whilst the  lower part of the face is relaxed into
a gentle smile.  The mouth is open; the jaw a little fallen; and, by
the relaxation of the lower lip, we just perceive the edge of the
lower teeth and  the tongue.
  In joy, the eyebrow is raised moderately, but without any an-
gularity; the  forehead is smooth; the eye full, lively  and sparkling;
the nostril moderately inflated and a smile is on the lips.
  This subject is, however,  interminable.  Enough has been said
to exhibit  the anatomy of  the varying characters of facial ex-
pression.  It wilt  be  found beautifully treated and illustrated
in the work  of Sir Charles Bell to which reference  has  been
made.
  From all that has been said, it is evident, that the countenance
is a good general index of the existing state of the feelings; but
farther than  this it cannot be depended  upon.   Yet, in all  ages,
it has been regarded as the index  of  individual character.  John
Baptist Porta and Lavater have endeavoured to establish a
science, by which we can be instructed, how to discover the secret
dispositions of the head and the  heart from the examination of
particular features.  The latter enthusiast, in particular, appears to
have carried his  notions to the most chimerical extent.   " No
study," he remarks, "excepting mathematics, morejustly deserves
to be termed a science than physiognomy.   It is a department of
physics including theology and belles lettres, and in the same Wan-
ner with these sciences may be reduced  to  rule.  It may acquire
a fixed and appropriate character.  It may  be communicated and
taught."
   In another place, he remarks, that no person can make a good
physiognomist  unless  he is a well-proportioned  and handsome
man; yet he  himself was by  no  means  highly  favoured in
these respects,  and  it  is, consequently, difficult  to say, accord-
ing  to  his  own theory, how  he attained  such progress in the
" science."
   There is one case, and perhaps, one only, in which physiognomy
can  aid us in the appreciation of character.  We have remarked,
that the facial expression will  accurately depict the existing emo-
tion.  If, therefore, any passion be frequently experienced, or
become  habitual, its character may  remain impressed  upon the
countenance, and an opinion be formed of the individual accord-
ingly.  No  one, who has seen the melancholy mad, can mistake
the piteous expression produced by  brooding over the  corroding
idea that engrosses him. 
408           MUSCULAR MOTION.--EXPRESSION.

                          Fig. 82.
  ki  the above sketch,  from Sir Charles  Bell, we  have the
testy, peevish countenance, bred of melancholy; of one who is inca-
pable of receiving satisfaction from whatever source it may be of-
fered, and who " cannot  endure  any man to  look steadily  upon
him, or even to speak to  him, or laugh, or jest, or be familiar, or
hem, or point, without thinking himself contemned, insulted, or
neglected."  SucK a countenance no one can  misapprehend.
  In lesser degrees particular features are found bearing, or seeming
to bear, the impress of particular emotions; and, accordingly, we are
in the daily habit of forming opinions at first sight, both of the in-
tellectual and moral characteristics of individuals,  by the  expres-
sion of the countenance.  Of course, we are frequently led into
error; inasmuch as the habitual feelings alone are indicated by the
physiognomy, whilst the natural disposition may be of a diametri-
cally  opposite  character.  The  fallaciousness  of this  mode of
judging of mankind has been proverbial, in all times.  When-
ever we attempt to  decide upon a man's intellectual powers, by
the rules laid down by  Lavater, we are constantly  deceived;
and in this  respect, he has himself evidently fallen into the grossest
errors. 
gestures.                       409
  What may be, not inappropriately, styled medical physiognomy
or the changes of features indicative of, and peculiar to, different
diseases and stages of disease, is a subject of much moment and has
not met with sufficient attention.   In  diseases of infancy, in parti-
cular, the appearance  of the countenance will often materially aid
us in discriminating the seat of the affection.   There is a marked
difference between the facial expression of one labouring  under
violent pain in the head, and that of one suffering from excruciat-
ing pain in the abdomen, even in  the adult.  Lesser  degrees of
pain are, of course,  disregarded, and it is only in severe cases, that
physiognomy can be  inservient  to  diagnosis; but,  in  the  infant,
which readily gives  expression to any pain or  uneasiness, the
countenance is an excellent medium  of discrimination, and will
frequently indicate, at the first glance, the seat of the derangement.
  The character, too, of the countenance, in serious disease, as to
anxiety, convulsion, &c., is often a subject of watchful interest with
the  physician.
  Mute expression  is not, however, restricted to the face, although,
as we have remarked,  in civilized man, whose nakedness is covered,
we  are shut out from the observation of many of the acts of this na-
ture.  During emotion, the skin, covering the body, may participate
with that  of the face, in its changes from pale to red;  and it may
be warm or cold, dry or bathed in perspiration, or during  parti-
cular depressing passions may creep and exhibit the rough charac-
ter  of the cutis anserina or goose skin.   Under particular emo-
tions, the erectile tissues of the organs of generation and of the
nipple in the female experience turgescence.  All  these changes
are  more or less concealed from view.   We are, therefore, more
familiar with the sight of those phenomena of expression, that af-
fect the whole body, as regards its different attitudes and model of
progression.   How tremulous and vacillating is  the  attitude of
one labouring strongly under fear ; and how different the port of
the meek and lowly from that of the proud  and haughty?   In
walking,  we  observe a similar difference;  and  can  frequently
surmise the character of the passion,  whether exhilarating or de-
pressing, under which a person, at a  distance, may be labouring,
merely from  the particularity of his progression.

                    " You may sometimes trace
           A feeling  in each footstep, as disclosed
             By Sallust in his Catiline, who, chased,
           By all the demons of all passions, showed
           Their work even by the way in  which he trode."

  Again,  on  the communication of sudden tidings of joy, we feel
a desire to leap up,  and to  give way to the most wild and irregular
motions; whilst the shrinking within  ourselves, as it were, and
the  involuntary shudder, sufficiently mark the reception of a  tale
of horror.
  Vol.  I.                    52 
410           MUSCULAR MOTION.--EXPRESSION.

  Many of the partial movements constitute an important part of
the language of expression, especially with the savage, and  with
those unfortunates, who are shut out from the advantages of spoken
language.
  In almost all nations, the motions of the head on the vertebral
column are used as signs of affirmation or negation ; the former be-
ing indicated by a sudden and short forward flexion of the head on
the column;  the latter, by a rapid and short rotation on the axis
or vertebra dentata.  The shoulders are shrugged, in testimony of
impatience, contempt,  &c.
  The upper extremities are extensively employed as a part of con-
ventional language, and were probably used for this purpose before
speech was invented.   The open and the closed hand are used to
communicate  different impressions  to the observer; the pointed
finger  directs attention  to the object we wish to indicate, &c.
When persons are  at  such a distance from each  other, that the
voice cannot  be heard, this is the only language they can have re-
course to; and the various important inventions, by which we com-
municate our feelings to distances, such as writing, telegraphing,
&c. belong to this variety of language.
  For the deaf and dumb, our ordinary spoken language is trans-
lated into gestures, by  which  a conversation can be held, sufficient
for all useful purposes; whilst the deaf, dumb, and blind, are re-
stricted to those gestures that are conveyed through their sense of
touch.
  Each acquired gesture is, like each acquired  movement of the
glottis, an evidence of the possession of intellect.   The infant and
the idiot have them not, because unable to appreciate their utility.
  The gestures resemble the spoken language in this and many other
respects. The eye sees the gesture,  to which the intellect attaches
an idea, as it does to the  sound conveyed by the organ of hearing;
and the will reproduces the gesture, in the same manner as it re-
produces the sound heard. The lower extremities are, also, slightly
concerned in the function of expression.   They are agitated when
we are impatient, and incessantly changing their position. The foot
is stamped upon the ground in anger; and, like the upper extremity,
is employed  to convey to the object  that has aroused the emotion—
the most unequivocal evidences of expression.  Occasionally,  the
lower  extremity is used as a part of conventional language, as when
we tread upon the toes, to arouse attention, or to convey insult.
  Nor are the internal organs foreign to the function of expression.
The respiratory movements are affected, the number of respirations
being  accelerated or retarded, or manifesting themselves under the
different modifications of sighing, yawning, laughing, and sob-
bing.   The  heart, too, will  throb, sometimes  to  such an extent,
that  its action is perceptible externally ; or it may be retarded or
hurried in its pulsations, from the state of syncope or  fainting to
that of the most violent palpitation. 
GESTURES.                       411
  Lastly, the excretions, especially some of them, are greatly con-
cerned in many of these moral changes. That of the tears is a well
known and characteristic expression, of grief more especially, but
occasionally of joy.  The mind is, however, at times, so possessed
by the emotion,  that the ordinary power over  the sphincter mus-
cles is more or less destroyed, and the contents of the rectum are
spontaneously evacuated.  The action of the stomach is, at times,
inverted; and, at others, the peristaltic action is augmented. Who
has not felt, whilst labouring  under anxiety or  dread, the constant
desire not only  to  evacuate  the  faeces, but also the urinary se-
cretion ?
  It is obvious,  from this detail, that there is scarcely a function,
which does not express some participation, when the mind is en-
gaged in violent emotion; and that it would be vain to attempt to
depict the various forms,  under which these manifestations may
occur.  What has been said will  suffice to attract attention to the
subject, which is not devoid of interest to  the anthropologist.
  In  conclusion, we may refer to the  question, which  has often
been  agitated, whether these rapid  and violent  movements, that
characterize the expression of emotions, be instinctive or natural
signs of the passions existing in the mind; or whether they be not
voluntary, muscular exertions, called for by the stress of the case,
and constituting the means of resistance,  or belonging  simply to
the outward manifestation of the inward emotion.  The supporters
of the latter view contend, that the various changes of facial ex-
pression or of gesture, which accompany the different mental emo-
tions and indicate their character, are, in all cases, the effect of
habit, or are suddenly excited to operate some beneficial purpose.
It is difficult,  however, to regard the different  concomitants of the
passion,  as separate from it.   Without them, the expression is in-
complete; and we observe the different gestures similarly developed
in all the various races of mankind, when labouring under the same
mental contention.  We must, consequently, regard the expressions
as constituting a natural language, in which each has its own ap-
propriate sign;  and this view is signally confirmed by the fact, that
there are certain muscles of  the face, which seem,  in our existing
state of knowledge, to be exclusively destined for expression; those
about the eyebrow  and angles of the mouth for example, on which
we have  already expatiated.   When the triangularis  muscle, N,
Fig.  31, and the levator menti, P, combine in their action, an ex-
pression is produced, which  is peculiar to man;  the angle of the
mouth is drawn down, and the lip arched and elevated; hence the
most contemptuous and proud expression.
   A question of a different character has,  however, been mixed up
with this:—whether the infant is capable instinctively or naturally
of comprehending the difference between the  facial expressions of
kindness or of frowns; some believing, that smiles are merely con-
sidered by it to be expressions of kindness, because accompanied 
412
MUSCULAR MOTION. —EXPRESSION.
   y endearments, and frowns as proofs of displeasure, because fol-
  Jowed by punishment. It is certain, however, that the infant inter-
  prets the countenance long before it  can trace such sequences  in
  its mind; but this does not remove the difficulty. The face of one,
  whom it has not been accustomed to  see, will, at a very early pe-
  riod, impress it unfavourably, even although the countenance may
  be unusually prepossessing;" and the alteration of the ordinary ex-
  pression of the maternal  countenance may be attended with similar
 results.  It is difficult, indeed, to comprehend how the child should
 be capable of discriminating between the smile and the frown, when
 first exhibited to it.  That organs may be associated, in the expres-
 sion of any encephalic act, is intelligible;  but that an act of judg-
 ment can be executed naturally or instinctively, appears inexplica-
 ble. Sir Charles Bell, who maintains the doctrine of the instinc-
 tive character of the expression of human passions, rejects the no-
 tion of instinctive expression in the  face of  the quadruped,  con-
 tending that, even in the  passion of rage, which is the most strongly
 marked of all, the changes, that occur in the features, are merely mo-
 tions, accessary to the great object of opposition, resistance, and de-
 fence.  " In carnivorous animals," he remarks,"the eyeball is terri-
 ble,and the retraction of the flesh of the lips indicates the most savage
 fury. But the first is merely the excited attention of the animal, and
 the other a preparatory exposure of the canine teeth."  It appears,
however, to be  a sufficient answer to this view, that no such expres-
sion is ever witnessed in other cases of excited attention, or in the
simple exposure of the canine teeth, when the animal is devouring
its food; unless, indeed, the  repast  may  be  effected, during the
prevalence of the passion.
  On a former  occasion,  it was remarked,  that the encephalon  is
exclusively concerned in the production of the  different passions;
 and that the parts to which they are  usually referred, attract our
 attention to them principally, in consequence of the sensation that
 accompanies them being  there chiefly experienced.  The same may
 be said of the different gestures, that accompany the various emo-
 tions.   They are dependent upon  the  influence, exerted by the
function of sensibility on the other functions.   Gall,  in his  sys-
 tem, has feebly attempted to show, that each gesture has a refer-
 ence to the encephalic situation of the organ, concerned in the pro-
 duction of the emotion of which it is a concomitant.  The idea was
 suggested to him, he asserts,  by the fact, which he  had observed,
 a thousand times, that  in fractures of the skull, the hand, (very
 naturally we should  think,) was carried  mechanically to  the seat
 of the fracture.  He farther remarks, that the organs of the memory
 of words and of meditation are seated in the forehead; and that the
 hand is carried thither, whenever we  are engaged in deep study:—
 that the organ of religious instinct corresponds to the vertex, and
 hence in the act of prayer, all the  gestures are directed  towards
 this part of the body.  Like every professed systematist  Gall is 
GESTURES.                       413
here pushing his principles ad absurdum.  They are, indeed, con-
troverted by facts.  The hand is usually carried, not to the part of
the encephalon, in which any passion is effected, but to the part
of the body in which its more prominent effects are perceptible, as
to the region of the stomach or heart; whilst, frequently, the ges-
ture is referable to the determinate action, which must be regarded
as a necessary effect of the passion.
   Finally, poetry and painting belong properly to the varieties
of expression;  but they are topics, that do not admit of elucidation
by physiology.

   With this subject we terminate the history of the animal func-
tions.  All these  have the common character of being periodically
suspended  by sleep.  By many physiologists, this  function has,
therefore, been examined in this place; but as the  nutritive and
generative functions are, likewise, greatly influenced by sleep, we
shall follow the example of Magendie, and defer its study, until
we have inquired into those functions. 
'114
NUTRITIVE FUNCTIONS.
                        CLASS  II.

                NUTRITIVE FUNCTIONS.

  The human body, from the moment of its formation to the ces-
sation of existence, is undergoing  incessant decay and renovation
—decomposition and composition:—so  that, at  no  two periods,
can it be said to consist of exactly the same constituents. The class
of functions, about to engage attention,  embraces those that are con-
cerned in effecting such changes.  They are seven in number:—
digestion, by which the food, received  into the  stomach, under-
goes such conversion, as fits it for the separation of its  nutritious
and excrementitious portions: absorption, by which this nutritious
portion, as well as other matters, is conveyed into the mass of blood:
respiration, by which  the products  of absorption and the venous
blood are converted into arterial blood: circulation,  by which the
vital fluid is distributed to every part  of the  system: nutrition,
by which these intimate  changes of composition and decomposi-
tion are accomplished: calorification, by which the  system is
enabled to  resist the effects  of greatly elevated  or  depressed at-
mospheric temperature, and to exist in the burning regions within
the tropics, or amidst the arctic snows: secretion, by which vari-
ous fluids and solids  are separated from the blood; some  to serve
useful purposes in the animal economy; others to  be  rejected from
the body.

                      OF DIGESTION.

  The food, necessary  for animal nutrition, is rarely found in such
a condition as to be adapted  for absorption.   It has, therefore, to
be subjected to various actions in the digestive organs;  the object
of which is to enable the nutritive matter to be separated from it.
These various actions constitute the function of digestion; in the in-
vestigation of which we shall commence with a brief description of
the organs, concerned in it.  These are numerous and of a somewhat
complicated  nature.

             Anatomy of the Digestive  Organs.

  The human digestive organs consist of a long canal, varying con-
siderably in  its dimensions in different parts, and communicating
externally by two outlets,—the mouth and the anus. It is usually
divided into four chief portions—the  mouth, pharynx and oeso-
phagus, stomach, and intestines. These we shall describe in suc-
cession. 
OIGESTIVE  ORGANS.
415
  1. The mouth is the first cavity of the digestive tube, and that
in which the food is immediately received, and subjected to the ac-
tion of the organs of mastication and insalivation.  Above and below,
it is circumscribed by the jaws,  and laterally by the cheeks;—an-
teriorly, by the lips and  their  aperture, constituting the mouth
proper:  and, posteriorly, it communicates with the next portion of
the tube,—the pharynx.
  It is invested by a mucous exhalant membrane, which is largely
supplied with follicles; and into  it the ducts from the different sa-
livary glands pour their secretion.
  Mastication is of essential importance to digestion, and  an inat-
tention  to this circumstance is a common  cause of dyspepsia.  In
all animals, furnished  with distinct digestive organs, some means
exist for comminuting the food, and  enabling the stomach to act,
with greater facility, upon it.
  These consist,  for the most  part, as in  man, of the jaws: the
teeth fixed into the jaws, and of  muscles by which the jaws are
moved.
  The jaws chiefly determine  the  shape and  dimensions of  the
mouth; the upper forming an essential part of the face, and moving
only with the head; the lower,  on the contrary, possessing great
mobility.
  Each of the jaws has a prominent edge, forming a semicircle,
in which the teeth are implanted.  This edge is called the alveolar
arch.
  The teeth are small organs, of a density superior to bone;  and
covered externally by a hard  substance, called enamel.  By many,
they have been regarded as bone, but they differ from it in many
essential respects, although they resemble it in  hardness and che-
mical composition.  At another  opportunity, we shall inquire into
their origin, structure and development. We may merely remark,
at present, that by De Blainville they are looked upon as ana-
logous to the corneous substances, which develope themselves in the
tissue of the skin.   He assimilates them to the hair, and believes,
that they are primarily developed in the substance of the membrane
lining the mouth, in the tissue of the gums; and that their enclosure
in the substance of the alveolar arches of the jaws occurs subse-
quently.
  The number of the teeth is sixteen in each jaw.   These are di-
vided into classes, according  to their shape  and use.  There are,
in each  jaw, four incisores; two cuspidati or canine teeth; four
bicuspidati; and six molares or grinders.
  Each tooth has three parts;—the crown, neck, and fang or root:
the first being the part above the gum: the second that embraced
by  the gum; and  the third the  part contained  in the alveolus or
socket.
  The crown varies in the different classes.  In the incisors, it is 
416                       DIGESTION.
wedge-shaped; in the canine, conical; and in the molars, cubical.
In all it is of extreme hardness, but in time wears away by the con-
stant friction to which it is exposed.
  The incisor and canine teeth have  only  one root; the molares of
the lower jaw, two; and of the upper, three.  In all cases, they  are
of a conical shape, the base of the cone corresponding to the corona;
and the apex to the bottom of the alveolus.  The alveolar margin
of the jaws is covered by a  thick, fibrous, resisting substance, call-
ed  the gum.   It surrounds accurately the inferior part of  the
crown of the tooth, adheres to it strongly, and thus adds to  the
solidity of the junction  of the teeth with the jaws.   It  is  capa-
ble of sustaining considerable pressure without inconvenience.—
But we  shall have  to  return to the subject of the teeth  here-
after.
  The articulation of the lower jaw is of such a nature as to admit
of depression and elevation; of horizontal motion  forwards, back-
wards and  laterally; and of a semi-rotation upon one of its con-
dyles.
  The muscles, that move it, may be thrown into two classes:  the
elevators ,and depressors.   These, by a combination of their con-
traction, can produce every intermediate movement between ele-
vation and depression.   The raisers or levator muscles of the jaw
extend from the cranium and upper jaw to the lower.   They  are
four in number;  the temporal, and  masseter, which  are entire-
ly concerned  in  this function; the  external pterygoid, which,
whilst it raises the jaw, carries it, at the same time, forward and
to one side; and the internal pterygoid, which, according as it
unites its action with the temporal or with the external pterygoid,
is an elevator of the jaw or a lateral motor.
  The depressors may be divided into immediate and mediate,  ac-
cording as  they are, or are not, attached to  the lower  jaw itself.
There are only three of the former class:  1, the digastricus,  the
anterior  fasciculus of which, or  that which passes from the  os
hyoides to the lower jaw, depresses the latter; 2, the genio-hyoideus;
and, 3, the mylo-hyoideus, which concur in the formation of the
floor of the mouth.
  The indirect or mediate depressors are all those, that are situated
between the trunk and lower jaw, without being directly attached
to the latter;—as the thyro-hyoideus, the sterno-thyroideus, and
the omo-hyoideus;  the names of which indicate their  origin and
insertion.  These, in the aggregate, form a muscular chain, which,
when it makes the trunk its fixed  point, depresses the lower jaw.
The arrangement of the elevators and depressors is such, that  the
former predominate  over the latter;  and hence, during sleep, the
jaws continue applied to each other, and the mouth is, consequently,
closed.
  The human organs of mastication hold an intermediate place be- 
DIGESTIVE  ORGANS.                  417
tween those of the carnivorous and herbivorous animal.   In the
Fig. 83.
Skull of the Polar Bear.
Fig. 84.
 carnivorous ani-
 mal,  which  has
 to seize hold of,
 and   retain  its
 prey between its
 teeth,  the jaws
 have  considera-
 ble strength; and
 the movement of
 elevation  is  all
 that  is  practica-
 ble;  or, at least,
 that  can  be  ef-
 fected to any  ex-
 tent. This is dependentupon orga-
 nization. The condyle is broader
 from side to side, which prevents
 motion in that direction: the gle-
 noid cavity is very deep, so that
 the head of the  jaw bone cannot
 pass out from it; and it is, more-
 over,  fixed in  its place by two
 eminences beforeand behind. The
 muscular apparatus is also so ar-
 ranged as to  admit of  energetic
 action on the  part of the muscles
 that raise the jaw; but of scarcely
 any in a horizontal direction.  The
 deep depressions, in the regions
 of the  temporal  and  masseter
 muscles, indicate their large  size
 in the purely carnivorous animal;
 whilst the  pterygoid muscles are
 extremely  small.  The teeth, too,
 are characteristic; the molares be-
 ing comparatively small, at the
 same  time, that  they  are much
 more  pointed.    On  the other
 hand, the cuspidati are remarkably large; and the incisors, in ge-
 neral, acuminated.
   The herbivorous animal has an arrangement the reverse of this.
The condyle or head of the lower jaw is rounded; and can, there-
fore, be moved in all directions; and as easily horizontally as up
and down.  The glenoid cavity is shallow, and  yields the same
facilities.   The  articulation,  which is very close in the carnivo-
rous animal, is here  quite loose.   The elevator muscles are much
  Vol. I.                     53
Skull of the Cow. 
418
DIGESTION.
more feeble; the temporal fossa is less deep; the zygomatic arch
less convex; and the zygomatic fossa less extensive.  On the other
hand, the pterygoid fossa  is ample, and the muscles of the same
name largely developed.   The molares are large and  broad; and
their magnitude is so great as to require, that the jaw should  be
much elongated, in order to make room for them.
  The joint of the lower jaw has, in man, solidity enough for the
jaws to exert considerable pressure with impunity; and laxity
enough that the lower jaw may execute horizontal  movements.
The action of the levator  muscles is the most extensive; but the
lateral or grinding motion is  practicable  to the necessary  ex-
tent; and the muscles of both kinds have a medium degree of de-
velopment.  The teeth, likewise, partake of the characteristics of
those of the carnivorous  and herbivorous animals;  twelve, viz.
the canine teeth and lesser molares corresponding to those of the
carnivorous, and twenty—the incisors and larger molares—to those
of the herbivorous.
  The tongue must be regarded as an organ of mastication. It rests
horizontally on the floor of the mouth; is free above, anteriorly, and,
to a certain extent, beneath and at the sides. Behind, it is united to
the epiglottis by three  folds of the mucous membrane of the mouth;
and  is supported at its base by the os hyoides, with which it
participates in its movements.  Of the tongue, as the organ of taste
and articulation, we have already spoken.  We have only, there-
fore, to describe the os hyoides and its attachment  to that bone.
The hyoid bone has, as its name imports, the shape  of  the Greek
letter «, (upsilon,) the convex part being before. (Fig. 76.) It is situ-
ated between the tongue and the larynx; and is divided into body or
central part; and into branches, one extremity of which is united
to the body by an intermediate cartilage, that  admits of  slight mo-
tion; whilst the other is  free, and is called  the greater cornu.
Above the point, at which the branch is articulated with the body,
is an apophysis or process, called the lesser cornu.
  The os hyoides is united to the neighbouring parts  by fibrous
organs, and by muscles. The former are;—above, the stylo-hyoid
ligament, which extends from the lesser cornu of the bone to the
styloid process of the  temporal bone; below, a fibrous membrane,
called the thyro-hyoid, passing between the body of the bone and
the  thyroid cartilage; and two ligaments,  extending from  the
greater cornua of the hyoid bone to the thyroid cartilage, called the
thyro-hyoid.  Of the muscles; some are  above the hyoid bone,
and raise it;—viz. the genio, and mylo-hyoideus, already referred
to;  the stylo-hyoid, and some fibres of the middle constrictor of
the pharynx.  Others are below, and depress it.  They are the
sterno-thyro-hyoideus, omo-hyoideus, and sterno-thyroideus.
  The base of the tongue is attached to the body of the bone by a
ligamentous tissue, and by the fibres of the hyoglossus  muscle. 
DIGESTIVE  ORGANS.
419
  Among the collateral organs of mastication  are those which se-
crete the saliva, and the various fluids, that are poured out into the
mouth,—constituting together, what has been termed the apparatus
of insalivation. These fluids proceed from different sources.  The
mucous membrane of the mouth, like other  mucous membranes,
exhales  a serous or albuminous fluid, besides  a mucous fluid se-
creted by the numerous follicles contained in its substance.   Three
glands likewise exist, on each side,  destined to secrete the saliva,
which is poured into the mouth by distinct excretory ducts. They
are the parotid, submaxillary, and sublingual. The first is  situ-
ated between the ear and the jaw; and its excretory duct opens into
the mouth opposite the second small molaris of the upper jaw. By
pressing upon this part of the cheek, the saliva can be made to issue
in perceptibly increased quantity into the mouth.
  The submaxillary gland is situated  beneath the base of the jaw;
and its excretory duct opens into the mouth at the side of the frae-
num linguae.
  The sublingual  gland is situated under  the tongue, and its ex-
cretory  ducts open at the sides of the tongue.
  These glands are constantly pouring saliva into the mouth; and
it has been  presumed, that the  fluids  secreted  by  them  may
differ from each  other  in  physical and  chemical  characters.
Such, at least, has been the  view of  some as  regards the sublin-
gual, the texture of which more nearly resembles that of the com-
pound follicles than of the  glands; but the circumstance  has not
been proved by any direct experiment.  The saliva, as met with,
is a compound of every secretion poured into the mouth; and it is
such fluid which has alone been subjected to analysis.  The secre-
tion of  the saliva  and  its various  properties belong, however, to
another division of the nutritive functions.
  The two apertures of the mouth are the labial and pharyngeal.
The former, as its name imports, is formed by the lips, which con-
sist externally of a layer of skin, are  lined internally by a mucous
membrane,  and,  in  their substance, contain  numerous muscles,
already described under the head of the Gestures.
  These muscles  may be  separated into constrictors and dilators;
the orbicularis oris being the only one of the first class,  and the
antagonist to the others, which are eight in number,  on each side—
the levator labii superioris alaeque nasi, the levator labii supe-
rioris proprius, the levator anguli oris, the zygomaticus major,
the zygomaticus minor, the buccinator, the  triangularis, and
the quadratus menti. (Fig. 31.)  To the two last muscles are
added some fibres of the platysma myoides.
  The pharyngeal opening is smaller than the labial, and  of a
quadrilateral shape.  It is bounded, above, by the  velum palati
or pendulous veil of the palate; below, by the base of the tongue;
and, laterally,  by two muscles, which form  the pillars of the 
420
DIGESTION.
 Jauces.  The pendulous veil is a musculo-membranous extension,
 constituting a kind of valve, attached to the posterior margin of
 the bony palate, by which all communication between the mouth
 and pharynx, or between the pharynx and nose can be prevented.
 To produce the first of these effects it becomes vertical; to produce
 the latter, horizontal.
   At its inferior and free margin, it has a nipple-like shape, which
 portion bears the name of uvula.
   It is composed of two mucous membranes and of muscles.  One
 of the membranes—that forming its anterior surface—is  a pro-
 longation of the membrane lining the mouth, and contains numer-
 ous follicles; the other, forming its posterior surface, is an exten-
 sion of the  mucous membrane lining the nose, and is redder, aud
 less provided with follicles than the other.  The muscles, that con-
 stitute the body of the velum palati, are—the circumflexuspalati
 or spheno-salpingo-staphylinus  of Chaussier;  the  levator pa-
 lati  or petro-salpingo-staphylinus; and the azygos uvulae  or
palato-staphylinus.
  The velum is moved by eight muscles.  The two internal ptery-
 goid raise it; the two external pterygoid stretch it transversely;
 the two palato-pharyngei or pharyngo-staphylini,  and the two
 constrictores isthmi faucium or glosso-staphylini carry it down-
 wards.
   The four last muscles form the pillars of the fauces;—the two first
 the posterior pillars; and the two last the anterior; between which
 are situated the tonsil glands or amygdalae; which are not really
 glandular, but composed of a congeries of mucous follicles.
   2.  The pharynx and oesophagus are two muscular canals, form-
 ing the media of communication between the mouth and stomach,
 and conveying the food from the former of these cavities  to  the
 latter.
   Thepharynxhas the shape of an irregular funnel; the large open-
 ing of the funnel looking towards the mouth and nose, whilst the
 under and smaller end terminates in the oesophagus. Into its upper
 part open,—the nasal fossae, Eustachian tubes, mouth, larynx, and
 oesophagus.   It  is inservient  to useful purposes in the production
 of voice, in respiration, and audition, as well as in digestion ; and ex-
 tends from the basilary process of the  occipital  bone, to which it
 is attached, as far as the  middle part of the neck.  Its transverse
 dimensions are determined by the os hyoides, the larynx, and the
 pterygo-maxillary apparatus,  to which it is attached. It is lined by
 a mucous membrane,  less red  than that which lines the mouth, but
 more so  than that of the oesophagus, and of the rest of the digestive
 tube* and it is remarkable for the development of its veins, which
 form a very distinct net-work. Around this is the muscular layer,
 the circular fibres of which are often divided  into three muscles,—
 the superior, middle, and inferior constrictors.  The longitudinal 
DIGESTIVE  ORGANS.                  421
 fibres form part  of  the stylo-pharyngei and palalo-pharyngei
 muscles.
    The pharynx is raised by the action of the two last muscles, as
 well  as  by  all those that are  situated between the
■ lower jaw and os hyoides, which cannot raise the lat-  Fig. 85.
 ter without, at the same time, raising the larynx and
 pharynx.  These  muscles are:—the mylo-hyoideus,
 genio-hyoideus, and the anterior belly of the digas-
 tricus.
    The oesophagus is a continuation of the pharynx; and a
 extends to  the stomach, where it terminates.  Its shape
 is cylindrical, and it is connected with the surrounding
 parts by loose and extensible cellular  tissue, which
 yields readily to its movements.  On entering the abdo-
 men, it passes between the pillars of the diaphragm,
 with which it is intimately united. The mucous mem-
 brane, lining it, is pale,  thin, and smooth; forming
 longitudinal folds, well adapted for favouring the dila-
 tation of the canal.  Above, it is confounded with that
 of the pharynx; but below, it forms several  digitations,
 terminated by a fringed extremity, which is free in the
 cavity of the stomach. It is well supplied with mucous
 follicles.   The muscular coat is thick, and  its texture
 denser than that of the pharynx:—it  cannot, like that
 of the pharynx, be separated into distinct muscles, but
 consists of circular and longitudinal fibres; the former
 of which are more  internal, and very numerous; the shewing thTime-
 latter external, and less numerous.                   "res.circu
    The marginal figure will exhibit  the situation and l0^udinaietTfi!
 arrangement of the two sets of fibres.                bres-
    3.  The stomach is situated in  the  cavity of the abdomen, and
 is the most dilated portion of the digestive tube.  It occupies the
 epigastric region, and a part of the  left hypochondre.   Its shape
 has been compared,  not inappropriately, to that of the  bag  of a
 bag-pipe. It is capable of  holding, in the adult male, when mode-
 rately distended, about three pints.  The left half of the organ has
 always much greater dimensions than the right.  The former has
 been called the splenic portion, because it rests upon the spleen:
 the latter the pyloric portion, because  it corresponds  to the py-
 lorus.   The inferior border of the stomach, which is  convex, is
 termed  the great curvature or arch; the  superior border, the
 lesser curvature or arch.   The two orifices are the oesophageal,
 cardiac or upper orifice,  formed by the termination of  the oeso-
 phagus;  and  the intestinal, pyloric or inferior orifice, which
 communicates with the small intestine.
Section, 
DIGESTION.
Fig. 86.
 A A. Anterior surface of stomach.—B. Enlargement at the lower part.—D. Cardiac orifice.—E. Com-
mencement of duodenum.—F and C. Coronary vessels.—H. Omentum.
   The three coats, which constitute the parietes of the stomach,
are arranged in a manner the most favourable for permitting varia-
tion in the size of the organ.   The outermost  or peritoneal coat
consists of two  laminae, which adhere  but slightly to  the  organ,
and extend beyond it, where they form the epiploons or omenta,
the extent of which is in an inverse ratio to the degree of  disten-
tion of the stomach.   The omentum majus or  gastro-colic epi-
ploon, is the part that hangs down from the stomach in Fig. 86.
   The mucous or  lining membrane is  of  a whitish, marbled, red
appearance: having a number of irregular folds, situated especially
along the inferior and superior margins of the organ.  These folds are
evident, also, at the  splenic extremity; and are more numerous
and marked, the more  the  stomach is contracted.   They  are ra-
diated towards the cardiac orifice; longitudinal towards the pyloric
orifice.  This membrane, like every other of the kind, exhales an
albuminous fluid from a multitude of delicate villi, which are more
perceptible in the  stomach than in any other part of the digestive
tube. It contains, also, many follicles,  which are especially abun-
dant in the pyloric portion.  Several, also,  exist in the vicinity of 
DIGESTIVE  ORGANS.                   423
the cardiac orifice, but in the rest of the membrane they are few
in number.
  The pylorus, or the  part at which the stomach terminates  in
the small intestine, is marked, externally, by a manifest narrow-
ness, as at C, Fig.  87.   Internally, the mucous membrane forms a
circular fold, which has  been called the  valve of the pylorus, be-
tween  the  two laminae  of which, a  dense, fibrous  tissue exists.
This has been called, by some authors, the pyloric muscle.

