HUMAN
PHYSIOLOGY;
ILLUSTRATED BY ENGRAVINGS.
                ROBLEY   DJUNGLISON,   M. D.

PROFESSOR OF MATERIA MEDICA, THERAPEUTICS, HYGIENE AND MEDICAL JURISPRUDENCE IN
      THE UNIVERSITY OF MARYLAND J ONE OF THE PHYSICIANS TO THE BALTIMORE
           INFIRM  ARY ; MEMBER OF THE AMERICAN PHILOSOPHICAL SOCIETY,
                                    ETC. ETC.
; Vastissimi studii primas quasi lineas circumscripsi."—Haller.
SECOND   EDITION,
WITH NUMEROUS ADDITIONS AND MODIFICATIONS.
IN  TWO VOLUMES

       VOL.  I.      ;
Co
                                                t
             PHILADELPHIA:
C*AREY,  LEA  &  BLANCH ARD.
1836.
V 

    32UtCVCtf> according to the Act of Congress, in the year  1835, by Roblky
Dunglison, in the  Clerk's Office  of the  District  Court of the Eastern District of
Pennsylvania. 
TO
                     JAMES  MADISON,

              EX-PRESIDENT OF THE UNITED STATES, &C &C

  Alike distinguished  as an illustrious  benefactor  of 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 testi-
mony  of  unfeigned respect for  his talents and  philanthropy,  and  of
gratitude  for  numerous evidences  of friendship,  by  his obedient and
obliged servant,
                                                 THE AUTHOR. 
 
PREFACE TO THE SECOND EDITION.
  The flattering reception, which this work has  met with from the pro-
fession, demands the grateful acknowledgments  of the Author, and his
utmost  zeal to render the work still more worthy of favour.  lie has,
accordingly, endeavoured to add to this edition whatever of importance
has been published since the appearance of the first edition in this coun-
try, and in the different  countries of Europe, on the various topics which
the work embraces; to deduce correct inferences from them, and to make
such alterations and improvements as suggested themselves on revision.
That  these have not  been to a trifling extent may be appreciated by a
comparison of this with the former edition.
  Kor the favourable notices, which have been taken of the work in the
different periodicals, the Author is sincerely thankful.   He has, on many
occasions, profited greatly by their strictures and suggestions.
  The Author cannot conclude this brief preface without congratulating
the profession, and the community in general, that the venerable patriot,
to whom he had the honour to dedicate the first edition, is still preserved
to his country; and it is  with  no little gratification,  that he embraces
another opportunity for expressing those sentiments, which he so  warm-
ly entertains for that distinguished individual.
Baltimore, Dec. 1, 1835. 
PREFACE TO THE FIRST EDITION
  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 Physiology," as it has been, not
inappropriately, termed.
  Of late,  the study  of Physiology  has become  much  more common
both with the professional  and unprofessional  inquirer.   The  necessity
for  studying  man physically, as well as morally, has been strongly in-
culcated  by some of the best writers on morals and legislation;  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 offer a view
of the  existing state of the science rather  than to  strike out  into  new,
and perhaps devious, paths.  To the labours of Adelon and Chaussier,—
especially of the former,—of Blumenbach, Richerand, Magendie, Ru-
dolphi, Broussais, Sir Charles 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 graphic delineations of the  last mentioned dis-
tinguished  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
unexceptionable  in certain  other  respects, as is  desirable;  but their
general execution reflects  credit upon Mr. Drayton, under whose super-
intendence they  were engraved.
  The author has to regret his not having seen a copy of the " Principles
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 not  reach him
in time to be available. 
CONTENTS OF  VOL.  I.
 Preliminary Observations
 Of Natural Bodies        ....
       Difference between Inorganic and Organized Bodies
       Difference between Animals and Vegetables
 (ir.NEriAL Physiology of Man
 On the Material Composition of Man
       I. Organic Elements that contain Azote
       II. Organic Elements that do not contain Azote .
       Of the Solid parts of the Human Body
       Of the Fluids of the Human Body
       Of the Elementary Structure of Animal Substances
       Physical Properties of the Tissues
 Of th>: Functions of man
       Table of the  Functions                 .

                                CLASS I.

 Animal Functions, or  Functions  of Relation
 Of Sensibility, or the Function of the  Sensations
       Of the Nervous System
 Physiology of Sensibility  .....
       Of the Sensations      ....
 External Sensations      .....
 Sect. I.—Sense of Tact or Touch   .
      Anatomy of the Skin, Hair, Nails, &c
      Physiology of Tact and Touch       .      .
 Sect. II.—Sense of Taste or Gustation
      Anatomy of the Organs of Taste
      Of Savours        .....
      Physiology of Taste   ....
Sect. III.—Of the Sense of Smell, or Olfaction
      Anatomy of the Organ of Smell
      OfOdours       .....
      Physiology of Olfaction
Sect. IV.—Of the Sense  of Hearing or Audition
      Anatomy of the Organ of Hearing 
CONTENTS.
      Of Sound   .....
      Physiology of Audition
Sect. V.—Of the Sense of Sight, or Vision
      Of Light      .....
      Anatomy of the Organ of Vision
      Accessory Organs     ....
      Physiology of Vision
      Phenomena of Vision  ....
Internal Sensations       ....
Of the Mental Faculties, &c.        ...
      Physiology of the Intellectual and Moral Faculties
Of Muscular Motion, especially of Locomotility or Voluntary Motion
      Anatomy of the Motory Apparatus
      Of the Muscles        ....
      Of the Bones     ....
      Table of the Bones    ....
      Physiology of Muscular Motion
Of the Attitudes      .....
Of the Movements        ....
Locomotive Movements      ....
      Walking   .....
      Leaping      .
      Running   .....
      Swimming    .....
      Flying     .....
Of the Function of Expression or of Language
Of the Voice      .....
      Anatomy of the Vocal Apparatus
      Physiology of the Voice  .
      Timbre, or Quality of the Voice
      Of Natural or Inarticulate Language
      Of Artificial or Articulate Language   .
      Of Singing        ....
Of the Gestures
	PAUE
	132
	137
	152
	153
	163
	. 173
	179
	197
	243
	. 246
	263
Motion	299
.	299
	. 299
	306
	. 310
	313
	. 361
.	367
	. 370
	370
	. 372
	374
	. 374
	378
	. 380
	380
	. 380
	384
	. 398
	406
	. 407
.	419
	. 421
                                CLASS II.

Nutritive Functions
Of Digestion
      Anatomy of the Digestive Organs .
      Of the Food of Man
      Physiology of Digestion
      I.  Digestion of Solid Food
      II. Digestion of Liquids
Of Eructation, Regurgitation, Vomiting, &c.  .
438
438
438
462
472
473
533
537 
HUMAN   PHYSIOLOGY.
PRELIMINARY   OBSERVATIONS.
                        OF 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 the organized, and forming a rigid and unbroken series.
   Crystallization has  been esteemed 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 mam-
 malia—from his Maker, they  have conceived  to  be occupied, in
 succession, by beings  of gradually increasing intelligence.
   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  catenation can-
 not 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.                        2 
10
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■  JXatural
Science.  Organized bodies have properties in common  with the in-
organic,  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 par-
ticles being merely in a, state of  aggregation, and their  motions are
regulated by certain fixed  and invariable laws.  The animal and the
vegetable, on the other hand, are the products of generation; they
riiust 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 has appeared, in their case, to warrant 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.                 11