                          Fig. 87.
A. The cesophagus.—B. The stomach.—C. The pylorus.—D. The duodenum.
   The muscular coat of the stomach, which is situated without
 the mucous coat,—as in the parts of the digestive tube we have al-
 ready described,—consists of several laminae of fibres, less distinct
 than those of the cesophagus; or rather more irregularly distributed.
 The most common opinion is, that there are three laminae; some
 forming an external, longitudinal series; a middle, transverse stra-
 tum; and an inner stratum with the fibres running longitudinally.
 Both circular and longitudinal fibres are separated from each other,
 especially in the splenic portion; the separation augmenting or di-
 minishing with the varying size of the stomach.
   The blood-vessels and nerves of  the stomach are more numer-
 ous than those of any other organ of the body.
   The arteries are disposed along the curvatures.  On the  lesser
 curvature are  the coronaria ventriculi, and the pyloric branch of
 the hepatic artery.  On the great curvature,  the right gastroepi-
 ploic, which is a branch of the hepatic; and the left gastro-epiploic,
 —a branch of the  splenic.  The splenic artery, too, furnishes  nu-
 merous branches to the left cul-de-sac, behind.  These are called
 the vasa brevia or gastro-splenic.
   The nerves of the stomach are of two  kinds.  Some  proceed
from the great sympathetic, from the coeliac  plexus, and accom- 
424
DIGESTION.
pany the arteries through all their ramifications.  Others are fur-
nished by the pneumo-gastric or eighth pair; the two  nerves  of
which  surround the cardiac orifice like a ring.
  The number of the nerves, and the variety of sources whence
they are derived, explains the great sympathetic influence exerted
upon the stomach by affections of other parts of the system.   It
sympathizes, indeed, with every protracted morbid change in the
individual  organs;  and  hence it was termed,  by Hunter, the
centre of sympathies.
  Like the teeth, the human stomach holds a medium  place be-
tween that of the carnivorous and  herbivorous animal.  As the
former make use of aliment, which is more readily assimilated  to
their own nature, and more nutritious, it is not necessary that they
should take food in such large quantity as the herbivorous animal;
or that it should remain so long in the stomach.   On this account,
the organ is generally of much smaller size..  On the other hand,
the herbivora, subsisting solely upon grass, which contains but a
small quantity of nutritious  matter, and that not easy of assimila-
tion to  their nature,  it is important that the  quantity taken  in
should be ample; and that it  should remain for  some time  in the
organ,  subjected to the action of its secretions; and, in  the rumi-
nant class, be returned into the  mouth, to undergo fresh mastication.
  In this class, the stomach, taken altogether, is of prodigious ex-
tent. It consists of four separate compartments in the ox, which we
                               may take as an example of the ge-
                               neral structure of the organ. The
                               first stomach, A A, Fig. 88, is the
                               ventriculus or paunch, which is
                               much the largest of the four. Ex-
                               ternally, it has two sacs  or ap-
                               pendices, and,  internally, it  is
                               slightly divided into  four com-
                               partments.
                                 The second stomach is the re-
                               ticulum, bonnet, or honeycomb
                             j) bag, B,  which appears to be a
                               globular appendix to the paunch.
                               It is situated to the right  of the
                               oesophagus,  G, and has usually a
                             Thethicker muscular  coat  than the
                               paunch.   Its inner surface is ar-
                               ranged in irregular pentagonal
cells, and is covered with fine  papillae.
  The third stomach, C, is the smallest, and is called omasum,  or
many plies.  It is of a globular shape, and has a thinner muscular
coat than the former.   It consists of numerous broad laminae, sent
off  from the internal coat, running in a longitudinal  direction, al-
 A A. The paunch.—B. The reticulum.—C. _.
omasum.—D. The abomasum.—E. The pylorus.
F. Duodenum.—G. Oesophagus 
DIGESTIVE  ORGANS.                  425
 ternately varying in breadth, and covered with small granular pa-
 pillae.
   The fourth stomach, D, is the  abomasum, ventriculus intesli-
 nalis, or cailletle.   It has a pyriform shape, and is next in size
 to the paunch.  It has large longitudinal rugae, covered with villi.
 The muscular coat is still thinner than that  of the former*  This
 stomach is the only one that resembles the human  organ; and, in
 in the young of the ruminant animal, with the milk curdled in it,
 forms the runnet.   The property  of curdling milk is, however,
 possessed by all digestive stomachs.
   The inner surface of the three first stomachs is covered with cuticle;
 whilst that of the  fourth is  lined by a true mucous or secreting
 membrane.
   There is in the interior arrangement of the stomachs of the  ru-
 minant animal, a sin-
 gular provision,  by                Fig.  89.
 which the food can be
 either  received  into
 the first  and second
 stomachs or be carried
 on into the third, if its
 character  be such  as
 to be fitted at first for
 the action of the oma-
 sum.
   From the oesopha-
 gus,  in  Fig.  89,  a
 gutter passes into the
 second and third  sto-
 machs.   The  third
 leads into the fourth
 by a  narrow  Opening,
 and the fourth terminates in the duodenum, which has a pylorus at
 its origin.   When the animal eats solid food, this is, after a slight
 mastication,  passed into the  paunch, and from  thence, by small
 portions,  into the second stomach.  When this has become mixed
 with  fluid, and kept for some time at a moderately high tempera-
 ture,  a morsel is thrown back with velocity from the stomach into
 the mouth, where  it is  "ruminated," and then  swallowed and
 passed on into the third stomach,—the groove or gutter being so
 contracted as to form a channel for  its passage through the two
 first.   In the third and  fourth  stomachs, more especially in the
 latter, true digestion takes place.
   When the  food is of such a character as not to require rumina-
tion it can be sent on directly into the third stomach, by the ar-
rangement just described.
   In the bird tribes, we see an  admirable adaptation of the struc-
ture to the functions which the  digestive organs have to execute.
   Vol. I.                     54
 
426                      DIGESTION.
Animals of this class may be divided into the granivorous and the
carnivorous.   It is in the former, however, that we are so much
impressed with the organization of this part of their economy.
  The grain, on which they feed, although more nutritious than
the grass, which constitutes the aliment of the herbivorous quad-
ruped, requires equal difficulty in being assimilated to the nature
of the being it has to nourish.  Added to this, it is in such a con-
dition, that the juices of the digestive organs  cannot readily act
upon it.  The bird,  having no masticatory apparatus within the
mouth,  the  grain must of necessity  be  swallowed  whole.  But
we find, that lower down in the  alimentary tube a  powerful mas-
ticatory apparatus exists, which has frequently been considered as
a part of the digestive stomach, but really seems destined for mas-
tication only.   The following is  the arrangement of  their  gastric
apparatus.

                          Fig.  90.
 
DIGESTIVE  ORGANS.                  427

     Fig. 91.
  The cesophagus terminates at the bottom of the neck in a large
sac—the ingluvies, or crop or craw, which is of the same struc-
ture with the oesophagus, but thinner.  On the  inner  side of the
crop are numerous glands, with very distinct orifices in large birds,
which secrete a fluid to assist in the solution of  the food.   To the
crop succeeds another cavity, in the shape of a  funnel, called the
ventriculus succenturiatus, infundibulum or second stomach.
This is seated in the abdomen  and is generally smaller than the
former.  It is usually thicker than the oesophagus, partly owing
to its numerous glands, which are very large and distinct in many
birds.  In the ostrich they are as large as the garden-pea, and have
very manifest orifices.   The infundibulum terminates  in the ven-
triculus callosus, gizzard or third stomach,—the most curious of
all the parts of the apparatus.
   In figures 90 and 91, we have an external and internal view of
the gastric apparatus of the turkey; a, representing the cesophagus
immediately below the crop, covered with a cuticle; b, the open-
ings of the gastric glands in the second stomach, placed on a sur-
face, that has no cuticular covering; c, horny ridges, between the 
428                     DIGESTION.
gastric glands and the lining of the gizzard ; d, a minutely granu-
lated surface, between the cavity of the gizzard and the duodenum;
and e,  the inner surface of the duodenum.   The figure accurately
represents the mode in which  the  second stomach  terminates  in
the gizzard, and the latter in the duodenum; the gizzard forming
a kind of pouch depending from the alimentary canal. The gizzard
is usually of a globular figure,  flattened at the sides, and is consi-
dered to consist of four muscles, remarkable for their great thick-
ness and strength:—a large hemispherical pair at the sides and a
small pair situated at the extremities of the stomach.  The gizzard
is covered, externally, by a beautiful tendinous expansion; and  is
lined  by a thick, strong, callous coat, which appears to be epider-
meous in its character. On this are irregularities, adapted  to each
other on the opposite surfaces.   The cavity of the organ is re-
markably small, when compared with  its outward  magnitude,
and its two  orifices, represented in Fig.  90, are very near each
other.
  In the pouch, formed by the small muscles at the lower part  of
the gizzard, numerous pebbles are contained, which seem to be in-
dispensable to the digestion of certain tribes,by acting.as substitutes
for teeth.  In the gizzard of the turkey, Mr. Hunter counted two
hundred; in that of the goose one thousand.
  The prodigious power, with  wThich  the digastric muscle, as  it
has been termed, acts,  and the callous nature  of the cuticle, are
strikingly manifested by certain experiments,instituted by the Aca-
demia del Cimento, and by Redi, Reaumur, and Spallanzani.
They compelled geese and other birds to  swallow needles, lancets,
and other hard  and pointed substances.  In a few hours afterwards,
the birds were  killed and examined.  The  needles and  lancets
were uniformly found broken off and blunted, without the slightest
injury  having been sustained by the stomach.
  In the carnivorous bird, the  food  being readily assimilated,  in
consequence of its analogy to the substance of the animal, the gas-
tric apparatus is as simple as it  is in the carnivorous mammalia.
  The cesophagus is of great size for  receiving the large substances
swallowed  by  these animals,  and for enabling the feathers and
other matters, that cannot easily be digested, to be rejected by the
mouth.  The stomach is a mere musculo-membranous sac; but the
secretion from  it is of a potent character, so as to enable the ani-
mal to dispense with mastication, and yet to admit of the stomach
and intestines being disposed within  a small compass, so as to give
them the necessary lightness to fit them for flight.
  We can thus, from organization, generally discover the kind of
food for which an animal is naturally destined;—in other words,
we can say  whether it  is naturally granivorous or carnivorous.
There are some striking facts, however,  exhibiting  the signal
changes exerted, even on organization, by restricting an animal  to
diet of a different character from that to  which it has been accus- 
DIGESTIVE ORGANS.                   429
Fig. 92.
tomed; or to one which is foreign to its nature.  In birds of prey,
the digastric muscle has the bellies, which  compose  it, so weak,
that, according to Sir Everard Home, nothing but an accurate
examination can determine its existence. But if a bird of this kind,
from  want of animal food, be  compelled to live upon  grain, the
bellies of the muscle  become  so large, that they would not be
recognised as  belonging to the  stomach of a bird of prey.
   Mr. Hunter kept a sea-gull  for a year upon grain;  and  found
the strength of the muscle very much augmented.
   This wondrous adaptation of  structure to the kind of food, which
the animal is capable of obtaining, is elucidated in  the cases of the
South American and the African ostrich.  The former is the native
of a more productive  soil  than the latter;  and, accordingly, the
gastric glands are less complex and numerous; and the  triturating
organ is less developed.
  4.  The intestines are  the lowest portion  of the digestive appa-
ratus; constituting a musculo-membranous canal,  extending from
the pyloric  orifice of the stomach to the anus.
   The human intestines  are  six  or eight times longer than the
body; and  hence the number of convolutions in the  abdominal
cavity.   They are attached to the
vertebral  column by folds of the
peritoneum,called the mesentery;
and, according to the length  of
these folds or duplicatures, the
intestine is bound down, or floats
in the abdominal cavity.  Their
structure is nearly alike  through-
out: a mucous membrane lines
them: immediately without this is
a muscular coat; and, externally,
a  serous  coat, formed by a  pro-
longation of the peritoneum.  The
mucous membrane is soft and vel-
vety, and is the seat of a similar  se-
cretion to that of other membranes
of the same class.   The muscular
coat is composed of two planes of
fibres, so  united, that they cannot
be separated; the innermost con-
sisting of circular; and the outer-
most of longitudinal  fibres; the
arrangement of which differs  in
the  small  and  large intestines
The SerOUS Or peritoneal  COat  re--M- Rectum.-k. Anus with sphincter ani.-
       .   .    .    ,  .          L, L. Levatores am.
ceives the intestine  between two
of its laminae, which, in  their passage  to it, form the mesentery.
The serous coat only comes in direct contact with the intestine at
 A, A. The liver.—B. The gall bladder.—C, C.
The stomach.—D, D, D, D. The small intestines.—
E. Commencement of the large intestines.—F,F,F.
The colon.—G, H. Sigmoid flexure, of the colon. 
430
DIGESTION.
the sides and  forepart.   Behind, or on the mesenteric side, is a
vacant space, by which the vessels and nerves reach the intestine.
These form their first net-work between the serous and muscular
coats; their second between the muscular and mucous.
  Between the upper  four-fifths of the intestinal  canal, and the
lower fifth, there is a well-marked  distinction; not only as regards
structure and magnitude, but function.  This has given occasion to
a division of the canal into the small intestine and the large; and
these, again,  have been subdivided in the various modes, which
will successively fall under consideration.
  As the small intestine fills so large a portion of the whole in-
testinal canal,  its convolutions occupy considerable space in the
abdominal cavity,—in the middle,the umbilical, and the hypogastric
regions,—and terminate in the right iliac region, in the large intes-
tine, (see Fig.  92.)   Its calibre differs in different parts; but it may
be regarded on the average as about one inch.  m It is usually di-
vided, arbitrarily, into three parts;—the  duodenum, jejunum,
and ileum.
  The duodenum is so called, in consequence of its length having
been estimated at about twelve fingers' breadth.  It is larger than
the rest of the small intestine; and has hence  received, also, the
name of the second stomach, and of ventriculus succenturiatus.
It is more firmly fixed  to the body than the other  intestines; and
does not, like them, float loosely in the abdomen.   In  its course,
until its termination in the jejunum, it describes a kind of Italic c,
the concavity  of which looks to the left.  From this shape it has
been separated into three portions;—the first, situated horizontally
beneath the liver;  the second descending vertically in front of the
right kidney;  and the third in the  transverse meso-colon.
  Its mucous  membrane  presents a number of circular folds, very
near each other, which  have been called valvulae connivenles. By
some anatomists, however, this name is not given to the irregular
rugae of its mucous coat; but to the folds of the lining membrane
of the jejunum. The valvulae are not simple rugae, passively formed
by the contraction of the muscular coat.  They are dependent upon
the original formation  of  the mucous  membrane;  and are not ef-
faced, whatever may be the distention of the intestine.
  On and between these duplicatures, the different exhalant and
absorbent vessels are situated, forming the villi of the intestine.
These villi give to the membrane a velvety appearance, and are
not simply composed of exhalants and absorbents,  but of nerves;
all of which are distributed on a cellular and perhaps on an erectile
tissue. Within the membrane are numerous follicles, which, with
the exhalants, secrete a mucous fluid, called by Haller succus
intestinalis..
  At about four or five fingers' breadth from the pylorus, the duo-
denum is perforated by the termination of the biliary and pancrea-
tic  ducts, which pour the bile and  pancreatic fluids into it  Gene- 
DIGESTIVE  ORGANS.
431
rally, these ducts enter the intestine by one opening; at times, they
are distinct, and lie alongside each other.
  The structure of the duodenum is the same as that of the whole
of the intestinal canal.   The muscular coat is, however, thicker,
and the peritoneal  coat only  covers its first  portion, passes before
the second, and is  totally wanting in the third; which we have des-
cribed as included  in the transverse meso-colon.
  The other two portions of the small  intestine are of considera-
ble length;  the jejunum commencing  at the duodenum, and the
ileum terminating, in the right iliac fossa, in the first of the great
intestines—the caecum.   They occupy the middle and almost the
whole of the  abdomen, being  surrounded by the great  intestine
EFFFGHI, Fig. 92.  The jejunum is so called, from being
generally found empty; and the ileum, from its numerous wind-
ings.   The line of  demarcation, however, between the duodenum
and jejunum, as well as between the  latter and the  ileum, is not
fixed : it is an arbitrary division.   The jejunum has,  internally,
the greatest number of valvulae conniventes and villi.  The ileum
is the lowest  portion.   It is  of a paler  colour, and  has fewer
valvulae conniventes.  The jejunum is situated  at the upper  part
of the umbilical region ;  the ileum at the lower part of  it,  extend-
ing as far as  the  hypogastric  and iliac  regions.  The  mucous
membrane of  the jejunum and ileum resembles, in  essential
respects, that  of the duodenum;  the  valvulae conniventes  are,
however, more numerous in the jejunum than in the duodenum;
and, in the course of the ileum, they gradually disappear,  and
are replaced by simple longitudinal rugae.   The villi, too, which
are chiefly destined for chylous absorption, abound in the jejunum,
but gradually disappear in the ileum.  The  mucous membrane of
both is largely supplied with follicles, called the glands of Peter,
Brunner, and Lieberkuhn, which secrete the succus intestina-
iis,—a mucous fluid, to which  Haller attached unnecessary im-
portance in digestion.  The  muscular coat is composed of circular
and longitudinal fibres;  and the outer coat is  formed by the pro-
longation of the peritoneum, which, after having surrounded the
intestine, completes the  mesentery, by which  the gut  floats, as it
were, in the abdominal cavity.
  The large intestine terminates the intestinal canal.  It is much
shorter than the  small, and considerably  more capacious, being
manifestly intended, in part, as a reservoir.  It is less loose in the
abdominal  cavity  than  the  portion of the  tube, which  we  have
described.   It commences at the right iliac fossa, (Fig. 92, E,) as-
cends along the right flank, as far as the under surface of the liver;
crosses over the abdomen to gain the left flank, along which it de-
scends into the left iliac region, and thence through the pelvis,
along the hollow of the sacrum, to  terminate at the anus.
  Like the small intestine it is divided into  three portions; the
caecum, the colon,  and the rectum. 
432
DIGESTION.
  The caseum or blind gut is the part of the great intestine into
which the ileum opens. It is about four fingers' breadth in length,
and nearly double the diameter of the small intestine.  It occupies
the right iliac fossa, in which it is bound down, so as not to be able
to change its position. The extremity of the ileum joins the caecum
at an angle; and if we examine the interior of the caecum, at the
point of junction, we find a  valvular arrangement, which has been
called the valve of Tulpius,  valve of Bauhin, ileo-excal valve, &c.

                           Fig. 93.
 Valve of Tulpius. AC Small intestine.—B B. Large intestine.—D. Appendix vermiformis cseci.

  Fig. 93 exhibits the nature of this  arrangement.  At the point
of union of the two intestines, a soft eminence exists, flattened from
above to below,  and elliptical transversely, which is divided into
two lips.  One of these seems to belong to the ileum and colon—
hence called ileo-colic; the other to  the ileum and caecum, and
termed ileo-cascal.
  From the disposition of these lips a valve results, so constituted,
that the lips, which form  it, separate when the faecal matters press
from the small  to the  large intestine; whilst they approximate,
cross, and completely  prevent all  retrogression, when the  faeces
tend to pass from the great intestine to the small. At the extremi-
ties of this valve are small tendons, which  give it strength, and
have been termed the frasna or retinacula of the valve of Bauhin.
  Although this valvular arrangement prevents the ready return
of the  excrementitious matter  into the small  intestine, we have
many opportunities,  in pathology,  for  discovering, that it is not
effectual in all cases.   In  stricture of  the large intestine, stercora-
ceous vomiting is a frequent concomitant, and there have been in-
stances of substances thrown  into the rectum, having been evacu-
ated  by vomiting. 
DIGESTIVE ORGANS.
433
  At the posterior and left side of the caecum, a small process de-
taches itself, called, from its resemblance to a worm, appendix ver-
miformis; and, from its connexion  with the  caecum,  appendix
caeci.  It is convoluted, variable in its length, and attached, by its
sides, to the caecum.   Its free extremity is impervious; the other
opens into the back part of the caecum.
  This appendage  to the caecum has all the characters of an intes-
tine.   Various hypotheses have been indulged regarding its uses.
Some have conceived it to be a reservoir for the faeces, but its di-
minutive size, in the human subject, precludes this  idea; others
have thought, that it secretes a ferment, necessary to their forma-
tion; and others, again, a mucus  for  preventing  the induration,
which  might result from the detention of the faeces in the caecum.
The opinion, that  it is a mere  vestige of the  useful and double
caeca, that exist in certain animals, is as philosophical as any.  M.
De Blainville, indeed, regards it as the true caecum, and what
is named the caecum as the  commencement  of the colon.  It is
manifestly of but little importance, as it has been found wanting or
obliterated in many subjects, and  has been extirpated repeatedly
with impunity.
  The colon is by much the longest of the large intestines, (FF F
GH, Fig. 92.)  It is a continuation of the caecum, from which it
cannot be distinguished; but is considered to  commence at the
termination of the ileum.   From the right iliac fossa it ascends
along the right lumbar region, over the kidney, to which it is con-
nected.  It is, in  this part, called the colon dextrum, ascending,
or right lumbar colon.  From the kidney it passes forwards and
crosses the abdomen in the epigastric and hypochondriac  regions,
being connected to the duodenum. This portion is called the great
arch of the colon, or colon transversum.  The right  portion of
the great arch is situated under the  liver and  gall-bladder;  and
hence is found after death tinged yellow, owing to the transudation
of bile. The left portion of the arch is situated under the stomach;
and, immediately  below it, are the convolutions  of the jejunum.
In  the left hypochondre, the  colon turns  backward  under the
spleen, and descends  along the left lumbar region, anterior to the
kidney to which it is closely connected.   This portion is termed
the colon sinistrum, descending or  left lumbar colon.   In the
left  iliac region, it forms two convolutions, which have been com-
pared  to the Greek s, or to the Roman s; and  hence this part of
the intestine has been designated the sigmoid flexure, or Roman
s, or iliac turn of the colon.  This flexure varies greatly in length
in different persons,  extending, frequently, into  the hypogastric
region, and, in some instances, as far as the caecum.   The colon,
through its whole extent, is fixed to  the body by the meso-colon.
   The coats of the great intestine are the same in  number and
structure with those of the small intestine, but they  are  thinner,
   Vol. I.                     55 
434
DIGESTION.
and not as easily separated by dissection.   The mucous membrane
is less villous and  velvety.  The most characteristic difference,
however, in the general appearance of the great and small intes-
tines is the pouched or cellular aspect of the former.  These pouches
are reservoirs for the excrement, and in them it becomes more in-
durated, by the absorption of the fluid portions.
  In torpor of this part of the intestinal  canal, the faeces are, at
times, retained so long, that they become hard balls or scybala;
and are  not unfrequently the occasion of the inflammation of the
lining membrane of the large intestine, which constitutes dysentery.
  The longitudinal muscular fibres are concentrated into three li-
gamentous bands or fasciculi, which run the whole length of the
intestine.  These fasciculi, being shorter than the intestine, pucker
it, and are the occasion of the pouched or saccated arrangement.
The inner or circular muscular fibres are, like those of the small
intestine, uniformly spread over the surface, and stronger than
those of the latter. Lastly, in the great intestine, especially in the
colon, are numerous processes of the  peritoneum, containing fat,
and hence called appendiculas epiploicas, or appendiculas pengue-
dinosas.  These are seen in greatest  abundance  in the  right and
left lumbar portions of the colon.
  The rectum terminates the intestinal canal, and extends from
the termination of the colon to the anus.   It commences about the
fifth lumbar vertebra,  and descends vertically into the pelvis, fol-
lowing the concavity of the sacrum and coccyx; and, consequently,
is not straight, as its name would import. At its upper part, there
are a few appendiculae  epiploicae; and a small duplicature of the
mesentery, called meso-rectum, attaches it to the sacrum.  It dif-
fers from the other intestines in becoming wider in its progress
downwards, and in its  parietes being thicker.  The lower part of
the mucous membrane exhibits several longitudinal folds or rugae,
which have  been considered as the effect of the contraction of the
circular fibres of the muscular coat. The longitudinal fibres of this
last coat have a different arrangement from that which prevails in
the other portions  of the large intestine. They are distributed over
the whole surface, as in the small intestine, or rather, as in the
oesophagus, excepting that, at the lower part of the rectum, they
are wanting.  On  the other hand, the circular fibres are more and
more marked, as they approach the outlet, and, by circumscribing
the margin of the anus, they form the sphincter ani muscle.   Im-
mediately within the anus is the widest portion of the rectum; and,
in this part, accumulations of indurated faeces will sometimes take
place in old people to a surprising extent, owing to torpor of the
muscular powers, concerned in the expulsion of the faeces.
   Lastly, there are a few muscles, which are concerned in the act
of expelling the faeces.  These require a short reference.   1.  The
sphincter ani or coccygeo-anal, which keeps the anus constantly 
DIGESTIVE  ORGANS.
435
 closed, except during defecation.   2.  The levator ani or subpu-
 bio-coccygeus, which, with the next muscle, constitutes the floor
 of the pelvic and abdominal cavities.   It restores the anus to its
 place, when pushed outwards during defecation. 3. The coccygeus
 or ischio-coccygeus, which assists the levator ani, in supporting or
 raising the lower extremity of the rectum;  and 4.  The transver-
 sus perinei or ischio-perineal, some  fibres of which unite both
 with the bulbo-cavernosi and with the sphincter ani muscles; and,
 consequently, it is associated slightly with the action of both one
 and the other.
   In regard to the intestinal canal, again, we find,  that man holds
 a medium place between the carnivorous and herbivorous animal,
 although approximating more to  the  latter.  In the  carnivorous
 animal, for reasons more than once  mentioned, it is unnecessary,
 that the food  should remain long, and, accordingly, the canal is
 very short.  In the herbivora, on  the other  hand, and for opposite
 reasons, the canal is long, and there is generally a large caecum
 and a pouched eolon.  Cuvier has given tables of the length of
 the canal, compared with that of the body;  but, where the compa-
 rison has been applied to man, the length of the body has included
 that of the legs.  Instead,  therefore, of the canal, in  man, being
 considered to bear the proportion of six to  one, it  ought to be
 doubled, or as twelve to one; a proportion  somewhat greater than
 prevails in the simiae or ape tribe.  It is not, however, in length
 always, that the canal  of the herbivorous exceeds that of the  om-
 nivorous animal; but, as a general principle, it may be affirmed,
 that the capacity of the canal is much more considerable.
   5. The abdomen, in which the principal digestive organs  are
 situated, and whose  parietes exert considerable influence on  the
 digestive function, will require a  brief description. It is that divi-
 sion of the body which is betwixt the thorax  and  pelvis; and is
 bounded, above, by the arch of the diaphragm;  behind,  by  the
 vertebral  column;  laterally, and anteriorly,  by  the abdominal
 muscles; and, below, by the ossa ilii, os pubis, and by the cavity
 of the pelvis.
   To connect the knowledge of the internal parts of the abdomen
 with the external, it is customary to mark  certain  arbitrary  divi-
 sions on the surface, which have been  called regions.
   The epigastric region, A, Fig. 94, is at  the upper portion of
 the abdomen, under  the  point of the sternum, and in the angle
 formed by the cartilages of the ribs. The hypochondriac regions,
 B  B, are covered by the cartilages of the ribs. These three regions
—the epigastric and right  and  left hypochondre—constitute  the
upper division of the abdomen, in which are seated the stomach,
liver, spleen, pancreas, duodenum, and part of the arch of the  co-
lon.  The space, surrounding the umbilicus, between the epigastric
region, and a line drawn from the crest of one os ilii to the other, 
436
DIGESTION.
is the umbilical region, C.

                 Fig. 94.
                           Here the small intestines are chiefly
                                          situated. This region
                                          is bounded  by lines,
                                          raised perpendicular-
                                          ly to the spine of the
                                          ilium; and the lateral
                                          portions,  on the out-
                                          side  of these lines,
                                          form  the  iliac re-
                                          gions, E  E; behind
                                          which, again, are the
                                          lumbar regions,  or
                                          the loins.   In these,
                                          the  colon and kid-
                                          neys are chiefly situ-
                                          ated.
                                           The hypogastric, D,
                                          is, likewise, divided
                                          into three regions,—
                                          the pubic (a) in the
                                          middle;  and an in-
                                          guinal (b)  on each
                                          side.
                                            The muscles, that
                                          constitute the  abdo-
                                          minal  parietes, are;
                                          first of all, above, the
                                          diaphragm,  which  is
                                          the   boundary  be-
                                          tween the thorax and
                                          abdomen; convex to-
                                          wards the chest, and
                                          considerably concave
        the  abdominal  cavity.  Below, if we add the  pelvic
        ■which, as it contains the rectum, and muscles, concerned
in the evacuation of the faeces, it may be proper to do,—the cavity
is bounded by the perineum, formed chiefly of the levatores ani
and coccygei muscles.  Behind, laterally and anteriorly, from the
lumbar vertebrae round to  the  umbilicus, the parietes consist of
planes of muscles and aponeuroses in superposition, and united  at
the median line, A D, Fig. 94, by a solid, aponeurotic  band, ex-
tending from the cartilago ensiformis of the  sternum to the pubes,
called the linea alba.  The abdominal muscles, properly so call-
ed, a*e,—reckoning the planes from  within to without,—the
greater oblique muscle, the lesser oblique, and the transversalis,
which are situated chiefly at the sides of the abdomen;—and the
rectus and pyramidalis, which  occupy the anterior  part.  The
towards
cavity,- 
DIGESTIVE  ORGANS.
437
greater oblique, obliquus externus or  costo-abdominalis;—the
lesser  oblique, obliquus internus or ilio-abdominalis, and the
transversalis,  transversus abdominis or lumbo-abdominalis,
support and compress the abdominal viscera; assist in the evacua-
tion of the faeces and urine, and in the expulsion of the foetus; be-
sides other uses, connected with respiration and the attitudes. The
rectus, pubio-sternalis or sterno-pubialis; and the pyramidalis
orpubio-sub-umbilicalis,are more limited in their action; and com-
press the forepart of the abdomen; besides having other functions.
  Lastly, a serous membrane—the peritoneum—lines the abdo-
men, and gives a coat to most
of the  viscera. The mode, in             Fig.  95.
which  its various reflections
are  made,  is singular, but
easily  intelligible, from the
accompanying figure.  It has
neither beginning nor  end,
constituting a shut sac;  and,
in reality,  having no viscus
within it. If we take the dia-
phragm, arbitrarily,  as the
part at which it commences,
we find it continued from the
surface of that  muscle  over
the  abdominal  muscles, D;
then reflected,  as exhibited
by  the dotted line, over the
bladder,  E; and,  in  the fe-
male,  over the  uterus, G;
from thence over the rectum,
F;  the kidney, H, envelop-
ing the intestine, B; and con-
stituting, by its two laminae,
the mesentery, C; giving a coat
to the liver, A; and  receiv-
ing the stomach between its
duplicatures. The use of this
membrane is to fix and sup-
port the different viscera; to
constitute, for  each, a pedi-
cle, along which the  vessels
and nerves reach the intes-
tine ; and to secrete a fluid, which enables  them to move readily
upon each other. When we speak of the cavity of the peritoneum,
we  mean the inside of the sac; and when it  is distended with fluid,
as in ascites, the fluid is contained between  the peritoneum lining
the  abdominal muscles, and that which forms the outer coat of the
intestines.
 
438
DIGESTION.
  The omenta or epiploa are fatty membranes, which  hang over
the face of the bowels, and are reflections, formed by the perito-
neum after it has covered the stomach and intestines. Their names
will sufficiently indicate their situation:—the  lesser epiploon or
omentum,—the omentum  hepato-gastricum;—the greater or
gastro-colic; and the appendices or appendiculas epiploicas, which
last have already been referred to, and may be regarded as so many
small epiploons.
  The abdomen is entirely filled by the contained viscera. There
are several apertures into it; three, above, in  the diaphragm, for
the passage of the oesophagus, vena  cava  inferior, and aorta; one
anteriorly in the course of the linea alba, but which is closed after
birth,—the umbilicus; and two anteriorly and  inferiorly; the one,
—the abdominal, inguinal or supra-pubian ring,—which gives
passage to the vessels, nerves, &c. of the testicle; and the other,—
the crural arch,—through which the vessels and nerves pass to the
lower extremity.  Lastly, two  others exist in  the inferior paries,
for the passage of the obturator vessels  and nerves,  and of the
sciatic arteries and nerves, respectively.
  Such is a brief view of the various organs, concerned in digestion.
To these might have been  added the general anatomy of the liver
and pancreas,—each of which organs furnishes a fluid, which is a
material agent in the digestive process,—and of the spleen, which
has been looked upon by some as inservient, in some  manner, to
the same function.   As, however, the  functions of these organs
will be considered in another place, we defer their anatomy for
the present.
                    Of the Food of Man.

  The articles, inservient to the nourishment of man, have usually
been considered to belong  entirely to the animal and the vegetable
kingdoms; but there seems to be no sufficient reason for excluding
those articles of the mineral kingdom that are necessary for the due
constitution of the different parts  of the body.  Generally, how-
ever, the term food or aliment, is  applied to  substances, which,
when received into the digestive organs, are capable of being con-
verted into chyle; but from this class  again, the products of the
mineral kingdom cannot, with entire propriety, be excluded.  We
have, indeed,  numerous examples of tribes, feeding, at particular
seasons more especially, on mineral substances. Kessler affirms,
that the quarriers on the Kyffhauser, in northern Thuringia, spread
a steinbutter or rock-butter (Jameson) on bread, which they
eat with appetite.  Labillardiere also  relates of the  inhabi-
tants  of  New Scotland, that they are  accustomed to eat a soft,
greenish kind  of steatite; which, he  says, serves to  allay the
sensation of hunger,  by filling the  stomach.   Vauquelin ana-
lyzed some of this, but was unable to extract any thing nutritive
from  it.   Long  ago Gumilla asserted,  that certain  tribes of 
FOOD of  man.
439
South America were in the habit of eating a kind of clay, alone or
with other substances; and he particularly mentions the Ottomaques
andGuamos. This practicewasobservedbyHumboldt. "TheOtto-
maques," he remarks, "on the banks of the Meta and the Orinoco,
feed on a fat, unctuous earth, or a species of pipe-clay, tinged with
a little oxide of iron.  They collect this clay very carefully, dis-
tinguishing it by the taste.  They kneed it into balls of four or six
inches in  diameter, which  they bake  slightly before a  slow fire.
Whole  stacks of  such  provision are seen  piled up in their huts.
These clods are soaked in water, when about to  be used; and each
individual eats about a pound of the material every day.  The only
addition, which they occasionally make to this unnatural fare, con-
sists in  small fish, lizards, and fern roots.  The quantity  of clay,
that the Ottomaques consume, and the greediness, with which they
devour  it, seem to prove, that it does more than merely distend
their hungry stomachs, and that the organs of digestion have the
power of extracting from it something  convertible into animal sub-
stance."
   Animals are, often, characterized by the kind of food on which
they subsist.   The carnivorous feed on flesh; the piscivorous on
fish; the insectivorous on insects; thephytivorous on vegetables;
the granivorous  on seeds;  the frugivorous on  fruits; the grami-
nivorous and herbivorous on the  grasses; and the omnivorous on
the products of both the animal and vegetable kingdoms.
   In antiquity, we find whole  tribes  designated according  to the
aliment they chiefly used.   Thus, there were the ^Ethiopian and
Asiatic Icthyophagi or fish-eaters; the hylophagi,  who  fed on
the young shoots  of certain trees; the elephantophagi, and struthi-
ophagi, the elephant, and ostrich, eaters, &c. &c.
   We have already shown, that the digestive apparatus of man is
intermediate between that of the carnivorous and the herbivorous
animal; that it partakes of both, and that man may, consequently,
be regarded omnivorous; that is,  capable of subsisting on both the
products of the animal and vegetable kingdoms; an important capa-
bility, seeing, that he  is destined to live in arctic regions, in which
vegetable food is  not to be  met with, as well as in the torrid zone,
which is esteemed more favourable for vegetable, than for animal,
life; whilst, in temperate regions, he can alone indulge in the com-
bination of both the one and the other to the full extent; or in the
diet for which his structure seems especially to  destine him.
   The  nature of the country must, to a  great extent, regulate the
food of its inhabitants; for although commerce can furnish us with
articles of luxury; and with many, which  are looked upon as ne-
cessaries; no nation is entirely  indebted to it for its  supplies; be-
sides, numerous extensive tribes of the  human  family are denied
the advantages  of commerce; and compelled to  subsist  wholly on
their own resources. This is the great cause, why the Esquimaux,
the Samoiedes, &c.  live wholly on animal food; and why the cocoa- 
440
digestion.
nut, the plantain, the  banana, the sago, the yam, the cassava, the
maize and the millet, form the chief articles of diet with the natives
of torrid regions.
  In certain countries, the scanty supply of the useful and edible
animals has given occasion  to certain prohibitory dietetic rules and
regulations, which have been made to form a part of the religious
creed, and, of course, are most scrupulously observed.  Thus, in
Hindusthan, animal food is not permitted to be eaten; but the milk
of the  cow is excepted.   Accordingly, to ensure  the necessary
supply of this fluid, the cow is  made sacred; and its destruction a
crime against  religion.   Amongst the laws of the  Egyptians are
similar edicts, but they seem to have been chiefly enacted for po-
litical purposes, and not in consequence of the unwholesome cha-
racter of the interdicted articles.
  The same remark applies to many of the dietetic rules of Moses,
forthe regulation of the tables of the Hebrews. Blood was forbidden,
in consequence, probably,  of the fear entertained,  that it  might
render the people too familiar with that fluid, and diminish the hor-
ror, which was inculcated against the shedding of blood: the parts of
generation were excluded from the table, because the taste might
interfere with the reproduction of the species, if it should become
indulged, &c.
  We have said, that, in the arrangement of his digestive organs,
man is intermediate between the carnivorous and herbivorous, ani-
mal.  Not the slightest  ground is afforded, by anatomy, for the
opinion of Rousseau, that man was, originally, herbivorous; or for
that of Helvetius, that he was exclusively carnivorous.  Brous-
sonet affirms, that he is more herbivorous than carnivorous; since,
of his thirty-two teeth, twenty  resemble those of the herbivorous,
whilst twelve only resemble those of the carnivorous animal. Accord-
ingly, he infers,  that, in the origin  of  society, his diet must have
been exclusively vegetable. Mr. Lawrence, too, concludes, that,
whether we consider the teethandjawsortheimmediateinstruments
of digestion, the human structure closely resembles that of thesimiae,
—the great archetypes,accordingto LordMoNBODDO  andRoussEAu
of the human race,—all of which  are, in their natural state, com-
pletely herbivorous.
  Again, we observe a wide discrepancy between  man and ani-
mals in the variety of their aliments.   Whilst the latter are gene-
rally restricted to either the animal  or the vegetable kingdom; and
to but a small part of  one or the other.   Man embraces an exten-
sive range, and, by means  of his  culinary inventions, can convert
a variety of articles from both kingdoms into materials of suste-
nance.  But, it has been  argued by those who are  sticklers for the
natural, that man probably confined himself, primitively, like
animals  to one kind of food; that  he adhered to this whilst he re-
mained in his  natural  state, and that his omnivorous practices
are a proof of his degeneracy. 
FOOD OF  MAN.
441
  Independently, however, of all arguments deduced from organi-
zation, experience sufficiently shows the inaccuracy of these asser-
tions.   If we trace back nations to their state of infancy, we find,
that then, as in their more advanced condition, the diet was am-,
mal, or vegetable, or both, according  to circumstances.  Of this
fact we have some signal examples, in a part of the  globe where
the lights of civilization have penetrated to a less extent than  in
most others; and where the influence  of circumstances, that pre-
vailed in ancient periods, has continued, almost unmodified, until
the present time.
  Agatharchides describes the rude tribes,  who  lived on the
coast of the Red Sea, and subsisted on fish, under the name Ich-
thyophagi.   Along both banks of the Astaboras, which flows on
one side of Meroe, dwelt another nation, who lived  on the  roots
of reeds growing in the neighbouring swamps.   These roots they
cut to pieces with stones, formed  them into a tenacious mass, and
dried them in the sun.  Close to them,  were the Hylophagi, who
lived on the fruits of trees, on vegetables growing in  the valleys,
&c.  To the west of these,  were the hunting nations, who fed on
wild beasts, which they killed with the arrow.  There were, also,
other tribes, who lived on the flesh of the elephant and the ostrich,
—the  elephant op hagi  and strut hiophagi.  Besides  these  he
mentions another and less populous tribe, who fed on locusts, which
came in swarms from the southern and unknown districts.
  The mode of life, with the tribes described by Agatharchides,
does not seem  to have varied for  the last  two thousand years.
Although cultivated nations are situated around  them, they have
made no progress themselves. Hylophagi are still to be met with.
The Dobenahs, the most powerful tribe amongst the Shangallas,
still live on the elephant; and, farther  to the  west, dwells a tribe,
who subsist, in the summer, on the locust; and, at other seasons,
on the crocodile, hippopotamus, and fish.
  In the infancy of society, mankind were probably almost wholly
carnivorous;  as the tribes, least advanced in civilization, still are
at the present day.  For a time, man in most situations, may have
confined himself to the vegetable banquet, prepared for him by his
bounteous Maker; but, as population increased, the means of sub-
sistence would  be too scattered for  him, whilst the crowding to-
gether of a number of nutritious vegetables into a small space, and
the cultivation of the earth, so as to multiply its produce, would
imply the existence of settled habits and institutions, which could
only arise after society had made some progress. Probably, much
before this period, it would have been discovered, that certain of
the beasts of the forest, and of the birds of the air, and some of the
insect tribes, could minister to his wants, and form  agreeable and
nutritious articles of diet;  and thus would arise their adoption  as
food.
  Vol. I.                    56 
442
DIGESTION.
  On the coasts of the ocean, animal food was perhaps employed
from the period of their first settlement; as well as on the banks of
the large streams, which are so common in Asia,—the cradle of
mankind.  The fish, left upon the land after the periodical inun-
dations of the rivers, or thrown on the sea-coast, administered to
their necessities, without the slightest effort on their part;  and,
hence, they had but little incentive to  mental or corporeal exer-
tion.  This is the cause of the abject condition of the Ichthyopha-
gous tribes of old; and of their comparatively low state of civiliza-
tion at the present day.
  Again, the  savages, in various  parts of the  globe, live  by the
chace or the fishery; and must, consequently, be regarded as essen-
tially carnivorous.
  It would not, however, be justifiable to regard barbarism as the
natural state of man: nor is it clear what the different writers on
this point of anthropology have meant  by the term.
  The Author of Nature has invested  man with certain  preroga-
tives, one of which is the capability of rendering the organized
kingdom subservient to his wishes and necessities; and, by  the in-
vention of the culinary art, of converting various organized bodies
into wholesome and agreeable articles of diet; which thus become
as natural to him as the restriction to one species of aliment is to
the animal.
  It has been remarked, that the exclusive or predominant use of
animal or of vegetable food, has a manifest effect upon the physical
and moral powers.  Buffon affirms, that if man were obliged to
abstain from flesh in our climates, he could not exist, or propagate
his kind.  Others, again, have depicted a state of ideal innocence,
in the infancy of society, when man lived, as they conceive, en-
tirely on vegetables:—

             " His food the fruits; his drink the crystal well;"

unsolicitous for the future, in consequence of the abundant sub-
sistence spread before him; independent, and always at peace with
his fellows, and with the other  animals; but he gradually sacri-
ficed his liberty to the bonds of society; and cruelty, with an insa-
tiable appetite for flesh and blood, were the first fruits of a de-
praved nature.  Either immediately or remotely, all the physical
and moral evil, by which mankind are afflicted, arose from these
carnivorous practices.
  In point of fact, however, we find, that the countries, in whichman-
kind are accustomed to be omnivorous, or to unite animal with vege-
table food,are those, thatare most distinguished for both mental and
corporeal endowments.  The tribes which feed altogether on ani-
mal food,—as the Laplanders, the Samoiedes, the Esquimaux, &c.
are far inferior, in both these respects, to the European or Europeo-
 American; and the same may be said, although not to the  like 
FOOD OF MAN.                     443
extent, of the various tribes in whose  diet animal food  predomi-
nates,—as the Indian inhabitants of our own continent.  A similar
remark is applicable to those, who live almost exclusively on vege-
tables, as the Hindoos, millions of whom are kept in subjection by
a handful of Europeans.
   Attempts have frequently been made to refer the  nutrient pro-
perties of all articles of diet to a particular principle of  a constant
character, and which, alone, of all the elements, is entirely capable
of assimilation.   Haller  conceived  this to be jelly;—Cullen
thought it to be oily, or saccharine, or what seems to be a combina-
tion of the two;—Becker, Stahl, Fordyce, &c. to be mucilage;
and  Dumas, mucus.  Richerand, again, attempts  to show, that
it is, in all cases, either gummy, mucilaginous, or saccharine.
   It is probable, that  there is no such particular principle, as the
one contended for;  andXhat, in all cases, the food is resolved into
its elements, in  the  formation of the chyle or reparative  fluid,
separated from it.  To  this  conclusion we are  necessarily im-
pelled, when we reflect,  that the chyle can be formed  from both
animal and vegetable  substances; in other words, that, when vege-
table substances are received into the  digestive apparatus, they are
capable of being converted into a substance, resembling the animal
they have to nourish; and, on the other hand, the  vegetable has
the power of reconverting  this  animal matter  into a substance of
its own nature; and hence the utility of manure in promoting ve-
getation.   In an early part of this work, we had occasion to men-
tion, that animals and vegetables are reducible into nearly the same
ultimate elements,—in some cases into precisely the same,—oxy-
gen, hydrogen, carbon and azote; the latter being wanting, how-
ever, in  most  vegetables  and  in several  animal substances.  It
is probable, therefore, that all organized bodies possess the power
of reducing substances, received as food, into their elements;
and of recomposing them, by virtue  of affinities, which are con-
trolled by the vital agency.
   As the different  parts  of the  animal body contain a considerable
portion of azote, a  question has arisen regarding its source; some
believing that it is  obtained from the food, others by respiration.
The latter adduce the cases of the herbivorous animals, which sub-
sist exclusively  on substances  containing  no  azote;  of nations,
which live almost wholly on vegetable food; of the negroes, in the
West India islands, who live almost  entirely on the juice of the
sugar cane, at  particular seasons, and yet  are unusually healthy
and thriving at those seasons ;  and  of caravans journeying across
the  African deserts,  and  possessing no other article of  diet, for
weeks, than gum  Arabic or gum  Senegal.  If we admit,  from
these and other  cases, that man can exist without food contain*
ing  azote, the origin of the  azote  of the body  must  be looked
for elsewhere than in the food.  Magendie, however, has pro-
perly remarked, that they do not lead legitimately to this conclu- 
444
DIGESTION.
sion.   Almost all the vegetables, eaten by man and  animals, con-
tain, in reality, more or less azote.  The raw sugar, used  by the
negroes, has a considerable quantity; and with regard to the tribes,
which  are said to feed almost exclusively on rice, Indian corn,&c.
they are in the habit of drinking milk with it, which is a highly
azoted substance.
  Magendie instituted some experiments with the view of deter-
mining this point.  These consisted in feeding animals, for the ne-
cessary time, on diet, whose chemical composition was rigidly de-
termined.
  He fed a dog, three years old and in good condition,  solely on
pure white sugar and distilled water.  For seven or eight days the
animal appeared to thrive well, was lively, and ate and drank with
avidity.  In the second week, he began to fall off,  although his ap-
petite continued good,  and  he ate six or eight ounces of sugar in
the twenty-four hours.   In the third week, he became emaciated,
his strength diminished, his gaiety was gone, and  his appetite im-
paired. An ulcer formed on each  eye, at the centre of the cornea,
which  subsequently perforated the cornea, and allowed the hu-
mours  of the eye to escape. The emaciation went on progressively
increasing, as well as the  loss of strength; and, although he ate
daily three or four ounces of sugar, the debility became  so great,
that he could neither chew nor swallow, nor execute the slightest
movement. He died on the thirty-second day from the commence-
ment of the experiment.   On dissection, the fat was found to have
entirely disappeared;  the muscles were reduced to less  than five-
sixths of their ordinary size; the stomach and intestines were much
diminished in size, and powerfully contracted; and the gall and uri-
nary bladders were filled with fluids, not proper to them.  These
were examined by M.  Chevreul, who found them  to possess  al-
most all the characters of  the bile and urine  of the herbivorous
animal. The urine, in place of being acid, as it is in  the carnivora,
was sensibly alkaline, and presented  no trace  of  uric acid or of
phosphates.   The bile  contained a considerable proportion of  pi-
cromel, like that of the ox  and the herbivora in general.  The ex-
crements  contained very little azote, which they usually exhibit
in abundance.
   A second dog was subjected to the like regimen, and with simi-
lar results.  He died on the thirty-fourth day of the experiment.
   A third experiment, having afforded analogous results, Magen-
die concluded, that sugar alone is incapable of nourishing the dog.
   In all these, ulceration of the  cornea occurred, but not exactly
at the  same period of the experiment.
   He  next endeavoured to discover, whether these effects might
not be peculiar to sugar ; or whether other non-azoted substances,
generally considered nutritious, might not produce like effects. He
took two young and vigorous dogs, and fed them  on olive oil and
distilled water.  For fifteen days, they were apparently well; but, 
FOOD OF  MAN.
445
after this, the same train of phenomena occurred as in  the other
cases, except that there was no ulceration of the cornea. They died
about the thirty-sixth day of the experiment.
  Similar experiments were made with gum  Arabic, and  with
butter; one of the animal substances, which does not contain azote.
The results were identical.
  Although the character of the excrements, passed by the different
animals,  indicated that the substances were well digested,  Ma-
gendie was desirous  of  establishing this  in a  positive manner.
Accordingly, after  having fed  animals for several days on oil,
gum, or sugar, he opened them, and found that each of  these sub-
stances was reduced into a particular kind of chyme in the stomach;
and that they afforded an abundant supply of chyle; that from the
oil  being of a manifest milky appearance, and that from  gum or
sugar transparent, opaline, and more aqueous than the chyle  from
oil;—facts which proved, that if the various  substances  did not
nourish the animals, the circumstance could not be attributed to
their not having been  digested.
  These results, Magendie thinks, render it extremely probable,
that the azote, found in different parts of the animal economy, is
originally obtained from the food taken in.  This is, however, ex-
tremely doubtful.  We have no proof, that the animals died simply
from privation of azote.   It is, indeed, probable, that the azote had
no agency in the matter; for there seems to be no reason why it
should not have been  obtained from the air in respiration, as well
as from that contained between the particles of the sugar, where
this substance was administered.
  It must be recollected, moreover, that the subjects of these ex-
periments were dogs;—animals which, in their natural state, are car-
nivorous, and, in a domestic state, omnivorous; and that they were
restricted to a  diet entirely foreign to  their nature, and to which
they  had not  been  exclusively accustomed.   Ought we, under
such  circumstances, to be surprised, that they should sicken and
fall off.
  Between the period of the publication of the first and  the second
edition of his  Pricis Elimentaire de  Physiologie, Magendie
found that his deductions were not, perhaps, as absolute or demon-
strative as he had at first imagined ; and additional experiments in-
duced him to conclude,—asDr.BosTOCxand SirCHARLEsBELLhave
since done, without being aware, apparently, of Magendie's obser-
vation;—"that variety and multiplicity of articles of food constitute
an important hygienic rule." " This," Magendie adds, " is indi-
cated to us by our instinct,as well as by the changes that wait upon the
seasons, as regards the nature and kind of alimentary substances."
  The additional facts,  detailed  by Magendie  in his second
edition, are the following:—
  A dog, fed at  discretion on  pure wheaten bread, and drinking
common water, does not live beyond  fifty days; whilst  another, 
446                       DIGESTION.
fed exclusively on military bread,—pain de munition,—seems, in
no respect, to suffer.
  Rabbits or Guinea-pigs, fed on a single substance, as on wheat,.
oats, barley, cabbage, carrots, &c. commonly die, with every mark
of inanition,  in  a fortnight;  and, at times, much  earlier.   When
these same substances are given together, or in succession, at short
intervals, the animals continue in good keeping.
  An ass, fed upon rice, lived  only fifteen days, refusing his food
for  the few last days; whilst a  cock was fed upon boiled rice for
several months, without his health suffering.
  Dogs,  fed exclusively on cheese, and  others on hard eggs, lived
for  a long time; but they were  feeble and lean, losing their hair,
and their whole appearance indicating imperfect nutrition.
  The substance, which, when given alone, appeared  to support the
rodentia* for the greatest length of time, was muscular  flesh.
  Lastly, Magendie found,  if an animal has subsisted for a certain
time on  a substance,  which,  when  taken  alone, is incapable of
nourishing him,—on white bread, for  instance,—for forty days,—it
is useless, at  the end of that time, to vary  his nourishment, and
restore him to his accustomed regimen.  He will feed greedily on
the new food presented to him; but will continue to fall off; and
will die at  the same period  as he would probably  have done, if
maintained on his exclusive regimen.
  Independently of showing the necessity of  variety of food for
animal sustenance, these experiments exhibit some singular anoma-
lies, and  sufficiently demonstrate, that we have yet  much to learn
on the subject.
  A great deal,  doubtless, depends on the habits of  the particular
animal or individual; and on the  morbid effects excited  by com-
pletely modifying the function of  assimilation, as it has been or-
dinarily  practised.   It  has been long known, that if  man,  pre-
viously habituated to feed upon both animal  and vegetable diet,.
be restricted  exclusively to one or the other, he will fall off, and
become scorbutic; and yet, that he is capable of subsisting upon
either one or the other exclusively, provided he be restricted  to it
from early infancy, has been sufficiently shown by the reference
we have  already made to carnivorous and herbivorous tribes, exist-
ing in different regions of our globe.
  The importance of variety of diet is  illustrated by the experi-
ments, which Dr. Stark, of Vienna, made upon his  own digestive
powers, and to which he ultimately became a martyr.   His object
was to discover the relative effect of various simple substances,
when used  exclusively as  articles of food for a long  space of time.
In all such cases, he found, that the system was  reduced  to a

 • The rodentia are gnawing animals, having large incisors in each jaw, with
which they divide hard substances.  They are the rongeurs of  the French natu-
ralists. The  squirrel, mouse,  rat, Guinea-pig,  hare,  rabbit, beaver, kangaroo,
porcupine, &.c. belong to this division. 
food of  man.
447
state of extreme debility, and that there was not a single aliment, that
is  capable, of itself, of sustaining the vigour of the  body for any
considerable period.   By this kind of regimen,  Dr.  Stark is said
to have so completely ruined his own health, as to  bring on pre-
mature  death.
   The  alimentary substances, employed by man, have  generally
been classed, either  according to the ultimate  chemical elements
entering into their composition; or to the chief proximate principle
or compound of organization.  In the former case, they have been
grouped into,  1, those which contain azote, carbon, hydrogen, and
oxygen;  2, those  which contain carbon, hydrogen, and oxygen;
and, 3, those which  contain neither azote nor  carbon.   The first
class, it is obvious,  will comprise most animal substances.  The
second  chiefly  vegetable substances; whilst water is perhaps the
only real alimentary matter, that belongs to the third.
   The  division, proposed  by Magendie, and adopted by Dr.
Paris,  is according to the proximate principles, which predominate
in the aliment.
   1. Amylaceous aliments; wheat, barley, oats,  rice, rye, In-
dian corn, potato, sago, salep, peas, haricots, lentils, &c.
   2. Mucilaginous aliments;  carrot,  salsify,  beet, turnip, aspa-
ragus, cabbage, lettuce, artichoke, melon, &c.
   3. Saccharine  aliments; the different kinds of sugar, figs,
dates, raisins, &c.
   4. Acidulous aliments;  the orange,  currant, cherry,  peach,
raspberry, strawberry, mulberry, grapes, prunes,  pears, apples,
tomatos, &c.
   5. Oily and fatty; cocoa, olives, sweet almonds,  hazelnuts,
walnuts, animal fats, oils,  butter, &c.
   6. Caseous aliments;  the different species of  milk, cheese,
&c.
   7. Gelatinous aliments; the tendons,  aponeuroses, skin, cel-
 lular tissue, the flesh of very young animals, &c.
   8. Albuminous aliments; the brain, nerves, eggs, &c.
   9. Fibrinous aliments; comprehending the flesh and blood of
 different animals.
   A few remarks are necessary with regard to the nutritive pro-
 perties of these different proximate principles.
   a. Fecula or starch is  very copiously diffused through the ani-
 mal kingdom.  It exists,  in great purity, in various farinaceous
 grains,—as in rice,  barley, Indian corn, &c.   It is  combined with
 gluten in wheat; with saccharine matter in some grains, as in oats
 and in many leguminous seeds, as haricot-beans, lentils, vetches,
 and peas; with viscid mucilage in rye, potatos, and  Windsor beans;
 with fixed oil  and mucilage in  the emulsive seeds, such as nuts,
 almonds, cocoa; in linseed, rapeseed,  hempseed, poppyseed, &c.
 Sometimes, also, it is united with a poisonous matter, as in the
jatropha manihot, from which the cassava bread is made.  Starch 
448
DIGESTION.
is artificially prepared, in great purity, from  various substances.
In the form of starch, so called, we have it from wheat and pota-
tos.   Arrow root is procured from the maranta arundinacea and
from various species of arum.   Cassada or cassava flour is from
the manioc root; salep from the orchideae in general; sago from
the pith of the  cycas circinalis  and various species  of palm;
tapioca  from the bitter and sweet cassava root, &c.  In all these
varieties,  starch forms a bland and wholesome  nutriment,  well
adapted for the sick and convalescent in particular.
  b. Mucilage or gum is a principal ingredient of our elementary
vegetables.  In Arabia,  Senegal, and in the East Indies, it is ob-
tained, in great abundance,  from various species of mimosa;  and,
where produced in sufficient quantity, it constitutes a chief article
of diet.  The Africans of Senegal are affirmed to live entirely upon
it, during the  gum harvest, eight ounces  being the daily and suffi-
cient allowance for each man.
  Mucilage is combined simply with  green  colouring matter  in
the leaves of beet and  spinach;  with bitter matter,  which may  be
prevented by the process of blanching, as in  endive and  lettuce,
or by using the plant very young, as in  the asparagus.  It exists,
also, in every part of the mallow tribe;  in many roots, as salsify,
Jerusalem artichoke, &c. and in the receptacle of the flower of the
artichoke.  It is combined with an acid in sorrel leaves; with sac-
charine matter in many fruits,  as in the  fig and date; in roots, as
the carrot, parsnip, and beet;  with slight acrimony in the turnip,
cabbage leaves, cauliflower, and broccoli; and with more acrimony
in the radish,  cress, and mustard.   It exists in considerable abun-
dance, combined  with a peculiar, nauseous principle, in onions,
garlic, leeks, &c; and, lastly, in small quantity, with much aroma,
in those vegetables that  are used  only for seasoning, as parsley,
thyme, &c.
  Wherever found, mucilage must be regarded as  nutrient;  and,
when modified by the presence of other principles, it is an agreeable
diet; alone, it  is insipid, and is, consequently, rarely used, except
medicinally.
  c. Sugar is likewise highly nutritious.  Chemically regarded,
it presents numerous varieties.  It exists in the greatest quantity,
combined with mucilage, in the juice of the sugar cane, of the su-
gar maple, the manna  ash tree, and the beet root.  It seems to be
a constant attendant upon the inflorescence of vegetables; and it is
a constituent of all the subacid and sweet fruits,  in  combination
with vegetable jelly.   It is collected by various animals.  Of these
the bee  is  most  familiar,  which culls  the sweets from various
flowerets.  A species  of locust in Australia covers the trees and
ground  with a variety  of sugar.  In all  animals, too, a principle,
bearing some  analogy  to sugar, exists in the bile;  and it is a pro-
duct of morbid action, in  the disease called diabetes.
  d.  The Acid, in the different acidulous aliments, is probably 
FOOD OF  MAN.
449
 possessed of no nutritive agency, but may aat as a condiment, by
 enabling the digestive organs to separate a larger quantity of nutri-
 tious matter, from the other principles usually contained in such
 fruits, than they would otherwise be able to do.
   Almost all the acidulous aliments, when ripe, are extremely
 grateful and refreshing.  Hence, they are valued articles of diet in
 sickness as well as in health.
   e. All animal and vegetable oils and fats are highly nutritious,
 being wholly convertible into chyme.  They are not, however, easy
 of digestion, especially when combined with insoluble woody fibre,
 as in many of the kernels.
   f.  Cheese is usually considered extremely difficult of digestion,
 and capable of affording  but little nutriment.   The experiments,
 however, of Sir Astley Cooper,—on dogs, it is true,—assign it
 as a substance easy of  digestion.  Chemistry would lead us to be-
 lieve, that it ought to be not only easy of assimilation, but very
 nutritious; as caseum is, of all the azoted immediate principles
 of aliments, the one in which azote is contained in the greatest pro-
 portion.                                                       %
   g.  Gelatine is highly nutritious, and has been supposed to be
 the most readily digestible of animal matters.  The dyspeptic and
 the convalescent find that such is not the fact; and much mischief
 is occasionally done by the  copious exhibition of strong soups and
 animal jellies in such cases.   The osmazome, which gives the fla-
 vour of meat to soup, is  contained in too small a quantity for any
 experiments to be made upon it.
   h.  Albumen, of which we have the best example in the white
 of egg,  is,  wherever met with, highly nutritious and easy of diges-
 tion.   In its strongly coagulated state, it is conceived to be com-
 paratively indigestible; and  the instance of the unwholesome cha-
 racter of the hard boiled egg is adduced in favour of this view. The
 unfavourable influence of heat, on  the digestibility of the egg is,
 however, chiefly exerted on the yolk, which contains a large quan-
 tity of animal oil; the coagulated albumen, constituting the white
 of egg,  being converted into chyme without difficulty.
   i. Lastly, fibrine, which  constitutes the great mass of the solid
 part of the muscles of animals, and also of the blood, is unquestion-
 ably pre-eminently nutritious in its natural forms of combination;
 bat we  have no experiments for ascertaining its nutritious proper-
 ties when used alone.
   To these proximate principles may be added gluten, which is
 the only vegetable compound of organization, that contains a no-
 table portion of azote in its composition. Hence its elements most
 nearly resemble those of the animal kingdom; and it has been termed
 the most animalized of the vegetable principles.  It is very generally
 met  with, though only in  a small proportion, in the vegetable
 kingdom;—in all the farinaceous seeds, in the leaves of the cabbage,
cress, &c.; in  certain fruits, flowers and roots, and in the green
   Vol.  I.                    57 
450
DIGESTION.
fecula  of vegetables jrt  general; but it is especially abundant in
wheat; and imparts to wheat flour the property of fermenting and
making bread.  Of the nutritious properties of gluten, distinct from
other principles, we know nothing precise: the superior nutritious
powers of wheat flour, over those of all other farinaceous substances,
sufficiently attest, that, in combination with starch, it is highly
nutritive; and it has been imagined, that the gluten of the green
fecula may  supply a certain portion of azote to the herbivorous ani-
mal, which may be requisite for its  support.
   It scarcely belongs to physiology to inquire into the character
of the different kinds of  food, employed by man; their  mode of
selection, preparation, &c. A few general remarks may, however,
be useful; inasmuch as they bear, indirectly at least, upon  our sub-
ject, and are  of universal interest.
   Animal substances, as a general principle, are safe articles of diet,
where  the animal has  been healthy.   This is, perhaps, universally
true with regard to the upper classes; but, in fishes and in the lowest
tribes of animated nature,  the exceptions  are very numerous. The
muscular flesh of quadrupeds consists chiefly of fibrine, with a quan-
tity of jelly united with it in  young animals, and  osmazome: the
tendons and aponeuroses,  the different  membranes, ligaments and
skin are formed principally of gelatine.
   The brain  and nervous substance, consist chiefly of albumen and
fatty matter.  The fat and  suet are different forms of oil.   The cel-
lular structure of the  bones contains a considerable proportion of
gelatine; which has been separated from it and converted  to useful
purposes, chiefly  through the labours of a distinguished native of
this country—Count Rumford—and of M.  Darcet.   Milk con-
sists of an emulsion of albumen, oil,  sugar and a peculiar principle,
suspended in a large quantity of water.
   The organs of the young quadruped abound more in gelatine than
those of the adult and aged; the latter containing more fibrine and
osmazome.
   Very young meats are by no means  as easy of digestion as the
older.   This is strikingly exemplified in  the case of veal and beef.
Even in the foetal state,  however, they are  not unwholesome; and
consequently no good reason  can be assigned for an enactment in
the reign of the first James of England; that no butcher should kill
any calf to  sell, being  under five weeks old.  The ancient Romans,
whose gastronomic habits are not exceeded  by the moderns, con-
sidered the foetal  pig as  a  bonne bouche, when served  up in the
manner to be presently mentioned.
   The sex has, also, an influence upon the character of the aliment;
the flesh of the female  being always finer-grained and more delicate
than that of the entire male.   As a  general principle,  too, the re-
moval  of the  ovaries of  the female,  and of the testes of the male,
improves the meat, in a .remarkable manner;  the neutral animal
seeming to be better adapted for  the table  than either the entire 
FOOD OF MAN.
451
male or female.  Spaying or castration must, however, be perform-
ed prior to puberty; otherwise, in the latter case, much of the rank-
ness and coarseness of the entire male will remain after the opera-
tion. The males of those races, in which the testes are active only
during certain seasons, as the deer, have the rankness of the entire
male disagreeably predominant at those periods only.
   The mode of feeding has, also, much to do with the  quality of
the meat of quadrupeds.  At one time, it was the custom, in Eng-
land, to feed oxen, intended for the  market, on  oil cake, but this
practice appears to be now almost laid aside, in consequence of the
beef acquiring from it an unpleasant rancidity.
   The effect of feeding is strongly exemplified in the case of the
hog; and it accounts for the reputation, which the bacon of certain
countries, has acquired over that of others.  In particular parts of
Virginia, the hogs are fattened chiefly on the refuse from the stills,
after the distillation of whiskey; and the inferiority of the meat,—
when thus forced, compared with the result of feeding them upon
corn, and allowing them to roam abroad and obtain their food from
the  acorns, chesnuts, &c  in the woods,—is universally admitted.
The Sardinian  pork probably derives its celebrity from  the  mode
of fattening the animal resembling that generally adopted in Vir-
ginia.
   In antiquity, the same diversity existed in the reputation of the
bacon of different places.  So inferior was that of the Romans, that,
according to Varro, bacon and sausages were imported, in large
quantities, from the Gauls, by whom they were prepared in great
perfection.  The Roman hog was kept up and fattened with milk,
figs and mulse, (a mixture of wine and honey).*
   The mode of killing for the table has differed, in different coun-
tries, in all  ages.  The Greeks strangled their swine, and ate them
with their blood.  The Romans thrust a red hot spit through the
body; and suffered them to die without bleeding; but if a sow were
about to farrow, they trampled, at the same time, upon her abdo-
men, bruising the foetal pigs and the  mammary  glands with the
milk and blood, and serving all up as a delicate dish.   This mode
of slaughter was replete with objections, if we regard it in an ali-
mentary point  of view solely.   The flesh of animals, thus  killed,
is dark-coloured from the retention of blood in the  vessels,  and
hence becomes speedily putrid.  The best mode of  slaughtering
cattle  appears  to us to be that practised by  the butchers  of the
Jewish persuasion. The Mosaic law strictly prohibiting the eating
of blood, the Talmud contains a series of regulations regarding the
killing of animals.  Their method is to cut the throat at once down
to the bone, so as to divide the whole of the large vessels of the
neck.  In  this way,  the  blood is discharged quickly  and com-

  • See, on the subject of the gastronomy of the Romans, an article by the author
in the second volume of the American Quarterly Review. 
452
DIGESTION.
pletely, and the meat is so much superior, that some Christians will
eat none but what has been slaughtered by a Jewish butcher.
   Animals are often subjected to some preparation before they are
killed.   They are commonly kept for a time without food, as, if
killed with  full stomachs, their flesh is considered not to keep so
well.  A very cruel method of preparation  for  slaughter  at  one
time  prevailed, but  is now happily obsolescent,  in regard  to  the
bull;  although the original object of the  custom was probably soon
lost sight of, and  it continued to be followed  as an inhuman sport.
Bull beef has always  been esteemed hard  of digestion and  un-
wholesome, requiring the most vigorous powers for its assimi-
lation ;  hence the mythical legend of Hercules feasting chiefly
on bull's flesh and  green figs.   To remove these objectionable
qualities of  the  flesh, bulls have been, from  the earliest  times,
either baited by dogs, hunted  by  men, or torn by lions.   By
some ancient  municipal  laws of England,  no butcher  was  per-
mitted to expose  bull beef for sale, unless it had been previously
baited,  a regulation adopted  for the  reason already  assigned.
Whenever animals have undergone great fatigue immediately  be-
fore  death, or have suffered from a lingering death, although their
flesh  may sooner become rigid, it also sooner becomes tender, than
when they have been suddenly deprived of life.  The flesh of
hunted  animals is soon tender and speedily spoils; and,  upon this
principle, the flesh of the pig is rendered more digestible by  the
revolting cruelty,—recommended in our older works on the culi-
nary art,* and said to be still  practised in  some countries,—of
whipping the animal to death.   It has long been a custom to cause
old cocks to fight before they are killed; and the Moors of West
Barbary, before they kill a hedge-hog, which  is esteemed  a princely
dish with them, as it was of yore with the Greeks, "rub his back
against  the ground, by holding his feet betwixt two, as  men do  a
saw  that saws stones, till it has done squeaking, and then they cut
its throat."
   In order that the flesh of animals, especially of the upper classes,
may be as tender as possible, it should be kept until its components
are about to assume  new affinities, or until the force of cohesion
between its particles has been diminished.   Meat cannot, in fact,
be kept too long  before it is dressed, provided only that its flavour
has not been interfered with.  And even when it has been so long
kept as to attain afumet, or the smell of putrefaction, in  particu-
lar articles of food,—as venison, hare, partridge, woodcock, and all

   • " To make a pig taste like a wild boar."—'Take  a living pig,  and let him
swallow the following drink, viz.:—boil together, in vinegar and water, some rose-
mary, thyme, sweet basil, bay leaves, and sage;  when you have let  him swallow
this, immediately whip him to death, and roast him forthwith.'—Booke ofCookrye,
by A. W. 1591.
   Again,—" how to still a cache for a weake bodie that is consumed."—' Take a red
eocke that is not too olde, and beate him to death.' 
FOOD OF  MAN.                    453
the meats included  under the  head of game,—the epicure soon
learns to disregard the offensive odour, owing to the extreme ten-
derness of the meat
  According to Dr. Roget, it is a common practice in  England
to give a spoonful or two of vinegar to poultry some time before
they are killed,—when they are to be dressed immediately after-
wards,—for the purpose of rendering the fibre mellow.   We have
adopted this plan and apparently with advantage.   It is  not im-
probable but that the acetic acid may act upon the  fibrine in the
living frame in some manner analogous to what we witness out
of the body.  Berzelius found, that when fibrine  is digested  in
concentrated acetic acid, it swells and becomes a bulky, tremulous
jelly, which dissolves completely, with the  disengagement of a
little azote, in a considerable quantity of hot water.
  All birds, as well as their eggs, are capable of serving for hu-
man sustenance, although, as in quadrupeds, much diversity exists
in the character of the meats they furnish.   Age influences them,
the young grown  bird being infinitely more tender  and digestible
than the more aged.   The same may be said of  the sex.   By  re-
moving the sexual organs at an early age, both sexes are much im-
proved for the use of the table, becoming larger, fatter, and more
tender, as we see in the capon and poulard.
  The manner in which birds are fed affects also their fatness and
flavour. In the various older writers—" De re rustica"—we find,
that great attention was paid to the fattening of edible animals of
all kinds.  At the present day, the fattening of fowls for the markets
of large towns, and especially for that of London, forms a consider-
able branch of rural economy.   The mode pursued is to  put them
into a dark place, and to cram them with a paste made of barley-
meal, mutton suet, and some molasses or coarse  sugar, mixed with
milk.  At the expiration of a fortnight, they are found to be com-
pletely ripe; but, if kept longer, the  fever, induced by  the con-
tinued state of repletion, renders them red, not vendible, and fre-
quently kills them.
  This plan of keeping them  in dark places, with the occasional
barbarous substitution of stiching up the eyes, was well  known to
the Romans and largely practised.  It was considered to render
the flesh  tenderer,  sweeter, whiter, and also,  as  was supposed,
wholesomer. It has long been imagined, however,  and seems now
to be pretty generally admitted, that animals, brought to this state
of artificial obesity, are never  so well flavoured in  the flesh, and
probably  not so salubrious, as  those  of the same species fattened
in a more natural way.
  But few reptiles are used as food, although  some of the greatest
luxuries of the table belong to this order, as the green turtle, and
many species  of the  testudo.   Several of the lizard tribe are also
eaten ; and the eggs of many, both of the testudo and lacerta kind, 
454
DIGESTION.
are used, even when the flesh is reputed bad.  The flesh of the
viper, and especially its broth, has long been recommended as a
diet to invalids;  and  that of the Rana esculenta, as well as of the
Rana taurina or bull-frog, is often  eaten.  The flesh is generally
delicate and gelatinous, the fibre  resembling that of chicken or
veal.
  Fish is not so  universally safe as any of the kinds of aliment we
have considered.  In  tropical climates,  especially at particular
seasons, different species become absolutely poisonous, and, hence,
great care is necessary in selecting the innocent and nutritious.
  No fish seems to partake of a poisonous property, unless it has
undergone  some morbid change;  so that the poison is probably
sui generis, and always most active after the vital powers of the
fish have ceased.  The following is a catalogue of poisonous fish
on the  authority of Dr. Burrows:—Batistes monoceros, (old
wife;) Tetrodon sceleratus,(tunny;) Ostracionglobellum, (smooth
bottle fish;)  Tetrodon  ocellatus, (blower  or blazer;) Murasna
major,  (conger  eel;)  Coryphaena splendens, (dolphin;) Sparus
chrysops, (porgee;)  Coracinus fuscus major,  (gray snapper;)
Coracinus minor, (hyne;) Perca  major of Browne, (esox barra-
cuda,  barracuda;)  Perca venenata, (rockfish;) Perca venenosa,
(grooper;)  Scomber maximus,   (kingfish;)  Scomber  thynnus,
(bonetta;) another species  of  scomber, (Cavalloe, horse eye,)
Scomber casruleo argenteusnudus,of Browne, (Spanish mackarel;)
Mormyra of Browne, (blue parrot fish;) Clupea thryssa, (yellow
billed sprat;)  Cancer astacus, (sea lobster;) Cancer ruricolus,
(land crab;) and  the mytilus edulis, (mussel.)
  Fishes consist of a much greater proportion of albuminous and
gelatinous matter; in some cases, united with a considerable quan-
tity of oil.
  The male of  fish  is usually, perhaps, preferred, although the
discrimination of the sexual characters is less easy in fishes than in
the animals already considered.  Castration and spaying were, at
one time, practised; but not at the present day.  A Mr. Tull, of
Edmonton, near London, first proposed and performed the opera-
tion.  He was a fishmonger, and his object was to prevent the ex-
cessive increase in  fish in some of his  ponds.   By castration, this
was not only effected, but the castrated fish grew much  larger than
the usual size; were more  fat; and, in addition, were  always in
season.
  In general, fish of  every kind are best some time  before they
begin to spawn:  and they are unfit for food for some time after-
wards.   Fish, that have not attained the age of spawning, are in
season all the year.
  The molluscous animals do not furnish many articles of human
sustenance;—the limpet, the  whelk, the oyster, the cockle, the
dam and the mussel being the chief.  The helix pomatia,a snail, 
                        FOOD  OF MAN.                    HO°

is reared and fattened, with great care, in some of the cantons of
Switzerland, as an article of luxury, and exported pickled.
  The Crustacea are generally esculent,—as the crab, lobster, cray-
fish, shrimp, &c.
  But few insects are employed as edibles.   In certain countries,
the locust  is said to  be  used  in  large quantities, both fresh and
salted, so as to afford some compensation for the ravages it commits.
  Lastly, vegetables are by no means as generally esculent as ani-
mals ;  and  some of them are positively deleterious.   Caution is,
therefore, necessary in making  use of any plant, or part of a plant
for food, when we are unacquainted with its nature.   All parts of
vegetables  are employed as food;  but the seeds of the cerealia fur-
nish an important part of diet in almost all climates.
  Many investigations have been  undertaken, with the view of
determining the digestibility of different articles of diet.
  M. Gosse, of Geneva,  found, by experiments  made upon him-
self, that animal and vegetable fibres, concrete  albumen, the white
and tendinous parts of animals, pastes made with fat and butyra-
ceous substances, and unfermented or slightly fermented matters,
remained longer in the stomach than the gelatinous parts of  ani-
mals, vegetables,  fermented bread, &c.   That the  latter only
required an hour for their solution, whilst the former were not re-
duced  to chyme until the expiration of several hours.   For these
experiments, M.  Gosse possessed unwonted facilities; being able
to cause his food to regurgitate at pleasure.  Spallanzani made
animals  swallow small tubes, filled with different kinds of food,
and pierced with holes;  and, by  removing these, after  a definite
period, he  was enabled to determine the comparative  digestibility
of different substances in various animals.
  M. De Montegre, who  possessed the faculty of rejecting the
contents of his stomach at pleasure, affirms, that the cellulo-vascu-
lar parenchyma of flesh is, in man, the slowest of all kinds of food
in undergoing chymification.  To determine the same point, Ma-
gendie killed different animals, whilst digestion was going on, and
he found, that animal substances  are most easily and completely
chymified.  Vegetable substances frequently  passed  through  the
whole canal without  change.   Fatty matters, tendons, cartilages,
concrete albumen, and mucilaginous and saccharine vegetables, ap-
peared to him  the least  digestible; whilst caseous, fibrinous, and
glutinous substances were most so.
  Lallemand and Sarlandiere, again, by attention to cases of
artificial anus in the Hotel Dieu of Paris, observed some interesting
facts, connected with this subject.  At one  time, it was universally
believed, that the substances, which approximate most to the nature
of the  being to be nourished, are  most speedily passed on into the
intestinal canal.  The observations of these gentlemen do not sup-
port this view of the subject.  They found, that the least nutritive 
456                      digestion.
 food, as the roots, stems, and leaves of vegetables and fruits, arrived"
 sooner at the opening than farinaceous aliments, milk, or meat.
 The difference in time was, indeed,  considerable.   The first came
 away in  an hour, an  hour and a half, or two hours, and without
 seeming  to have undergone any change: the  others  were not
 discharged until the expiration  of  three  or four hours, and ap-
 peared to be completely converted.  Broussais concludes, from
 these experiments, that the internal gastric sense repels the food
 that contains the least  nutritive matter;  and  retains, with  com-
 plaisance, that which is nutritious. They certainly are the strongest
 evidences we possess of the exertion of a  vital action of selection
 in this part of the digestive process.
   Sir Astley  Cooper, likewise, instituted experiments for the
 purpose of testing the comparative  digestibility of  different sub-
 stances.
   He fed dogs  on  different  kinds  of  raw meat without fat, and
 found the loss, sustained by 100 parts of each, in the stomach of
 the  animals, when  they were killed,—one, two, three, and four
 hours after feeding,—to be as follows:—