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,  thorinium, aluminium, ..yttrium,
glucinium,  magnesium, calcium, strontium,  barium,  sodium, po-
tassium,  lithium,  manganese,  zinc,  iron, tin, arsenic,  molybdena,
tungsten, columbium, chromium, antimony, uranium, cerium, cobalt,
titanium, bismuth, cadmium, copper, tellurium, lead, mercury, nickel,
osmium, rhodium, 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 con-
sist of but one element; and, when composed of more, the combina-
tion is rarely higlier 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 oxy-
gen, carbon, and hydrogen; the simplest animal, of oxygen, hydro-
gen, 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;  com-
pounds are formed to  be again decomposed, and this happens from
the earliest period of foetal 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 chemis-
try.   In the former, it  means a substance, which, in the present 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-eight years  since the alka-
lies were found to be composed of  two elements.  Previously, they
were considered simple.  In the animal and  the vegetable, we find
substances, also called elements, but with the epithet organic, because
only found in organized or living bodies, and therefore the exclusive
products of organization and life.  For example, in both animals and
vegetables  we  meet with  oxygen, 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 constitute the various  organs, and which,  there- 
12
NATURAL BODIES.
fore, have been termed organic elements or compounds of organiza-
tion;  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  chemical affinities; but, in the  organized,
the formation is produced  by the force, that presides over  the forma-
tion 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 set 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, which is 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 organ-
 zed body.  If we  break  the branch from a  tree, the stem  itself
participates more or less in the injury; the detached branch speedily
undergoes  striking changes;  it withers; becomes shrivelled, and, in
the case of the succulent vegetable, undergoes decomposition; a por-
tion of its constituents, no longer held in control by the vital agency,
enters into new combinations, is  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, un-
controlled, 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,—established  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
structure; and we readily discover, that it consists of various parts;
—in the vegetable, of wood, bark, leaves, roots, flowers, &c; and in 
INORGANIC AND ORGANIZED.
13
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  in 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.
   Characteristic differences exist in the nature of the  exterior of
the two divisions, as well as in  their mode of increase.   Inorganic 
14
NATURAL BODIES.
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 inservient
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, that is, 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 developement 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,—circumstances premonitory of 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  kingdoms 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.
   Such are the chief distinctions to be  drawn between  the two
great divisions of natural bodies,  the inorganic  and the organized. 
ANIMALS AND VEGETABLES.
15
By the comparison which has been instituted, the  great  objects of
physiology, the phenomena of life, have been indicated.   To inquire
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
wc 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, plastic, or organic—nutrition and reproduction for exam-
ple.   But vegetables are endowed with these only.  All organized
bodies must necessarily have the  power of assimilatingjbreign mat-
ters to their own substance, and 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 con-
dition is called animality.   This division  of the functions into animal
and organic  has been adopted, with more  or less modification, by
the generality of physiologists.
   Between animals and vegetables, that are situated high in their
respective classes, no error can possibly  be  indulged.   The charac-
ters 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 animal;
and it is  not until of modern date, that the sponge  has been uni-
versally 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 immova-
ble as the lichen is to the  slate, and almost  equally deficient in the
 usual characteristics of animality.  In  general, however,  wre 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 ad-
 dition by the animal; yet there are many animal substances, as we
 shall see, that contain  no  azote.  Plants  have scarcely any; 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 
16
NATURAL BODIES.
 a vegeto-animal matter have been detected by the chemist, but they
 have only been traces.  In consequence of this  difference of com-
 position, animal substances  are  easily known  from vegetable by
 burning;—a fact, which, as Dr. Fleming has remarked,  is interest-
 ing 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, of coral, or other zoophytic 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 observable.
 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 vesicles, 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.   This
 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 ani-
 mals are devoid of muscular and nervous tissues, of splanchnic cavi-
 ties, and apparently of vessels, and distinct organs; whilst Messrs.
 Dutrochet, Brachet,  and others,  admit the existence  of a  rudi-
 mental nervous system, even in vegetables.
  3. Sensation  and voluntary motion.—One manifest distinction ex-
 ists  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 body or any of its parts at the will of the being  Veffe-
tab les are possessed of spontaneous, but not of voluntary motion.
Of the former we have numerous examples  in the  direction of the 
ANIMALS AND VEGETABLES.
17
branches and upper surfaces of the leaves, although repeatedly  dis-
turbed, 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 experiences all the de-
sires 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 exter-
nal 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
towards the Gulf of Florida, is the almost interminable quantity of the
Fucus nutans, Flatnda 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, Mimosa  pudica, the
various leaflets collapse in rapid succession.  In the barberry bush,
Berberis vulgaris, we have another  example of the possession of  this
faculty.  In the flower, the six stamens, spreading moderately,  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 con-
cussion be  given to  the whole.  After awhile, 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  contractility
or irritability, the nature of which will fall under consideration here-
after.  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 animal without
  VOL.  I.                        3 
18
NATURAL BODIES.
consciousness, and therefore necessarily without volition. It is exei ted
in the heart, in the muscular tunic of the intestines,—in every muscle,
indeed, of involuntary, as well as of voluntary motion.  Its existence
in the vegetable does  not,  consequently,  demonstrate  that  it  is
possessed of consciousness; and we can hence understand, how cer-
tain 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 supplies
from the materials around, and in contact with it; and the absorbing
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 re-
ceived into a  central organ, or  stomach, for the purpose of under-
going changes, by a  process termed digestion, which adapts it for
the nutrition of the individual.  The absorbing vessels of nutrition
arise, in this case, from the  internal or lining membrane  of the ali-
mentary 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  animalibus
ventriculus,  ventriculus sicut  humus" Mas an aphoristic  expression
of universal  reception.  With similar feelings, Boerhaave asserts,
that animals have their roots of nutrition in their intestines;  and Dr.
Alston has fancifully termed a plant an inverted 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 vary in the two kingdoms.  In the plant, the super-
fluous 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 be-
tween 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
hand, the approximation of the sexes is always voluntary,  and effect-
ed consciously—the birth of the new individual being not only per-
ceived, but  somewhat aided by  volition.  Fecundation alone  is
involuntary and irresistible.
   Again, in the vegetable the sexual organs do not exist at an  early 
ANIMALS AND VEGETABLES.                  19
period,  and are  not developed  until reproduction is  practicable.
They are capable of acting for once only, and perish after fecunda-
tion ;  and if the plant be vivacious, they fall off after  each repro-
duction, and are annually renewed.  In the animal, on the contrary,
they exist from the earliest period of foetal developement, 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 incapable
of constant, unremitting exertion.   Sleep, therefore, becomes neces-
sary.   The  animal is also capable of expression or of language, 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 characteris-
tics as they at first appear.   There are many animals, which are as
irresistibly  attached to the  soil as the vegetables themselves.  Like
the latter, they must, of necessity, be  compelled  to absorb their food
in the state m which it is presented to them.  Sensibility and loco-
motility appear, in the zoophyte, to be no more necessary than in the
vegetable.   No nervous, no muscular system is required;  and, ac-
cordingly, none can be traced in them;  whilst many of those spon-
taneous motions of the vegetable, which have been  described, have
been  considered by some to indicate the first rudiments of sensibility
and locomotility: and Linnaeus has  regarded 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. 
20
             GENERAL PHYSIOLOGY  OF MAN.


   The observations made on  the difference between animals and
 vegetables have anticipated many topics, which would  require con-
 sideration under this  head.  Those general properties which man
 possesses, along with other animals, have been referred to in a cur-
 sory manner.  They will now demand a more special investigation.

               ON THE MATERIAL COMPOSITION OP 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 vertebra, with the skull as a  capital—itself
 regarded as a vertebra by De Blainville.  This base 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  abdomen,
 thorax, and head.   These contain the most  important organs of the
 body—those  that effect the functions of  sensibility, digestion, respi-
 ration, circulation, &c.  The head comprises the face, which con-
 tains the organs of four of the senses—those  of sight, hearing, smell,
 and  taste,—and the cranium, which lodges the  brain—the organ of
 the mental manifestations, and the most elevated part of the nervous
 system.  The thorax or chest contains the lungs—organs of respira-
 tion—and the heart, the great organ of the circulation.  The abdomen
 contains 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 instruments 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, emanating  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 them, and  convey the  blood back
to the heart—the veins;  whilst a third set  communicate also with 
MATERIAL COMPOSITION OF MAN.
21
 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 inor-
 ganic, and the organic, which are compound, and formed only un-
 der the principle of life.
   The chemical or inorganic elements, met  with, are—oxygen, hy-
 drogen, carbon, azote, phosphorus, calcium; and, in smaller quanti-
 ty, 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—that is, 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 has been caught.   Carbonic  acid has been detected
 in an uncombined state  in  urine, by Proust, and by Vogel  in the
 blood.  Carbonic acid gas likewise exists  in the intestines  of ani-
 mals ; 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 car-
 bonic acid.
   4. Azote.—This gas is likewise widely distributed  as a component
 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 uncom-
 bined state, in the swim-bladder  of certain fishes.
   5. Phosphorus is found united with oxygen—in the state of phos-
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,
 ammonia, and magnesia, in  other parts.  It is supposed to give rise 
22
MATERIAL COMPOSITION OF MAN.
to the luminousness of certain animals—as of the fire-fly, the Pyro-
soma 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 falla-
cious grounds, that this gas is the vehicle of the contagious principle
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 considered
to be, in  the first of these fluids, in the  state of phosphate or sub-phos-
phate.  Berzelius,  however,  showed, that this  was nQt the case;
that the ashes of the colouring matter always yielded  oxide of iron
in the proportion of 1-200th 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 che-
mist, 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 mu-
riatic 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.  Children
has made similar observations,  and Messrs. Tiedemann and Gmelin,
Professor Emmet,  and the author have found it in considerable quan-
tity, in the healthy gastric secretions of man.
   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, carbonic,
and sulphuric acids. 
ORGANIC ELEMENTS.
23
  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 somS other parts, but always in combination  with the  phos-
phoric acid.

  The organic  elements, proximate principles, or compounds of
organization are the primary combination of two or more of the ele-
mentary  substances, in definite proportions.  Formerly, four only
were admitted—gelatine, fibrine,  albumen, and oil.   Of late years,
however, organic chemistry has pointed out numerous others, which
are divided into  two classes—first, 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 secondly, 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, sugar of  dia-
betes, picromel,  the colouring principle of the bile, and that of other
solids and liquids.

              I.  Organic Elements that contain Azote.

   1. Albumen.   This is  one of the most  common organic constitu-
ents, 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 mem-
brane, and in the synovial secretion.  It is colourless  and transparent,
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 elas-
tic ; insoluble in water, alcohol, or oil, but readily soluble in alkalies.
   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, in some form
or other, the great  constituent of tumours.
   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
in acids and alkalies; insoluble  in alcohol, ether,  and  in the fixed 
24                material composition of man.

and volatile oils.  Alcohol precipitates it from its solution in water.
It  consists of carbon, 47.881; hydrogen,  7.914; oxygen, ^l.zm,