   Pork,     -  -  10   -  -  -  20 -  -  -  98   - -   100
   Mutton,  -  -   9---  46  ---87--     94
   Beef,     -  -   0  -  -  -  34  -  -  -  37   - -     75
   Veal, •    -  -   4  -  -  -  31   -  -  -  46   - -     69
   In another experiment,  after  four hours, the digestibility ap-
 peared to be in the following order:—cheese, mutton, pork,  veal,
 and  beef.
   He found,  by other experiments, that fish is a very digestible
 substance.  Potato  is so to a  less degree; the skin covering it
 passing into .the duodenum unchanged.   He likewise, made several
 trials with the  same substance,  prepared  in different ways, and
 found, that boiled veal is two-thirds more digestible than  the same
 substance roasted.  Different other matters were subjected to ex-
 periment.   Muscular flesh was sooner digested than skin; the skin
 a little more so than cartilage; this  than tendon; and this, again,
 than bone.  Of bones, he found the scapula one of the most diges-
 tible.   One hundred parts of this bone were digested in six hours;
 whilst thirty parts only of  the femur were digested in the same
 time.
   Many of these results are such as experience has  proved to be
 applicable  to  the human stomach.  The  lean  part  of pork and
 mutton are  found decidedly the  most easy of assimilation of any
 of the grosser meats; but the kind of digestion, effected in the sto-
 mach of the dog, which is capable of reducing the firmest bones,
 is so little  analogous to that of the  human subject,  as to suggest
 caution in the deduction we make from  experiments instituted on
the former, as to the comparative digestibility of different articles 
FOOD  OF MAN.                     457
of food in the human stomach.   It will be seen, too, hereafter, that
the digestibility of different aliments is affected by many extraneous
circumstances.
   By far the most important modifications are produced on aliments
by the culinary processes  to which  they are submitted.   But few
articles of diet are employed in the raw state.  Almost all require
the agency of heat, to render them  more agreeable, or to improve
their digestibility.
   It would  be a curious matter of investigation to  trace, how far
the art of cookery,  and the varying extravagance of the table,
might be esteemed indicative of the comparative degree of advance-
ment or prosperity of any individual nation, at different periods of
its history;  or of the rank, which it, from  time to time, occupied
as regarded others; but this would  lead us away from our present
object.
   Dr. Paris has hazarded the strange assertion, that, " if we in-
quire into the culinary history of different countries, we shall trace
its connexion with the fuel most accessible to them." " This fact,"
he adds,  "readily explains the prevalence  of the peculiar species
of cookery,  which  distinguishes the French table, and which  has
no reference, as some have imagined, to the dietetic theory, or
superior refinement of the inhabitants."   This idea has  been pro-
pounded without sufficient reflection.  No two systems of cookery
can differ more than  those of France and Virginia; yet the kind
of fuel employed is  the same  in both  countries.    The truth  is,
that the essential difference between  the modes of cookery, adopted
in different countries, is not so much in the boiled, or the roast; in
the joint, or the made dish; as it is in the  quantity of grease em-
ployed; and in the greater or less use of condiments.
   The mode, in which different organized  textures are modified,
chemically and mechanically, by different culinary processes, is as
follows:—
   By boiling, the principles that are not properly soluble, are ren-
dered softer, and more readily acted upon  in  the stomach.   The
meat is, however, deprived of most of those principles that are so-
luble in hot water; the albumen is coagulated by the heat, and the
gelatine, which is not dissolved in the water, is converted into a
gelatinous substance.   If, therefore, the meat be  too  long, or too
fast boiled,  we obtain, where the  albumen predominates,—as in
beef,—a  hard mass, like an over-boiled  egg; or where  the ge-
latine  predominates, as in young  meats,—such  as veal,—a ge-
latinous substance, equally  injurious to the  digestive function.
The loss,  occasioned by boiling, depends partly upon the  melting
of the  fat, but chiefly on  the solution of the  gelatine and osma-
zome.  Mutton is affirmed to lose about one-fifth; and beef about
one-fourth of its original weight.
   The effect of boiling on vegetables is to render  them softer, and,
consequently, more digestible.
   Vol. I.                      58 
458
digestion.
  By roasting, the fibrine is corrugated; the albumen coagulated;
the fat melted; and a portion of the water evaporated.   The sur-
face becomes brown, and then scorched ; and the tendinous parts
are rendered softer and gluey. Animal matter loses more by roast-
ing than by boiling; parting with about one-third of its weight.
The loss arises from  the melting out of the  fat, and the evapora-
tion of  the water; but the nutritious matter remains in the meat;
whilst, in boiling, the gelatine  is in part removed.  Roast meats
are, hence, more nutritive than boiled. It has been computed,—of
course only  approximatively,—that, owing to the dissipation of
the nutritive juices  by boiling, one pound of roast,  contains as
much nourishment as two of boiled, meat.
  Frying is properly considered to be perhaps the most objec-
tionable of culinary processes; the heat being applied through the
medium of boiling oil or fat, which is thus rendered empyreuma-
tic, and, therefore, extremely liable to disagree with the stomach.
  By the sudden browning or hardening of the  surface in broil-
ing, the evaporation of the juices of the meat is prevented, which
imparts a peculiar tenderness to it.  It is the form selected, as the
most eligible, hy those who seek to invigorate themselves by the
art of training.
  Lastly. Baking consists in heating the substance in a confined
space, which does not permit the escape of the fumes arising from
it: the meat is, therefore, owing to the retention of its juices, more
sapid  and tender. Baked meats are, however, not so digestible, on
account of the greater retention of their oils, which are, besides,
in an  empyreumatic  state.
  Thus much for the solid food of man.   He requires,  however,
drinks or liquids more imperiously even than solids; in conse-
quence of the constant drain of fluid from the system, by the va-
rious  secretions, the pulmonary and cutaneous  transpiration, the
urine, &c; and  of the large proportion, which the fluids, compos-
ing the animal body, bear to the solids.
  The different drinks may, like the solid food, be classed accord-
ing to  their chemical character:—1.  Water of different kinds.
2.  Vegetable and.animal juices and infusions, as lemon-juice,
orange-juice, whey,  tea,  coffee, &c.  3. Fermented  liquors, as
wines,  beer, cider,  perry,  &c:  and 4. Alcoholic  liquors, as
brandy, alcohol, kirschwasser, rum, gin, whiskey, arrack,  &c. &c.
  An inquiry into the  different properties of these various liquids
does not belong to the physiologist.  We may remark, however,
that the arguments,  regarding  the natural, have  been extended
also to  this variety of  aliments;  and it has been contended, that
water is the most natural drink; and that ail others, which are the
products of art, ought to be avoided.  The  remarks, we have al-
ready made on this subjeet, will be sufficient.  Water was, doubt-
less, at one period, the only beverage of man; as  nakedness  and
the use of raw aliment, and the most profound ignorance of the 
FOOD  OF MAN.
459
universe was his original condition; but no one will be presumptu-
ous enough  to  declare that he ought to continue naked, abjure
cookery, and be plunged in his primitive darkness, on the plea
that all these changes are so many artificial sophistications.
  Water is, doubtless, sufficient for all his wants; but the mode-
rate use of fermented liquors, even if habitual, except in particular
constitutions, is devoid, we think, of every noxious result.  They
are grateful; and many of them are even directly nutritious, from
the undecomposed sugar and mucilage which they contain.   Dr.
Kitchener has, for this reason, termed beer, not inaptly, "liquid
bread." With regard to distilled spirits, no evil would perhaps re-
sult from their total rejection from the table.  Although they may,
by  their action on the digestive organs, be the indirect  means of
nutrition, they themselves contain no alimentary property.  They
are received into the vessels of the stomach by imbibition; and al-
ways produce, when taken  even to a small amount, undue stimu-
lation. This may be productive of little or no mischief, provided
they are only used  occasionally; but  if taken habitually, serious
visceral and mental disorder may sooner or later ensue.
   It has been a question, whether water be  capable  of affording
any nourishment to animals; and, in favour of the negative side, it
has been affirmed, that the rabbit and sheep can live a long time,
or  altogether, without this fluid.  There would seem, however, to
be  some deception here, for their vegetable food is succulent, and,
consequently, consists, itself, largely of water. On the other hand,
Dr. Fordyce kept gold fish for six months in distilled water; and
thought himself justified in concluding, that animals might live on
water and air alone.  Pouteau allowed some of his patients no-
thing but water for several weeks, without their materially falling
off; and the histories  of shipwrecked mariners demonstrate with
how little solid food man can subsist, provided  he has a sufficient
allowance of water; whilst, without water, or  a substitute, no quan-
tity of  solid food can  support him beyond a few days.   It is not
probable, that, in these  cases, any separation of the water into its
elements occurs.  The liquid passes immediately into the veins of
the stomach by imbibition; thus supplying the  perpetual drain of the
fluids; and the necessary quantity of solid materials being obtained
by the absorption, effected  on the adipous deposits in various parts
of the body
   Lastly. There are certain substances, called condiments, em-
ployed  in diet, not simply because they are nutritive,—for many of
them possess no such properties,—but because, when taken with
food  capable of nourishing the frame, they promote its digestion,
correct  some injurious property it possesses, or  add to its sapidity.
Dr. Paris has divided these into the saline,  the spicy or aroma-
tic, and the oily.   It may be remarked, however, that certain ar-
ticles are called, at times, aliments, at others, condiments, ac-
cording as they may constitute the basis or  the accessory to any 
460                      DIGESTION.
dish;—such are cream, butter, mushrooms, olives, &c. The advan-
tage of condiments to animal digestion is strongly exemplified by
many cases. The bitter principle, which exists in grasses and other
plants, appears to be essential to the digestion of the herbivora;—
acting as a natural stimulant; and it has been found, that cattle do
not thrive upon grasses which are destitute of the principle. Of the
value of salt to  the digestive function of his cattle, the agriculturist
has ample experience; and the salt licks of our own country demon-
strate how grateful  this  natural stimulant is to  the beasts of the
forest. Charcoal, administered with fat,—as it  is done in rural eco-
nomy for fattening  poultry in many parts of England,—strikingly
exhibits the advantage of administering a condiment: it is a substance
which of itself contains  no nourishment,  but can put the digestive
function into a  condition for separating more nutritious matter from
the food taken  in, than  it could otherwise accomplish.  A similar
effect is produced by  the plan,—adopted for the  same purpose in
some parts of Great Britain,—of giving walnuts, coarsely bruised,
with the shell,  and cramming the  animal with this diet. This is as-
serted, by many rural economists, to be the most effectual plan for
fattening poultry speedily; the coarse shell, in passing along  the
mucous membrane of the chylopoietic organs,  stimulates it to aug-
mented action; and a more bountiful separation  of nutritious mat-
ter or of chyle  is the consequence.  The aromatic condiments act
in a similar manner.
   These general remarks, upon the food of man, will introduce us
to the mode in  which the various digestive processes are accom-
plished.

                   Physiology of Digestion.

   The detail, into which we entered regarding the various organs
concerned in digestion, will have  induced the anticipation, that the
history of the function must be multiple and complex.  The food
is not, in the case of the animal  as it is in  that of  the vegetable,
placed in immediate contact with  the being it has to nourish; con-
sequently, an act of volition is necessary to procure it, and to con-
vey it to the upper  orifice of the  digestive tube.   This act of voli-
tion is excited  by an  internal sensation—that of hunger—which
indicates to the animal the necessity for taking fresh nourishment
into the system. Both the appetite and hunger, and the prehension
or reception of food must, therefore,  be regarded as a part of  the
digestive operations.  These may be enumerated and investigated
in the following order:—1st.  Hunger, or the sensation which ex-
cites us to take food.  2d. Prehension of food, the voluntary mus-
cular action, which  introduces  it  into  the mouth.   3d.  Oral or
buccal digestion, comprising the changes wrought  on the food in
the mouth.  4th. Deglutition, or the part taken by the pharynx
and oesophagus  in digestion.  5th. Chymification, or the action 
hunger.
461
of the stomach on the food.   6th.  The action of the small intes-
tine.  7th.  The action of the large intestine.  And 8th.  The ex-
pulsion of the fasces.
   All these processes are not equally concerned in  the production
of chyle.  It is separated in the small intestine:  the first six con-
sequently belong to it;— the remainder relate only to the excremen-
titious part of the food.
   The digestion of solid food requires all the eight processes. That
of liquids is more simple; comprising only thirst, prehension, deglu-
tition, the action of the stomach, and that of the small intestine. The
fluid  rarely reaches the large intestine.
   In  inquiring  into this important and interesting function, we
shall  first attend to the digestion of solids,  and afterwards to that
of liquids.

                 I. Digestion  of Solid Food.

   1.  Hunger.—Hunger is really  an internal sensation, the seat of
which is invariably referred  to the stomach.   Like every internal
sensation,  it proceeds from changes in the  very texture of the or-
gan.   It is not produced by any external  cause; and to it are ap-
plicable all those observations, which were made, on a former oc-
casion, on the internal sensations in general.
   In its slightest condition, it is merely an appetite; but if this be
not heeded, the painful sensation of hunger supervenes, which be-
comes more and more acute and lacerating,  unless food be taken.
If this be the case, however, the uneasiness gradually  abates; and
if additional food be still taken, a  feeling of satiety is produced.
   The sensation usually occurs, in the  healthy state, after the sto-
mach has been for some time empty, having finished the digestion
of the substances taken in at the previous meal.  Habit has a great
effect in regulating this  recurrence; the appetite always appearing
about the time at which the stomach has been accustomed to receive
food.  This artificial desire may  be checked by various causes;—
by the exciting or depressing passions, the  sight  of a disgusting
object, or  any thing that excites intense mental emotion; or it may
be appeased by filling the stomach with substances that contain no
nutritious properties:  as, however, the feeling of true hunger, arises
from the wants of  the  system, the natural  and instinctive sensa-
tion  soon appears,  and  cannot be long postponed by any of these
means.  Hence  it has  been proposed to make a distinction between
the appetite and hunger; applying  the former term  to the artifi-
cial,  the latter to the natural, desire.   In  these  respects,  there is
certainly a wide distinction  between them, as well as in the capri-
ciousness, which occasionally characterizes  the former, and gives
rise to  the most singular and fantastic preferences.
   The sensation of hunger varies in intensity according to differ-
ent circumstances.   It  is more  powerful  in  the child and the 
462                       DIGESTION.
youth, than it is in the adult, who has attained  his full height.
In the period of second childhood, it is  likewise urgent, proba-
bly owing to the  diminished power of assimilation requiring,
that more aliment should be received  into the stomach.   In the
state of disease, the sensation is generally suppressed, and its place
supplied  by loathing or disgust for food: at times, again, its in-
tensity makes it a true disease, as in bulimia, and in  pica;  in  the
latter of which the appetite is, at times, irresistibly directed to sub-
stances, which the person never before relished, or which are not
edible,—as chalk, earth, slate pencil, &c.
  The appetite is, also, modified by the degree of  exercise or in-
activity, to which the individual has been subjected;—regular exer-
cise, and the exhilarating passions; a cold and dry atmosphere, &c.
augmenting it, whilst it is blunted  by opposite circumstances.
  Long-continued exertion, with a scanty supply of nourishment,
if not continued so long as to injure the tone of the stomach, pro-
duces, occasionally, in adults, a voracious appetite and rapid diges-
tion.  Mr. Hunter hasquoted,in illustration of this point, the follow-
ing extract from Admiral Byron's narrative. After describing the
privations he had suffered, when shipwrecked on the coast of South
America, the admiral incidentally  refers  to  their effect upon  his
appetite.  " The governor," he says, " ordered a table to be spread
for us with cold ham and fowls, which only we three sat down to,
and in a short time dispatched more than  ten men with common
appetites would have done.   It is amazing, that our eating to that
excess, we had done from the time we first came among these kind
Indians, had not killed us, as we were never satisfied, and used to
take all opportunities for some months after, of filling our pockets,
when we were not seen, that we might get up two or three  times
in the night to cram ourselves."
  Authors have distinguished, in hunger, the local from the general
phenomena. Many of their assertions, however, upon these points
appear to be imaginative.   We are told by  Adelon  and others,
that the stomach becomes contracted,  and that this change is ef-
fected by the sole action of its muscular coat;—the mucous or lining
membrane becoming wrinkled, and the peritoneal coat, externally,
permitting the organ to retire between its laminae.   Such  MM.
Tiedemann and Gmelin assert is the result, also, of their obser-
vations.   Magendie,  however, affirms,  that after  twenty-four,
forty-eight, and even sixty hours of complete  abstinence, he  has
never witnessed this contraction of the stomach.  The organ had
always considerable dimensions, especially in its splenic portion.
It was not until after the fourth or fifth day, that it appeared to him
to close upon itself, to diminish greatly in capacity, and to change
its position slightly; and these effects were not observed unless the
fasting was rigorously maintained.
  At the same time, that the stomach changes its shape  and situa-
tion, it is affirmed to draw the duodenum slightly towards it; that 
HUNGER.
463
its parietes appear thicker,—and the mucous follicles and  nervous
papillae project more into its interior.   Its cavity is void  of food,
and contains only a little saliva, mixed with bubbles of air, a small
quantity of mucus, and, according to some, a little bile and pan-
creatic juice, which the traction  of the duodenum has caused to
flow into it.  Much dispute has arisen  as to whether the circula-
tion of the blood in the stomach experiences any mutation.  Dumas
was of opinion, that when the organ is empty, it receives less blood
than when full; either on account of the great flexion of the vessels
in the former case, or on account of the compression, experienced
by the nerves, in consequence of the contracted state of the organ.
He thinks that, under such circumstances, a part of the blood,
which is distributed to that viscus, reflows into the liver, spleen,
and omentum; and he regards these organs as diverticula  for the
blood of the stomach, especially as the liver and spleen  are then
less compressed, and the omentum more extensive, owing to the
retraction of the stomach.
   Bichat denies both the fact and its explanation.  He affirms
that, on opening animals suffering under hunger, he never observed
the vessels of the stomach less full of blood, the mucous membrane
less florid, or the vessels of the omentum more turgid.   It is not
true, he adds, that the vessels of the  stomach are more  flexuous
when the organ is empty : being connected with the serous coat,
as well as the nerves, they are unaffected by changes of size in the
organ; besides the retraction of the stomach could never be strong
enough to compress the nerves.   He denies, moreover, that the
liver and spleen are more free, and the omentum larger, whilst the
stomach is empty, as the abdominal parietes contract in  the same
proportion as  the stomach. Magendie, however, contests this last
assertion of Bichat.   He affirms, on the  faith of positive experi-
ments, that the pressure, sustained by the abdominal viscera, is in
a ratio with the distention of the stomach.   If the stomach be full,
the finger introduced into the cavity of the abdomen, through an
incision in its parietes,  will be strongly pressed upon, and the vis-
cera will be forced towards the opening ;  whilst,  if it be empty,
the pressure is inconsiderable, as well as the  tendency of the vis-
cera to escape through the opening.   During the  state of vacuity
of the organ, he remarked, that the different reservoirs  in the ca-
vity of the abdomen,—as the bladder and gall-bladder,—were more
easily filled by their proper fluids.  With  regard  to the  quantity
of blood circulating through the  stomach in the  empty and full
state;—he is  disposed to think, that it receives less in the former
condition; but instead of its differing in this respect from the other
abdominal viscera, he thinks,  that such is the case with every or-
gan  in the abdomen.
   The general effects, said to be produced by hunger, in contra-
distinction to  the local, are;—debility  and diminished action of
every organ.  The circulation  and respiration slacken;  the heat of 
464                       digestion.
the body sinks; the secretions diminish, and all the functions are
exerted with more difficulty, if we except absorption, which, it is
affirmed, and with much probability, is alone augmented.
   If the abstinence be so long protracted as to cause death, the de-
bility of the functions becomes real, and not sympathetic. Respi-
ration and circulation languish: all the animal functions totter;
whilst absorption continues, and the blood is supplied by the de-
composition of the different  organs.    The fat, the various liquid
matters, other than the blood, the tissues and the organs themselves
are successively subjected to  its action.  It  is  obvious, however,
that, with the constant drain perpetually taking place, this state of
affairs cannot long exist; the blood becomes diminished in quan-
tity, and insufficient in every respect  to vivify the organs.   The
functions  of the brain are perverted, and, in many instances, we
are told, the most furious delirium closes the scene; whilst, at
others, the miserable sufferer sinks passively into the sleep of death.
   Occasionally, again, so dreadfully  painful are   the sensations,
caused by protracted privation of food, that the most violent anti-
pathies and the dearest affections are overcome ; and numerous in-
stances have occurred in  which the sufferer has attacked his  own
species, his  friends, his  children, and  even  the substance of his
own body.  The horrible picture of  the shipwreck, in the Don
Juan of Byron, is not a mere romance.   It is but the actual fact,
expanded somewhat by the imagination of the poet.
   Dr. James Currie has related the case  of a  person, who  died
of inanition, from  stricture  of the  oesophagus,   the particulars
of which  may exemplify the phenomena, presented  by  some of
those, who perish from abstinence.  The records of such cases are
rare.
   From the 17th of October  to the 6th of December, the patient
was supported without the aid of the stomach, by means of broth
clysters,—and was immersed in a bath of milk and water;—circum-
stances, however, which probably modified the symptoms but lit-
tle, inasmuch as we shall find hereafter, that but little absorption
can be effected through the cuticle. At one period  he had a parch-
ed mouth; a blister discharged only a thin, coagulable lymph; and
the urine was  scanty, extremely high-coloured,  and intolerably
pungent  The heat of the body was  natural and nearly uniform,
from first to last; and the pulse was perfectly natural until the last
days.   His  sleep was sound and refreshing; his spirits even; and
his intellect unimpaired, until the four last days of existence, when
the clysters  were no longer retained. Vision was deranged on the
first of December, and delirium followed on  the succeeding day ;
yet the  eye was unusually sensible, and the sense of touch remark-
ably acute.  The surface and extremities were, sometimes,  of a
burning heat; sometimes clammy and cold.   On  the fourth, the
pulse became feeble and irregular, and the inspiration laborious;
and, in ninety-six hours after all means of nutrition as well as all 
hunger.
465
medicine had been abandoned, he ceased to breathe. He was never
much troubled by hunger. Thirst was, at first, troublesome, but it
was relieved by the tepid bath. This was one of the cases in which
the patient sinks tranquilly to death.  In  others, the distressing ac-
companiments, above described, are  met with; and the death is
that of the furious maniac.
  The period at which death will occur from protracted abstinence
is dependent on many circumstances.  As a  general principle it
may be assumed, that the young and robust will expire sooner
than the older; and this will have to be the guidance in questions
of survivorship, which may  arise, when several  individuals have
perished together from this cause.  The picture  given by  Dante
of the sufferings and death of Count Ugolino  della Gherar-
descha, who  saw his sons  successively expire  before him from
hunger, in this respect, is true to nature:—

       " Now when our fourth sad morning was renew'd,
         Gaddo fell at my feet, outstretch'd and cold,
         Crying:—'Wiltthou not, father! give me food?'
       There did he die; and as thine eyes behold
         Me now, so saw I three fall, one by one,
         On the fifth day and sixth: whence in that hold,
       I, now grown blind, over each lifeless son,
         Stretch'd forth mine arms.  Three days, I call'd their names,
         Then Fast achiev'd what Grief not yet had done."
                                        Inferno, Canto XXXIII.

  The sensation of hunger resembles every other internal sensation
in the mode in which it is accomplished. There must be an action
of impression,  of conduction, and of perception.   That the brain
is the organ of the last part of the process is proved by all the ar-
guments used in the case of the  internal  sensations in general.
Without its intervention, in  this, as in every other case, no sensa-
tion can be accomplished. The stomach is the organ in which the
impression is effected; and,  by means of the nerves, this  impres-
sion is conyeyed to the encephalon.
  The eighth pair,  or pneumogastric nerves, have generally been
regarded as the agents of this transmission; and it has been affirm-
ed by Baglivi, Valsalva, Haller, Dumas, Legallois,  Chaus-
sier,  and others, that if these  nerves be divided in  the neck, al-
though the stomach may be, in other respects, favourably  circum-
stanced for the development of the impression of hunger,  and the
brain  ready for its reception, there is  no sensation. MM. Leuret
and Lassaigne, however, deny that such effect follows the division
of these nerves; and they affirm, that horses have eaten as usual,
and apparently with  the same  appetite, after they had removed
several  inches  of the  pneumogastric nerves; and that they even
continued to eat after the stomach was filled.  To these experiments
we shall have occasion to refer hereafter.  They by no means ex-
  Vol.  I.                     59 
466
DIGESTION.
hibit, that this internal sensation  differs from others; and  that the
three actions are not equally necessary for its accomplishment.
   The difficulty, which the physiologist has always felt, regards
the precise nature of the action of impression.   Its seat is clearly
in the stomach.   To that organ all our feelings refer it.  It  is de-
pendent upon some modification, occurring in the very tissue of
the viscus;  and in the nerves, which, as has been shown, are the
sole agents in all the phenomena of sensibility.   These nerves are
spread over the stomach, so that the  precise seat of the impression
cannot be as accurately defined as in the case of the organs of ex-
ternal sense.  Moreover, the nerves of the stomach proceed from
two essentially different  sources,—from the eighth pair, and from
the great sympathetic. The question consequently arises,—on which
of these is the impression made?  The experiment of  cutting the
eighth pair in the neck would appear to decide in favour of the
former.
   As to the proximate or efficient cause of hunger, we cannot ex-
pect to arrive at any satisfactory conclusion.  It is a sensation; and,
like all  sensations, necessarily inscrutable.  Theories, however, as
on all obscure topics, have been numerous, and these have generally
been of a mechanical or a chemical nature.   Some have attributed
it to the mechanical friction of the parietes of the stomach against
each other, in consequence of the contraction of the organ; in which
state, they affirm,  the mucous coat is rugose, and its papillae and
follicles prominent. It is manifest, however, from the structure of
the organ, that no such friction can possibly take place.  Yet this
view was embraced by the illustrious Haller. Others, again, have
accounted for the sensation by the  action of the gastric juice, which
is supposed to have a tendency to corrode the internal membrane.
In proof of this, they refer to a case, mentioned by Hunter,  in
which the mucous membrane, in a man who died of fasting, was
found corroded. The gastric juice is, however, incapable of eroding
living animal matter; and the numerous cases, which have occurred,
since that of Hunter, have sufficiently shown, that the corrosion
and perforation, which we  meet with on dissection, are to be re-
ferred to an action after  death, and,  consequently, totally uncon-
nected with the sensation felt during life.   We have, indeed, no
reason for believing that  the gastric juice can ever attain a state of
acridity, and act upon the surface, by which it is secreted.   It has
been already remarked, that it is a law of the animal economy,
that no  secretion acts upon the part  over which it is  destined to
pass^ provided such part be in a healthy condition.  Yet Soemmer-
ing  ascribes the pain, from long-continued fasting, to the action of
the gastric juice; and Dr. Wilson Philip is manifestly induced to
believe, that the influence of the  gastric juice on the stomach is,
in some mode or other, productive of the sensation; his remarks,
however, tend simply to show,—what we have so many opportuni- 
                    prehension  of food.                 467

ties of observing,—that the sensation can be postponed by exciting
vomiting, or by inducing, for the time, a morbid condition of the
stomach.
   Bichat, again, attributed it to the lassitude or fatigue of the sto-
mach, occasioned by the contraction of its muscular coat, when
prolonged beyond a certain time. In answer to this, it may be re-
marked, that, if any thing impedes the nutrition of the body, hunger
still continues, although the stomach  may be distended.  This
happens incases of scirrhous pylorus, where  the  nutritive  mass
cannot pass into the small intestine, to be subjected to the action
of the chyliferous vessels, and the losses of the body cannot, there-
fore, be repaired;—facts which would seem to show,  that hunger
is a sensation, excited in the stomach by sympathy with the wants
of the  constitution; and that  it is immediately produced by some
alteration in the condition of the nerves of the organ, which is in-
appreciable to us.
  2. Prehension of food.   The arms and the mouth have  been
described as the organs of prehension.   It is scarcely necessary to
say, that the hands seize the food and convey it to the mouth, under
ordinary circumstances; but there are cases in  which the mouth is
the sole or chief organ of prehension. Most animals are compelled
to use the mouth only.   When the food is conveyed to the mouth
by the hands, it must open to receive it.  The mode in which this
is effected has given rise to much controversy; and strange to say
is not yet considered determined.
   Whilst some physiologists have asserted, that  the lower jaw
alone acts in opening the mouth moderately; others have affirmed,
that both the jaws separate a little; the lower, however, moving
five or six times as much as the upper.   That the latter is the cor-
rect view can be proved by positive experiment.  If, when the
mouth is closed, we place the flat side of the blade of a knife against
the teeth of both jaws; and, holding the knife immovably, separate
the jaws; we find, that both jaws move on the blade; but the lower
to a much greater extent than the upper.  Now, as the upper jaw
is fixed immovably to the head; the whole head must, of necessity,
participate in this movement; and  the question  arises, what are
the agents that produce it?  Boerhaave, Monro and Pringle
attribute it to a slight action  of the extensor muscles of the head;
and they affirm, that, whilst  the depressors of the lower jaw carry
it downwards, the extensors of the  head draw the head  slightly
backwards, and thus raise the upper jaw.
  Magendie and Adelon assert, that when the mouth is opened
moderately, the  upper jaw does not participate;  but, that if the
motion  be "forced" or extensive, the upper jaw  participates
slightly.  The experiment, however, of the knife, which is even
adduced by Adelon, completely overthrows this notion, and shows
that both jaws act,  whenever the mouth is slightly opened.
  Magendie  agrees with Boerhaave, Monro,  and Pringle, 
468
DIGESTION.
that whenever the upper jaw is raised, it must be by the head being
thrown back on the vertebral column; and* he properly remarks,
that where there is a physical impediment to the depression of the
lower jaw, the mouth must be opened solely by the retroversion
of the head on the spine.
  Ferrein conceived, that  the motion of the upper jaw is occa-
sioned by the action of the stylo-hyoideus muscle, and of the pos-
terior belly of the digastricus; and he affirmed, that whilst the an-
terior fasciculus or belly of the digastricus depresses the lower jaw;
the posterior belly, with the stylo-hyoideus, carries the head back-
wards, and, with it, the upper jaw.   The attachments, however,
of these muscles sufficiently show, that they cannot be the agents:
the mastoid process, to which the posterior belly of the digastric
muscle is attached,  is near the articulation  between the head and
atlas;  whilst the  styloid process, to which the stylo-hyoideus is at-
tached, is anterior to the articulation, and its effect ought, therefore,
to be  rather to depress the upper jaw.
  The view of Professor Chaussier is the most probable.   He
ascribes the slight elevation of the upper jaw to the mechanical ar-
rangement of the joint of the lower jaw.  According to him, the
temporo-maxillary articulation is not formed by a  single condyle,
but by two, which are so disposed, that the lower cannot roll down-
wards during the depression of the lower jaw, without causing the
upper condyle to roll upwards, and,  consequently, to slightly ele-
vate the upper jaw.
  Under ordinary circumstances, then, the jaws cannot be at all
separated without both participating; but if we determine to fix the
upper jaw we can make the lower the sole agent.
  As soon  as the food is introduced into the mouth, the jaws are
closed to retain it, and subject it to mastication.  Frequently, how-
ever,  they  assist in  the act of prehension, as when we bite into a
fruit,  to separate a portion from  it;—the incisor teeth acting, in
such case, like scissors.   This is chiefly produced by the contrac-
tion of the muscles, that raise the lower jaw; and it is probable,
that the action of the stylo-hyoideus is concerned in this movement;
—drawing the head and upper jaw with it downwards and forwards.
The levator muscles of the jaw act here with great disadvantage;—
the lower jaw representing a lever of the third  kind; the fulcrum
being in  the joint;  the power at the insertion of the levator mus-
cles; and the resistance in the substance between the teeth.   The
arm of the resistance is,  consequently, the whole length of the
lever; and we can readily understand why we are capable of de-
veloping so much more force, when the resistance is placed be-
tween the molares;  and why old  people, who have become tooth-
less, and are, consequently, constrained to bite  with the anterior
part of the jaws,—the only portion, that admits of contact,—cannot
bite with any degree of strength.
  The size of the body, put between the incisor teeth, also influ- 
prehension of food.
469
ences the degree  of force  that can be brought to bear upon it.
When small, the force can be much greater, as the levator mus-
cles are inserted* perpendicular to the lever to be  moved; and the
whole of their power is advantageously exerted ;  but if  the  body
be so large, that it can scarcely be received into the  mouth, and
be resisting withal, the incisors can scarcely penetrate it;—the in-
sertion of the levator muscles  into the jaw being  rendered very
oblique; and the greater part of the force they develope being con-
sequently lost. This will be readily seen by the illustration, Fig. 96.
When the mouth is closed, or nearly so, the masseter and temporal
muscles, represented respectively by the lines B E and 3 j, are in-
serted nearer the perpendicular; but when the lower jaw is depress-
ed, so that the situation of these muscles is represented by the dotted
lines B e and J k,  the direction, in which the muscles act, will be
much more oblique, and, therefore, more disadvantageous.
 A. The frontal bone.—B. The temporaL-C The parietal.—D. The occipital.—E. The coronoid
process of the lower jaw, to which the temporal muscle is attached.—F. The condyloid process or head
of the lower jaw.—G. The lower jaw.—H. The mastoid process.—I. The upper jaw.—J. The cheek
bone.—K. The orbit.—L. The meatus auditorius externus.—L*. The coronal suture.—M. The squamous
suture.—N. The lambdoidal suture.—£. The lower jaw depressed.

  When the muscles of the  jaws are incapable,  of themselves, of
separating the substance,  as in the case of the apple, the assistance
of the muscles of the hand is invoked; whilst the muscles on  the 
470
DIGESTION.
posterior part of the neck, which are inserted into the head, draw
it backwards; and, by these  combined efforts, the substance is for-
cibly divided.
  3. Oral or buccal digestion.—The changes, effected upon the
food in the  mouth, are important preliminaries to the function
which has to be executed in the stomach and duodenum. As soon
as the food enters the cavity, it is subjected to the action of the
organ of taste; and its sapid  qualities are duly appreciated.  By its
stay there, it also nearly acquires the temperature of the cavity.
This is, however, a change of little moment, unless the food be so
hot, that it would injure the stomach, if  passed rapidly into it.
Under such circumstances, it  is tossed about the mouth, until it
has parted with its caloric to various portions of the parietes of the
cavity; and then,  if in a fit state for the action of deglutition, it is
transmitted along the cesophagus; but the most important parts of
oral digestion, are the movements of mastication and insalivation;
by which the solid food is comminuted, and imbued with  the se-
cretions, that are  poured into the interior of the mouth, and which
we  have shown to be of a very compound character.
  Under the sense of taste,  the influence of the agreeable or disa-
greeable character of the food upon the digestive function was ex-
patiated upon. It  is unnecessary, therefore, to do more than allude
to the subject here. We find them mutually influencing each other:
whilst a luscious aliment excites us to prolonged  mastication, and
the salivary  glands to  augmented secretion, the  masticatory and
salivary organs, by dividing and moistening the  food, permit the
organs of gustation to enjoy the savour in successive applications.
  When the food is received into the mouth, if it be sufficiently
soft, it is commonly swallowed immediately; unless the flavour be
delicious, when it is detained for some time.  If solid, and, espe-
cially,  if of  any size or density, it is  divided  into separate  por-
tions, or is chewed,—the action constituting mastication.
  If the consistence of  the substance be moderate, the tongue, by
being pressed strongly against the bony palate, is sufficient to effect
this division; bruising it, and, at the same time, expressing its fluid
portions. If the consistence  be greater, the action of the jaws and
teeth is required.   For this purpose, the lower jaw is successively
depressed  and elevated by the action of its depressors and levators;
and the horizontal or grinding motion is produced at pleasure by
the action of the pterygoid muscles. Whilst these muscles are act-
ing, the tongue and  the  cheeks are incessantly moving, so as to
convey the food between the  teeth, and insure its comminution.
Mastication is chiefly effected by the molares.  There is advantage
in using them, independently of their form, in consequence of the
arm of the resistance being much shortened, as has already been
shown.
  The teeth are well adapted for the service they have to perform.
The incisors, as their name  imports, are used for cutting; hence 
ORAL DIGESTION
471
their coronae come to an edge;  the canine teeth penetrate and la-
cerate, and their coronae are acuminated; whilst the molares bruise
and  grind, and their touching surfaces are tuberous. The first, hav-
ing usually no great effort to sustain, are placed at the extremity
of the lever;  the latter, for opposite reasons, are nearest the ful-
crum.   To preclude displacement, by the efforts they have occa-
sionally to sustain, they are firmly fixed in the alveoli or sockets;
and, as the roots  are  conical, and the alveoli accurately embrace
them, the force, as in the case of the wedge, is transmitted in all
directions, instead of bearing  altogether upon the jaw, which it
would do, were the fangs  cylindrical.   The  molar teeth, having
the greatest efforts to sustain, are furnished with several roots; or
with one, which is extremely large.
  The gums add  materially to the solidity of the junction  of the
teeth with the jaw. They are themselves formed of highly resisting
materials, so  as to withstand the pressure of hard and irregular sub-
stances.  Whenever they become spongy, and fall away from the
teeth, the latter become loose; and are frequently obliged to be ex-
tracted, in consequence of the loose tooth acting  as an extraneous
body, and inflaming the lining membrane of the alveolus. The ar-
rangement of the jaws i3 likewise well adapted to the function; the
lower jaw passing behind the upper at its anterior part; but coming
in close  contact  at the sides, where mastication is chiefly  ope-
rated.
  During the whole time that mastication is going on, the>cnouth is
closed ;—anteriorly, by the lips  and teeth, which prevent the food
from falling out of the cavity; and, posteriorly, by the velum palati,
the anterior surface of which is  applied to the base of the tongue.
At the same  time, the food is undergoing admixture with the va-
rious fluids poured into the mouth, and particularly with the sa-
liva, the secretion of which is augmented, not only by the presence
of food, but  even by the sight of it, especially if the food be desira-
ble;—giving rise  to what  is called  " mouth-watering." It is pro-
bable, that, independently of the mental association, the action  of
the secretory organs  is increased by the agitation of the  organs
themselves during  the masticatory movements.  It has,  indeed,
been asserted, that  the parotid  glands are so situated, as regards
the jaws, that the movement of the lower jaw presses upon them,
and forces out the saliva;  but Bordeu  and J. Cloquet have de-
monstrated,  both  anatomically and by experiment, that such is not
the case.
  It has been supposed, by some, that the admixture with the sa-
liva communicates to the food its first degree of animalization; or
in other words, its first approximation to the substance of the ani-
mal it has to  nourish.   It is more probable, however, that the great
use of mastication and insalivation is to give the food the necessary
consistence,  in order that the stomach and small intestine may exert
their action upon it,  in the most favourable manner; and that, conse- 
472
DIGESTION.
 quently, the changes effected upon the aliment in the mouth, are
 chiefly of a mechanical character.
   In the case of many substances,—as sugar, salt, &c.—a true solu-
 tion takes place in the saliva; and this probably  happens to  sapid
 bodies in general;  the particles  being  separated by imbibing the
 fluid. Krimer, of Leipzig, held in his mouth a piece of ham, weigh-
 ing a drachm, for three hours.  At the expiration of this time, the
 ham was white on its surface, and  increased in weight twelve grains.
 Krimer, it may be remarked, believes, that the tears assist in di-
 gestion, and that they flow  constantly by the posterior nares into
 the stomach.
   Both mastication  and insalivation are of great moment, in order
 that digestion shall  be accomplished in perfection; and,accordingly,
 we find,  that they who swallow the food without due mastication,
 or waste the saliva by constant and profuse spitting, are more liable
 to attacks of dyspepsia, or imperfect digestion.
   The degree of resistance, and  the sapidity of the food, apprize
 us when mastication and insalivation have been sufficiently exerted.
 When such is the case, it is  subjected to the next of the digestive
 processes.   Some physiologists have affirmed, that the uvula is the
 organ which judges when the food is adapted for deglutition. Adelon,
 whose views are generally worthy of great favour  and attention,
 asserts, " that it judges by its mode of sensibility, of the degree in
 which the aliment has been prepared in the mouth; of the extent to
 which it  has been chewed, impregnated with saliva, and reduced to
 paste; and, according to the impression it receives from the aliment,
 it excites, sympathetically, the action of all those parts; directs the
 convulsive contraction of  the muscles, that raise the  pharynx, and
 even  keeps  the stomach on the alert, and disposes it to receive fa-
 vourably or to reject the food passing to it."
   Such a function would be  anomalous.  It is, indeed, impossible
 for us to  conceive, how so insignificant an organ could be possessed
 of these elevated attributes.  Observation, also, proves that the no-
 tion is the offspring of fancy.  Magendie asserts, that he has known
 several persons,  who had entirely lost the uvula, either by venereal
 ulceration or by excision,  and yet he never  remarked, that  their
 mastication experienced the slightest modification, or that they swal-
 lowed inopportunely.  Our experience corresponds accurately with
 that of Magendie.  At this very time, we have, under  our eye,
 an individual in  whom there  is not the  slightest vestige of uvula,
 yet he tastes, chews, and swallows like other persons.
  4. Deglutition.—The act of swallowing, although executed with
 extreme rapidity, and apparently simple, is the most complicated of
 the digestive operations.   It requires the action of the mouth, pha-
 rynx, and cesophagus.  It has  been well analyzed by Magendie,—
 first of all in a thesis, maintained at the Ecole de Midecine of Paris,
in  1808, and subsequently,  in his Precis ilimentaire  de Phy-
siologic   To facilitate its study, he  divides it into three stages. 
deglutition.
473
In the first, the food passes from the mouth into the pharynx;  in
the second, it clears the apertures of the glottis and nasal fossae, and
attains the cesophagus; and, in  the  third, it clears  the oesophagus
and enters the stomach.
   1. When the food has been  sufficiently masticated and  imbued
with saliva, it is collected by the action of the cheeks and tongue
upon the upper surface of this last organ;—the mass being more  or
less  rounded, and hence, usually termed the alimentary bolus.
Mastication now  stops, the tongue is raised and applied against the
bony palate, in succession from the  tip to the root, and the  alimen-
tary bolus, having no other way of escaping from the force pressing
it, is directed towards the pharynx.  Previous to this, the pendulous
veil of the palate has been applied to the base of the tongue.  The
bolus now raises it to the horizontal position ; the circumflexus pa-
lati muscles render the velum tense, so that the food cannot pass
into the nasal fossae; and the muscles, that constitute the pillars  of
the fauces—the palato-pharyngei and  the glosso-staphylini—con-
tribute to this effect.  By this  combination  of results, the  food  is
impelled into  the pharynx.
   The muscles, which, by their action, apply the tongue to the roof
of the mouth  and to the velum palati, are the proper muscles  of
the organ,—the linguales and  genio-hyoidei, aided  by the mylo-
hyoidei.
   In this first stage of deglutition, the motions are voluntary, except
those of the velum palati. The  process is not executed with rapidity
and is  easily intelligible.  Such is  not the  case with the  second
stage.  The actions in it are complicated, and executed with so much
celerity, that they have been regarded as a kind of convulsion.
   2. The distance, over which the bolus has to travel, in this second
stage, is trivial: the rapidity of  its course is owing to the larynx  or
superior aperture  of the windpipe, which opens into the  pharynx,
having to be cleared  instantaneously, otherwise  respiration would-
be arrested, and the most serious effects ensue.  The mode, in which
this second stage is accomplished, is as follows. As soon as the ali-
mentary bolus comes in contact with the pharynx, all is activity ;
the pharynx contracts,  embraces, and  presses the bolus; and the
velum  pendulum, drawn down  by the palato-pharyngei and glosso-
staphylini muscles, fulfils a similar office.  At the same  time, the
genio-glossus,  by applying the tongue to the palate, from the tip  to
the root, raises the os hyoides, the larynx, and, with it, the anterior
paries of the pharynx.   The same effect is directly induced by the
contraction of the mylo-hyoidei, and genio-hyoidei, muscles; which,
instead of acting as depressors of the lower jaw, as they do during
mastication, take the jaw, as their fixed point, and act as levators of
the os hyoides.  The larynx is  thus elevated, carried forwards, and
meets the bolus, to render its passage over the aperture of the la-
rynx shorter, and, therefore, more speedy. To aid this effect, when
  Vol. I.                     60 
474                       DIGESTION.
we make great efforts to swallow, the head is inclined forwards on
the thorax.
   Whilst the os hyoides and the larynx are raised, they approach
each other,—the upper margin of the thyroid cartilage passing behind
the body of the hyoid bone: the epiglottic gland is  pushed back-
ward,  and the epiglottis is depressed, and  inclined backwards and
downwards, so as to cover the entrance to the larynx. The cricoid
cartilage executes a rotatory motion  on the inferior  cornua of the
thyroid cartilage, which occasions the entrance of the  larynx to be-
come oblique, from above to below, and, of course, from before to
behind.  The bolus thus glides over its surface; and, forced on by
the veil of the palate, and by the constrictors of the pharynx, reaches
the cesophagus.
   At one time, it was universally believed that the epiglottis is the
sole agent in preventing substances  from passing into the  larynx.
The experiments of Magendie have, however, demonstrated, that
this is the combined effect of the motions of  the larynx just de-
scribed, and of the muscles, whose office it is to close the glottis; so
that, if the laryngeal and recurrent nerves be divided  in an animal,
and the epiglottis be left in a state of integrity,  deglutition is ren-
dered extremely difficult;—the principal cause, that prevented the
introduction of aliments into the glottis, having been removed by
the section.  Magendie  refers to two cases  of individuals, who
were totally devoid of epiglottis,  and yet, who swallowed without
any difficulty; and  he remarks, that if, in laryngeal phthisis, with
destruction of the epiglottis, deglutition is laboriously and imper-
fectly accomplished, it is owing to the carious condition of the ary-
tenoid cartilages, and to the lips of the glottis being so much ulcer-
ated as not to  be able to  close the glottis accurately.   Whilst the
bolus, then, is passing over the  top of the larynx, respiration must
be momentarily suspended, owing to the closure of the glottis; and
if, owing to distraction of any kind, we attempt to speak, laugh, or
breathe, at the moment of deglutition, the  glottis  opens, the food
enters, and cough is excited, which is not appeased, until the cause
be removed.   This is what is  called,  in common language, "the
food goipg the wrong way."
   As soon as the bolus has cleared the glottis, the larynx descends,
the epiglottis rises,  and the glottis opens to give passage to the air.
This is owing to the relaxation  of the muscles, that had previously
raised the larynx and closed the glottis.  Chaussier thinks, that
the sterno-hyoidei muscles now act,  and aid in  producing the de-
scent  of the parts.
  The velum  pendulum, then,  protects the posterior nares  and the
orifices of the Eustachian tube from  the entrance of the food ;  and
the epiglottis, the elevation of the larynx,  with the  contraction of
the muscles, that close the glottis, are  the great agents in prevent-
ing it from passing  into the larynx. 
DEGLUTITION.
475
  The whole of this second stage consists of rapid movements, of
an entirely involuntary character.
  3. In the third stage, the pharynx, by its contraction, forces the
alimentary bolus into the oesophagus,  so as to somewhat dilate the
upper part of the organ. The upper circular fibres are thus excited
to action, and force the food onward.   In this way, by the succes-
sive contraction of the circular fibres, it reaches the stomach.   In
the upper part of the oesophagus, the relaxation of the circular fibres
speedily follows their contraction;  but this is  not the case in the
lowest third, the circular fibres remaining contracted, for some time
after the entrance of the bolus into the stomach,—probably to pre-
vent its return into the cesophagus.
  The passage of the bolus along the oesophagus is by no means
rapid.   Magendie  affirms, that he was struck,  in the prosecution
of his experiments, with the slowness of its progression.  At times,
it was two or three minutes before reaching the stomach; at others,
it stopped repeatedly, and  for some time.  Occasionally, it even
ascended, from the inferior extremity of the cesophagus towards the
neck, and subsequently descended again. When any obstacle existed
to its entrance into  the stomach, this movement was repeated a
number of times, before the food was rejected.  Every one must,
indeed, have felt the slowness of the progression of the food through
the cesophagus, if a  rather larger morsel than usual has been swal-
lowed.  When it stops, we are  in the habit of aiding its progress by
drinking some  fluid, or by taking a piece of bread to drive  it on-
wards.  Occasionally, however, the probang is necessary to move it.
The pain, produced in these cases, according to Magendie, is owing
to the distention of the nervous filaments, that surround the pectoral
portion of the canal.
  In the case of a female, labouring under a disease, which permitted
the interior of  the stomach to be seen, Halle noticed, that when-
ever a portion of food  passed  into the stomach, a sort of ring or
bourrelet was formed at the cardiac orifice, owing to the mucous
membrane of the oesophagus being forced into the stomach, by the
contraction of the circular fibres of the canal.
  The mucous  fluid from the different follicles,  pressed out by the
passage of the bolus, materially facilitates its progress.
  Notwithstanding the facility with which deglutition is accom-
plished, almost every part  of  it  is uninfluenced by volition, being
dependent upon organization,  and exerted instinctively. If the ali-
mentary matter, contained in the mouth, be not sufficiently  masti-
cated;  or if it have not the shape, consistence, and dimensions, that
it ought to possess; or if the ordinary movements, that precede
mastication, have not been executed, whatever effort we may make,
deglutition  is impracticable.   We constantly  meet  with persons,
who are unable to swallow the smallest pill; yet they can swallow
a much larger mass, if certain preliminary motions are permitted;
which, in the case of the pill, are inadmissible, in consequence of 
47b
DIGESTION.
its being usually of a nauseous character.  It appears, that the invo-
luntary parts of the function are excited by the stimulation of the
aliment; for,  if we attempt to swallow the saliva several times  in
succession, we find that, after a time, the act is impracticable, owing
to the deficiency of saliva.   Every one  must have experienced the
difficulty of deglutition, when the mouth and  fauces are not duly
moistened by  their secretions.
  Some individuals are capable of swallowing  air;  and,  according
to Magendie, it is an art that can be attained  by a little practice.
In the  stomach,  the air acquires the  temperature of the viscus,
becomes rarefied, and distends the organ;  exciting, in some, a feel-
ing of burning heat; in others, inclination to vomit or acute pain.
Magendie thinks it probable, that its chemical  composition under-
goes change;  but,  on this point, nothing certain is known.
  The time of its stay in the stomach is variable.   Commonly,  it
ascends into the cesophagus, and makes  its exit  through the mouth
or nostrils.  At other times,  it passes  through the pylorus, and
spreads through the whole of the intestinal canal as far as the anus,
distending the abdominal eavity, and simulating tympanites.  Ma-
gendie refers to the case of a  young conscript, who  feigned the
disease  in this manner.
  5.  Chymification. When the food has  experienced the changes,
impressed upon it  by the preceding process, it reaches the cavity of
the stomach, where it is retained for several hours, and undergoes
the first portion of the true digestive action; being converted into a
pultaceous mass, to which the term chyme has been applied; and to
the process chymification.
  It does not seem, that all physiologists have employed these terms
in this  signification; some  having confounded the chyle  with the
chyme; and chylification with chymification. The former of these
processes is distinctly a duodenal act; whilst the  latter is exclusively
gastric.
  The aliment, as  it is sent down by repeated efforts of deglutition,
descends into  the splenic portion of the  stomach; and this without
difficulty, as regards the first mouthfuls.   The stomach is but little
compressed by the surrounding viscera;  and its  parietes readily se-
parate to receive  the alimentary  bolus;  but  when food is  taken in
considerable quantity, the distention  becomes gradually  more dif-
ficult, owing  to the  compression of the  viscera and the distention
of the parietes of the abdomen. The accumulation takes place chiefly
in the splenic  and  middle portions.                          i
  Whilst the stomach is undergoing this distention  by the food, it
experiences changes in its size, situation,  and connexion with the
neighbouring organs.
  The dilatation does not affect its three  coats  equally.  The two
laminae of the peritoneal coat separate, and permit the stomach to
pass farther between them.   The muscular membrane experiences a
true distention; its fibres lengthen, but still so as to preserve the 
chvmification.                    477
particular shape of the mouth; whilst the  mucous  coat yields, in
those parts especially where the rugae are numerous;—that is, along
the great curvature  and  in  the splenic  portion.  In place, too, of
being flattened at its anterior and  posterior surfaces, and occupying
only the epigastrium and a part of the left hypochondrium, it as-
sumes  a rounded appearance.  Its great cul-de-sac descends  into
that hypochondre and  almost entirely fills  it, and the greater  cur-
vature descends towards  the umbilicus, especially on the left side.
The pylorus,  alone, preserves its  position;  and  its  connexion with
the surrounding parts;—being fixed  down by a fold of the perito-
neum.   It is chiefly forwards, upwards and  to the left side, that the
dilatation occurs.  The posterior surface cannot dilate on account
of the resistance of the vertebral column, and of a ligamentous for-
mation, which prevents the stomach from pressing on the great ves-
sels behind it.  Its cardiac and pyloric portions are also fixed; so
that, when it is undergoing distention, a movement of rotation takes
place, by which the great  curvature is directed slightly forwards;
the posterior surface inclined downwards, and the superior upwards.
A wound, consequently,  received in  the epigastric  region, will pe-
netrate the stomach in a very different part, according as it maybe,
at the time, full or empty.
   The dilatation  of the stomach produces changes  in the condition
of the abdomen and its viscera. The total size of the cavity is aug-
mented. The belly becomes prominent; and the abdominal viscera
are compressed, sometimes so much  so, as to excite a desire to  eva-
cuate the contents of the bladder or rectum.  The  diaphragm, too,
is crowded towards the thorax; and is depressed with difficulty; so
that, not only is  ordinary  respiration cramped, but speaking and
singing become laborious.
   Where the distention of the stomach  is pushed  to an enormous
extent, the  parietes of the abdomen  may  be painfully distended,
and the respiration really difficult.  It is in these cases of over-dis-
tention,that an energetic contraction of the  oesophagus is necessary;
and hence the advantage of the strong muscular arrangement at its
lower portion.
   In proportion as the food accumulates in the  stomach, the sensa-
tion of hunger diminishes; and, if we still  go on swallowing addi-
tional portions, it entirely disappears, or is succeeded by nausea and
loathing.  The quantity, necessary to produce this effect, varies ac-
cording to the individual, as well as to the character of the food;  a
very luscious  article sooner  cloying, than  one  that is  less so.  A
due supply of liquid with our solid aliment also enables us to pro-
long the repast with satisfaction.
   As the stomach, when distended,  presses upon the  different vis-
cera and upon the abdominal parietes, it is obvious, that it must ex-
perience a proportionate reaction.  An interesting  question conse-
quently arises;—to determine the causes, which oppose the passage
of the food baek along the cesophagus, as well as through the pylorus. 
478
DIGESTION.
   Magendie found, in his vivisections, that  the lower  portion of
 the cesophagus experiences, continuously, an alternate motion of con-
 traction and relaxation.   This contraction begins at the junction of
 the two upper thirds with the lower third; and is propagated, with
 some rapidity, to the termination of the cesophagus in the stomach.
 Its duration, when once excited, is variable;—the average being, at
 least, half a minute.  When thus contracted, it is hard and elastic,
 like a cord strongly stretched.  The relaxation, which succeeds the
 contraction, occurs suddenly and simultaneously in all the  contracted
 fibres; at times, however, it appears to take place from  the  upper
 fibres towards the lower.  In the state of relaxation, the oesophagus
 is remarkably flaccid;—forming a singular contrast with  its state of
 contraction.
   This  movement of the oesophagus is, according to Magendie,
 under the dependence of the eighth pair of nerves.  When these
 nerves were divided in an animal, the oesophagus no longer con-
 tracted.   Still it was not in the  state of relaxation.  Its fibres, thus
 deprived of nervous influence, were shortened with a certain degree
 of force; and the canal  remained in a state intermediate between
 contraction and  relaxation.
   The lower part of the  oesophagus of the  horse, for an extent of
 eight  or ten inches, is  not contractile  in the  manner of muscles.
 Magendie found, that when the eighth pair of nerves was irri-
 tated;  or when  the parts were  exposed to  the galvanic stimulus,
 no contraction  was produced.  The oesophagus of this  animal is,
 however,  highly  elastic;  and  its lower  extremity is kept so
 strongly closed, that, for a long time after death, it is difficult to in-
 troduce  the finger into it; and considerable  pressure is required to
 force air into it.  This arrangement Magendie considers to be the
 true reason, why horses  vomit with such difficulty, so as occasionally
 to rupture the stomach by their efforts.
   The alternate motion of the cesophagus, which we have described,
 opposes  the return of the food  from  the stomach.  The more the
 stomach is distended, the more intense  and  prolonged is the  con-
 traction,  and the  shorter the relaxation.   The  contraction, too,
 commonly coincides with inspiration ;  the  time at which  the sto-
 mach is, of course, most strongly compressed.  The relaxation is
 synchronous with expiration.
  The pylorus prevents the alimentary mass from passing into the
 duodenum.   In  living  animals, whether the  stomach be filled or
 empty, this aperture is constantly closed by the constriction of its
 fibrous ring, and the contraction of its circular fibres ; and, so accu-
 rately is it closed, that,  if air be forced  into the stomach from the
 cesophagus, the organ must be distended, and considerable exertion
 made to overcome the resistance of the pylorus. Yet,  if air be
 forced  from the  small intestine  in  the  direction  of the  stomach,
the pylorus offers  no resistance; suffering  it to enter  the organ
 under the slightest pressure;—a  circumstance that accounts for the 
chymification.
479
facility with which the bile  enters the stomach; especially when
there exists any unusual inverted action of the duodenum.
   To the  pylorus, however, a more active part has been assigned,
in the passage of the chyme  from  the stomach into the intestine.
" Nothing in the animal economy," says Sir Charles Bell,  " is
more curious and wonderful  than the action of that class of organs
of which the pylorus affords a remarkable example.  If a portion
of undigested food present itself at this door of the stomach, it is not
only not permitted to pass, but the door is closed against it with*
additional  firmness:  or, in other words, the muscular fibres of the
pylorus, instead of relaxing, contract with more than ordinary force.
In certain  cases, where the  digestion is morbidly slow, or where
very  indigestible food  has been  taken, the mass is carried to the
pylorus before it has been duly acted on by the gastric juice : then,
instead  of inducing the pylorus  to relax, in order to allow of its
transmission to the duodenum, it causes it to contract with so much
violence as to produce pain, while the food,  thus retained in the sto-
mach longer than natural, disorders the organ : and if the digestion
cannot ultimately be  performed, that disorder  goes  on  increasing
until vomiting is excited, by which means  the load that oppressed
it is expelled.   The pylorus  is a guardian placed between the  first
and the second stomach, in order to prevent any substance from pass-
ing from the foimer until it  is in a condition to be acted upon by
the latter: and so faithfully does this guardian perform its  office;
that it will often, as we have seen, force  the stomach to reject the
offending matter by vomiting rather than allow it to  pass in an un-
fit  state:  whereas,  when chyme, duly prepared, presents itself,  it
readily opens a passage for it  into the duodenum."
  This view of the functions of the pylorus has antiquity in its fa-
vour.  It is, indeed, as  old as the name, which  was given to it, in
consequence of its being believed to be a faithful porter  or janitor,
(irvXapoi;, a porter :)  but it is doubtless largely  hypothetical.   We
constantly see substances traverse the whole extent of the intestinal
canal, without having experienced the slightest modification in the
stomach;  yet the pylorus allows them free passage.   Buttons, half-
pence, &c. have made their way through, without difficulty ; as  well
as  the tubes and globes, employed  in the experiments of Spallan-
zani, Stevens  and others.  There are certain parts of fruits, which
are never digested, yet the janitor is always accommodating. Castor
oil is capable of being wholly converted into chyme:  and would be
so,  if it  could be retained  in the  stomach ; yet there is no agent,
which arrests its onward progress. The action of the pylorus would
seem, indeed, rather to be restricted to  preventing  the  passage of
the food into  the duodenum, unless it has undergone the necessary
change, as regards consistence; and farther than this its agency is
perhaps doubtful.
  The presence of  food in the stomach, after a meal, soon excites 
480
DIGESTION.
 the organ to action, although no  perceptible change in the food is
 perceptible for some time.  The  mucous membrane becomes more
 florid, in consequence of the larger afflux of blood; and the different
 secretions appear to take place in greater abundance; become mixed
 with the food,and exert an active and important part in the changes,
 which  it experiences  in the stomach.  Direct experiment  has
 proved, that such augmented secretion actually occurs. If an animal
 be kept fasting for some time,  and then be made to swallow dry
 food, or even stones, and be restricted from liquid aliment, the sub-
 stances, swallowed, will be  found,—on killing it some time after-
 wards,—surrounded by a considerable quantity of fluid.  Such is not
 the case with animals, killed after fasting.  The stomach then con-
 tains no fluid matter. The augmented secretion, in the former case,
 must therefore, be owing to the presence of the dry food in the sto-
 mach. That it is not simply the fluid, passed down by deglutition,—
 the salivary and mucous secretions, for example,—is proved by the
 fact, that the same thing occurs when the cesophagus has been tied.
 Besides, if the stomach of a living animal be opened, and any stimu-
 lating substance be applied to its inner surface, a secretion is seen to
 issue, in considerable quantity, at the points of contact;  and,  again,
 if an animal be made to swallow small  pieces of sponge,—attached
 to a thread  hanging out of the mouth, by means of which they can
 be withdrawn,—the  sponge becomes filled with the fluids secreted
 by the stomach, and, on withdrawing it, a sufficient quantity can be
 obtained for analysis. Such  experiments have been repeatedly per-
 formed by MM. Reaumur, Spallanzani and others.
   This admixture with the  fluids  of the mucous membrane of the
 stomach, and the secretions, continually sent down from the mouth,
 by the efforts of deglutition, is the only apparent change, witnessed
 for the  first hour after the reception of solid food.  At  the expira-
 tion of this time, and  sooner  or later  according to circumstances,
 the pyloric portion cf the organ contracts; sending, into the splenic
 portion, the food it contains: to the contraction dilatation succeeds;
 and this alternation of movements goes on,  during the whole of di-
 gestion.  After this time, chyme only is found in the pyloric por-
 tion, mixed with a very small quantity of unaltered food.
   This  motion of contraction and relaxation has been called peris-
tole; and it  appears, at first, to be limited to the pyloric portion of
the organ, but it gradually extends to the body and splenic portion,
so that,  ultimately, the whole stomach participates in it. It consists
 in an alternate contraction and relaxation of the circular fibres of
the stomach; and the gentle oscillation, thus produced, not only fa-
cilitates the  admixture of the food with  the gastric secretions, but
exposes fresh portions continually to their action. The experiments
of Bichat satisfied him, that the peristole is more marked, the
greater the fullness of the stomach.  He made dogs swallow forced-
meat balls, in the centre of which he placed cartilage, and he found. 
chymification.
481
that when  the stomach was greatly  charged, the cartilages were
pressed out of the balls. This did not happen, when the organ con-
tained a smaller quantity of food.
  In addition to the peristaltic movement, the stomach is subjected
to more or less succussion from the neighbouring organs.   At each
inspiration, it is pressed upon  by the diaphragm ; whilst the large
arterial trunks in its vicinity, as well as the arteries distributed over
it, subject it to constant agitation.
  We have already remarked, that the peristaltic movement of the
stomach,—and it extends likewise to the intestines,—is effected by
the muscular coat of the organ. It is, however, an involuntary con-
traction, and  appears to be little influenced by the nervous sys-
tem ; continuing, for instance, after the division of the eighth pair of
nerves; becoming more active, according to Magendie, as animals
are more debilitated ; and  even at death; and existing, even after
the alimentary canal has been removed from the body.  MM. Tie-
demann and  Gmelin, however, affirm, that, by  irritating the
plexus of the eighth pair of nerves, which is situated around the
cesophagus, with the point of a scalpel, or by touching it with alco-
hol, the peristaltic action of both stomach and intestines can be con-
stantly excited.
  This involuntary function, as well as that, exerted by the heart
and other involuntary organs, affords us a striking instance of the
little nervous influence, that seems to  be requisite for carrying on
those functions, that have to be executed independently of volition,
through the whole  course of existence;  and which appear to be
produced, chiefly, by the presence of appropriate  excitants:—of
food,  in the case of the peristaltic action of the stomach; of blood,
in that of the heart, &c.   Regarding the action of the latter organ
we  shall have  to refer to some singular facts hereafter.
  The gentle, oscillatory or vermicular motion of the stomach, and
the admixture with the fluids, secreted by its internal membrane,
as well as by the different follicles, &c. in the supra-diaphragmatic
portion of  the alimentary canal, are, probably, the main agents in
the digestion, operated in the stomach.
  Much contrariety of sentiment has existed regarding the precise
organs, that secrete the  fluid, which oozes  out as soon as food is
placed in contact with the mucous coat of the stomach. Whilst some
believe it to be exhaled from that membrane; others conceive it to
be secreted by the  numerous  follicles, seated in the membrane, as
well as in that of the lower  portion of the cesophagus ; or by what
have been termed the gastric glands.  The analogy of many ani-
mals, especially of birds, would render the  last opinion the  most
probable.   In them we find, in the second stomach, the cardiac or
gastric  glands largely developed ; and it  is probable that they are
the great agents of the secretion of the digestive fluid. (See Fig. 90.)
MM. Tiedemann and Gmelin affirm, that the more liquid portion
of the gastric fluid is exhaled, and that the thicker, more ropy and
  Vol. I.                      61
<; 
482
DIGESTION.
mucous portion is secreted by the follicles. Rudolphi assigns them
a double origin;—from the exhalants and gastric glands or follicles:
whilst Leuret and Lassaigne ascribe their formation exclusively
to  the villi.
  A like difference of opinion  has prevailed regarding their chymi-
cal character; and this has  partly arisen from the difficulty of ob-
taining them identical.  The true fluid, secreted by the gastric fol-
licles or mucous membrane, can never, of course, be obtained for
examination, in a state of purity. It must always be mixed, not only
with  the other secretions of the stomach, but with all those sent
down into the organ, by the constant efforts of deglutition.  It is,
consequently, to this mixed fluid, that the term, gastric juice has
really been applied; although  the term is more  especially appro-
priated  to the particular fluid,  presumed to  be  secreted  by the
stomach, and to  be the great agent in digestion.   To the nature of
the gastric juice  and its effect in the process  of digestion, we shall
have occasion to recur presently.
   It is probably  owing to the quantity of fluid, secreted by the sto-
mach, that it is so largely supplied with blood-vessels ; and that the
mucous membrane is more injected, during the presence of food in
the stomach. Experiments, by  Mr. Brodie and others, would seem
to  show, that this secretion is under the influence of the eighth pair
of nerves.  Having administered arsenic to  different  animals,—in
some of which he had divided  the eighth pair of nerves,—he found,
that, whilst the stomach of those, in which the nerves were unaffect-
ed, contained  a  large quantity of a thin, mucous fluid ; in those,
whose nerves were divided, the organ was  inflamed and entirely
dry.  Leuret and Lassaigne, however, affirm,  that the division
of these nerves had no influence on the gastric secretion.  But more
of this presently.
   Before entering into the views of different physiologists on  chymi-
fication ; or, in other words, on the theories of digestion ;  it will be
well to  refer to the physical and chymical properties of the  chyme.
Whether the changes,  induced upon the food, are simply physical
or chymical, or whether the first stage of animalization is effected
within the stomach, will be a topic for future inquiry.
   Chyme is a soft, homogeneous substance, of a grayish colour;
and sweetish, mawkish taste;  most commonly acrid; and preserv-
ing certain of the properties of the food, whence it has been formed.
   Such is the most common appearance it presents;  it varies, how-
ever, according to the food that has  been taken, as may  be easily
observed, according to Magendie, by feeding animals on different
simple alimentary substances, and killing them during the  process
of digestion.   This difference,  in its properties,  accounts  for the
discrepancy, observable in the  accounts of writers on this subject.
  The change, wrought on the aliments, is, doubtless, of a chymical
nature;  but the new play of  affinities is controlled by circum-
stances, inappreciable to us.  In the case of a female patient, at the 
chymification.                    483
hospital La Chariti, of Paris, who had been gored by a bull, and
had a fistulous opening in the stomach, an opportunity was afforded
for witnessing many fac\s connected with  chymification.  In her
case, the food, during its conversion into chyme, appeared to have
acquired an increase of its gelatine; a greater proportion of the mu-
riate and phosphate of soda and phosphate of lime, and a substance,
in appearance, fibrinous.  Marcet, however, affirms that he could
never discover gelatine in the chyme.
   It has been said, again, that the food becomes decarbonized and
more azoted; that the carbon, which disappears, is removed by the
oxygen of the air swallowed with the food, or by that contained in
the food itself; and that the azote proceeds, in greater quantity, from
the secretions of the stomach, or predominates, simply because the
food is decarbonized. Adelon has properly remarked, that the fact
and the explanation are here equally hypothetical.  Generally, the
chyme possesses acid properties.  MM. de Montegre, and Magen-
die, and Tiedemann and Gmelin always found it so. Haller and
Marcet found it to be neither acid nor alkaline. In the chyme, ex-
amined by the latter gentleman, he detected albumen, an animal mat-
ter, and some salts, differing, however, slightly, according as it pro-
ceeded  from animal or from vegetable food.  In the latter case, for
example, it afforded  four times  as much carbon as in  the former,
but  less saline matter; and this consisted of lime and an alkaline
chloruret.
   MM. Leuret and Lassaigne analyzed the chyme from the sto-
mach of an epileptic, who died suddenly in a fit, five or six hours
after having eaten.   The chyme was of a white, slightly yellowish
colour,  and of a strong, disagreeable taste.   On analysis, it afforded
a  free  acid,—the lactic; a white, crystalline, slightly saccharine
matter, analogous to the sugar of milk;  albumen, soluble in water;
a yellowish, fatty, acid matter, analogous to rancid butter; an ani-
mal matter, soluble in water, having all the properties of caseum;
and a little muriate of soda, phosphate of soda, and much phosphate
of lime.
   Lastly, Prout affirms, that a quantity of muriatic acid is present
in the stomach, during the process of digestion.   He detected it in
the stomachs of the rabbit, hare, horse, calf, and dog, and in the sour
matter, ejected from the stomachs of persons, labouring under indi-
gestion :—a fact which has since been confirmed by Mr. Children.
   MM. Tiedemann and Gmelin affirm, that the secretion of acid
commences, as soon as the stomach receives the stimulus of a foreign
body, and that it consists of the muriatic and acetic acids.
   The experiments of these last gentlemen were not confined to
the chymous mass, obtained from digestible food.  They examined
the fluids, secreted by the  mucous membrane, when  flints were
swallowed, and the acid character seems to have been equally mani-
fested.  These experiments, consequently, remove an objection,
made by Bostock, regarding the detection of the muriatic acid by 
484
DIGESTION.
 Prout;—that, as there did not appear to be  any evidence of the
 existence of this acid, before the introduction of food into the sto-
 mach, it might rather be inferred, that it is, in some way or other,
 developed during the process of digestion.
   The principal theories on chymification have been the following:—
   1.  Coction, or elixaiion.—This originated with Hippocrates,
 and was vaguely used by him to signify the maceration and matu-
 ration from the raw state, experienced by the food in the  stomach.
 The doctrine was embraced by Galen, who ascribed to the organ,
 an attracting, retaining, concocting, and expelling quality.
   At a later period, the  word was translated literally;  and certain
 physiologists,—doubtless conceiving that they had the  opinions of
 the ancients in their favour,—maintained, that  digestion is a  true
 coction or boiling of the food.  In proof of this, they affirmed, that
 the heat of the stomach is increased during chymification; that the
 process is more rapid in  the warm, than in the cold-blooded animal;
 that it is aided by artificial heat, and continues even after  death, if
 care be taken  to keep up the heat of the body ; that in the experi-
 ments on artificial digestion, made by Spallanzani, heat was al-
 ways necessary, and the greater the degree of heat  the more easy
 and complete  the digestion.  It is hardly necessary, however, to say,
 that the heat of the stomach is totally insufficient to excite any coc-
 tion or ebullition, in the physical sense of the term.  This applies,
 particularly, to the  cold-blooded animal, which  must digest, if not
 with the same, with due, rapidity.
   2.  Putrefaction.—The next great hypothesis was that of putre-
faction, which, we are informed by Celsus, was embraced by Plis-
 tonicus, a disciple of Praxagoras of Cos, who flourished upwards
 of three hundred years before the birth of  Christ.   Of late, it has
 had no advocates, but it appears to have been the view embraced by
 Cheselden.  The reasons,  urged in favour of it, have been;—the
 putrescible character of the materials, employed as food; the favour-
 able circumstances of a heat of 98° or 100°, and  of  moisture;  and,
 by some, the foetor of the excrements. The objections are, 1.  That
 when the contents of the stomach are rejected, during chymifica-
 tion, they exhibit no  evidence of putridity.   2. That, in all the ex-
 periments, which have been made on the comparative digestibility
 of different substances, where it has been necessary to kill the ani-
 mals, at different stages of the digestive process, there has not been
 the slightest sign of putrefaction.   3. That opportunities frequently
 occur, for witnessing ravenous fishes and reptiles with an animal or
 part of an animal,—which has been too large to be entirely swal-
 lowed,—partly in the stomach and the remainder in the gullet and
 mouth. This, we have seen  more than once, in the case of the pike,
 which has been choked by attempting to swallow a trout larger than
 itself. In all these cases, where the food has remained in this situation
 for some days, the part of it, contained in the throat, has been found
 putrid, whilst that  in the stomach  has been entirely sweet; and, 
theories on chymification.
485
 lastly, in Spallanzani's experiments, to be detailed presently, he
 found, that, when food, in a state of putridity, was  taken into the
 stomach, it recovered its sweetness.  It has been already observed,
 that it is the custom, in  some countries, to eat the gibier or game
 in a state of incipient putrefaction; yet the breath is not in any way
 tainted by it.
    3. Trituration.—The mathematical physiologists,  after the ex-
 ample of Erisistratus, attempted to refer the whole process  of
 digestion to trituration, imagining, that the food is subjected,  in
 the stomach, to an  action, similar to that of the pestle and mortar
 of the apothecary, or of the millstone, and that the chyle is formed
 like an emulsion.
   The most plausible arguments, in favour of this view of the sub-
 ject, are drawn from the presumed analogy of the granivorous bird,
 whose stomach is capable of exerting an astonishing degree of pres-
 sure on substances, submitted to its power.
   There is no analogy,however, between the human stomach and the
 gizzard of birds. The latter is a masticatory organ, and therefore pos-
 sessed of the surprising powers, which we have elsewhere described;
 whilst mastication, in man, is accomplished by distinct organs. No
 comparison can, indeed, be instituted between the gentle oscillatory
 motion  of the stomach; and the forcible compression, exerted by
 the digastric muscle  of the gizzard.  The simple introduction of the
 finger, through a wound of the abdomen, has shown, that the com-
 pression exerted by it on its contents is totally insufficient to bruise
 any resisting substance.  Moreover, we constantly see fruits,—as
 raisins and currants,—passing through  the whole intestinal canal
 unchanged; whilst worms remain in the stomach,—reside there,—
 unhurt; and, we shall see presently, that the experiments of Reau-
 mur and Spallanzani proved,  most convincingly, that digestion
 is effected independently  of all  pressure.  The futility, indeed, of
 this mode of viewing the subject, is signally illustrated by the fact,
 that, whilst Pitcairne estimated the power of the muscular fibres
 of the stomach at 12,951 pounds, Hales thought that twenty pounds
 would come nearer to the truth; and Astruc valued its compres-
 sive force at five ounces.
  4. Fermentation.—The system of fermentation had many par-
 tizans; amongst whom may be mentioned Van Helmont, Willis,
 Boyle,  Grew, Charleton, Lower, &c.  Digestion, in this view,
 was ascribed to the chymical reaction of the  elements  of the food
 upon each other, during their stay in the stomach;—the action being
excited by some of the food, which had already undergone diges-
tion, or by a leaven, secreted, for the purpose, by the stomach itself.
  In favour of this view,  it was attempted to show, that air is con-
stantly generated in the stomach, and that an acid is always pro-
duced as the result of fermentation; the formation of chyme being
assigned, by the greater number of physiologists, to the vinous and
acetous fermentations. 
486                    . digestion.
  The objections to the doctrine of fermentation are;—that diges-
tion ought to be totally independent of the stomach, except as re-
gards temperature;  and that the food ought to be converted into
ehyme, exactly in the same manner,—if it were reduced to the same
consistence, and placed in the same temperature,—out of the body;
which is found not to be the case.  Bones are speedily reduced to
chyme in the stomach of the dog, although they would remain un-
changed for weeks, in the same temperature, out of the body.  The
facts of the voracious fishes likewise prove the insufficiency of this
hypothesis; according to which, digestion ought to be accomplished
as effectually in the oesophagus as in the stomach.  Yet it is found, in
these cases, that, whilst  the portion in  the stomach  is digested,
the other  may be  unaltered, or it may be putrid.  The objection,
urged by Adelon, that fermentation requires a longer time  than
chymification, is invalid.   The dyspeptic, who has long laboured
under heartburn, will suffer from it considerably, in  the course of a
few minutes after he has taken a  weak solution of saccharine matter;
and, if any solution of the alkaline carbonates be taken, the disen-
gagement of gas sufficiently indicates the presence of acid in the
stomach.
  The truth is, that, in healthy digestion, fermentation does not
occur; and, whenever the elements of the food react upon  each
other, it is an evidence of imperfect digestion; and, hence, is one of
the most common signs of dyspepsia.
  5. Maceration.—Haller supposed,  that  the food is  merely
diluted and  softened by the fluids in the stomach; and that this ma-
ceration is favoured and accelerated by the warmth of the part, by
incipient putrefaction, and by the gentle  and constant motion, by
which the food is agitated.  Maceration, however, requires a much
longer time to destroy the cohesive  force of resisting substances
than digestion; and, moreover,  it never produces any alteration in
their character.  It is, consequently, insufficient for the explanation
of the process.  Haller's opinion  was chiefly formed from the
forced analogy of ruminant animals, in which the food is subjected
to fresh mastication and comminution, before  it descends into the
third and fourth stomachs.  Independently, however,  of the  fact,
that no parallel can be  drawn between the stomach of the herbivo-
rous animal and that of man, it must be borne in mind, that the im-
portant, and truly digestive changes, effected  upon the food,  take
place in the fourth stomach, and not in those concerned in rumina-
tion.
   6.  Chymical solution.—The  theory of chymical solution, as
proposed by Spallanzani, has met with more favour from  phy-
siologists than any of the others, that have been mentioned.  Ac-
cording to  him, chymification  is  owing  to the solvent action of a
fluid, secreted by the stomach,  accumulating in that viscus be-
tween meals and during hunger, and acting as  a true menstruum
on the substances exposed to its action.   This fluid,—to which he 
THEORIES ON CHYMIFipATION.
487
gave the name gastric juice,—he affirmed to be peculiar in each
animal, according  to  its kind of alimentation,  corresponding, as
regards its energy, with the rest of the digestive apparatus,  and
differing in its source in the series of animals; proceeding, in some,
from the follicles of the oesophagus; in others from those of the sto-
mach itself; but always identical in the same  animal; generally
transparent, slightly yellow, of  a saline taste, bitter,  slightly vola-
tile, and stronger in animals with a membranous than in those with
a muscular stomach, and than in ruminant animals.
   To obtain this juice, Spallanzani opened animals,  after they
had been made to fast for some  time;  and collected  the juice, ac-
cumulated in their stomachs; or he made them swallow tubes, pierced
with holes, and filled with small sponges.  By withdrawing these
tubes,  by means of a thread attached to them, and suffered to hang
out of the mouth, and expressing the sponges, he obtained the fluid,
in quantity sufficient for examination.
   To determine whether this fluid, obtained from the stomach of
fasting animals, was intended to chymify the food,  Spallanzani
tried the following experiments.  He caused numerous animals to
swallow tubes filled with food, but pierced with  holes, so  that the
juices  of the stomach might be able to get into their interior; and
he found that  chymification was effected, when  he had taken the
precaution to chew the substances  before they were put into the
tubes,or to triturate them; and the process was always more readily
accomplished, the more easy the access of the fluids.  On repeating
these experiments on animals of all kinds, with a muscular or mem-
branous, or musculo-membranous  stomach; on pullets,  turkeys,
ducks, pigeons, rooks, frogs, salamanders, eels, serpents, sheep, cats,
&c, he always obtained the same results; and hence he affirmed,
that trituration cannot be the essence of chymification;  and that it
does not exist in animals with a membranous stomach. Reaumur,—
then a believer in the doctrine of trituration,—had previously proved
this fact by experiments of a similar kind.
   Spallanzani next  repeated  those experiments  upon  himself.
Having well chewed different articles of food, he inclosed them in
wooden tubes, pierced  with  holes, and swallowed  them; but, as
these  tubes excited pain in the bowels, he substituted small bags of
solid linen.  The substances contained in the interior of  the bags
were digested, without the bags being torn:  a fact, which  proved
that digestion  must have been  accomplished  by means of a fluid,
which penetrated through them.  In. 1777, Stevens repeated these
experiments.  He made an individual swallow balls of metal, filled
with masticated food,  and pierced  with holes; when these balls
were voided,—thirty-six or forty-eight hours afterwards,—they were
entirely empty.
   Lastly.—Spallanzani was desirous of seeing whether this sol-
vent juice could effect digestion  out of the body. He put some well
masticated food in  small glass tubes, and mixed gastric juice with 
488                      digestion.
it.  These  tubes he placed in his axilla, in order that they might
be exposed to the same degree of heat as in  the stomach; and he
affirms, that in the space of fifteen hours, or of two days,—more or
lesSj—the substances appeared to be converted into chyme.   In
these experiments he found it important to  employ gastric juice,
which  had not previously been used, and to have a sufficient quan-
tity of it.
  From all these experiments, Spallanzani  conceived it to be de-
monstrated, that chymification is a true chymical solution; and  he
endeavoured to deduce from them the degree of digestibility of
different substances.
  With regard to the precise  nature of this gastric juice  of Spal-
lanzani, we have already observed, that great contrariety of sen-
timent has prevailed;  and that it is impracticable to procure it un-
mixed with the other  fluids  of the digestive mucous membrane.
Spallanzani affirmed, that the only properties he detected in it,
were,—a slightly salt, bitterish taste; but that it was neither acid nor
alkaline.  Gosse found it to vary according to the nature of the
animal,—whether  herbivorous or carnivorous; and to be always
acid in the former.  Dumas held the same sentiments; and proved,
by experiments on dogs, that it was acid or alkaline, according as
the animal was fed on vegetable or on animal diet. He declared it,
moreover, to be mawkish, thick, and viscid.
   Viridet, Werner, Hunter, and others, affirm that it is always
acid.  Scopoli analyzed the gastric juice of the rook, and found it
to consist of water, gelatine, a saponaceous matter, muriate of am-
monia, and phosphate of lime.
   Carminati describes it as salt, and  bitter, and frequently acid;
and MM. Macquart  and Vauquelin, in the  gastric juice of the
ruminant animal, found albumen and free phosphoric acid.
   All these analyses were made on the mixed fluid,  to which the
term gastric juice has been applied.
   That such a mixed fluid does exist in the stomach, at the time of
chymification, and is largely concerned in the process, is proved by
the facts already mentioned, as well as by the following.
   Magendie asserts,  that one of his  pupils,—M. Pinel,—could
procure, in a short time after swallowing a little water or solid
food, as much as half a pint of it.  M. Pinel "possessed the faculty
of vomiting at pleasure." In this way, he obtained from his stomach,
in the morning, about three ounces of the fluid, which was analyzed
by Thenard, who found  it composed of a considerable quantity of
water, a little mucus, some salts with a base of soda and  lime:  but
it was not sensibly acid, either to the tongue or to  reagents.   On
another occasion, Pinel obtained two ounces of  fluid, in the same
manner.  This was analyzed by Chevreul, and found to contain
much water, a considerable quantity of mucus, lactic acid,—united to
an animal matter, soluble  in water, and insoluble in alcohol; a little
 muriate of ammonia, muriate of potassa, and  some muriate of soda. 
CHYMIFICATION.
^489
  Tiedemann and Gmelin procured the gastric fluid by making
animals, that had fasted, swallow indigestible substances, such as
flints.  It always appeared to them to be produced in greater quan-
tity, and to have a more acid character, in proportion as the alimen-
tary matter was less digestible and less soluble; and they assign it
as constituent elements,—muriatic acid; acetic acid;  mucus; no,
or very  little, albumen; salivary  matter;  osmazome; muriate,
and sulphate of soda.   In the ashes, remaining after incineration,
were,—carbonate, phosphate and sulphate of lime,  and chloride of
calcium.
  Lastly, Leuret and Lassaigne assign its  composition,  in one
hundred parts, to be,—water, ninety-eight; lactic acid; muriate of
ammonia; muriate of soda; animal matter soluble in water; mucus
and phosphate of lime, two parts.
  The diversity of the results obtained by chymical analysts; the
difficulty of comprehending how the same fluid can digest substances
of such opposite character; and the uncertainty we are in, regarding
the organs concerned in its production, have led many physiologists
to doubt the existence of any such gastric juice or  solvent, as that
described by Spallanzani.
  Montegre, for example, in the year 1812, presented  to the
French Institute a series of experiments, from which he concluded,
that the gastric juice of Spallanzani was nothing more than saliva,
either  in a  pure state or changed by the chymifying action of the
stomach and become acid.  As Montegre  was able  to vomit at
pleasure, he obtained the gastric juice, as it had been done by pre-
vious experimenters, in this manner, whilst fasting.  He found it
frothy, slightly viscid, and turbid; depositing, when at rest, some
mucous flakes, and commonly acid, so much so, indeed, as to irri-
tate the throat, and to render the teeth rough.  He  was desirous of
proving, whether this fluid was in any manner inservient to chy-
mification.   For  this  purpose, he began by rejecting  as much as
possible by vomiting; and, afterwards, swallowed magnesia to neu-
tralize  what remained of it.  On eating after this, the food did not
appear less chymified; nor was it less acid; whence he concluded,
that, instead of this fluid being the agent of chymification, it was,
itself, nothing more than the  saliva and the  mucous secretions of
the stomach, changed  by the chymifying action of that viscus.   To
confirm himself in this view, he repeated, with this juice, Spallan-
zani's experiments on artificial digestion; making, at the same time,
similar experiments with saliva, and the results were  the same in
the two cases.
  When gastric juice, not acid, was put into a tube, and placed in
the axilla,—as in Spallanzani's  experiments,—in  twelve hours it
was in  a complete state of putrefaction.  The same occurred  to sa-
liva, placed in the axilla.
  Gastric juice, in an acid state, placed in the axilla, did not become
putrid, but this seemed to be owing to its state of acidity ; for the
  Vol. I.                     62 
490
DIGESTION.
same thing happened to the saliva, when rendered acid by the addi-
tion of a little vinegar, and even to the  gastric juice, used in the
experiment just referred to,—when mixed with a little  vinegar.
Again, he attempted artificial digestions with the gastric juice, acid
and not acid, fresh and old;  but they were unsuccessful.  The food
always became  putrid, but  sooner, when the juice employed was
not acid; and, if it sometimes liquefied, before becoming putrid, this
was attributed to the acidity of the juice, as the same effect took
place,  when  saliva, mixed  with a little vinegar, was  employed.
Montegre, moreover, observed, that the  food, rejected from the
stomach, was longer in becoming putrid, in proportion to the time
it had been subjected to the chymifying action of the stomach; and
he concluded, that the fluid, which is sometimes contained in the
stomach when empty, instead of being a menstruum, kept in reserve
for chymification, is nothing more than the saliva, continually sent
down into that viscus, and that its purity or acidity depends upon
the chymifying action of the stomach.
  As regards the  fluid, met with in the stomach of fasting animals,
Montegre's remarks may  be true in the main;  but we have too
many evidences in favour of the chymical action of some secretion
from the stomach during digestion  to permit us to doubt for a
moment of the fact.  Besides, some  of  the experiments of Mon-
tegre have been repeated and with opposite results.  MM. Leu-
ret and Lassaigne, for example, performed those relating to arti-
ficial digestion,  after the manner of Spallanzani, and  succeeded
perfectly; whilst  they failed altogether in producing  chymification
with the saliva, either in its pure state, or acidulated with vinegar.
  The following are some of the overwhelming evidences in favour
of the  existence of some secretion from the stomach,  concerned in
the digestive changes in that organ.—Besides the fact of the most
various and firm substances  being reduced into chyme in  the  sto-
mach, we find the  secretions from its lining membrane possessing the
power  of coagulating albuminous fluids.  It is upon the coagulating
property of these secretions, that the method of making cheese is
dependent.  Rennet, employed for this purpose, is an infusion of
the digestive stomach of the calf, which, on being added to milk,
converts the albuminous portion of it into the state of curd; and it
is surprising how small a quantity of the rennet is necessary to pro-
duce this striking effect.  Fordyce and Young found, that six or
seven grains of the inner coat of a calf's stomach, infused in water,
afforded a liquid,  which coagulated more than one hundred ounces
of milk;—that is, more than six thousand eight hundred and fifty-
seven times its own weight; and yet its weight was probably but
little diminished.   What the substance is, that  possesses this pro-
perty, is not known to the chymist.   It appears not to be very so-
luble in water;  for the inside of a calf's stomach, after having been
steeped in water for six hours, and then well washed, still furnishes
a liquor on infusion, which coagulates milk. 
CHYMIFICATION.
491
  Mr. Hunter made numerous experiments upon the coagulating
power of the secretions of the stomach, which show, that it exists
in the stomachs of animals of very different classes.  The lining of
the fourth stomach of the calf is in common use, in a dried state, for
the purpose mentioned above;  and it has  been proved, that every
part of the membrane possesses the same property.
  Hunter found, by experiment, that the mucus of the  fourth ca-
vity of a slink calf, made into a solution with a small quantity of
water, had the power of coagulating  milk;  but  that found in the
three first  cavities, possessed no such power.   This  mucus, even
after it had been kept several days, and was beginning to  be putrid,
retained  the property. The duodenum and jejunum, with  their con-
tents, likewise coagulated milk; but the process was so slow, as to
give rise to the suggestion, that it might have  occurred indepen-
dently of the intestines employed for the purpose.   He found, that
the inner membrane of the fourth  cavity  in  the  calf, when old
enough to be killed for veal, had the  same property.   Portions of
the cuticular part, of the massy glandular part, and  of the portion
near the  pylorus of the boar's stomach, being prepared as rennet, it
was found, that no part had the effect of producing coagulation but
that near the pylorus, in which part  the gastric glands of the ani-
mal are especially conspicuous.
  The crop and gizzard of a cock were salted, dried, and afterwards
steeped in  water.   The solution, thus obtained, was added to  milk.
The portion  of the  crop coagulated  it in  two hours, that of the
gizzard in half an hour.
  The contents of a shark's stomach  and duodenum coagulated
milk immediately.   Pieces of the stomach were washed  clean and
steeped for sixteen hours in water.   The solution coagulated milk
immediately.  Pieces of the duodenum produced the  same effect.
When the  milk was  heated to 96°, the coagulation took place in
half an hour;  when  it was cold, in an hour and  a quarter.
  The stomachs  of  the salmon and  thornback, made into rennet,
coagulated  milk in four or five hours.
  But these experiments of Mr. Hunter do not inform  us of the
particular secretions,'that are productive of the effect.  They would,
indeed, rather seem  to  show, that it is a  general property of the
whole internal membrane.
  To discover the exact seat of the secretion, and especially  whe-
ther it be not in the gastric glands,  Sir Everard Home selected
those of the turkey;  which, from their size, are better adapted for
such an experiment than those of any other bird, except the ostrich.
A young turkey was kept a day without food, and was then killed.
The gastric glands were carefully dissected separately  from the
lining of the cardiac  cavity ; cutting off the duct of each before it
pierced the membrane, so that no part but  the  glands themselves
were removed. Forty grains, by weight, of these glands were added
to two ounces of  new milk ; add  similar experiments were made 
492                      DIGESTION.