^GeTat^/ne'ariy in a pure  state, forms ti* air-bag of different
kinds of fishes,  and is well known under the name of isinglass.
It is used also extensively in the arts, under the  forms of glue and
size,  on account of its adhesive quality.  What is  called portable
soup is dried jelly, seasoned with various spices.
  3.  Fibrine.—This proximate principle exists in the chyle; enters
into  the composition of the blood ; forms the chief part of muscular
flesh, and  may be looked upon  as one of the most abundant  animal
substances.   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
washings with  cold water.  Fibrine is solid, white, flexible, slightly
elastic, insipid, inodorous, and heavier  than  water.  It is  neither
soluble in  water, alcohol, nor acids; it 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 buffy 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 frag-
ments, is macerated  in successive portions of cold water, the albu-
men, 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 consist-
ence of ari 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 boiling point,—and by not forming a jelly when its solution
is concentrated by evaporation.
  Osmazome exists in the muscles  of animals^n the  blood, and in
the brain.  It gives the peculiar flavour of meat to soups ; and, ac-
cording 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 according
to the source whence it is derived.   Its leading characters may be
exemplified in that derived from the nostrils, wriich has the following
properties.—It is  insoluble  in alcohol  and water,  but imbibes a
little of the latter, and becomes transparent.   It is neither coagu-
lated by heat, nor rendered horny;  but is coagulated by  tannin.
   Mucus, in a liquid state, serves as a protecting covering to diffe-
rent parts.   Hence  it differs somewhat  in its  characters, accord- 
ORGANIC ELEMENTS.                      25
ing to the office it has to fulfil.  When inspissated, it forms, accord-
ing 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, p.,' horny parts;  and it is contained in considera-
ble 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 coagulated;  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 substance, insoluble
in water, but readily soluble in the alkalies, especially in ammonia.
It  possesses considerable analogy with albumen.  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 they are in a state of health.   In human urine it is
less abundant  after a meal,  and it nearly  disappears in diabetes, and
in affections 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, in the excrements of the
silk-worm, and  very  frequently in urinary calculi.  It is obtained
by dissolving  any  urinary calculus which contains it, or the sedi-
ment of human urine, in warm liquid  potassa, and precipitating  the
uric acid by the muriatic.   Pure  uric acid is  white, tasteless, and
inodorous.  It is insoluble 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
observed, that Engelhart and Rose, German chemists, had detected
iron in the red globules of the blood, and had not found it in the other
principles  of  that  fluid.  It has been considered probable,  there-
   vol. i.                       4 
26
MATERIAL COMPOSITION OF MAN.
fore, that  it has something to do with the colour.   Engelhart s ex-
periments have  not, however,  determined the manner in wmcn 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 colouring 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 pre-
pared, the colouring particles are  no  longer of a bright red colour,
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 tempera-
ture between 167° and 190°, the mass is tough, hard, and  brilliant.
   10.  Yellow colouring principle of the Bile.—This substance is pre-
sent in the bile of nearly all animals.   It enters into  the composition
of almost all  gall-stones, and is deposited in that organ  under the
form of magma.  It is solid, pulverulent when dry, insipid,  inodorous,
and heavier than water.  When decomposed by heat,  it  yields car-
bonate 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 cvsap,  suet,—the latter Elaine, or  Oleine, from eXaiov, 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  mut-
ton 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 pos-
sess the singular property of giving rise to phosphoric acid bV calci-
nation, without there being any evidence of an acid or  a  phosphate
in their composition.   They may be obtained by repeatedly boiling 
ORGANIC ELEMENTS.
27
the cerebral substance in alcohol, filtering at each time, mixing the
various liquors, and suffering them to cool:—a lamellated 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 dissolved, whilst the alco-
hol 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; has  been found by Professor Emmet
and the author to  be contained in  the gastric  secretions in  health,
and is one of the constant products of the putrid fermentation of ani-
mal or vegetable substances.  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;  oxvgen, 20.02; hydrogen,
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 the 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 chem-
ists.  Berzelius himself, indeed, now considers  it to be  acetic acid,
disguised by animal matter; and Tiedemann and  G'ntelin are of  the
same opinion.
  7. Sugar of milk.—This substance is so called, because it has a
saccharine  taste, and exists only in 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 commonly
crystallizes in regular parallelopipedons, terminated by pyramids with
four faces.   It is white, semi-transparent, hard, and of a slightly sac-
charine taste,  and is  formed of carbon, 38.825; oxygen, 53.831; and
hydrogen, 7.341.
  8. Sugar of diabetes.—In the disease, called diabetes melitus,  the
urine, which is passed in enormous quantity, contains, at the expense of
the economy,  a large quantity of peculiar saccharine matter, which, 
28                MATERIAL COMPOSITION OF MAN.
 when properlv purified, appears identical, both in properties and com-
 position, with vegetable sugar, approaching nearer to the sugar of
 grapes than to that of the cane.  It is obtained in an irregularly crys-
 talline  mass,  by evaporating diabetic  urine  to  the  consistence of
 syrup, and keeping it in a warm place for several days.   It is puri-
 fied by washing in  cold, or, at  the  most, gently heated alcohol, till
 the liquor comes off colourless, and then dissolving 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 patients, of the specific
 gravity 1.034, afforded a straw-coloured extract, 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 por-
 tion 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 analy-
 sis of Gay Lussac and  Thenard, this sugar consists  of hydrogen,
 7.341;  carbon,  38.825 ;  oxygen, 53.834.
   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 filtered liquor by the  subacetate 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, sul-
 phuretted hydrogen is  passed to separate the lead;  the solution is
 then filtered, and the acetic acid driven off 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 is ob-
 tained, which  has both a bitter and a sweet taste, and yields a pre-
 cipitate 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, 43.651
and hydrogen, 1.82                                   jh  > 
SOLID PARTS.
29
  10. Colouring principle of the bile.—Of the nature of this princi-
ple, which exists in the bile of different animals, we have no definite
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 them, and  to investigate their properties; but all the in-
formation 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 textures might
exhibit very different chemical characteristics, could  our researches
be directed  to them under those circumstances.   Whenever, there-
fore, the physiologist has to apply chemical elucidations  to opera- ""
tions 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 affections 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-
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 
30                MATERIAL COMPOSITION OF MAN.

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; lometimes 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 pro-
longation, inter articular cartilages, and cartilages of ossification.
  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 division,
by some anatomists, into ligaments of the bones—as the ligaments of
the joints, and into  ligaments of muscles—as the tendons and apo-
neuroses.
  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,) chyliferous, lymphatic, and
secretory vessels.
  6. The nerves  are solid cords,  consisting of numerous fasciculi.
These are connected with the brain, spinal marrow, or great sym-
pathetic ; and they are the organs by which impressions are conveyed
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 ner-
vous filaments.   The term is  likewise  applied,  by many  modern
anatomists, to a similar interlacing of the ramifications of a lympha-
tic vessel.   Ganglions may, consequently,  either be nervous or vas-
cular; and the latter, again, may be  divided into  chyliferous or lym-
phatic, according  to  the kind of vessel in which they may appear.
Professor Chaussier, a distinguished  anatomist and physiologist,
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
gland, the thyroid gland, &c.
  8. Follicles or crypts  are secretory organs,  shaped like  mem-
branous ampullae  or vesicles, always seated in the substance of one
of the outer membranes of the body—the skin or  the mucous sur-
faces, 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. 
SOLID PARTS.
31
  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 are 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.
   Sdly. 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 serofibrous, as the pericardium ; sero-mucous,
as the gall-bladder, at its lower part;  and fibro-mucous, as the ureters.
   In  the view of Raspail, the truly simple  animal membrane  is the
parietes  of a vesicle.  In this state of simplicity it is so transparent,
that it is only perceptible by the plaits or folds it forms on being
moved, but if it were a compound membrane, the rays of light would
be reflected.   On this ground he disputes the accuracy of the observa-
tions of Sir Everard Home, Edwards, and others, maintaining that the
pretended globules, seen  and figured by them,  were optical illusions,
produced by the play of  light on the  different folds of the membrane.
   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, lamellas, 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. 
32                MATERIAL COMPOSITION OF MAN.
   This circumstance led the ancients to endeavour  to  discover an
 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 demonstration, and
 that it is visible only  to  the "mind's  eye,"—"invisibilis  est ea fibra,
 sola mentis acie  distinguimus."  It must be regarded, indeed, as a
 pure abstraction;  for, as different animal substances have different
 proportions of carbon, hydrogen, oxygen and azote, it is fair to con-
 clude, 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 '
 anatomical elements, are usually admitted,—the cellular or laminated,
 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 organ-
 ized 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 assem-
 blage of thin laminae of delicate, whitish, extensible filaments, inter-
 lacing 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.
            Prochaska, a  distinguished  anatomist of Vienna, main-
            tains, that the ultimate  fibre or  filament of  muscular
            tissue is discernible; that it is, in every part, of the same
             magnitude—about Tyh part of the  diameter of the red
            globule of the blood, or about ^fWh part of an inch
            in diameter.  It is probable, however,  that were our
            means of examining minute objects  still  further  im-
            proved, 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.
33
of membranous expansions or muscular  coats, differ from  proper
muscles chiefly in the mechanical ar-            Fig. 3.
rangement of their fibres. (Fig. 3» a Sf
b.)  The physical and chemical char-
acters  of both  are  identical.   The all
fibres, instead of being collected into  MM
fasciculi, are in layers, and, instead of
being 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  transmitting  impressions  to  the
mind.  Of it, the  brain, cerebellum, medulla  spinalis, nerves and
their ganglia are composed.  The ultimate nervous filament is con-
sidered by Fontana, Reil, and others, 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  anatomist 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 com-
pound 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 externally, and
cartilaginous at its extremities.
   Bichat was  the first anatomist, who possessed ajry clear  views
regarding the constituent tissues of the animal frame; and whatever
merit may accrue to after anatomists and physiologists, he is entitled
to the credit of having pointed out the path, and facilitated the la-
bours of the anatomical analyst.   The following table exhibits the
compound tissues generally admitted.
Systems.
vol. I.
1.  Cellular.

2.  Vascular
3.  Nervous
4.  Osseous.
Arterial.
Venous.
Lymphatic.
Cerebral.
Ganglionic. 
34                MATERIAL COMPOSITION OF MAN.
5.  Fibrous
                               ( Fibrous.
                             .  ) Fibrocartilaginous.
                               ( Dermoid.
                               I Voluntary.
6.  Muscular                  -  j Involuntary.
Systems. <  7.  Erectile.
            8.  Mucous.
            9.  Serous.
                                           c PHeous.
           10.  Corneous or Epidermic     -  j Epidermoid.
           11.  Parenchymatous      -     -    Glandular.