with rennet; with the lining of the cardiac  cavity of the turkey;
and with the inner membrane of the fourth cavity of the calf's sto-
mach.   Coagulation and the separation  into curds and whey was
first  effected by the  rennet.  Next  to  this, and  simultaneously,
came the gastric glands, and  the fresh stomach of the calf; and last-
ly the cardiac membrane of the turkey.
  From these experiments, Sir Everard concluded, that the power
of coagulation is in the secretion of the gastric glands; and  that
this power is communicated to other parts, by their becoming more
or less impregnated with it.
  The marginal figure, copied from  an engraving by  Sir Eve-
                                           rard Home, of the
denum. It also resembles them, in the secretion it produces coagu-
lating  milk, whilst none  of  the  inspissated juices, met with in
these cavities, according to Sir Everard, affect milk in the same
way. From these facts, he thinks, there can be no longer any doubt
entertained, that the gastric glands have the same situation respect-
ing the cavity of the stomach as in birds.  Yet M. Montegre de-
nies that the gastric juice has any coagulating power!
  Another property, manifestly possessed by the secretion in ques-
tion, is that of  preventing putrefaction, or of obviating it, in sub-
stances, exposed to its action. Montegre and Thackrah, however,
deny it this property also, but there can be no doubt of its existence.
Spallanzani and others  have ascertained, that, in those animals, 
CHYMIFICATION.
493
that frequently take their food in a half putrid state, the first opera-
tion of the stomach is to disinfect,  or  remove the fcetor from, the
aliment received into it.  We have already alluded to many facts,
elucidative of this power. Helm of Vienna, in the case of a female,
who had a fistulous opening in her stomach, observed,  that sub-
stances, which were swallowed in a state  of acidity, or putridity,
soon lost those qualities in the stomach.   The same power of re*
sisting and obviating putrefaction  has been exhibited in experi-
ments, made out of the body.
  The explanation of this property, as well as that of coagulation,
has been  a stumbling-block to the chymical physiologist.  " We can
only say concerning it," says Dr. Bostock, "that it is a chymical
operation, the nature of which, and  the successive steps by which it
is produced, we find it difficult to explain; at the same  time, that
we have  very little, in the way of analogy, which can assist us in re-
ferring it to any more general principle, or toanyT of the established
laws of chymical affinity."
  The cases of what are termed digestion  of the stomach after
death afford us, likewise, remarkable examples of the presence of
some powerful agent in the stomach ; as well as of the resistance to
chymical action, offered by living organs.  Powerful as the action
of the  gastric juice may be in dissolving alimentary substances, it
does not exert it upon the coats of the stomach during life.  Being
endowed with vitality, they effectually resist it.  But when that
viscus has lost its vitality; its parietes yield to the chymical power
of the contained juices; and become softened ;  and, in part, de-
stroyed.   Hunter found the lining membrane of the stomach de-
stroyed,  in several parts, in the  body of a criminal, who, for some
time before his  execution, had been prevailed upon, in considera-
tion of a  sum of money, to abstain from food. Since Hunter's time,
numerous examples have occurred, and  have  been recorded by
Baillie, Allan Burns, Havii.and, Grimaud, Pascai.is, Cheese-
man, J.  B. Beck, Chaussier, Yelloly, Gardner, Treviranus, >
Goedecke, Jaeger and others.
  The fact is of  importance in  medical jurisprudence ; and,  until
a better acquaintance with the subject would, doubtless, have been
set down as strong corroborative  evidence in cases of suspected
poisoning.  It is now established, that  solution of the stomach may
take  place after death, without  there being the slightest reason for
supposing, that any thing noxious has been swallowed.
  The experiments of Dr. Wilson Philip are signally  corrobora-
tive of this physiological action  of the gastric juice. On opening the
abdomen of rabbits, which had  been killed immediately after hav-
ing eaten, and were allowed to lie undisturbed for some time before
examination,  he  found the great  end of the stomach soft, eaten
through,  and sometimes  altogether consumed;  the  chyme  being
covered  only by the peritoneal coat,  or  lying quite bare for the 
494
DIGESTION.
space of an inch and a half in diameter; and, in this last case,a part
of the contiguous intestines was also destroyed; whilst the cabbage,
which the animal had just taken, lay, in the centre of the stomach,
unchanged, if we except the alteration, that had taken place, in the
external parts of the mass it had formed, in consequence of imbib-
ing  gastric  fluid from  the half-digested  food in contact with it.
Why the perforation takes place, without the food being digested,
is thus explained by Dr. Philip.
  Soon after death, the motions of the stomach, which are constantly
carrying on towards the pylorus the most digested food, cease. The
food, which lies next to the surface of the stomach, becomes, thus,
fully saturated with gastric fluid, neutralizes no more, and no new
food being presented to it, it necessarily acts on the stomach itself,
now deprived of life, and equally subject to its action with other
dead animal matter.  It is extremely remarkable, however, that the
gastric fluid of the rabbit, which, in its natural state, refuses animal
food, should so completely digest its own stomach as not to  leave a
trace of the parts acted upon.
  Dr. Philip remarks, that he  has  never  seen the  stomach eaten
through except in the large end; but, in other parts, the external
membrane has been injured. Mr. A. Burns, however, affirms, that,
in several instances, he found the forepart of the stomach perforated,
about an inch from the  pylorus, and midway  between  the smaller
and larger curvatures.
  From all these facts, then, we are justified in concluding, that the
food in  the stomach is subjected to the action of a secretion, which
alters its properties, and is the principal agent  in converting it into
chyme.
  But many physiologists, whilst they admit, that the change effect-
ed in the stomach is of a chymical character, contend, that  the na-
ture of  the action is unlike what takes place in any other chymical
process, and that it is therefore  necessarily organic and vital, and
appertaining to  vital chymistry.  Such  are the sentiments of For-
dyce, of Broussais, and of Chaussier and Adelon. The physio-
logist should  not, however, have recourse to this explanation, until
every other has  failed him.  It is, in truth, another method of ex-
pressing our ignorance, when we affirm, that any function is exe-
cuted in an organic or vital manner; nor is this mode  of explain-
ing the  conversion of the aliment into chyme necessary.  The se-
cretion of the fluid which  is the great  agent of chymification is
doubtless vital; but when once secreted, the changes, effected upon
the food, are probably unmodified by any vital interference, except
what occurs from temperature,  agitation, &c. which can only be re-
garded as  auxiliaries in the function.
  It is,  in this way, that digestion is influenced by the nervous sys-
tem. The effect of the different emotions upon the digestive function
is often  evinced, and has already been alluded to; but the importance 
chymification.
495
 of the nervous influence to this function has been elucidated, in
 an interesting manner to the physiologist, of late years chiefly.
  Baglivi, having tied the two nerves of the  eighth pair in dogs,
 found that they were affected with  nausea and vomiting, and  that
 they obstinately refused food.
   Since Baglivi's time, the same  results  have been obtained by
 many physiologists.
   De Blainville, having repeated the operation on pigeons, found
 the vetch, in their crops, entirely unchanged, and chymification to-
 tally prevented.   Legallois, Brodie,  Philip,  Dupuy,  Clarke
 Abel, Hastings, and others, on  carefully repeating the experi-
 ments, also announced, that, after this operation, the digestive  pro-
 cess was entirely suspended.
   The result of  these experiments  was, however,  contested by se-
 veral physiologists  of eminence, who affirmed, that, after the divi-
 sion of the eighth pair of nerves, digestion continued nearly in the
 natural state, or, at most, was only  slightly impeded. Mr. Brough-
 ton asserted, that he had made the section on  eleven rabbits, one
 dog, and two horses; and that digestion was not destroyed.  Ma-
 gendie expressed his belief, that the annihilation of chymification
 was owing to the disturbance of respiration, caused by the division
 of the nerves; and he affirmed, that digestion continued, when  care
 was taken to cut the nerve, within the thorax, lower down  than the
 part, which furnishes the pulmonary branches. MM. Leuret and
 Lassaigne also assert,  that they found chymification continue,  not-
 withstanding the division of these  nerves.  In opposition to these
 experiments, those of Dupuytren  may be adduced.  He  divided,
 separately, the portions of the eighth pair of nerves, distributed to
 the pulmonary, circulatory, and digestive apparatuses, and always
 found, that, when the section  was made only below the pulmonary
 plexus, chymification was suspended.  But how are we to explain
 the discrepancy between these results and those of  MM. Brough-
 ton and Magendie ?
  Adelon has supposed, as the eighth  pair is not the only nerve
 distributed to the  stomach,—the  great sympathetic sending nu-
 merous filaments to it,—that these filaments, in the experiments of
 MM. Broughton and Magendie,  may have been sufficient to keep
 up for some time the chymifying action of the stomach; and, again,
 he suggests, whether the nervous influence of the stomach may not
 have still  persisted for sometime after the section of the nerve, like
 other nervous influences, which,he conceives,continue for some time,
 even after death; and, lastly, he thinks it probable, that, in the cases,
 in which chymification continued,  the experiment was badly  per-
formed. Most of these reasons, however, would apply with as much
force to the experiments on the other side of the  question.  Why
was not this agency of the great sympathetic, and this continuance
of the nervous influence for some time after the section of the nerve,
evidenced in the experiments of Dupuytren, and of Wilson Phi- 
496
DIGESTION.
lip, Hastings, and others ? The last remark of Adelon is, indeed,
the only one that is applicable, and probable.
  More recent experiments by Wilson Philip, Breschet, Milne
Edwards, and Vavasseur,  have shown, that  the mere division
of the nerves, and even the retraction of the divided extremities for
the space of one-fourth of an  inch, does not prevent the influence
from being transmitted along them  to the stomach; but that if a
portion of the nerve be actually removed, or the ends folded back,
chymification is wholly, or in part, suspended.
  Most of the experimenters agree with Mr. Brodie in the opinion,
that chymification is suspended, owing to the secretion of the gas-
tric juice having been arrested, by the division of the nerves, under
whose presidency it is accomplished. MM. Breschet and Milne
Edwards, however, conceive, that the effect is owing to paralysis
of the muscular fibres of the stomach produced by the section of the
nerves; in consequence of which the different portions of the ali-
mentary mass are not  properly brought into contact with the coats
of the  stomach,  so  as to be exposed to the action of its secretions;
and they affirm, that, when the galvanic influence is made to pass
along the part of the nerve attached to the stomach, its  effect is to
restore the due action of the fibres; and, that a mechanical irritation,
applied to the lower end of the  divided nerves, produces a similar
kind of change on the food in the stomach; from which they con-
clude, that the use of the par vagum, as connected with the func-
tions of the stomach,  is to bring the alimentary mass into the ne-
cessary contact with the  gastric juice.   These experiments were
repeated in London by Mr. Cutler, under the  inspection  of Dr.
Philip and Mr. Brodie ; but the effect of mechanical irritation of the
lower part of the divided nerve did not correspond with that ob-
served by MM. Breschet and  Milne Edwards.
  On the whole, the proposition of Dr. Philip,—that if the eighth
pair of nerves be divided in such a manner as to effectually intercept
the passage of the nervous influence,  digestion  is  suspended,—is
generally considered to be established. The inferences to be deduced
from it, regarding the agency of the nervous and galvanic influences
in the process of secretion, will  engage us hereafter.
  Finally, Dr. Philip found, that every diminution of the nervous
influence,—the section of the medulla spinalis at the inferior part,
for example,—deprives the stomach of its digestive faculty; and
MM. Edwards and Vavasseur obtained the same result by the
removal of a certain portion of the hemispheres of the brain, or by
the injection of opium into the veins in a sufficient quantity to throw
the animal into a deep coma.
  Of all these theories of chymification, that of chymical  action,
aided by the collateral circumstances  to  be  presently mentioned,
can alone be embraced; yet, how  difficult is it to comprehend,
that any one secretion can act upon the immense variety of  animal
and vegetable substances, which are employed as food.  The disco- 
CHYMIFICATION.
497
very of the acetic and muriatic acids, in the secretion, aids us a little
in solving the mystery, but not much.  There is not a tissue of the
body, which is not dissolved, if subjected long enough to the action
of the former of these acids; and organic chymistry may hereafter
exhibit to us some chymical agent, which has hitherto escaped de-
tection, and which is capable of rapidly reducing to chyme all sub-
stances—both animal and vegetable—when placed under the favour-
able circumstances in  which the gastric juice is situated in the sto-
mach.
   In the existing state of our knowledge, however, regarding this
wonderful and mysterious process, we might perhaps be justified in
adopting the well-known pithy and laconic observation of Dr. Wil-
liam Hunter. " Some physiologists will have it, that the stomach
is a mill; others, that  it is  a fermenting vat; others, again, that it is
a stewpan;—but, in my view of the matter, it is neither a mill, a
fermenting vat, nor a  stewpan;—but  a stomach, gentlemen, a sto-
mach."
   In conclusion:—Let us inquire into the various agencies to which
the food is exposed during the progress of chymification.  First.  It
becomes  mixed with the secretions, already existing in the stomach,
as well as with those excited by its presence.  Secondly. It is agi-
tated by the  movements of the  neighbouring organs,  and by the
peristaltic motion of the stomach itself.  Thirdly. It is exposed to
a temperature of from 100° to 102° of Fahrenheit; and, perhaps,
during digestion, to one even higher than this.
   After the food has been, for some time,  subjected to  these influ-
ences,  the conversion into chyme commences.   This always takes
place from the surface towards the centre: the nearer it lies to the
surface of the stomach, the more it is acted on; and that part of  it,
which  is in contact with the lining membrane, is more digested than
any  other; appearing  as if corroded by some chymical substance
capable of dissolving it.
   A piece of the coagulated white of egg is affected precisely as if
it had  been placed in  weak vinegar, or in a solution of potassa; and,
if the food be covered by an indigestible stratum, the solution takes
place within it, whilst the envelope remains unacted upon.
   The new food, it seems, is never mixed with the old; the former
being always found in the  centre, surrounded on all sides by the lat-
ter.  If the  old and new be of different kinds, the line of separation
between them is so evident, that the  old may be completely re-
moved without disturbing the  new; and, if they be of different co-
lours,  the line of demarcation can  frequently be distinctly traced
through the parietes of the organ, before they are laid open.
   The conversion of the food into chyme commences in the splenic
portion, is  continued in the body of the viscus, and is completed in
the pyloric portion.   On this point, the observations of Dr. Philip
differ somewhat from  those of Magendie; the former appearing to
think that chymification is chiefly accomplished in,the splenic por-
   Vol. I.                     63 
498                       digestion.
tion and middle of the stomach;  whilst the latter affirms that it is
chiefly in the pyloric portion that  chyme is formed; the alimentary
mass appearing to pass into it by little and little,  and, during its
stay there, to undergo the transformation.  He further affirms, that
he has frequently seen chymous matter at the surface of the alimen-
tary mass filling the splenic half;  but that, commonly, it preserves
its properties in this part of the stomach.
  The precise steps of this change into chyme cannot be indicated.
Some of the results,  at different  stages of the process, have been
observed on animals; and pathological cases have occasionally oc-
curred, which enabled the  physiologist to witness what was going
on  in the interior of the stomach; but these opportunities have not
been improved to the full extent.   Helm, of Vienna, published a
case of this kind, to which reference has already been made; and an
interesting case of fistulous opening in the stomach, which commu-
nicated externally, occurred at the Hospital La Chariti of Paris,
which sheds some little light on the subject.  The aperture, which
was more  than an inch and a half long and an inch broad, exposed
the interior of the organ.   At the admission of the female into the
Hospital, she ate three times as much as ordinary persons. Three or
four hours after a meal, an irresistible feeling compelled her to remove
the dressings from the fistulous opening, so as to allow the escape of
the food, which the stomach could no longer contain, when the con-
tents came out quickly, accompanied by  more or less air.  They
possessed  a faint smell, but had neither acid  nor alkaline properties;
the grayish paste, of which they consisted,  when diluted with dis-
tilled water, not affecting the vegetable blues.   The digestion was
far from complete; yet, frequently, the odour of wine was destroy-
ed; and bread was reduced to a soft, viscid, thick substance, resem-
bling fibrine recently precipitated by  the acetous  acid, and swim-
ming in a stringy fluid of the colour of common soup.
   Experiments, made on  this half-digested food, at the Ecole de
Midecine, showed, that the changes, which  it had  undergone, were
an  increase of gelatine ;  the formation of a substance like fibrine;
and a considerable  portion  of muriate and phosphate of soda and
phosphate  of lime.  This  patient could  never sleep until she had
emptied her stomach, and washed it out by drinking infusion of cha-
momile.   In  the morning, it contained a small quantity of thick,
frothy liquid, analogous to saliva, which did not  affect vegetable
blues ;  with matters  of greater consistence ; and some  completely
opaque, albuminous flocculi, mingled with the liquid portion.   The
results  of  chymical  experiments, on  this liquid, were  similar to
those obtained on the analysis of  saliva.
  In proportion as the food is digested in the splenic portion of the
stomach, it is gently moved along towards the pyloric portion. As
the layer, which lies next  to the mucous membrane, first experi-
ences the requisite  change, and is propelled onwards by the muscu-
lar  action of the organ, the portion, lying next to  it, becomes sub- 
CHYMIFICATION.
499
jected to the process.  The gastric fluid, at the same time, pene-
trates, in a greater  or less degree, the entire alimentary mass, so
that,  when the central portion comes in contact with the surface of
the stomach, its conversion is  already somewhat  advanced.   The
chyme, thus successively formed, does not remain in the stomach,
until  the whole alimentary mass has undergone chymification ; but,
as it  is completed, it is transmitted, by the peristaltic action, through
the pylorus into the duodenum.  ,
   The time, required for the complete chymification of  a meal, is
stated, by the generality of physiologists, to be about four or five
hours.  We believe that, in by far the  majority of cases, a longer
time  than this  is necessary ; and in laborious digestions, the  pre-
sence of food can be distinguished, by the eructations, for more than
double the time. It is manifest, indeed, that no fixed period can be
established for the production of this effect.  It must vary, accord-
ing to the digestive capability  of the individual; the state of his
general health  ; and the relative digestibility of the  aliments em-
ployed; all which, as we have already seen, admit of great diver-
sity.                                                   .
   During chymification, only a very small quantity of air is found
in the stomach ; sometimes, none.  When met with, it is near the
cardiac orifice, or at the upper  part of the splenic portion. Magen-
die collected that which was contained in the stomach of a criminal,
and had it analyzed by Chevreul, who found it to consist of oxy-
gen, llparts; carbonic acid, 14; pure hydrogen, 3.55; and azote, 71.45
in the hundred.
   The small quantity of air> discovered in  the stomachs of animals,
disproves the idea  of Chaussier, that we swallow a bubble of air
at each effort of deglutition. If so, the stomach ought to be always
inflated, especially after eating, which is  not the case.  Leuret
and Lassaigne found the air, obtained from the stomach of a dog,
fed on meat, to consist of carbonic acid, 43 parts ;  sulphuretted hy-
drogen, 2 parts ; oxygen, 4 parts; azote, 31 parts; and carburetted
hydrogen,20 parts.  Whence these gases proceed—will be a subject
for future inquiry.
   In a robust  individual, chymification is effected without consci-
ousness of the process.  He finds, especially if the stomach be over-
distended, that the feeling of fullness and the oppression of respira-
tion, produced  by the distention of the organ, gradually disappear.
 It is  not uncommon, however, for slight shivering or chilliness to
be felt at this time ; for the sensations, and mental and moral mani-
 festations to be blunted; and for a disposition to sleep to be expe-
 rienced. " This concentration of the whole vital activity," accord-
ing to Adelon, " is so natural to the animal economy, that there is
always danger in opposing or crossing it by any extraneous or or-
ganic influence ; as by bathing, the use  of medicine, violent exer-
cise, any mental emotion, intense intellectual effort, &c."
   Where the  digestion is imperfect, the signs, already mentioned, 
500
DIGESTION.
will be accompanied by the disengagement of air and consequent
eructations; a sense of weight, or heat, or unusual distention in the
epigastric region, &c; but these, as well as the developement of sul-
phuretted hydrogen, discharged by eructation, are the products of or-
dinary decomposition or fermentation, and appertain to the patholo-
gical condition  of the function, or to indigestion.  Yet as Magen-
die has remarked, it does not seem, that these laborious digestions
are much less profitable than others. The food, habitually received
into  the stomach, contains  far more nutritive  matter than is neces-
sary to  supply  the wants of the system ;  and, in the cases in ques-
tion, enough chyle  is always separated  in the small intestine, to
supply the losses,  and even to add to the bulk of the body.
   It has been already observed, that the chyme, first formed,  does
continue in the stomach, until the whole  meal has undergone  chy-
mification ; but that, as soon as it has experienced the  necessary
changes, it passes through the pylorus into the duodenum. It would
appear, that the accumulation of chyme,  in the  pyloric portion of
the stomach, never exceeds four ounces at any one time.  Magen-
die states, that, in  the numerous experiments, in which he  has had
an opportunity of noticing it, he  uniformly found, that, when the
quantity amounted to about two or three ounces, it was admitted to
pass through the pylorus into the duodenum.   This passage of the
chyme  is effected by the peristaltic action, to which reference has
been made. At the commencement of digestion, the duodenum  con-
tracts inversely, and the pyloric portion of the stomach, at the same
time, drives  its contents into the splenic.  This movement is, how-
ever, soon followed by one in an opposite direction ; and, after a
time, this  inverted action ceases, and the motion  is altogether in
one direction,—from the stomach towards the intestine.
   The motion, by which  the chyme is immediately sent into the
duodenum is thus effected :—the  longitudinal  fibres, which pass
from the cardiac to the pyloric orifice, contract, and approximate
the two orifices.  The pyloric portion then contracts, but not  so as
to repel the chyme into the splenic portion ;  but towards the  duo-
denum.  In this manner, the chyme passes from the stomach;  and,
as fresh portions are formed,  they are successively evacuated ; the
peristaltic motion  becoming more  and  more marked and frequent,
and  extending over a larger portion of the organ, as chymification
approaches its termination.  As the chyme is discharged into the
small intestine, the stomach gradually returns to its former dimen-
sions and situation.
   6. Action  of the small intestine.—The changes produced upon
the alimentary mass in the small intestine, are  not less important
than those we have already considered.   These consist in a farther
change, by which the chyme is converted into a substance, whence
chyle can be extracted, by the action of the  chyliferous vessels or
lacteals.  Whether  chyle  be separated in the intestine, in a  state
fit for chyliferous  absorption, or be formed by those vessels, will 
action  of the small intestine.
501
have to be canvassed  hereafter.   In common language, however,
it is said to be formed in the small intestine, and the process, by
which this is accomplished, is called chylification.
  As the chyme passes into  the  duodenum it readily  finds space,
until towards the end of chymification, when the intestine not un-
frequently experiences  considerable  dilatation.  The presence of
the alimentary mass augments the secretions from the mucous mem-
brane;  and occasions  a  greater flow of the biliary and pancreatic
juices. Leuret and Lassaigne found, when they applied vinegar,
diluted with water, to  the internal surface of the small intestine, in
a living animal, that a  considerable  quantity of serous fluid was
immediately  exhaled.  The same application, made to  the follicles
of the intestine, excited the secretion of a greater quantity of mucus;
and its application to the mouths of the choledoch and pancreatic
ducts caused the orifices to dilate, and a greater  discharge of the
bile and pancreatic juice.  It is in this local manner, that many of
the cholagogue purgatives produce their effect.  Calomel exerts its
agencjr on the upper part of  the intestinal canal  more especially ;
and the irritation it induces in the mucous membrane, at the mouth
of the ductus communis choledochus, is propagated along the ducts
to the liver, the secretion of which is thus augmented,—but not by
any specific action exerted on the liver, as has been often  imagin-
ed.  As the chyme is acid, it necessarily induces the same effects
as  the  acid employed  in the experiments of Leuret and  Las-
saigne.
   The chyme does not remain so long in the intestine, as the food
does in the stomach.   The successive arrival of fresh portions pro-
pels the first onwards; and the same effect is induced by the peris-
taltic action of the intestines,—an involuntary, muscular movement
of an irregular, undulatory, oscillatory or vermicular character, which
consists in an alternate contraction and dilatation of the organ, pro-
ceeding generally from above to  below, s© as  to propel the chyme
downwards.   When the chyme reaches any point of the intestine,
its contact excites the  contraction of the circular fibres  of the part;
so  that it  is sent forwards to  another part  of the canal; the circular
fibres  of  which contract, whilst the former are relaxed ; and this
occurs successively through the whole extent of the intestines. The
longitudinal fibres, by their  contraction, shorten the intestine, and
in this manner meet the chyme, so as to facilitate its progress ; but
their effect cannot be  considerable. When digestion is not going on,
the peristaltic action  occurs only at intervals; always slowly and
irregularly; and, perhaps,as has been suggested, only when  a quan-
tity of mucous secretion  has collected on the inner coat of the intes-
tine sufficient to provoke it.  During digestion, it is much more ener-
getic and  frequent, and is more marked in the  duodenum and  small
intestine than in the large; occurring not continuously, but at inter-
vals, as the chyme arrives and excites it.  When the small intestine 
502
DIGESTION.
is surcharged, it may take place in several parts of the canal at once;
and, at times, the action is inverted.
   The secretions, poured out  into the intestinal canal,  lubricate it
and facilitate the progress of the chyme.  This is, also, aided by the
free, and floating condition  of the intestine; and  by the agitation
from the diaphragm and abdominal muscles in respiration. Yet the
course of the chyle along the small intestine is slow.   The chyme
is not transmitted from the stomach continuously; and the peristal-
tic action  of the intestines occurs only at intervals.   Moreover,
owing to the convolutions of the intestinal canal, the chyme must, in
many cases, proceed against  its own gravity ; and it must be retard-
ed  by the  numerous valvulae  conniventes, which  bury  themselves
in the chyme, when the canal is contracted by the action of the cir-
cular fibres.  All these circumstances must cause the chyme to pro-
ceed slowly along this part of the canal,—a point of some import-
ance, when  we reflect that  a very essential change is  effected in
it through the influence chiefly of the bile and pancreatic juice, and
that its nutritive portion is here absorbed from it.  In the duodenum,
the course of the chyme is slow.   In the jejunum  it is more rapid,
whence the name,—which indicates, that it is almost always found
empty: in the ileum  it is  again  slower, on account of the great
consistence  the matter  has acquired, by  the  absorption  of its
chylous portion.   Whilst the food is  in progress along the small
intestine, it  experiences that  change  in  its  physical  properties,
which enables the chyle to be separated from it by  absorption ; and,
as soon as this change is produced, the chyle is taken up from it.
These two actions have been termed respectively chylification and
the absorption of chyle; although by some the former term has been
applied to both processes.
  Above the point, at which the common choledoch and pancreatic
ducts open  into  the duodenum,  no change is observable in the
chyme.   It preserves its colour, semi-fluid  consistence, sour smell,
and slightly acid taste; having been simply mixed with the exhaled
and follicular  secretions of  the lining membrane.  But, immedi-
ately after it  has  passed the part, at which the hepatic and cystic
bile and the  pancreatic juice are poured into the intestine, it as-
sumes a different appearance, its colour is found to be changed; and
it becomes  yellowish ;  of  a  bitter taste; its sour  smell dimi-
nishes;  and  chyle can now be separated from it by the lacteals.  Ac-
cordingly, at this part of the canal, chyliferous vessels are first per-
ceptible.
  The change, effected upon the chyme  in the small intestine, is
probably,—like that produced on the food in the  stomach,—of an
entirely physical character. The chyle itself, we shall endeavour to
show hereafter, is  formed by an action  of elaboration and selection
exerted  by the chyliferous vessels. No difference is observable be-
tween the chylous and excrementitious portion of the chyme, in any 
ACTION  OF THE SMALL INTESTINE.           503
part of the small intestine; nor can it be separated by pressure or
any other physical process. Magendie, indeed, has affirmed, that if
the chyme proceeds from animal or vegetable substances,that contain
fat  or oil, irregular filaments are observed to form, here and there,
on the surface,—sometimes of a flat, at others, of  a round  shape,—
which speedily attach themselves to the surface of the valvulae, and
appear to be brute chyle; but this is not observed when the chyle
proceeds from  food which  does not contain  fat.  In this case, a
grayish  layer, of greater or  less thickness, adheres to the mucous
membrane, and appears to contain the elements of the  chyle. Leu-
ret and Lassaigne also state, that if an animal  be opened, whilst
digestion is going on,—on the surface  of the  chyme  between the
pylorus and  the orifice of the  ductus communis choledochus,  a
substance, of  a grayish-white appearance, homogeneous, dense,
fluid and acid,  is perceived applied to  the villi of the  intestine.
Neither  of these, however, is chyle.   It is merely the substance
whence chyle is obtained by the action  of the chyliferous  vessels.
  The fact, mentioned by Magendie,—regarding the appearance
of irregular filaments, where animal or vegetable substances, con-
taining fat or oil, have been taken as diet,—has been the occasion of
other erroneous deductions of a pathological character.   Frank
asserts, that he was requested to see a prince, who was attacked
with epilepsy.   His physician,—a respectable old practitioner,—
assured  Frank that he could make his patient void at pleasure thou-
sands of filiform worms. As he was unable to define either the genus
or species of these worms,—the quantity of which, from his account,
seemed  to be prodigious,—Frank requested to be a witness of the
phenomenon.   The  physician administered a dose of castor oil,
which  produced numerous evacuations, containing thousands of
whitish  filaments, similar to small eels; but, on an attentive exami-
nation of these pretended worms, they were found  to  consist en-
tirely of the castor oil, in a state of coagulation.
  The change, effected in the small intestine, is probably of a chy-
mical nature, yet its essence is impenetrable.   It has,  accordingly,
been conceived to be organic and vital.   The same remarks are ap-
plicable here, as were indulged on the  supposed organic  and vital
action of the stomach, exerted in the formation  of chyme.  The
agents of this conversion are;—the fluids secreted from the mucous
membrane of the small intestine, and  the  biliary and pancreatic
juices, aided by the temperature  of the  parts, and the peristaltic ac-
tion.  Haller was of opinion, that the first of these is a principal
agent.   Reflecting on the extensive surface of  the small  intestine,
on the number of arteries, distributed to the organ, and on the size
of these arteries, he asserted, that the lining membrane of  the in-
testine, at the time of chylification, secretes a juice, which he esti-
mated at the enormous quantity of eight pounds  in the twenty-four
hours.   To this he gave the name—succus intestinalis,—and as- 
504                       digestion.
signed it as important a part in chylification, as he attributed to the
gastric juice in chymification.
   It is probable, however, that the fluids, secreted by the mucous
membrane of this  portion of the canal, resemble those of the rest of
the intestinal mucous membrane;  and that  their main  function is
that of lubricating the  intestine, and of still farther diluting the
chymous mass.  Leuret and Lassaigne endeavoured to procure
some of them, by making animals swallow small sponges, enveloped
in fine linen, whilst fasting, and  killing the animals twenty-four
hours afterwards.  Some of these sponges had not gone farther than
the stomach and were filled with  gastric juice; others,  which had
reached the small intestine, had imbibed  the succus intestinalis,
which was more yellow, and  manifestly less acid than  the other.
On attempting to  dissolve, artificially, a crumb of bread, in both of
these juices, they  discovered that the gastric juice gave a sour smell
to the bread;  but  that the intestinal juice allowed  the bread to be
precipitated, and dissolved no part of it.
   From this experiment, it has been concluded, that the succus in-
testinalis is not  the great agent of  chylification.  This deduction is
probably correct;  but no weight can be placed upon results obtained
in so unsatisfactory a manner; for it is obvious that no certainty
could exist as to  the identity between the gastric and intestinal
juices, and the fluids  respectively found in the different  sponges.
   We have strong reason for believing, that,  even if food should
escape the action of the stomach, it  is capable of being digested in the
small intestine.  This may be owing to some  of the true gastric juice
passing into the intestinal canal, and impregnating it, or it  may be
produced by some similar secretion from follicles seated there.  The
lining membrane of the small intestine possesses  the property of
coagulating milk;  and pathological cases occur, in which the stomach
is, to all appearance, completely disorganized.   Yet the individuals
survive so long  as to  compel us to presume, that digestion must have
been effected elsewhere than in the stomach.
   Magendie placed  a piece of raw  meat  in the duodenum  of a
healthy dog.  At  the expiration of an hour, it had reached the rec-
tum, and  its weight was found to be  but slightly diminished; the
only change appeared to be at its surface, which was discoloured.
In another experiment, he fixed a piece of muscle, with a thread, so
that it could not pass out of the small intestine. Three hours after-
wards, the animal  was opened.  The piece  of meat had lost about
half its weight.  The fibrine was especially  attacked; and what had
resisted,—which was  almost wholly cellular,—was extremely fetid.
   This fact sufficiently shows, that a solvent property is exerted  in
the small intestine.
   The biliary and  pancreatic juices are the great agents  in  chylifi-
cation.  We have already remarked, that the chyliferous vessels do
not begin to appear above the part  at which these juices are poured 
DIGESTION  IN  THE SMALL INTESTINE.          505
 into the duodenum; that, in the rest of the small intestine, they are
 less and less numerous as we recede from the duodenum; and  that
 the chyme does not exhibit any change in its properties, until after
 its admixture with those fluids.   Direct experiments  have, also,
 been made for the purpose of testing the use of the bile in digestion.
 Mr. Brodie tied the ductus communis choledochus in  young cats,
 so as to prevent both the hepatic and cystic bile from reaching the
 intestine.  He found that chylification was  interrupted, and  that
 there were neither traces of chyle in the intestines nor in the chy-
 liferous vessels.  The former contained only chyme, similar to that
 of the stomach, which became solid at the termination of the ileum;
 and the latter, a transparent fluid, which appeared  to be a mixture
 of lymph and of the more liquid portion of the chyme.
   Magendie, however,  repeated these experiments on adult ani-
 mals, and with dissimilar results. The greater part  died  of the con-
 sequences  of opening the abdomen, and of the operation required
 for tying the choledoch duct.   But in two cases, in which the ani-
 mals survived some days, he  discovered that digestion had per-
 sisted; that white chyle had been formed, and stercoraceous matter
 produced.  This last had not the usual colour, which, as he remarks,
 is not surprising, as it contained no bile.
   The experiment  was likewise repeated by  MM. Leuret  and
 Lassaigne, and with results similar to those obtained by Magen-
 die.   In the duodenum  and jejunum, a whitish chyme  adhered to
 the parietes of the organ; and,  in the thoracic duct, a fluid existed,
 of a rosy-yellow colour, which  afforded, on analysis, the same con-
 stituents as chyle; although the animals, which were the subjects of
 the operations, had been  kept, for some time, without food.
   Notwithstanding the discordant results of these experiments, we
 can scarcely doubt, that  the bile and the pancreatic fluids  are the
 chief agents in the conversion effected in the duodenum.
   As to the mode in which these fluids act on the chyme, we have
 only conjectures to guide us.  MM. Tiedemann and Gmelin sug-
 gest, that the soda of the bile unites with the muriatic and acetic
 acids of the chyme; whilst, at the same time, the latter precipitates
 the mucus  of the  bile, its colouring principle and resin; which are
 evacuated with the excrements.   The majority of physiologists be-
 lieve, that  the bile is divided into two parts, by the action of the
 chyme; the one, which contains  the alkali, the salts, and apart of the
 animal matter, uniting with the  chyle; the other, which contains the
 coagulated  albumen, the coloured, concrete, acrid, and bitter oil, uni-
 ting with the faeces, and being discharged with them.
   According to this view, the action of the bile would  be entirely
 chymical; a part would be recrementitial or taken up again  into the
system; and a part excrementitial,  and giving to the excrements
their smell, colour, and, according  to some, the necessary stimula-
ting property for soliciting the peristaltic action of the intestines so
as to produce their evacuation,   It is more than doubtful, however,
   Vol. I.                     64 
506                      DIGESTION.
whether the bile has any such influence as the last.   It is a law in
the economy, that no secretion irritates the part over which it passes
or is naturally destined to pass, unless such part be in a morbid con-
dition: and, moreover, were it otherwise the mucous  membrane of
the intestine would be soon accustomed to  such stimulation;  and,
consequently, the effect be  null.
   We are not better instructed with regard to the precise uses of the
pancreatic juice; although many have been  assigned to  it; which,
being founded in utter ignorance of its nature and properties, it would
be a  waste of time to notice.   Tiedemann and Gmelin affirm  that
it yields to the chyme the richly azoted principles, which enter into
its composition; and, consequently,  aids in its assimilation.  In tes-
timony of this, they remark, that the pancreas is larger in herbivo-
rous than  in carnivorous animals; and that, in proportion as the chy-
mous matter proceeds along the intestinal canal, it exhibits itself less
rich in albumen and other azoted matters, which have probably been
abstracted from it  by absorption.
   Marcet discovered in the chyme of the small intestine a notable
development of albumen; which was first perceptible at a few inches
from the pylorus, and did not exist  in the large intestine.
   The influence of the temperature  of the interior of the intestine,
and of the peristaltic motion, in  chylification, can only be looked
upon as accessory and indirect.
   Whilst the chyme is passing through the small intestine, it is sub-
jected to the action of the chyliferous vessels, which extract from it
the nutritious part, called chyle:—the fluid especially destined for
the renovation of the  blood.  How this is accomplished  will be
treated under the head of absorption.
   In proportion  as this absorption is effected, the chyme changes its
apparent properties.  In the commencement of the jejunum, it is the
same as in the duodenum; but, lower down, the grayish layer, which
existed at its surface, is observed to  gradually disappear. It assumes
greater consistence; its yellow colour becomes more  marked; and,
in the ileum, it has a greenish or brownish  tint;  and becomes less
and less acid;  until, at the lower part of the small intestine, it seems
to be the useless  residue of the alimentary matter, and of the various
secretions from the digestive apparatus.  It is now merely excre-
mentitious matter or faeces, although not yet possessing the odour.
   During the formation of chyle, gases are almost always present in
the small intestine. These were first examined by Jurine; but chy-
mical analysis was by no means as perfect at that day as it  now is.
Magendie and Chevreul  have more recently analyzed those,
which they found  in the small intestines of three criminals; all of
whom were young and vigorous.   One of these was twenty-four
years of  age.  He had eaten, about two hours before execution,
bread and gruyere cheese; with red wine for drink.  The gas of the
small intestines consisted of oxygen, 0.00; carbonic acid, 24.39; pure
hydrogen, 55.53; azote, 20.08.
* 
digestion in the large intestine.
507
  The second of the criminals was twenty-three years old.  In other
respects he was circumstanced like the last.  The gas, in his case,
contained:—oxygen,  0.00; carbonic  acid, 40.00; pure  hydrogen,
51.15; and  azote, 8.85.
  The third was twenty-eight years old.  He had eaten—four hours
before execution—bread, beef, and lentils; and had drunk red wine.
The gas contained :—oxygen, 0.00; carbonic acid, 25.00; pure hy-
drogen, 8.40; and azote, 66.60.
  These gases might originate in  various ways.   They might, for
example, proceed from the stomach with  the chyme.  There is this
objection, however, to that view;—that the air in the stomach con-
tains oxygen and very little hydrogen: whilst a considerable quantity
of the latter gas  is almost always found in the small  intestine, and
never any oxygen.
  Again, they might be secreted by the  mucous membrane of the
intestine.  So far as we know, however, carbonic  acid and azote
are alone exhaled from the tissues. We should still have to account
for the existence of the hydrogen.
   Lastly, they might arise from the reaction of the  elements  of
the chyme upon each other, and this is  the  most probable origin.
Magendie has  frequently seen bubbles of gas escaping  from the
chymous mass, contained between the mouth of the ductus commu-
nis choledochus  and the ileum; but never from that of the ileum,
from the upper part of the duodenum, or stomach; and he affirms,
that Chevreul found, in prosecuting some experiments not yet pub-
lished, that, when the mass, obtained from the small intestine, was
suffered  to ferment, for some time, in a stove, at the temperature of
the body, precisely the same gases were  obtained as those met with
in the small intestine.
   When the food has attained the lower part of the ileum, the pro-
cess of chylification has been accomplished, and the residuary matter
is transmitted into the large intestine, by the same peristaltic action,
which has been so often described. The movement, however, recurs
very irregularly and at long intervals.  On the living animal, it can
be rarely perceived; but may be noticed on one recently killed.  It
appears to  have  no coincidence with that of the pylorus.
   7. Action of the  large Intestine.—The large intestine acts as a
reservoir and excretory canal for the faeces.  The  residue of the
alimentary matter is sent on, through the valve of Bauhin, by the
peristaltic  action of the ileum.   This valve, we have seen,  is so
situated, at the point of union between the ileum and caecum, as to
permit a free passage from the former to the latter, but to prevent
its return.   The chymous mass is, also,  as yet, sufficiently soft to
pass readily; and the quantity of mucus,  poured out from the lining
membrane, facilitates its course.
   When it has reached the large intestine, it first accumulates in the
caecum; which being cellular or pouched, like the colon, necessarily
detains it for some time.   In proportion, however, as the caecum 
50S
digestion.
becomes filled, the same peristaltic action is  established as that
which occurs in the small intestine, and the matter is sent on into
the colon, the cells of which are successively filled; first, those of
the ascending, and then those of the transverse and descending
colon; after which it is  forced by the  peristaltic action  into  the
rectum.
  The whole  of  its  progress through the large intestine is very
slowly accomplished.  Independently of the pouched  arrangement,
which retards it,  a part of the colon ascends, so that the faecal mat-
ter must proceed  contrary to  its gravity.   It  becomes, moreover,
more and more inspissated,  in its progress towards the outlet; and
the peristaltic action recurs at greater intervals,  than  at the upper
portions of the tube.  At length, the contents reach the rectum, and,
not being able to  escape, owing  to the closure of  the anus, by  the
contraction of its  sphincter muscle, they distend it uniformly, so as,
at times, to form  a mass, several pounds in weight.  The arrange-
ment of the rectum is favourable to this.   It is extremely dilatable,
and the whole of  its lower portion is devoid of peritoneal covering.
  The importance of such a reservoir as the large intestine, is  ob-
vious.  Without it, we should be subjected to the inconvenience of
evacuating the faeces incessantly.
  Before the excrementitious matter reaches the large intestine, it
has not  the fetid odour peculiar to human faeces; but it acquires this,
after having remained in it for a short time. The brownish-yellow
colour becomes deeper; but its consistence, smell, and colour, vary
considerably, according to the character of the alimentary matter;
the mode and  degree in which chymification and chylification have
been accomplished; the habit of the individual, &c. &c.
  The faecal matter, as we find it, consists of the excrementitious
part of  the food, as well as of the  juices of the  upper part of  the
canal, which have, also, been subjected to the digestive process; of
the secretions, poured out from the lower part of the intestine; and,
also, of  those  substances, which have escaped the  digestive actions
of the stomach and small intestine, and are often perceptible in  the
evacuations.
  The peculiar faecal impregnation is probably dependent upon a
secretion from appropriate follicles, situated towards the extremity
of the small, and in the large, intestine; and we can thus understand,
if we take into consideration the digestion of the different secre-
tions, why faecal  evacuations  may exist, when  the individual  has
not eaten for some time, or has taken but  little nourishment.
  Some physiologists have believed, that  chylification is continued
even in the large intestines,  and  that chylous absorption is  more
or less effected there. Viridet asserted, that the caecum is a second
stomach, in which a last effort is made to separate from the food the
digestible and soluble portions it still contains. In herbivorous ani-
mals, according to him, an acid, solvent, fluid is secreted in it.  MM.
Tiedemann and  Gmelin,  two of the latest writers on digestion, 
digestion  in  the  large  intestine.         509
seem to admit this fact;  and they likewise think, that the fluid, se-
creted by the inner membrane of this intestine, assists in the assi-
milation of the food by the albumen it contains, and that the faecal
matter is formed in this intestine.
  The physical characters of the faeces we have already described.
When  extruded,  they have the shape of the large intestine, or of
the aperture, through which they are evacuated.   If, therefore, the
shape of either of these be modified, that of the excrement is so
correspondently.   In stricture of the colon, especially about the
sigmoid  flexure, the faeces are squeezed through the constricted
portion, and often evacuated in the shape of ribands. The quantity
must, of course, vary, according to  circumstances, and cannot be
rigidly estimated. Approximately, they have been presumed to be,
in the adult male, from a quarter to half a pound in the twenty-four
hours, the evacuation being usually made once only in this time.
  The biliary secretion appears to exhibit considerable influence on
the appearance of the faeces.  If, as in cases of jaundice, it is pre-
vented from flowing into the intestine, the evacuations are clay-co-
loured.   Adelon affirms, that, under such circumstances, they are
more frequent.  This is not the  result of our experience, nor does
it appear to be deduced from his  own; as, a few pages before, he re-
marks that " it is certain, that if the bile does not flow, the excre-
ments are dry, devoid of colour, and there is constipation."
  On the, other hand, if the bile flows in too great quantity, the
faeces are darker coloured.   It is doubtful, however,  whether the
varying quantity of the biliary secretion has much influence on the
number of the evacuations, unless the  canal, over which it has to
pass, is in a morbid  condition.   Many of the appearances in the
faeces, which are conceived to be owing to a morbid  condition of
the biliary secretion, are the effect of admixture with the products
of morbid changes in the stomach or intestines.   In elucidation of
this, it may be observed, that the green evacuations of children are
often referred to some pathological condition of the  biliary secre-
tion; whereas the colour is  commonly owing to unusual formation
of acid in the stomach, the  admixture  of which with healthy bile
produces the colour in question.
  The chymical properties of the faeces have been repeatedly exa-
mined.   These must of course vary according to the nature of the
food, its quantity, and  the kind of digestion, &c.   They are dif-
ferent  in each animal species.   Those of the herbivora contain less
animal matter than those of the  carnivora and  omnivora; and the
agriculturist is well aware, that  the  excrements  of all animals are
not equally valuable as manure.  The dung of the pigeon is alkaline
and caustic; and, hence, has been employed in tanning for softening
the skins.   The excrement of dogs, which have fed only on bones,
is white, and appears to be almost wholly composed of the earthy
matter of bone.   It has not, however, been examined by modern
ehymists.   This white excrement is the album grascum, cynoco- 
510                       DIGESTION.
prus,spodium Graecorum,album canis, or stercus caninum album
of the older writers.   It was formerly employed as a discutient to
the inside of the throat in quinseys, but is now justly discarded.
  Vauquelin, in comparing the nature and quantity of the earthy
parts of the excrements of  fowls, with those of the  food on which
they had subsisted, arrived  at some  results  which are of deep in-
terest to the physiologist.   He found, that  a  hen devoured, in ten
days, 11111.843 grains troy of oats.  These contained of phosphate
of lime, 126.509 grains; and of silica, 219.548 grains; in the whole,
356.057 grains.
  During these ten days she laid four eggs,  the shells of which con-
tained 98.779 grains of phosphate of lime;  5S.494 grains of carbo-
nate of lime, and 185.266 grains of silica.  Consequently,  the fixed
parts, thrown out of the system, during  the  ten  days, amounted
to—
       Phosphate of lime,     -    -    -   274.305 grains.
       Carbonate of lime,     -    -     -   511.911
       Silica,       -----   1S5.266
Given out,   -                   971.482
Taken in,                   -    356.057
           Surplus,      -                   615.425
  The quantity of fixed matter, therefore, given out of the system
in ten days, exceeded the quantity taken in, by this last amount.
    The silica, taken in, amounted to     -    136.509 grains.
    That given out,  to   -     -     -     -    274.305
                                           137.796
There must, consequently, have been formed, in this fowl, 137.796
grains of phosphate of lime, besides 511.911 grains of the carbonate.
The inferences, deduced from these experiments,  were, that lime,
and perhaps also phosphorus, is not a simple substance, but a com-
pound,  and formed of ingredients, which  exist  in oats, water, or
air, the only substances to which the fowl had access; and that silica
must enter into its composition, as  a part had disappeared; but, if
so, it must be combined with a great quantity of  some other sub-
stance.
   Before, however, we adopt these conclusions,  the experiments
ought to be more than once repeated.   The  chicken should be fed
on oats some time before the  excrements and shells are subjected
to analysis; as the carbonate of lime and the excess of phosphate of
lime, detected on analysis, might have proceeded from the food, as
well as  from the earthy matters previously swallowed.  Care should
also be taken,  that it has no access to  any calcareous earth; and it
must  be certain, that it has not  diminished  in weight; as,  in such
case,  the calcareous earth may have been  supplied from its own
body.  These precautions are the more requisite, seeing, that expe- 
digestion  in  the large  intestine.
511
riments appear to have shown, that certain birds cannot produce
eggs unless they have access to calcareous earth.
  We have, however, some very remarkable instances of chymical
changes, in the mysterious actions, more immediately concerned in
the decomposition and renovation of the frame; or, in what has been
abstractedly termed—the  function of nutrition.  Dr. Henry has
announced, that the following substances have been satisfactorily
proved  to  exist in healthy urine:—water, free phosphoric acid,
phosphate of lime, phosphate  of magnesia, fluoric acid, uric acid,
benzoic acid, lactic acid, urea,  gelatine, albumen, lactate of ammo-
nia, sulphate of  potass, sulphate of soda, fluate of lime, muriate of
soda, phosphate of soda, phosphate of ammonia, sulphur, and silex;—
yet we have no proof that these substances are obtained from any
other source than the food; and some of them  are, with difficulty,
obtained any where.   Every one of them is necessary for the con-
stitution of the  urine; and many must  be formed by a chemical
union of their elements under the vital agency.  Some are met with
in the animal body exclusively.
  Berzelius found, in 100 parts of human faeces:—water, 73.3;
unaltered residue of animal and vegetable substances, 7.0; bile, 0.9;
albumen, 0.9; peculiar extractive matter, 2.7; substance, formed of
altered bile, resin, animal matter, &c.  14; and salts,  1.2.  Seventeen
parts of these salts contained, carbonate of soda, 5; muriate of soda,
4; sulphate of soda, 2; ammoniaco-magnesian phosphate, 2; phos-
phate of lime, 4.
  The excrements have likewise  been examined by Leuret and
Lassaigne, and by Prout  and others; but  none of the analyses
have shed much light on the physiology of digestion.
  In the large intestine, gases are also  met with,  along with  the
faeces. These were examined by Magendie and Chevreul, in the
three criminals  already referred to.  In  the first, 100 parts of  the
gas contained;—oxygen, 0.00; carbonic acid,43.50;  carburetted and
some traces of sulphuretted hydrogen, 5.47; azote, 51.03.   In the
second, oxygen, 0.00; carbonic acid, 70.00; pure and carburetted
hydrogen,  11.60; azote, 18.40.  In the third, the gas, found in the
caecum, was analyzed  separately from that of the rectum.   These
were found to contain respectively in 100 parts:—
Oxygen,...... Carbonic acid, -----	Caecum.	Rectum.
	0.00 12.50	0.00 42.86
Pure hydrogen, - - - - -Carburetted hydrogen, -Azote,......	7.50 12.50 67.50	11.18 45.96
Traces of sulphuretted hydrogen, -	Some.	Some.
	100.00	100.00
 
512                       digestion.
  The results accord with those of Jurine, obtained long ago, as
regards the nature of the gases; but they do not accord with what
he says relating to the carbonic acid; the quantity of which, accord-
ing to Jurine, goes on decreasing from the stomach  to the rectum.
The analyses, given, show that the proportion increases  instead of
decreasing.
  Concerning the origin of these gases, the remarks  made on those
of the small intestine are equally applicable  here.
  When the faecal matter has accumulated to the necessary extent
in the rectum,  its expulsion follows; and to this function the term
defecation has been appropriated.
  The faeces collect gradually in the rectum, without  any conscious-
ness on the part of the  individual.  Sooner or later, the desire or
want to evacuate them arises.  This is usually classed among the
internal sensations or desires.  It is, however, properly, of a mixed
character. That it is not always in a ratio with the quantity of faeces
is shown by the fact,  that, occasionally, the rectum will be filled
without the want arising; and, if the faeces be unusually thin or
irritating, the desire is developed when an extremely  small quantity
of matter is present,—as in cases of tenesmus.
  The period, at which the desire returns, is variable, according to
the quantity and  character of the food employed, as  well as to  the
habit of the individual.   Whilst the generality of persons evacuate
the bowels, at least once in the day,—and this at a period regulated
by custom,—others will pass a week or  two, without any alvine
discharge, and yet be in perfect health.  Nay some of the collectors
of Cas rares have affirmed, on the authority of Rhodius, Pana-
rolus, Salmuth, and others,  that persons may continue  in health,
with the bowels  moved not oftener than once  a  month, three
months, half a year, two years,  and even  seven years, without se-
rious mischief!
  When the desire has once  exhibited itself, it generally persists
until the faeces are expelled. Sometimes, however,  it  disappears and
recurs at an uncertain interval; and, if again resisted, becomes  the
source of great pain, and ultimately commands  implicit obedience.
That the pressure and irritation of the faeces develope the sensation
is evidenced by the circumstance, that the relief experienced, when
the desire is urgent, is usually accompanied  by a manifest return of
the faecal matters into the colon.
  In evacuating the faeces, the object to be accomplished  is,—that
the  contents of the rectum shall be pressed upon with a force supe-
rior to the resistance, presented by the muscles of  the anus.   The
contraction of  the  rectum is generally  insufficient  to effect this
object, notwithstanding the considerable thickness  of its  muscular
layer.  In cases, however, of great irritability of  the  rectum, the
sphincter is incapable of resisting the force developed by the proper
muscular fibre of the rectum.
  Under ordinary circumstances, the aid of  the diaphragm and ab- 
                         defecation.                      513

dominal muscles is invoked, and it is chiefly through these muscles,
that volition influences the act of defecation,—suspending, deferring,
or accelerating it as the case may be.   After a full inspiration, the
muscles, which close the glottis, and the expiratory muscles,—espe-
cially those on the anterior part of the abdomen,—contract simulta-
neously.  The air cannot escape from the lungs; the diaphragm  is
depressed upon the abdominal viscera, and the whole thorax  pre-
sents a resisting body; so that all the expiratory power of the abdo-
minal muscles bears upon the viscera, and presses them against the
vertebral column.  In this way, considerable force is exerted upon
the contents of the rectum; the resistance of the sphincter,—already
diminished by the  direct exertion  of volition,—is surmounted;  it
yields and  the faeces are extruded.  The levator ani and ischio-coc-
cygeus, aided by the transversus perinei muscles, support the anus
during the  propulsory efforts, and restore it to its place, after these
efforts have ceased.
   Whilst the straining is effected by the diaphragm and abdominal
muscles, the longitudinal muscular fibres of the rectum contract, so
as to shorten the intestine, and, consequently, the space over which
the faeces have to pass.   On the other hand, the circular fibres  con-
tract, from above to below, so as to propel the  excrement down-
wards, and to cause the mucous membrane to extrude,  and form a
ring or bourrelet, like that which occurs  at the cardiac orifice  of
the stomach.  When  this extrusion occurs to a great extent it  con-
stitutes the disease, called prolapsus ani.
   When the faeces are firm, considerable muscular effort is  neces-
sary to expel them; but, when  they are of a softer consistence, the
contraction of the rectum is  sufficient.
   The air, contained  in  the intestinal canal, readily moves about
from place to place, and  speedily reaches the rectum by the peris-
taltic action alone.  Its  expulsion, however, is  commonly accom-
plished  by the aid of the abdominal  muscles, when it issues with
noise.   If discharged, by the contraction of the rectum alone,  it  is
generally in silence.
   Children are extremely subject to flatulence, but in the adult  it
is not common.  Some kinds  of diet favour its production more
than others, especially in those of weak digestive powers, of which
it is, indeed, generally an indication.  The leguminous and the suc-
culent vegetables, in general, belong to this class. Where digestion
is tardily accomplished, they undergo  fermentation and the disen-
gagement of gas is the consequence.  Too often, however, the dis-
gusting habit of constantly discharging  air streperously from the
bowels is encouraged, rather than repressed; and there are those,
who arc capable of effecting the act almost as frequently as  they
attempt it.
   The noise, made by the air,  as it passes backwards and forwards
in the intestinal canal, constitutes the affection called borborygmus.
   So much for the  digestion of solid food.
   Vol. I.                     65 
514
DIGESTION.
                  II.  Digestion of Liquids.