  In combining to form the different structures, the solids are  ar-
ranged in a variety of ways.  Of these,  the chief are in filaments or
elementary fibres, tissues, organs, apparatuses, and systems.
  The filament, we have seen, is the elementary solid.  A fibre con-
sists of a number of filaments united together.   Occasionally, this is
called a tissue:—the term tissue usually, however, means a particu-
lar  arrangement of fibres.   An organ is a compound of several tis-
sues.  An apparatus  is an assemblage of organs, concurring to the
same end:—the digestive apparatus consists of the  organs of mas-
tication, insalivation, and deglutition, of the stomach, duodenum, pan-
creas, 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 ap-
paratus.  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 the 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.  When we first see the
embryo, it appears to be almost entirely fluid.   As it becomes gra-
dually developed, the solid parts  increase in their relative propor-
tion, until the adult  age;  after which the proportion  becomes less
and less as the individual advances in life.  During the whole of ex-
istence, 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.  Rich-
erand says, that they are in the ratio of six to one; Chaussier, of nine 
FLUIDS.
35
to one.  The latter professor put a dead body, weighing one hundred
and twenty pounds, into a heated oven, and dried it.   After desicca-
tion, 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 was too high.  In the Egyptian mummies, which are com-
pletely deprived of fluid, the solids are extremely light, not weigh-
ing 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, as well
as the dried preparations of the anatomical theatre, afford additional
instances of this reduction by desiccation.  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 1830, 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 had formerly been 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, and  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  hali-
tus 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  pitu-
ita, and atrabilis; and each of these was conceived to abound in one
of the  four ages, seasons, climates, or temperaments.  The blood
predominated in youth, in the  spring, in cold mountainous regions,
and in the sanguine or inflammatory temperament.  The  pituita or 
36
MATERIAL COMPOSITION OF MAN.
phlegm had the mastery in old age, in winter, in low and moist coun-
tries? and in the lymphatic temperament.   The bile predominated in
mature age, in summer, in hot climates, and in the bilious tempera-
ment;  and lastly, the atrabilis was the characteristic of middle age,
of autumn,  of equatorial  climes, and of the melancholic tempera-
ment.   This was their grand  humoral system, which has vanished
before a better observation of facts, and more improved methods of
physical and metaphysical investigation.   The atrabilis was a crea-
ture of the imagination; the pituitous condition is unintelligible to us;
and the doctrine of the influence of the humours on the ages, tem-
peraments, &c. is 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 arrange them,
according to their uses in  the economy, into 1, recrementitial fluids,
or those intended to  be again absorbed; 2, excrementitial, those that
have to be expelled from the body; and 3, those  which participate
in both uses, and are hence termed excremento-recrementitial.  BIu-
menbach divided them into crude humours, blood, and secreted hu-
mours, 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 humours
of the  body, all of which will have to engage attention hereafter.
  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  colouring  matter of the skin, the
colouring matters of  the uvea and choroid of the eye, the three hu-
mours  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  transpiration  the
pulmonary transpiration, the perspired humours of the digestive ap-
paratus, and those of  the urinary and genital organs.   In the female
during the time she is capable  of fecundation, a monthly exhalation
takes place,  called the catamenia, or menses; and, after deliverv, a
similar secretion occurs, called the lochia.
  4. Thefollicular fluids are—the sebaceous humour of the skin, the
cerumen, the humour of Meibomius, that  of the caruncula lachrv- 
ELEMENTARY STRUCTURE.
37
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, Cowper's
glands, &c.
  5. The  glandular fluids are—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
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 Leeuenhoek,
an  announcement that gave rise to much controversy, which  has
continued indeed till the present time, and has engaged the attention
particularly of Prochaska, Fontana, Sir Everard Home, Mr. Bauer,
the brothers Wenzel, Dr. Milne Edwards, MM. Prevost and Dumas,
Dutrochet, Hodgkin, Raspail, and others.
   The observations and experiments of Dr. Edwards especially have
occasioned  much interesting speculation and inquiry.  They may
perhaps be taken as the foundation on which the believers in the glo-
bular structure now rest their opinions.  The views of Dr. Edwrards
were first published in 1823, in a communication, entitled "Memoire
sur la structure  elementaire des principaux tissus  organiques  des
Animaux;" and in a second  article  in the Annales des Sciences
Naturelles, for December, 1826, entitled liRecherches microscopiques
sur la structure intime 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 through a powerful lens, it
seemed 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 same size, that is, about the titts^1 or
*?rWh of an inch in diameter;  (Fig.  4.)  separated  from each 
'i»
MATERIAL COMPOSITION OF MAN-
Fig. 4.
sect
                    other, and lying in various directions, cross-
                    ing and interlacing; some of the rows straight,
                    others bent, and some  twisted, forming lrre-
                    o-ular 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 smooth part  of  an  inch in  diameter.
                    Here,  however,  the  rows  of globules are
                    always  parallel.   The  fibres never  inter-
                    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 arrangement 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, Dr.
                    Edwards  differs materially from an accurate
                    and experienced  microscopic observer, Mr.
                    Bauer, who asserts that the cerebral globules
                    are of various sizes. (Fig. 6.)
                       From the results of  his own diversified ob-
                    servations, Dr. Edwards concludes, that "sphe-
                    rical corpuscles, of the  diameter of 3-^th 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, which 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 as-
tounding, it was affirmed, that the microscope proved it also to be
constituted of globules  exactly like those of  the animal, and of the
same magnitude,  ^-ennyth of an inch in diameter; hence, it was as-
sumed, that all organized bodies possess the same elementary struc-
ture, and of jiecessity, that the animal and the vegetable are readily
 
ELEMENTARY STRUCTURE.
39
convertible into each other under favourable circumstances, and that
they differ only in the greater or less complexity of their organiza-
tion.  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 in size,  it would by no means follow, that they
should be identical in intimate composition.
  The discordance, which 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 3'ear
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 series of
still smaller globules.
  Dr. Edwards, in his experiments, found that the  globules  of the
nervous  tissue, whether  examined in  the brain, in fhe spinal cord,
in the ganglia, Or in the nerves, have the  same shape and diameter,
and that no difference can be distinguished in them, from whatever
animal the tissue is 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 medul-
lary or nervous substance, which  is capable of becoming concrete
by the action of heat and of acids.  This structure, he remarks, is
strikingly evidenced in certain molluscous animals; and
he instances the small  pulpy nucleus, forming  the cere-  Fig. 7.
bral hemisphere  of the  Umax  rvfus,  and the  helix
pomatia, composed of  globular, agglomerated  cellules,
on  the^parietes of which a  considerable 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  elementary fibres, which enter into their composi-
tion, do  not consist  simply  of rows of globules, according  to  the
opinion of Edwards and others, but that they are cylinders of a dia-
phanous 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  situated internally. After detailing
this difference of structure between the brain and the nerves, the for-
mer consisting chiefly of nervous corpuscles, the  latter  chiefly of
cylinders or fibres, Dutrochet announces  the  hypothesis, which  ex-
hibits too many indications of having been formed prior to his  mi-
croscopic investigations,—that these cerebral corpuscles are destined
for the production of the nervous power, and that the nervous fibres
are tubes, filled with a peculiar fluid, by the agency of jvhich nervi-
 
40                MATERIAL COMPOSITION OF MAN.

motion is  effected.   For further developements of the analysis of
Crochet, the reader is  referred to tl/work itself, which  exhibits
all the author's ingenuity and  enthusiasm, but can scarcely be con-
sidered 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.
Hodo-kin.  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 deception;
and we have again to refer the most minute parts of the  cellular
membrane, muscles, and nerves  to  the striated or fibrous arrange-
ment.  A part  of the discrepancy  between- Messrs. Edwards and
Dutrochet may be explained by the fact of the former using an in-
strument  of greater magnifying power than the latter, who employ-
ed the simple microscope  only.  It has been observed,  that when
Dr. Edwards  used an ordinary lens, the arrangement of a tissue ap-
peared cylindrical, which,  with the compound microscope, was dis-
tinctly globular.  The discordance between  Messrs. Edwards and
Hodgkin  is reconcilable  with more difficulty.  On the whole sub-
ject, indeed, our minds 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 them-
selves, 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.
  Still more recently, M. Raspail has ranged himself amongst those,
who  consider, that the ultimate structure of all organic  textures is
vesicular, and that the organic molecule, in Its simplest form, is an im-
perforate  vesicle, endowed with the faculty of inspiring gaseous and
liquid substances, and of expiring again such of their decomposed
elements,  as it cannot assimilate;—properties, which he conceives it
to possess under the influence of vitality.
  Lastly, J. F. Meckel,  from his observations, infers, that all the
solids and fluids of the human body are formed  of two elementary
substances : first, of an amorphous matter, which is  concrete in the
former and fluid in the latter; and secondly, 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
amorphous substance, which, in the solids, serves as a bond of union,
and in which the globules  are immersed in the fluids.   This anato-
mist believes that the globules differ in shape, size, and number, in
different animals, and in different parts of the  same animal, and even
in the same part, according to age. 
PHYSICAL PROPERTIES OF TISSUES.
41
               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 inherent, are so disposed through
the body, as to be kept in a  state of distention by the mechanical cir-
cumstances 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. are, in this manner, 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
divided 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,
contractuitc de tissu, contractilite par dtfaut d''extension,  SfC
  The  other properties—-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 deve-
loped 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 nuchce, or the strong.
ligament, which passes from the spine to the head of the quadruped,
—are very extensible and elastic.
  Another physical property,, possessed  by animal substances, is a
     vol. i.                      6 
42                MATERIAL COMPOSITION OF MAN.

kind of  contractility,  accompanied with  sudden corrugation and
curling  This  effect,  which  Bichat terms racornissement, 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 eva-
poration 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 em-
ployment of such substances as hygrometers. According to Chevreul,
many of the tissues are indebted  for their physical properties to the
water they contain, or with which they are imbibed.  When de-
prived of this fluid,  they become unfit for the purposes for which
they are destined in life, and resume them as soon as they have re-
covered it.
   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 years.   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 areola? 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 within to  without: 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 con-
cluded, that whenever an organized cavity, containing a fluid, is im-
mersed 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 impul-
sion;"  and he conceives it to be a new power,—a " physico-organic
or vital  action."   Subsequent experiments  showed that a reverse
operation could likewise take place.  If the internal fluid was rarer
than the external, the  transmission occurred in  the  opposite direc-
tion.   To this reverse process, Dutrochet gives the name exosmose,
or " outward impulsion."
  Soon after the appearance of Dutrochet's essay,  similar experi-
ments were  repeated, with some modifications, by Dr. Faust, and by
Dr.Togno  of Philadelphia, and with like results. The fact of this im-
bibition and  transudation was singular and impressive ;  and, with so 
PHYSICAL PROPERTIES OF TISSUES.
43
enthusiastic an individual as Dutrochet, could not fail to give birth
to numerous and novel conceptions.   The energy of the action  of
both endosmose  and exosmose is  in  proportion, he asserts, to the
difference between the specific gravities of the two fluids; and also,
independently 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. Mitch-
ell, of Philadelphia, " on the penetrativeness of fluids," many of the
visionary speculations of Dutrochet have been sensibly animadverted
upon.   It is there shown, that  Dutrochet had asserted, in the teeth
of some of his most striking facts, that the current was from a  less
dense to a more dense fluid; and that it was from positive to nega-
tive, dependent not on an inherent power of filtration, a power always
the same when the same membrane is concerned, but modified at
pleasure by  supposed electrical  agencies.  This view was subse-
quently abandoned by M. Dutrochet, in favour of the following prin-
ciple.   It  is  well known  that porous  bodies, as sugar, wood,  or
sponge, are capable of imbibing liquids, with which they are brought
in contact.  In such case the liquid is not merely  introduced  into
the pores  of the  solid, as it  would  be into an empty space, but it
is forcibly absorbed, so that  it will rise to a height considerably
above its former level.   This  force is molecular, and is  the same
that we witness  in the phenomena presented by the  capillary tube,
which affords us the simplest case  of the insinuation of a liquid  into
a porous body.  This force alone  cannot, however, cause the liquid
to  pass entirely through the  body.   If a capillary tube, capable of
raising water to the height of six inches, be depressed,  so that one
inch only be  above the surface, the water will rise to the top of the
tube, but  no part of it will  escape.   Even if the tube be inserted
horizontally  into the side of  a vessel  containing water, the water
will only pass to the end of the tube.  The same thing occurs when
a liquid is placed in contact with one side of a porous membrane: it
enters the pores, passes  to the  opposite  side,  and is there arrested.
But if this membrane communicates with a second vessel containing
a different liquid—as a  saline solution, capable  of mixing with the
first, and affected to a different degree by the  capillary attraction—
then a new phenomenon will  be presented.   It will  be found  that
both liquids enter the pores, and pass through to the opposite  side.
They will not, however, be carried through with the same force;
that which has the greatest capillary ascension,—that is, which will
rise the  highest  in  a  capillary  tube,—will  pass  through  in  the
greatest quantity, and cause an accumulation of liquid in the opposite
side. 
 44                MATERIAL COMPOSITION OF MAN.

   The facts and arguments, adduced by Dr. Mitchell, clearly exhi-
 bit 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 ana-
 logous subject, to which, as M. Magendie has observed, little or no
 attention has been paid by physiologists—the permeability of mem-
 branes by gases.  " The lamina?,"  Magendie remarks, " of which
 membranes  are constituted, are so arranged that the gases can pene-
 trate 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  presides
 over one of the most important acts of life—respiration—and it con-
 tinues after death."
   Dr. Mitchell is the first individual, who directed his observation 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 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 common air was shut
 up in the  short leg, and was in communication with the membrane.
 Oyer this end, in the mercurial trough, was  placed  the vessel con-
 taining 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  compared the  gases with
 common air, and subsequently, by the same instrument, and in  bot-
 tles, with  each other, I was able to arrange the following gases ac-
 cording to their  relative facility of transmission, beginning with the
 most powerful:   Ammonia, sulphuretted hydrogen, cyanogen, car-
 bonic acid, nitrous oxide,  arsenuretted hydrogen, defiant gas  hy-
 drogen, oxygen, carbonic oxide, and nitrogen."
  He found  that ammonia transmitted  in  one minute  as much in
 volume as sulphuretted hydrogen did in two minutes and a half;
 cyanogen, in three minutes  and a quarter;  carbonic acid,  in  five
 minutes and a half;  nitrous oxide, in  six minutes and a half; arsenu-
\TltV?l^en-  m, twe?ty;Seven minutes and a ^lf; olefiant gas. in
twenty-eight minutes; hydrogen, in thirty-seven minutes and a half; 
PHYSICAL PROPERTIES OF TISSUES.
4.r>
oxygen, in one hour and fifty-three minutes; and carbonic oxide, in
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 gold-beater's skin, moistened so as to resemble
the natural state.   The same results, and in the same order, followed
as with the gum elastic.  The more fresh the membrane, the more
speedy and extensive was the effect; and in living'animals the trans-
mission 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 to  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 vis mortua. 
46                     FUNCTIONS OF MAX.
              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
[S)—that  it fulfils a special and  distinct  office in the economy, for
which it  has an organ or an instrument,  or an evident apparatus of
organs.
   Physiologists have not, however, agreed on the number of distinct
offices which are so performed; and hence the difference, in the num-
ber  and classification of the functions, that prevails amongst them.
   The oldest division is  into the vital, natural,  and animal; the vital
functions including those of such importance as not to admit of inter-
ruption, such as circulation, respiration, and the functions of the brain
and spinal marrow ; the natural functions including those that effect
nutrition,  as  digestion,  absorption and  secretion; and the animal,
those possessed exclusively by animals, as sensation, locomotion, and
voice.  This  classification is  the basis of that which generally pre-
vails at the present day.
   The character of this  work will not admit of a detail of every clas-
sification  which has been proposed by the physiologist; that of Bi-
chat, 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  -i
i)ie individual,  and functions  of reproduction, or life of the species.  *
Nutrition  requires  that  the being  shall  establish relations  around
him  to obtain the materials of which he may stand in need ;  and, in
animals, the functions, which  establish such relations, are under the
volition and perception of the being. Hence they are divided into two
sorts;—those, that commence or precede nutrition, consist of exter-
nal relations,  are dependent upon the will, and executed with con-
sciousness ; and those that are carried on within the body, spontane-
ously, and without consciousness.   Bichat adopted this basis,  and to
the  first aggregate of functions he  applied the  term  animal life,
because it comprised  those that characterize  animality;  the lat-
ter he called organic life, because  the functions comprised under it
are common to every organized body.  Animal life included sensation,
motion and expression; organic life, digestion, absorption, respiration,
circulation, nutrition, secretion, &c.
  In animal life, Bichat recognized two series of actions, opposed to
each other,  the one* proceeding from without and terminating in the
brain, or passing from circumference to centre, and comprising the 
FUNCTIONS OF MAN.
47
external senses ; the other, commencing in the brain and acting on
external bodies, or proceeding from centre to circumference, and in-
cluding the internal senses,  locomotion, and voice.  The brain,  in
which one series of actions terminates and the other begins, he con-
sidered the centre  of animal  life.
  In organic life he likewise recognized two series of actions; the
one proceeding from without to within, and effecting composition; the
other passing from within to withoujt, and effecting decomposition.
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 calori-
fication.   In the latter, that absorption, which takes up parts from the
body ; the circulation, which conducts those parts or materials 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 movements
of composition and decomposition; and,  as the heart is  the great or-
gan of the circulation, he considered it the centre of organic life ;
and, lastly, as the  lungs are  united  both with animal  life, in the re-
ception of air, and with organic life, as the organs of sanguification,
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, will be that  embraced by
Magendie; and, after him, by Adelon, who  has written one of the
best systems of human  physiology w7hich we possess.
   The first class, or functions of relation, or animal  functions, in-
cludes those  that  establish our  connexion with the bodies surround-
ing us ; the sensations,  voluntary motions and expressions.   The se-
cond class, or functions of nutrition, comprises digestion, absorption,
respiration, circulation, nutrition, calorification, and secretion, and the
third class,'the functions of reproduction,—generation.

                      Table of the Functions.

                                           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.
I. Animal or of Relation.
II. Nutritive
III. Reproductive. 
48
FUNCTIONS of man.
  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 develope-
ment, and the application of such developement to other departments
of medical science,  not immediately concerning the physiologist,—
and shall next detail what has been called the mechanism of the func-
tion, 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 ne-
cessary  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 ingenious;
others too fanciful to be indulged, by the reflecting, for a moment;
and, as might be expected, the number of these fantasies generally
bears  a direct proportion to the difficulty and obscurity  of the sub-
ject.   It will not be proper to pass over the most prominent of these,
but they will not be dwelt upon, whilst the results of direct observa-
tion and experiment will be fully detailed; and, where differences
prevail amongst observers, such differences will be attempted  to be
reconciled, where practicable.
   The functions, executed by different organs of the body, can be de-
duced by direct observation, although the minute and molecular ac-
tion, 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, and the vessels that convey it, ramifying in the texture of
the viscus, and becoming so minute as to escape vision, even  when
aided by a powerful microscope.  We find, again,  other vessels be-
coming perceptible, gradually augmenting in size, and ultimately ter-
minating in a  larger duct, that  opens into the small intestine.  If we
examine  each of these orders of vessels  in their -most minute appre- "i
ciable  ramifications, we discover, in the one, always blood, and,  in the
other,  always  a very different fluid,—bile.  We are hence led to
the conclusion, that in the intimate tissue of the liver, and in  some
part, communicating'directly or indirectly 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 oc-
cur 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, that the results, at which we arrive in this manner,
are by  no means the least satisfactory. 
FUNCTIONS OF MAN.                     49
  The forces that preside over the various functions are either gene-
ral,—that is, physical or chemical; or special,—that is, organic or
vital.   Some of the organs afford us examples of purely physical in-
struments.  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 station
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 explain-
ing on any physical or chemical principle, and  are  constrained to
esteem vital.
vol.  i.
7 
50
SENSIBILITY.--NERVOUS SYSTEM.
                        CLASS  I.

ANIMAL FUNCTIONS, OR FUNCTIONS OF  RELATION.

  The functions of relation consist, first, of sensibility, and secondly,
of muscular motion, including expression or language.  All these
actions  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 in-
fluenced 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 se-
cond, organic; the latter being common to animals and vegetables,
and presiding over the organic functions of nutrition, absorption, ex-
halation, secretion, &c.; the former 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 or-
gans, that are composed of the nervous or pulpy tissue.  In man, it is
constituted of three portions; first, of what has been called the cere-
brospinal axis, a  central part having the form of a  long cord, ex-
panded  at its superior extremity, and contained within the cavities
of the cranium and spine;  secondly, of cords,  called nerves, in num-
ber  thirty-nine pairs, according  to  some,—forty-two according 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 contents
of the cranium, namely, the  cerebrum or brain proper; the cerebel- 
OF THE TUTAMINA CEREBRI.
51
lum 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 natu-
ral position, we find that there are many distinct parts, and appear-
ances of numerous  and separate organs.  So various,  indeed, are
the prominences and depressions observable on the dissection 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 understood by the ana-
tomist.
   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
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 deranged, it was necessary that it should be securely
lodged, and protected from injuries.  Accordingly, it is placed  in a
round, 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, which  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 advantage
of, and an arrangement somewhat similar  to that which exists na-
turally on  the head, has been adopted  with regard to the helmet.
 The metallic  substance, of which the ancient  and modern helmets
 arc formed, is readily thrown into vibration ; which vibration, being
 communicated 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 hel-
 met worn by  the Roman soldier.
   There  can be no doubt»Jikewise, 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 
52
SENSIBILITY.--NERVOUS SYSTEM.
 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 which  have been passed
 upon  them  by Dr. Arnott,  the  greater part are admirably adapted
 for the contemplated  object.  It is  impossible, indeed, for  the unini-
 tiated to rise from the perusal of his interesting essay, without being
 ready to exclaim with the poet, " how wonderful, how complicate is
 man! how passing wonder  He that made  him such!"
    Sir Charles  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,—so called from  the bones seeming as if
 they were stitched together.  Each
 bone consists  likewise of two  ta-
 bles; an external, fibrous and tough,
 and an  internal, of a harder cha-
 racter and more brittle, hence called
 tabula vitrea. These two  tables are
 separated  from each  other by  a
 cellular  or cancellated   structure,
 called  diploe.  On examining the
 mode in which the tables form  a
junction with each other at  the su-
tures, we find additional evidences
of design exhibited.  The edses of        a  t. SkuU'
*U     ?  *  i_i        *u^ cugcs oi        A. The parietal bone.
the outer table are serrated, and so        B  The fr°*t*i  bone.
arranged as to be accurately dove-        £ ?S 2%%tt£Z.
tailed into  each other; the tough         E  The 8phenoid bone-
 