  In examining into the digestion of liquids, we shall  follow the
same order as that observed in the digestion of solids; but,as many
of the acts are accomplished in precisely the same manner, it  will
not be necessary to dwell upon those.
  1.  Thirst.—Thirst or the desire for drink is  an  internal  sensa-
tion; in its essence resembling that of hunger, although not referred
to precisely the same organs.   It arises from the necessities of the
system, from the constant drain of the fluid portions of the  blood,
and is instinctive or essentially allied to organization.
  The sensation differs in different individuals, and is rarely alike
in the same person.   Usually, it consists of  a feeling of dryness,
constriction, and heat in  the back  part of the  mouth, pharynx,
cesophagus, and  occasionally in the stomach; and, if prolonged, red-
ness and tumefaction of the parts supervene, with a clammy condi-
tion of the mucous and follicular—and diminution and viscidity of
the salivary—secretions. These phenomena are  described as being
accompanied by restlessness, general heat,  injected  eyes, disturbed
mind, acceleration  of the circulation, and short breathing, the
mouth being frequently and largely open, so as to admit the air  to
come in  contact with the irritated  parts, and thus to afford momen-
tary relief.
  Thirst is a very common symptom of disease, especially of those
of an inflammatory character, in which the fluid is desired, in  con-
sequence of the local relief it affords,—especially when the drink
is cold,—to the parched and heated membrane  of the alimentary
canal.  It is also developed by circumstances exterior to us; as  in
summer, when the body sustains considerable loss of fluid, as well
as in those diseases,  as dropsy,  diabetes, &c. which produce the
same effect.
   There are many other circumstances, however, that excite it; such
as long speaking or singing;  certain kinds of diet—the saline and
spicy, for example—and especially the habit, acquired by some, of
frequently drinking.  Whilst such individuals may require several
gallons a day, to satisfy their wants;—others, who have, by resist-
ance, acquired the habit of using very little liquid, will be enjoying
good health and not experiencing the slightest inconvenience from
its privation; so completely are we, as regards  the character and
quantity of our aliment, the creatures of habit.  This privation, it is
obvious, can not  be absolute  or  pushed beyond a certain  extent.
There must always be fluid enough taken  to administer to the  ne-
cessities of the system.
   As in the production of every internal sensation, three acts  are
required in accomplishing that of thirst:—the acts of impression,
conduction and perception. The last, as in every similar case, is ef-
fected by  the brain, and the second  by the nerves passing between
the part impressed and the brain. 
DIGESTION  OF LIQUIDS.
515
  It is the act of impression—its seat and cause—which will alone
arrest our attention; and we shall find, that we are still less instruct-
ed  on these points, than on the  physiology of hunger.  With re-
gard even to the seat of the impression, we are in a state of uncer-
tainty. It appears to be chiefly in the back  part  of the mouth and
fauces; but, whether primarily there, or produced by sympathy with
the condition of the stomach,  is by no means clear.  The latter opi-
nion, however, appears the more probable.   In a remarkable case,
published by Dr. GAiRDNERof Edinburgh, it was found impractica-
ble to allay the thirst, by merely supplying the mouth, tongue and
fauces with fluid.  A man had cut  through the oesophagus.  An in-
satiable thirst arose; several pailfuls of water were swallowed daily,
and discharged through the wound, without allaying the thirst; but,
on  injecting water, mixed with a little spirit, into  the  stomach,
it was soon  quenched.  That the sensation is greatly dependent
upon the quantity of fluid  circulating in the  vessels, is shown
by the fact, mentioned by Dupuytren, that he succeeded in allay-
ing the  thirst of  animals,  by injecting  milk,  whey,  water or
other fluids into the veins;  and Orfila states, that in  his toxi-
cological experiments, he frequently allayed in this  way, the ex-
cessive thirst of animals, to which he had administered  poison;
and which  were incapable of  drinking, owing  to the oesophagus
being tied.   He found, also, in his experiments, that the blood
of  animals was more and more deprived of its watery portions, as
the abstinence from liquids was more prolonged.
   Like all other internal sensations, that of thirst arises from a mo-
dification of the nerves of the organ, which is inappreciable : hence
all the hypotheses, that have been proposed, to account for its cause,
have been mere phantasies and undeserving of enumeration.
   2. The prehension of liquids differs somewhat from that of solids.
The fluid may be simply poured into the mouth, when it enters by
its own  gravity ; or a vacuum may be formed in the cavity of the
mouth, and the pressure of the atmosphere may force in the fluid.
 When we drink from a vessel, the mouth  is applied to the surface
 of the  fluid; the chest is then dilated, so as to diminish the pres-
 sure of the atmosphere on the portion of the surface of the liquid,
 intercepted by the lips; and  the atmospheric  pressure on  the sur-
 face of the fluid in the vessel forces it into the mouth, to replace the
 air which has been removed from the  mouth by the dilatation  of
 the thorax.
    In sucking, the mouth may be compared to an ordinary syringe;
 the nozzle of which is represented  by the  lips; the body by the
 cheeks, palate, &c. and the  piston by the  tongue.   To put this in
 action, the lips are accurately adjusted around the body, from which
 the liquid has to be extracted.  The tongue is likewise  applied,
 but it soon  contracts, and  is  carried  backwards;  so that an ap-
 proach to a vacuum  is formed  between its upper surface and the 
516                       DIGESTION.
palate.   The  fluid,—now, no longer compressed equally by the
atmosphere,—is displaced and enters the mouth.
   As neither  mastication nor insalivation is required in the case of
liquids,  they  do not remain long in the mouth ;  unless their tem-
perature is too elevated to admit of their being  passed down into
the stomach immediately, or they be  of such a luscious character,
that their prolonged application to the organ of taste affords plea-
sure.  -
   The deglutition of liquids is effected by the same mechanism as
that of solids; and,—as they yield readily to the slightest pres-
sure,—with less difficulty. Their accumulation in  the stomach takes
place in  much the same manner.  They arrive by successive mouth-
fuls; and, as they collect, the thirst disappears with all its local and
general  attendants.  If, however, the organ  be  over-distended, a
disposition to vomiting is induced.
   The changes, which liquids undergo  in the stomach, are of dif-
ferent kinds.   All acquire the temperature of  the viscus, and be-
come mixed with the secretion from its internal surface, as well as
from that of the supra-diaphragmatic portion of the digestive tube.
Some, however, undergo the operation of chymification; others not.
To the latter class belong,—water, weak alcoholic drinks, the vege-
table acids, &c.   Water experiences the admixture already men-
tioned; becomes turbid, and gradually disappears, without undergoing
any transformation.  Part passes into the small intestine; the other
is directly absorbed. When any strong alcoholic  fluid is taken, the
effect is different.   Its stimulation causes the stomach to contract,
and  augments the secretion from the mucous membrane; whilst, at
the same time, it coagulates all the albuminous and mucous portions;
mixes with the watery part of the mucous and salivary fluids, and
rapidly disappears  by absorption; hence, the speedy supervention
of inebriety, or death after a large quantity of  alcohol has been
taken into the stomach.  The substances, that have been coagulated
by the action of the alcohol, are afterwards digested like solid food.
We  can thus understand the good effects of a small quantity of alco-
hol, taken after a substance difficult of digestion,—a  custom which
has existed from high antiquity and has physiology in its favour. It
is, in such cases,—to use the language of the eccentric Kitchener,—
a good "peristaltic persuader."
   Of the liquids, which are capable of chymification, some  are so
altogether; others in part, only.   Oil belongs to the first class; and
hence it  remains longer in the stomach than any other liquid. Milk,
as is well known, coagulates  in  the stomach, soon after it is swal-
lowed, after which the clot  is digested, and the whey absorbed.
Yet the existence  of coagula, in the stomach, is constantly regard-
ed, by the unprofessional, as a pathological condition!  Where the
1 u id, aqueous  or spirituous, holds in  suspension the immediate
principles of animals or vegetables, as gelatine, albumen, osmazome, 
ERUCTATION, REGURGITATION, &C.           517
sugar, gum, fecula, colouring  matter, &c, a separation  occurs, in
the stomach, between the water, or alcohol and the substances com-
bined with them.  The latter  remain in the stomach and undergo
chymification; whilst the aqueous or spirituous portions are absorbed.
The salts, united with these fluids, are taken up along with them.
In soup, for example, the water and the salts are absorbed; and the
gelatine, albumen, fat and osmazome undergo digestion.
  Red wine, according to Magendie, first becomes turbid by ad-
mixture with  the juices, formed  in, or carried  into, the stomach:
the albumen of these fluids speedily undergoes coagulation, and be-
comes flocculent;  and,  subsequently, its colouring  matter, entan-
gled, perhaps, with the mucus and  albumen, is deposited  on the
mucous membrane of the stomach. The aqueous, and alcoholic por-
tions soon disappear.
  Liquids reach the small intestine in two forms;—in the  state of
chyme; and in their unaltered condition.  In the former case, they
proceed like the chyme obtained from solid food. In the latter case,
they undergo no essential change;  being simply united with the
fluids poured into the small intestine,—the mucous  secretions, the
bile, and the pancreatic juice.   Their absorption goes on  as  they
proceed; so that very little, if any, attains the large  intestine.
  The mode, in which liquids have  to be expelled, is the same as
in the case of the solid excrements.

        OF ERUCTATION,  REGURGITATION, VOMITING, &C

  Although the contraction of the cesophagus  generally prevents
the return of matters from the stomach; occasionally this  occurs,
giving rise to eructation, regurgitation, or vomiting.
   1. Eructation or belching is the escape of gas from the stomach.
Whenever air exists in the stomach,  it is necessarily situated, as we
have seen, near the cardiac orifice.   When the aperture relaxes, it
passes in, and, unless forced back by the contraction of the oeso-
phagus, speedily reaches the pharynx, causing the edges  to vibrate;
and hence the sound by which it is accompanied.
  2. Regurgitation.—If, instead of air, liquid or solid food ascends
from the  stomach into the mouth, the action is  called regurgita-
tion. Of this we have an instance in  the puking of the infant at the
breast; and in the  adult, when the stomach is surcharged.  Occa-
sionally, too, it occurs when the stomach is empty; in the morning,
for example, when it is frequently preceded by eructation, by which
the air, contained in the organ, is got rid of.
   The mode, in which it takes place, is analogous to that  of  eruc-
tation.  The substances, contained in  the stomach, become accident-
ally engaged in the cardiac orifice, during the open  state of the ori-
fice and the relaxation of  the lower part of the cesophagus; owing
to the direct pressure of the stomach on its contents, and the abdo-
minal muscles contracting'and compressing that viscus.  When the 
518                       DIGESTION.
food has once passed into the oesophagus, the latter contracts upon
it, but inversely, or from below to above.  In this way the food as-
cends into the pharynx, and ultimately into the mouth.
  Generally, regurgitation takes place in  an involuntary manner;
but there are some who are capable of effecting  it at will; and can
thus discharge the contents of their stomach at pleasure. To accom-
plish this,—a deep inspiration is taken, by  which the  diaphragm is
forcibly depressed upon the stomach ; the abdominal muscles are
then  contracted,  so as to  compress the organ ; and this effect is
occasionally aided by pressing strongly with the  hands on the epi-
gastric region.  When these efforts are simultaneous with the re-
laxation of the lower third of the oesophagus, the alimentary  mat-
ters pass  into the  oesophagus.  This voluntary regurgitation seems
to be what is called vomiting at pleasure.
  3. Rumination.—Some individuals  have  taken advantage of
this power to chew  the food over again; and subject it to a second
deglutition.  The  function of rumination is peculiar to certain ani-
mals. Yet man has, in this way, occasionally possessed it.  Peyer
has given numerous examples in his Merycologia; and Percy and
Laurent, in the  article Merycisme  of  the Dictionnaire des Sci-
ences Midicales.
  The wife of a frotteur or rubber  of the floors, in the establish-
ment of the then Duke of Orleans,—now king Louis Philip, could
bring up a glassful of water into her mouth immediately after she had
swallowed it.  Dr. Copland, who published the last edition of the
English  translation of Richerand's physiology, appears to have
seen more than  one instance of human  rumination, and he de-
scribes it as  an affection rather to be courted than shunned, so far
as regards  the  feelings of the  individual.   Under usual circum-
stances, according to him, rumination commences from a  quarter to
an hour and a half after a meal.  The process is never accompanied
with the smallest  degree of nausea, or with any pain or disagreeable
sensation.  The returned alimentary bolus is attended with no un-
pleasant  flavour;  is in no degree acidulous; is equally agreeable;
and is masticated with additional pleasure, and with much greater
deliberation than  when first taken.  The whole  of the food, taken
at a meal, is not  returned, in order  to undergo  the  process; but
chiefly the part that has been insufficiently masticated.  The more
fluid portions are sometimes, however, returned along with the
more solid; but when  the stomach is distended by a copious meal,
the fluid contents are  frequently returned and  subjected to the
process.
  4.  Vomiting.—The inverted action of the stomach, preceded, as
it always is, by manifest local and general disturbance, cannot pro-
perly be regarded as within the domain of physiology. It is, how-
ever, so nearly allied to the phenomena we have just considered,
and has engaged so much of the time of the physiologist, as well as
of the pathologist, that it requires mention here. 
VOMITING.                      519
  From regurgitation it differs essentially,—in the sensation  that
precedes,  the retching that accompanies, and the fatigue, which ge-
nerally succeeds, it; in short, whilst in regurgitation  no indisposi-
tion may  be felt; in vomiting this is always present, more or less.
  The sensation of the desire to vomit is termed nausea. It  is an
indescribable feeling of general indisposition;  sometimes accompa-
nied with a sensation of circumgyration, either in the head or epi-
gastric region; trembling of the lower lip, and copious flow of the
saliva: along with these  signs there is manifest diminution of the
powers of the vascular and nervous systems:  hence  the  utility of
nauseating remedies when these systems are inordinately excited.
  The causes, that produce nausea, show that  it may be either an
external or internal sensation.  Those, that occasion it directly or ex-
ternally, are certain emetic substances; too great distention of the
stomach, or the presence of food in it which disagrees by its quality;
morbid secretions; the reflux of the bile from the duodenum, &c.
All these are so many immediate irritants, which develope the sen-
sation, as  the external sensations in general  are developed.  In other
cases, however,  the  cause acts at a distance.  Between  the sto-
mach and various  organs of the body, such extensive sympathetic
relations  exist, that if one of these  be long and painfully affected,
the stomach sooner or later sympathizes, and nausea, or vomiting, or
both are produced.   In many instances, indeed, the cause  is much
more remote than this:  the sight of a disgusting object, an offen-
sive smell, or nauseous taste will as certainly produce the sensation
as  any of the more direct agents.
   To this class of causes belongs the nausea, produced by riding in
a carriage with the back to the horses, by swinging, and particular-
ly  by sailing on the ocean.
   How the motion, which obviously excites  the nausea, in  these
 cases, acts, has been the subject of many speculations, especially as
 regards sea-sickness. Darwin refers it to an association with  some
 affections of the organs of vision, which, in the first instance, pro-
 duces vertigo; and Bourru, in his French translation of the  work
 of Gilchrist,—" on the utility of sea voyages in the cure of dif-
 ferent diseases,"—ascribes it to irritation of the optic nerves, caused
 by the impossibility of fixing the eyes on objects soon  after em-
 barking.   The objection to these views is,  that the sickness ought
 to  be prevented by simply covering  the eyes, and that  the  blind
 ought to  be exempt from  it, which  is  not  the  case.   Wollaston
 attempted to explain  it, by some change in the distribution of the
 blood; the descending motion of the vessel tending to cause an ac-
 cumulation of blood on the brain, as  it causes the mercury to rise in
 the tube  of a barometer.  But  this explanation  is  too  physical.
 The mercury, in an unyielding tube, is readily  influenced by the
 motions of the vessel; but the blood in the living animal is situated
 far otherwise.  It is under the influence of a vital force, which  inter-
 feres greatly with  the action  of  causes, that are purely  physical. 
520
digestion.
Were it otherwise we should be liable.to alarming accidents, when-
ever the body is exposed to the slightest concussion.
  The generality of pathologists consider, that the first effect is upon
the brain, and that the sensation is produced consecutively, through
the influence of that organ on the stomach; and it is difficult not to
accord with this view; whilst we admit, that the precise manner,
in which this is effected, is entirely beyond our cognizance,—like
every other phenomenon, indeed, of  the nervous system.  In the
case of nausea,  produced by the sight  of  a  disgusting object, we
have this catenation of actions somewhat more clearly evidenced.
  The impression must, manifestly, in this  case, be conveyed to the
brain by the optic nerves, and  from that organ the  sensation  must
emanate. It is probable, too, that when emetics are injected into the
veins, the first effect takes place on the brain, and the stomach is
affected secondarily.
  When the state of nausea, however produced,  continues for any
length of time, it is usually  followed by vomiting.   The rejected
matters are generally from the  stomach,  but  if the  retching or
violent contractile efforts of the muscles concerned be long con-
tinued, the contents of the small intestine also form part; hence,
we account for  the  universality  of  the presence  of bile in the
rejected matters after an emetic  has been taken, which is therefore no
evidence, in the generality of cases, of  the persons being, what is
termed, bilious.   The contents of the small intestine are  returned
into the stomach by an antiperistaltic action.   The  longitudinal
fibres take their fixed point below, and  contract from above down-
wards; so that the chymous mass is forced towards the upper part
of the canal, whilst the circular fibres contract from below to above.
  In cases of colica ileus, or the  iliac passion, the inverted action
extends through the  whole intestinal canal; so that faecal matters,
and even substances, injected into the rectum, will force the ileo-
caecal valve, and be discharged by the mouth.
  Of old, it was universally  maintained, that vomiting is caused by
the sudden and  convulsive inverted contraction of the stomach; and
they, who admitted that the  diaphragm and abdominal muscles take
part in the action, looked upon them simply as accessories. Fran-
cis Bayle, Professor in the University of Toulouse, in 1681, ap-
pears to have been the first, who suggested, that the stomach is nearly
passive in the act; and that vomiting is caused, almost exclusively,
by the pressure, exerted upon that organ, by the diaphragm and ab-
dominal muscles.  His reason  for this  belief was founded on the
fact, that, having introduced  his finger into the abdomen of a living
animal, whilst it was vomiting, he could not perceive any contrac-
tion of the stomach.  In 16S6, Chirac repeated the experiment with
similar results;  after which the views of Bayle  were embraced by
many of the most eminent physiologists and pathologists,—by Senac,
Van Swieten, Schulze, Schwartz, and  at a later period, by the
celebrated John  Hunter, who maintained, that the contraction  of 
VOMITING.
521
the muscular fibres of the stomach is not essential to the act of vo-
miting.
  Many distinguished  physiologists, however, ranged themselves
on the opposite side.  Littre maintained, that the stomach is pro-
vided with considerable muscular bands, capable of powerful con-
traction ; and that vomiting is often caused without the participation
of the abdominal muscles, as in the case of ruminant animals.   We
have seen, however, that the rumination of animals more resembles
regurgitation.  Lieutaud argued, that, according to Bayle's the-
ory, vomiting ought to be a voluntary phenomenon;  that the sto-
mach is too deeply-seated to be  compressed by the neighbouring
muscles, so as to empty it of its contents; and he details the singular
case of a female, who, whilst labouring under an affection, for which
emetics seemed to be required, resisted the action of the most pow-
erful substances of that nature.  After her death, Lieutaud, feeling
desirous to detect the cause of this resistance, had the  body opened
in his presence,  when the stomach was  found enormously dis-
tended, but its structure unaffected.   He,  consequently, inferred,
that the stomach had become paralyzed from over-distention, and
that the effect produced was similar to that, so often met with in the
bladder, when it has been long and largely distended.  This case
seemed to prove to him, that the stomach is most concerned in the
act of vomiting, as the  abdominal muscles and diaphragm appeared
healthy, and no obstacle existed  to their contraction.  It is singu-
lar, however, that the  emetic substances should not  have excited
the contractions  of the diaphragm and abdominal muscles; espe-
cially as there is reason for believing, that many of them at least,
under ordinary circumstances, are taken into the blood,  and affect
the brain first and through its agency the muscles, concerned in the
act of vomiting. The case seems to have been one of unusual resist-
ance to the ordinary effects of nauseating substances, and cannot be
looked upon as either  favourable or unfavourable to the  views of
Bayle.  We find, that vomiting does not follow the  exhibition of
the largest doses of the most powerful emetics, if the energy of the
nervous system be suspended by the inordinate use of opium or by
violent injuries of the head.
  Lieutaud farther remarks, that, according to his theory, vomit-
ing occurs at the time of  inspiration; but this cannot be, as the
lower part of the cesophagus is,  at this time contracted, and  if the
vomited matters  could reach  the  pharynx, they  would pass into
the larynx.
  Dr.  Marshall Hall has recently attempted and successfully,
to show, that the larynx is closed during vomiting; andhas concluded,
that the act is a modification of expiration, or that the muscles of ex-
piration, by a sudden and violent contraction, press upon the contents
of the stomach, and project them through the cesophagus.
  Haller maintained the ancient doctrine, that the stomach, alone,
is competent to the operation.   His views were chiefly founded on
  Vol. I.                     66 
522
DIGESTION.
his theory of irritability, which compelled him to admit contraction,
wherever there are muscular fibres; and on certain experiments of
Wepper, who  asserted, that when he produced vomiting by me-
tallic substances, he observed the stomach contract.
  The Acadimie des Sciences of Paris, unsatisfied with the results
of previous observations, appointed Duverney to examine into the
question, experimentally and otherwise;  who, although he did not
adopt the whole theory  of Chirac, confirmed the accuracy  of the
facts on which it rested. He demonstrated, that the stomach is but ,
little concerned in the act; and that it is chiefly dependent upon the
contraction of the diaphragm and abdominal muscles,  which close
the stomach as in a press, so that its contents are compelled to return
by the cesophagus.
  In 1771, Portal, in his lectures at the college of France, endea-
voured to show, on the other  hand, that the stomach is the great
agent in vomiting.  He administered to two dogs arsenic, and nux
vomica, which produced vomiting. The abdomen was immediately
opened; and, according to Portal, the contractile movements of the
stomach could be  both seen and felt; and  it was noticed, that instead
of the vomiting being dependent upon the pressure of the diaphragm
upon the stomach, it occurred at the time of expiration; and was arrest-
ed during inspiration, because the depressed diaphragm then closesthe
inferior extremity of the cesophagus;—with such  strength, indeed,
that the contents cannot be forced into the  oesophagus, when we
press upon the organ,  with both hands.
  The views of Portal, as regards the agency of the stomach, were
confirmed by the experiments of Haighton.  He opened several
animals during the efforts  of vomiting; and he states, that he dis-
tinctly saw the contractions of the stomach.
  In  more recent times, the physiological  world has been  again
agitated with this question.
  In  1813, M. Magendie presented to the French institute the
result of a series of experiments on dogs and cats,—animals, which
vomit  with facility. .
  Six grains of tartarized antimony were given to a dog; and, when
he became affected with nausea, the linea alba was divided, and the
finger introduced into the abdomen, to discover the state of the sto-
mach.  No contraction was felt; the organ appeared simply pressed
upon by the liver and intestines, which  the  contracted diaphragm
and abdominal muscles crowded upon it. Nor was any contraction
perceptible to the eye; on the contrary, the  stomach appeared full
of air and three times  its usual size. This air manifestly came from
the oesophagus, as a ligature, applied  round  the  cardia, completely
prevented its appearance. From this experiment Magendie inferred,
that the stomach is passive in vomiting.
  A solution of four grains of emetic  tartar in two ounces of water
was injected into the veins of a dog; and, as soon as  nausea took
place, an incision was made into the abdomen, and the stomach drawn 
VOMITING.                      523
out of the cavity.  Although the retching continued, the viscus re-
mained immovable, and the efforts were vain. If, on the other hand,
the anterior and posterior surfaces of the stomach were pressed upon
by the hands, vomiting occurred, even when no emetic  tartar was
administered; the  pressure provoking  the  contraction of the dia-
phragm and abdominal muscles, and thus evidencing the close, sym-
pathetic connexion, which exists between these acts.  A slight pull
at the oesophagus was attended with a similar result.
   In another dog, the abdomen was opened; the vessels of the sto-
mach tied  and  the viscus extirpated.  A solution  of two grains of
tartar emetic in an ounce and a half of water was then injected into
the veins of the animal; when nausea and fruitless efforts to vomit
supervened. The injection was repeated six times;  and always with
the same results.
   In another dog, the stomach was extirpated; and a hog's bladder
fitted to the oesophagus in its stead; containing a pint of water which
distended, but did not fill it. The whole was put into the abdomen;
the parietes of which were closed by suture. A solution of emetic
tartar was now injected into the jugular vein of the animal; when
nausea—and afterwards vomiting—supervened, and the fluid was
forced from the bladder.
   On another dog, the phrenic nerves were divided; by which three-
fourths of the diaphragm were paralyzed: the dorsal pairs being the
only nerves of motion remaining untouched.  When  emetic tartar
was injected into the veins of this  animal, but slight  vomiting oc-
curred; and this ceased, when the abdomen was opened and the sto-
mach forcibly pressed upon.
   In another dog, the abdominal muscles were detached from the
sides and linea  alba; the only part of the parietes remaining being
the peritoneum. A solution of emetic tartar was now injected into
the veins; when nausea and vomiting supervened; and, through the
peritoneum, the stomach was observed to remain immovable; whilst
the diaphragm  pressed  down the  viscera so strongly against the
peritoneum, that it gave way, and the linea alba alone resisted.
   In a final experiment, Magendie combined the two last.  He
cut the phrenic nerves to paralyze the diaphragm; and removed the
abdominal muscles.  Vomiting was no longer excited.
  From these different results, he decided, that vomiting takes place
independently of the stomach; and  on the other hand, that it cannot
occur without the diaphragm  and abdominal muscles; and he con-
cluded that the stomach is  almost  passive in the act; that the dia-
phragm and abdominal muscles, especially the first,  are the principal
agents; that air  is constantly swallowed  at the time of vomiting, to
give the stomach the bulk which is necessary, in order that it may
be compressed by those muscles; and lastly, that the diaphragm and
abdominal muscles are largely concerned in vomiting, as indicated
by their evident and powerful contractions during the  act, and by 
524                       DIGESTION.
the fatigue, which is felt in them afterwards.  Magendie likewise
refers, in corroboration of his view, to the cases of scirrhous pylorus,
in which there is constant vomiting, although a part of the tissue of
the stomach has become cartilaginous, and, consequently, incapable
of contraction.
   Clear as the results, obtained by  this  dexterous experimenter,
seem  to be, they have been controverted; and attempted to be over-
thrown  by similar experiments.
   Soon  after the appearance of Magendie's  memoir, M. Main-
gault laid before the Society of the Faculti de Midecine of Paris,
a series  of experiments, from which he deduced very different  re-
sults.   In all, vomiting was produced without  the aid of the dia-
phragm and abdominal muscles.  The vomiting was excited, in
these  experiments,  by pinching  a  portion of the  intestine, which
acts more speedily than the injection of substances into the veins.
   The abdomen of a dog  was opened, and a ligature passed around
a portion of intestine. The whole was then returned into the abdo-
men;  the wound closed by suture;  and vomiting took place.  All
the abdominal muscles were next extirpated; the skin, alone, form-
ing the  paries of the cavity.  This was brought together, and the
vomiting continued.
   On another dog, three-quarters of the diaphragm were paralyzed
by the section of the phrenic nerves. The abdomen was now open-
ed, and  a ligature placed round a portion of intestine. Vomiting oc-
curred.
   Lastly, these two experiments were united in one. The abdomi-
nal muscles were  cut crucially, and removed; whilst  the phre-
nic nerves were divided; and the muscle even cut away from  its
fleshy portion towards its tendinous centre; leaving only, under the
sternum, a portion as broad as the  finger.  At the  same time, the
integuments were  not brought together;  yet  vomiting continued.
As these results were obtained in numerous repetitions  of  the  ex-
periment, Maingault conceived himself justified, in deducing in-
ferences, the very opposite to those of Magendie, namely,—that  the
contraction of the diaphragm and abdominal muscles is only acces-
sory to  the act of vomiting; and that the  action of the stomach is
its principal cause;  that the latter is not a convulsive contraction,
which  immediately strikes the eyes;  but a  slow, antiperistaltic
action;  and that the only convulsive movement is the contraction
of the cesophagus, which drags  the stomach  upwards.
   Maingault, besides, adduces various considerations in favour of
his deductions.  If the stomach, he asks, be  passive, why does it
possess  nerves, vessels, and  muscular  fibres?  Why  is vomiting
more energetic, when the stomach is pinched nearer  to its pyloric
orifice ?   Why are the rugae of the mucous membrane of the sto-
mach, during vomiting, directed in a divergent manner from  the
cardiac  and pyloric orifices towards the middle portion of the  or- 
VOMITING.                       525
gan ? If the diaphragm does all, in the act of vomiting, why do we
not vomit whenever the diaphragm contracts forcibly?  Why does
not the diaphragm produce the discharge of urine in paralysis of
the bladder ?  Why is vomiting not a voluntary phenomenon ? and,
lastly, how is it that vomiting occurs in birds, which have no dia-
phragm?
  The minds of physiologists were of course  distracted by these
contradictory results.  Richerand embraced the views of Magen-
die; and affirmed, that he had never observed contraction of the
stomach; and that it seemed to him the least contractile of any part
of the intestinal canal.   With regard to the experiments of Main-
gault, he considered that the stomach had not been wholly sepa-
rated from the surrounding muscles; that the action of the pillars of
the diaphragm, and the spasmodic constriction of the hypochondres
are sufficient  to compress the viscus; that, besides, nothing is more
difficult to effect than the section  of the phrenic nerves, below their
last root; and, moreover, such section does not entirely paralyze the
diaphragm, as the muscle still  receives twigs from the  intercostal
nerves and the  great sympathetic;  that the cardia, being more ex-
panded than  the pylorus, the  passage of substances  through it is
rendered easy;  and  that it is incorrect to say, that the cardiac ori-
fice, during inspiration, is closed between the pillars of the diaphragm.
Again, to object that, according  to the  theory of Magendie, vo-
miting ought to be a voluntary phenomenon, is a feeble argument;
for it is admitted, that  the muscles, which, at  the time, compress
the stomach, act convulsively.  If the diaphragm, in paralysis of the
bladder, cannot effect the  excretion of the urine, it is because that
reservoir  is  not favourably  situated, as regards the muscle: and,
lastly,  the arguments deduced from birds, which are  capable of vo-
miting, although they have no diaphragm, is also insufficient; for it
is not  absolutely necessary that it should be a diaphragm, but any
muscle, which can compress the stomach.
   When the  memoir of Maingault was presented  to the society
of the Faculti de  Midecine, M.  Legallois and Professor Be-
clard were named  reporters.  The experiments were repeated  be-
fore them by  M. Maingault,  but, instead of appearing contra-
dictory to those of Magendie, these gentlemen declared that they
were not sufficiently multiplied,  nor sufficiently various, to lead to
any positive conclusion.  MM.  Legallois and Beclard, subse-
quently, repeated those experiments; varied  them, and instituted
others; from which they deduced corollaries, entirely conformable
to those of Magendie.
   Begin boldly  affirms," without fear of being contradicted  by
facts, that there is no direct or  authentic experiment, which de-
monstrates the  activity of the stomach during vomiting:"—and he
adds, " I have repeated the greater part of the experiments of Ma-
gendie; he has performed all, in presence of a great number of spec-
tators, of whom I was one; and  I can say, with the commissioners 
526
DIGESTION.
of the Acadimie des Sciences, that I have seen,examined,.touched,
and my conviction is full and entire."   Still there are  many emi-
nent physiologists who hang on to the idea, that the stomach is the
main agent in vomiting; and amongst these is Broussais.  He ma-
nifestly, however, mixes up the phenomena of  regurgitation with
those of vomiting; which,  we have  endeavoured to  show,  are
distinct
  On the whole, we are perhaps justified in concluding,  that the
ancient doctrine, regarding vomiting, is full of error, and ought to
be discarded;—that the stomach is, of all the organs concerned, the
one  whose action  is the least energetic and  necessary,—that the
pressure, exerted on the parietes of the stomach by the diaphragm
and abdominal muscles, is the most powerful  cause,—and that the
more or less complete paralysis of the  diaphragm or the  destruction
of the abdominal muscles renders vomiting much  more feeble and
slow in manifesting itself.
  The order of the phenomena seems'to be as follows:—The brain
is affected directly  or indirectly by the cause exciting vomiting; by
the brain, the diaphragm  and abdominal muscles  are thrown into
appropriate contraction,and press upon the stomach; this organ pro-
bably contracts from the  pylorus towards  the cardia; and, by the
combination of efforts, the contents are propelled  into the cesopha-
gus, and out of the mouth. These efforts are repeated several times
in succession, and theri cease,—at times, to reappear.
  Whilst the rejected matters pass through  the pharynx and mouth,
the glottis closes; the velum  palati rises and becomes horizontal, as
in deglutition; but, owing to  the convulsive action of the  parts, these
apertures are less accurately  closed, and more or less of the vomited
matter passes into the larynx or nasal fossae.   On account of the
suspension of respiration impeding the return  of blood from  the
upper parts of the body, and partly owing  to the force, with which
the blood is propelled by the arteries, the face is flushed or livid,
the perspiration flows in abundance,  and  the secretion of tears is
largely augmented.
end of vol. i. 
 
 
 
NLM023328590