OF THE SKULL.
53
fibrous texture of the external plate being well adapted for such a
junction.   On the other hand, the  tabula vitrea, which, on  account

                               Fig.  9.
Disarticulated bones of the skull.
  1  The frontal bone. (The central division between the two bones does not exist in the adult.;
—2 Parietal bone—3. Occipital bone.—4. Temporal bone.—5. Ethmoid bone.—6. Sphenoid bone.—
7. Superior maxillary bone.—8. Cheek bone.—9. Palate  bone.—10. Lachrymal bone.—11. Nasal
bone.—12. Inferior -maxillary bone.
of its greater  hardness, would be liable to  fracture, to chip  off,  is
merely united  with its fellow at the suture,  by what  is called har-
mony : the tabula? 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 fcrtal state, the  sutures do not exist.  They are fully formed in
youth, are distinct in  the adult age, but, in after periods of life, be-
come entirely obliterated, the bone then forming a solid spheroid.   It
does not seem, however, that after the  sutures are established, any 
H
SK .VSIBILITY.--NERVOUS SYSTEM.
displacement  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, which have a
membranous union, is of striking advantage  to the foetus in parturi-
tion.   It enables  the bones to overlap each other; and, in this way,
to occupy a much smaller space than if ossification had united them,
as in after life.  It has,  indeed, been imagined by some, that there is
this advantage in the pressure made on 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, and as it forms, at the same
time, a bond  -of  union  and of separation, a fracture might be  in-
flicted 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.   It will generally happen, that a blow, intended  to  cause
nous bodily injury, will  be sufficient  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
sudden 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.
  The cerebrum, as well as the cerebellum, consists of two  hemi-
spheres;  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. 
OF THE  ENCEPHALON
55
Fig. 10.
Posterior view of the encephalon.
  Fig. 10, 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 margin
of which  is the superior  longitudinal sinus, d d.  The falx passes
between the hemispheres in the mode exhibited at a a, Fig.  11.—c c,
Fig. 10, 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 injuriously on the
cerebellum, B B.   A process of the dura mater passes also between
the hemispheres of the cerebellum, B B.  Independently of the pro-
tection 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 Herophili or confluence of
Uie sinuses at d (Fig. 10 & 11), and ultimately proceed in the direction
c c, constituting the lateral sinuses, which pass through the temporal
bone, and form  the internal jugular veins, one of which is represent-
ed at e, Fig. 11. 
56               SENSlKILITY--NERVOUS SYSTKM.

                             Fig. 11.
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, maybe small,
the amount, when all  are  concerned, is considerable.  The great use
of this intervertebral substance is to prevent the jar, that  would ne-
cessarily 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 return 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/, and enable it to resist—in the same manner as a
steel spring—any force acting  upon it in a longitudinal direction. 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 comparatively of late
years, that any ex-professo treatises have  appeared on the subject.
  Besides the protection  afforded by the bony structure to the  deli-
cate medulla, Magendie has pointed out  another, which he was the
first to detect.   The. canal, formed by the dura mater around the  ■ 
ENCEPHALON.
57
 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 tuta-
 mina 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 situated 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 ge-
 nerally conceived to consist of the minute terminations of the cere-
 bral 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 be-
 hind.  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 depressions, called
 anfractuosities.   (See Fig. 13.)   In the brain of man, these convo-
 lutions 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, misolobe  or great commissure.   If we examine
 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 middle or temporal, filling the middle  and lateral parts of
 the base of the cranium, and separated from the former by a consi-
 derable depression, called the fissure  of Sylvius,—and a posterior,
 which rests on the tentorium cerebelli.  This part of the cerebrum
 is divided into two  very distinct portions by the  medulla oblongata.
Anterior to it are the crura cerebri or cerebral peduncles,—by most
 anatomists  considered to be a continuation of the anterior fasciculi
which form the spinal marrow and medulla oblongata, and proceeding
  VOL i.                       8 
58                 SENSIBILITY--NERVOUS SYSTEM.

to form the hemispheres of the brain.   Between  the  anterior  ex-  . J
tremities of the peduncles are two hemispherical projections, called > |
eminentice mamillares, which  are  possessed by man  exclusively,   1
have the  shape of a pea, and are formed of the white nervous tissue  *m
externally, of the gray within.   Anterior to these again is the infun-   *
dibulum, and a little farther forwards the chiasma of the optic nerves,    i
ox the part at which these nerves decussate.
  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    .f
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-    1
factory nerve has been conceived to arise.  It is called the olfactory
tubercle or lobe.                                                     \

                             Fig. 12.
                           Base of the Brain.
 A A. Anterior lobes of the brain—B B. Middle lobes— C C Posterior lobes—D D. Cerebellum—a.
Medulla oblongata—ft. Pons Varolii—c. Chiasm of the optic nerves—d. Olfactory'nerves— e. Cruwi
cerebri—/. Cms cerebelli.

  When we examine the interior of the brain, we find a number of
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 of separation between the two hemispheres.   It is distinctly per-
ceived, on separating  these parts from each other, in the form  of a
long and broad white band.  Beneath  the  corpus  callosum is the 
ENCEPHALON.
50
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 mamillares.  (Fig. 12.)
At the sides it has the thalami nervorum opticorum.
   In  the lateral ventricles, situated on each side of the corpusr cal-
losum, some parts exist which demand attention.   In the  upper or
anterior  half, commonly  called the anterior cornu, and in the ante1*
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 esteemed, 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 divided
 vertically,  an arborescent appearance  is presented,—the  trunks
 of the arborizations beiag white,  the surrounding substance gray.
 This appearance is called arbor vitcr.   The part where all  these
 arborizations  meet, near the centre of the cerebellum, is  called cot-
 pius  denticwlatum vrt rhomboidale.  Gall is of opinion, that this body 
60
SENSIBILITY--NERVOUS SYSTEM.
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.
 11. Section of the corpus callosum—2 2. Lateral ventricle: the septum being removed—3 3. The
fornix—4. Third ventricle—5. Pineal gland—6. Tubercula quadrigemina—7. Fourth ventricle—8.
Iter a tertio ad quartum ventriculum—99. Internal carotid artery—10 10.  Artery of the corpus cal-
losum—1111 11 II. Superior longitudinal sinus—12 12. Fourth sinus—A A. Cerebrum—B. Cerebel-
lum—C. Pons varolii—E E. Medulla spinalis—F. Medulla oblongata.

   The medulla oblongata is so called,  because it  is the continuation
of the medulla  spinalis in the cavity of the cranium.   It is  likewise
termed mesocephale, from its being continuous with the spinal  mar-
row  in one direction, and sending towards  the brain strong  pro-
longations—the crura cerebri;  and to the cerebellum  similar  pro-
longations—the crura cerebelli;  so-that it appears to be the  bond of
union between  these various parts.  In its lower portion, (Fig. 12, a.)
it appears to be merely a continuation of the medulla spinalis, except
that it is more  expanded superiorly where it joins the pons varolii,
b.   This portion of the medulla oblongata is called,  by some, the
tail of the medulla oblongata; by others, the rachidian bulb; and by
others again it is regarded  as  the whole medulla oblongata.  Its
lower surface,  seen in the figure,  rests on the basilary gutter of the 
SPINAL MARROW.
61
occipital bone, and exhibits a groove, which divides the spinal cord
into  two portions.   On each side of this furrow are two oblong
eminences, the innermost of  which is called corpus pyramidale,  the
outermost,  corpus olivare,  (Fig. 14.) which arise from the anterior
column of the medulla spinalis, or are a continuation and subdivision
of this  column.   On the posterior surface  of the medulla oblongata,
the posterior fasciculi separate  to form the fourth ventricle;  (Fig.
13, 7.)  at the sides of this ventricle are the corpora restiformia, 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 pyra-
mid.   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 interesting points of anatomy, but are
not yet of much importance physiologically; if we except, perhaps,
the  views promulgated 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
ponsvarolii, tuber annulare, and nodus cerebri; and to this are attached,
superiorly, the corpora or tubercula quadrigemina.   In the very cen-
tre of the pons, the crura cerebri bury themselves; and are, by many,
considered to decussate ;  and by others,  to be prolongations of  the
anterior column of the spine.  Sir C. Bell thinks, that the pons varo-
lii stands in the same relation to the lateral portions of the cerebellum
that  the corpus callosum does to the cerebrum : 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 fo-
ramen magnum of the occipital bone, above, to the cauda equina, be-
low.   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 scrip-
torius  in the fourth ventricle, and the rima—formed by the corpora
pyramidalia, before—two fissures extend downwards, which divide
the spinal marrow into lateral portions.  The two lateral portions are
divided into an anterior and posterior, so  that the cord has four  dis-
tinct 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 envelopes
the medulla at the occipital foramen, being firmly united to the liga- 
62
-SENSIBILITY--NERVOUS SYSTEM.
 ments, but farther down it constitutes  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 substance 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 vanish-
 ing 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 encephalon, are and hence called encephalic
 nerves;  thirty from  the medulla spinalis, and hence termed spinal.
 The encephalic nerves emerge from the cranium by means of fora-
 mina 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 oculi, or common oculo-muscular, which send filaments to most
 of the muscles of the eye ; the fourth  pair, trochleares, pathetici, or
 internal oculo-muscular, distributed to the greater oblique muscle  of
 the eye ;  the  fifth pair, trifacial, trigemini, or symmetrical nerves of
 the head, (Bell,) which  send their branches  to the eye,  nose, and
                                       tongue;  the sixth  pair,  abda*
                                       centes, or  external oculo-muS'
                                       cular, which are distributed to
                                       the  abductor  or rectus exter-
                                       nus 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 mol-
                                       lis of  the seventh pair, which
                                       passes to the organ of hearing;
                                       the eighth pair, pneumogastric,
                                       par vagum, or middle sympa-
                                       thetic, which is  dispersed par-
                                       ticularly to the larynx, lungs,
                                       heart, and stomach ; the glosso-
 Base of the brain and origin of the encephaUe nerves.   pharyngeal, often Considered as
 A. Anterior lobes of the brain.  B. Middle  lobes,  nart of  thp  lncr  ctnA raVinep
C.  Posterior lobes. D. Cerebellum. E. Pons varolii.  ^     .  ,.  e  l&!i}>  an<1 ,Wn0SG
F.  Medulla oblongata. G. Crura cerebri. H. Crura ce-  name indicates its distribution
nbeJli.   I. Fissure  of Sylvius,  K. Kminentiae ma-  *,. +u^ x,.          ,   •
millares. L. Infundibulum. M Corpora pyramidalia:  l° lne tongue and  pharyTOl  \
N. Corpora olivaria. o. Roots of olfactory nerves. 11-  the   {Treat hlJTV)frln<!<il/<l  ninth
Olfactory nerves. 2 2. Optic  nerves.   3 3. Motores    .  »'CUl 'lyj^glOSSUS,  ninm
oculorum. 4 4. Pathetici.  5 5. Trigemini.  6  6. Ab-  pair,  Or Ungual ntTVC.   dis-
dueeiKes.  7 7. Portio mollis and pcrtio dura. 8. Glos-  i  -i  . j  .   °,                ,
so-pharyngeal.  Par vagum, and Spinal Accesaory. 9 9.  lnDUtea  tO tfte  tOHgUe ;  and
Hypoglossal.                               tf,e  spinai  accessory of  Wil-
 
.NERVES.
63
 lis, which arises from the spinal cord  in the cervical region, as-
 cends into the cranium, and issues, by one of the foramina, to be dis-
 tributed to the muscles of the neck.  All these proceed from the me-
 dulla oblongata;—the brain and cerebellum not furnishing one.
   The  spinal nerves are thirty in number on each side.   They 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 otlier by the ligamentum
 denticulare; but they unite beyond this ligament, and, near the inter-
 vertebral foramina, present one of those knots, known under the name
 of ganglions, or ganglia, 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 distributed, ram-
 ifying more arid  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, without communica-
 ting 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
 th© nerves of the upper extremities,  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  distribu-
. ted 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 sym-
 pathetic.
   Each nerve consists of numerous fasciculi, surrounded by cellular
 membrane;  and, according to Reil, of an external envelope, called
 neurilemma, which, in the opinion of most anatomists, is nothing more
 than a  cellular envelope, similar to that which surrounds the vessels
 and muscular fibres.
   Until of late years, the nerves were universally divided, according
 to their origin, into encephalic and spinal;  but, more recently,  an
 anatomical division has been proposed, based upon the uses they ap-
 pear to fulfil in the economy.   For one of the most beautiful arrange-
 ments of this kind we are  mainly indebted to Sir Charles Bell. We
 have already seen, that the encephalic nerves are connected with the
 encephalon by only one root, whilst the spinal nerves arise from two ;
 tfee one connected with the anterior part of  the spinal marrow, the
 other with the posterior.  If these different roots be experimented on, 
64
SENSIBILITY--NERVOUS SYSTEM.
we meet with results varying considerably 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 sensibility.   We conclude, there-
fore, 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 for one of these exclusively, and that they
are either nerves of motion or of sensation, according as their roots
arise from the  anterior or the posterior column of the  medulla ob-
longata.
                              Fig. 15.
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, accord-
 ing to  some anatomists, is composed of three fasciculi or columns
 on each side ; an anterior, middle, and posterior ; and it has been af-
 firmed by Sir Charles Bell, that whilst the anterior column gives ori-
 gin to nerves of motion, and the posterior to nerves of sensibility, the
 middle  gives rise to a third species, having the function of presiding
 over the respiratory movements, and which Sir Charles accordingly
 calls  the 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 phrenic nerve, and another—having the same
 origin as the last—the external respiratory.  Sir Charles Bell's views,
 if admitted, 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 be capable of others of a different kind,
by means of the nerves that are uninjured.
  The accompanying plate exhibits the system of respiratory nerves,
as given by Mr. Shaw, the son-in-law of Sir Charles Bell, who, some
years ago, was prematurely snatched from existence, after having
made numerous useful' contributions to medical and surgical science. 
 
SYSTEM OF KB.si'IBATOKY  NKKVKS.
 
It f.lV l  I, Alt, UK  (iTWMKTKll'.VL  NKItVES.
~/^

 
 
NERVES.
05
   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 branches 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 portijydura passing 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 acces--
 sory.
   11.  Branches of the last nerve proceeding  to the muscles of the
 shoulder.
   12  12  12.  Internal respiratory  or phrenic passing to the dia-
 phragm.
   The origins of  this  nerve are seen to be  much higher up  than
 they are generally described.
   13.  Inferior external respiratory, to the muscles on the side of the
 chest.
   To  Sir Charles Bell we are indebted for a further arrangement of
 the nerves, infinitely more natural  and philosophical than  the  un-
 meaning numeration 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,  Magendie, Meckel,
 and one or two others, that we owe the  great improvements in our
 knowledge of the  structure and functions of the nervous system.
   According to Sir Charles 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 ence-
 phalon by two roots, and to have a ganglion upon the posterior root.
 It is, accordingly classed with the spinal nerves, and, like them, con-
 veys  both motion and  sensibility to the  parts to which it is distri-
 buted.
   These regular nerves are common to all animals, from the  zoo-
     VOL. i.                    9 
66               SENSIBILITY--NERVOUS SYSTEM.
 phyte to man.  They run out laterally; or in other words, in a di-  ^
 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,  fhey 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 diaphragm;
 the spinal accessory, to the muscles of the shoulders; and the exter-,
 nal 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 des-
 tined 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, the cerebellum, C C,  the crura cerebri, D D, the crura cerebelli,
 E E  E, the 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-occipi-
 tal.   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 i)een  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   '"
 nerves to the same nature as  the spinal 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 ac-
 counts for the separation of the roots into distinct nerves by the
large developement of the central mass of the nervous system  within
the cranium; and 2dly, by the existence, within the cranium, of par-     {
ticular organs  for the senses, which keep the roots  separate from
 each other. 
NERVES.                           67
  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 innova-
tion to be accepted, were they even devoid of the weighty objections,
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 trisplanchnic,
ganglionic, and great intercostal, is»constituted of a series  of gan-
glions, joined to each other by a nervous trunk, and extending down
the side of the spine, from the  base of the cranium to the os coccy-
gis or lowest bone of the spine.  It communicates with each of the
spinal nerves, and with several of the encephalic;  and from  the gan-
glions, formed by such  communication,  it sends off nerves, which
accompany the arteries, and are distributed particularly to the or-
gans of involuntary functions.  At its upper part, it is situated in the
carotid canal, where it appears under the form of a ganglionic plex-
us, two filaments of which proceed to join the sixth pair of encepha-
lic nerves, and  another to meet the vidian twig of the fifth pair.  By
moans of  the  fifth pair,  it communicates also with the  ophthalmic
ganglion, which Bichat considered to belong 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; five in the  loins, the lumbar ;  and three or four
in the sacrum, the sacral.   Wherfit reaches the coccyx, it termi-
nates  by a  small ganglion, called coccygeal, or by uniting  with the
great sympathetic of the opposite side.
  The ganglions are of an irregular, but generally roundish, shape.
They consist of nervous filaments, surrounded by a reddish gray, pul-
py, albuminous, or gelatinous substance, which differs from the gray
matter of the brain.  Authors  are by no means agreed, with regard
to their uses.    Willis, Haller,  and others, considered 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 ganglia are larger and more numer-
ous when the brain is deficient in size.  Lancisi and Vicq d'Azyr re-
garded 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 approximation, and the plexuses  he regards as
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
thinks, that they are  secondary sources of nervous influence, the spe-
cific office of which  is to receive supplies of it from all parts of the 
68                SENSBILITY--NERVOUS SYSTEM.

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 Johnstone,
Reil, and Bichat, that their use is to render the organs, which derive
their nerves from them, independent of the  will.   The sympathetic
is, indeed, the great system of involuntary nerves; and although con-
nected with the brain by the branches of the  fifth and sixth pairs of   ,
encephalic nerves, and with the'spinal cord bythe spinal  nerves, it
does not appear to be directly influenced by either; as the functions of
the parts to which its  ramifications 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
regarding 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 stimu-
lant influence and applying it to movements, which are independent
of the centre of perception.   In like manner, he affirms, when irri-
tation 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 functions.
   The great sympathetic is esteemed  to  be the visceral nerve, par
excellence;  in other words, the nerve that supplies the different vis-
cera 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 examining the course
of  the great sympathetic,  we  find many filaments proceeding from
the cervical and thoracic ganglions, interlacing and forming the car-
diac plexus, from which the nerves of the heart and great vessels arise.
The same thoracic ganglions furnish a branch to each intercostal ar-
tery.  A nerve of the great  sympathetic—called the great splanch-
nic or visceral—proceeding  from some of  'the thoracic  ganglions,
passes through the pillars of the diaphragm into the abdomen, and
terminates in the large plexus or ganglion, called the semi-lunar, and
this, by uniting with its fellow of the opposite side, constitutes the still
more extensive interlacing, the solar plexus.  From this, numerous
filaments proceed, which—by accompanying the coronaria ventri-
culi, hepatic, splenic,  spermatic, renal, superior and inferior mesen-  ' '
teric, and hypogastric arteries—are distributed to the parts, which are
supplied with blood by  these  arteries,—the stomach, liver, spleen,
testes,-kidneys, intestines, &c.
   Weber,  however,  a German  anatomist  of distinction, who ex-
amined the great  sympathetic in different animals, has  afforded 
NERVOUS SYSTEM.
69
reason for believing that the splanchnic may not be the sole visceral
nerve, but that the eighth pair, or par vagum may share in the func-
tion.  He states,  that the great sympathetic  is less  developed, the
lower the animal; whilst the par vagum is more and more developed
as we descend in the scale, and at length is the only visceral nerve
in some of the mollusca.
   According to the experiments  of Flourens, the semilunar is the
only ganglion, which exhibits  any marked  sensibility, and hence it
has been considered as a sort  of intervention  to connect the viscera
with the encephalon.
   We are justified then, perhaps, in dividing the nerves with Lepel-
letier into five classes :—the first  comprising  the  nerves of special
sensibility—the olfactory, optic, lingual branch of the fifth pair, and
the auditory:—the second, the nerves of general sensibility, the fifth
"pair; and the spinal nerves, through their posterior root:—the third,
comprising the voluntary motors, the  spinal  nerves, by their anterior
roots, the motores oculorum or common oculo-muscular, the external
oculo-muscular, and the hypo-glossal:—the fourth, instinctive motors,
involuntary,  respiratory nerves of Sir Charles  Bell, the pathetic,
facial, glossopharyngeal, pneumogastric, and spinal accessory; and
the ftfthpnervcs of vital association and nutrition—the filaments and
plexuses of the ganglionic system.

   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 to a greater  or  less ex-
tent in all cases of parturition, whilst the head is passing  through the
 pelvis, without the child sustaining any injury.
   On examining, however, the  consistence of different  brains, 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  dis-
 ease, constituting the ramollissement du ccrveau, or mollescence of the
 brain, to which the attention of pathologists has been directed of late
 years but without much important advantage to science.
   When the encephalon is fresh, it has a faint, spermatic, and  some-
 what 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;
\ 
70
SENSIBILITY--NERVOUS SYSTEM.
 sulphur, acid phosphates of potassa, lime,  and magnesia, 5.15.  In
 the spinal cord, there is more fatty matter, and less osmazome, albu-
 men, and  water.   In the nerves, the albumen predominates, and
 the  fatty matters  are less  in  quantity.  Researches by Lassaigne
 show, that water  constitutes Tyhs  of the  nerves, and j^ths of the
 brain; whilst the proportion of albumen, in  the former, is -fV^ths; in
 the latter, Troths.
   Neither chemical  analysis,  nor 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.
   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 corti-
 cal,  cineritious, or pulpy substance; the latter, the  white, medullary,
 or fibrous.  The gray substance is not  always, however, at the ex-
 terior, nor the medullary in the  interior.   In the  medulla spinalis,
 their situation is the reverse of what it is in  the brain.  Ruysch con-
 sidered, that the  cineritious portion owes its  colour to the  blood-
 vessels which enter it; and, in the opinion,  Haller  and Adelon con-
 cur ; but this is not probable, and it has by no means been demon-
 strated.   The medullary portion has the appearance of being fibroua
 and it has been so regarded by Leeuenhoek, Vieussens, Steno,  and
 by Gall  and  Spurzheim. Malpighi believed the gray cortical sub-
 stance 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 follicles.   Gall and Spurzheim, on the
 other hand, conjecture,  that the use of  the cineritious is to be the
 source or nourisher of the white fibres.  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 feetus
 the medullary is developed before  the cortical portion, and  he con-
 ceives 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 surface  of the hemis-
 pheres, without derangement or  oppression of mind during  the
 patient's life;  and hence he  concludes,  that the  cineritious matter
 of the brain  is the seat  of the intellect, and  the medullary of the
 subservient parts.   A similar use has been ascribed  to the cineri-
 tious portion, from  pathological observations, by M M. Foville and
 Pinel Grandchamp.
  This view would afford considerable support to the opinions of
 Gall, Spurzheim, and  others, who  consider  the organs of the cere-
bral faculties to be constituted of expansions of the columns of the 
NERVOUS SYSTEM.
71
spinal marrow and medulla oblongata, and to terminate by radia-
ting fibres on the periphery of the brain; as well as 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  indi-
vidual of rank in the British  army  of India, the anterior lobes of
which were in such a state, that neither medullary nor cortical por-
tion could be distinguished,  both one  and the other appearing to be
broken down into a semi-purulent, amorphous fluid;  yet the intel-
lectual faculties  had been nearly unimpaired, although the morbid
process must have been of considerable duration.
   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 extravasation
of blood may suddenly give rise to the abolition of the faculties; 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,—-two internal carotids, and two
vertebrals; to these may be added the spinal artery or middle artery
of the dura mater,—the arteria meningaa media.  The carotid  arte-
ries enter the head though 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, which inosculate with corresponding branches of the ca-
rotids, and form a kind of circle  at the base of the brain, which has
been called the circulus arteriosus of Willis.
   The passage  of the blood-vessels  is extremely tortuous, so that
the blood does not enter the  brain 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  transmitted  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; as
well as in ordinary cases  of what are called determinations of blood to
the head.   Here, too large an amount 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, and 
72
SENSIBILITY--NERVOUS SYSTEM.
then  congestion  or accumulation of blood may  arise from very
different causes.                                  .       ,
   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. 11.)
   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,
with  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.
   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, of easy  explanation.   It is  owing  to  the  pulsation
of  the  circle of  arteries   at  the  base of  the  brain  elevating
the* organ  at each systole  of the heart.   The  other movement
is not  so  readily  intelligible.    It  has  been  attributed to  the
resistance, experienced  by  the blood in its passage through the
lungs during expiration, owing to which  an accumulation of blood
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, the sinking down of the brain, during
inspiration, is explicable:—the blood is rapidly drawn to the heart;
the quantity in the veins is consequently diminished, and 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, as we have seen, does not fill the  vertebral
canal, but the cephalo-spinal fluid  exerts  upon  it the  necessary
pressure; added to which, the pia  mater seems  to press more upon
this organ than upon the rest of the cerebro-spinal system. A cer-
tain degree  of pressure appears, indeed, necessary for the due per- 
NERVOUS SYSTEM.
73
  formance  of its functions, and if this be either suddenly and consi-
  derably augmented, or diminished,  derangement of function 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 fluid, which
  is drawn off by the surgeon when he punctures in  a case  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 of ignorance to ascribe to it.  The opinion
  has universally prevailed, that all nerves  are  exquisitely  sensible.
  We shall have many opportunities for remarking how far this senti-
  ment 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 insensible, in the common acceptation of the term;
  that is, we may prick, lacerate, cut,  and even cauterize  it,  yet no
  painful impression will be produced.   Experiment leaves no doubt
  regarding the truth of this, and we find the fact frequently confirmed
  in pathological 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 cannot resist  stating,
  that on the riiorning on which 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 himself, 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 oppo-
- site side of the head, and extracted it.
    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 hemisphere has been removed ; nay, that  in cer-
  tain animals, as reptiles, no change  is  produced in  their habitudes
  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 chord 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
  as we have seen, have  been  esteemed 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 an-
  terior part of the medulla  oblongata, and is very feeble in the tuber-
  cula quadrigemina of the mammalia.
    It has been shown, that the spinal nerves, by means of their poste-
      vol i.                    10 
74
SENSIBILITY--SENSATIONS.
rior  roots, convey general sensibility to the parts to which they are
distributed. But there are other nerves, which, like the brain, are them-
selves entirely devoid of general sensibility.  This has given occasion
to a distinction of nerves into those of general and of special sensibility.
The nerves, which must be considered as insensible or devoid of gene-
ral  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 appro-
priate 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 re-
quires  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 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 OF SENSIBILITY.

   Sensibility we have defined to be—the function by which an animal
experiences feeling, or has the perception of an impression.  It in-
cludes  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 or-
gan ; 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 with-
 in 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 numerous, but they may all be comprised in
 two divisions,—the external and the internal.   Vision and audition
 afford us examples of the former, in which the impression, made up-
 on the organ, is external to the part impressed.  Hunger and thirst
 are instances of the latter,  the cause here being 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, 
SENSATIONS.
75
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 object, 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-
pendent 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  succeeded
in threading  his  way through  a crowded street,  carefully avoid-
ing every obstacle, yet so little impressed by the objects around him
as not to retain  the slightest  recollection  of  them 1   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 without.
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 illusions, 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, wifc 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. and  a sense of
numbness in  the extremities,  are referable to this cause,  as  well as
the singular fact well known to the operative  surgeon, that a pain is
often felt in a particular part of a limb, for years after the limb has
been removed from the body.
  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 
76
SENSIBILITY--SENSATIONS.
 as insensible, provided we were aware of the precise circumstances
 under which their sfensibility 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 surgical
 practice especially.  As  the bladder consists principally of mem-
 brane, it was agreed for ages by all lithotomists, that it would be im-
 proper to cut or divide any part of it; and therefore, in order to ex-
 tract  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, me-
 ninges of the brain, different serous membranes, arteries, and veins,
 entirely insensible;  yet we  know, that these parts  are exquisitely
 sensible when attacked with inflammation.  One of the most painful
 affections to which man is liable is  the variety of whitlow that  im-
 plicates the periosteum ; and in  all affections of the bone, which in-
 flame 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    j
 sensibility when  a  particular irritant is  applied.   Bichat, • for  ex-    1
 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,    4
 we must have submitted it to every kind of  irritation.   Adelon af-    ^
 firms, that there is no part but what may become painful by disease.
 From this  assertion the cuticle might safely be excepted.  It is,    ,
 so far as we know,  totally devoid of blood-vessels  and  nerves,—   d
 the  elements of sensibility,—and appears to be extra-organic.   If   "i
 we are right, indeed, in our view of its origin and uses, as described   , J
 hereafter,  sensibility would be of no  advantage to it, but the con-   1
 trary.   In the present state, then, of our knowledge, we are justified
 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 may receive.   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 atmo-
sphere, and it is more philosophical in us to presume, that the reason 
SENSATIONS.
77
 we do not discover nerves in these parts may be owing to the imper-
 fection 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 conductor
 of the  impression between the part impressed and that organ.   If a
 ligature be put around a nerve, sensation is lost below the ligature,
 but it 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 marrow is  sensible
 along the whole of its  posterior column,  but it also  acts  only as a
 conductor of  the impression.   Flourens  destroyed the  spinal cord
 from below, by slicing it away, and he found that  sensibility  was
 gradually extinguished in the parts corresponding  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.   M. Julia Fontanelle has indeed
 concluded, from a review of all the observations made on this matter,
 that, contrary  to the common   opinion, death by the guillotine  is
 one  of the  most painful,  that  could  be  invented:  that the pains
 of decollation are horrible, and  endure even until there  is an entire
 extinction of animal heat!
   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 Magendie,
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  conversely—one of the 
78                   Vr.VSHilUTY--SENSATIONS.

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 shall 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 the 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 fluid, for example.
   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 between
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  Ara-
bians, 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  the belief,
were, first, that as the brain receives  so much more blood  than is
necessary for  its own nutrition, it must be an organ of secretion; 
SENSATIONS.
79
 secondly, 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 cortical 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  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 Physiologies of Haller, who was himself 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 sufficient  evidence,  direct  or
 indirect, of the existence of any nervous fluid of the  kind described.
 Notwithstanding the recent observations of Ehrenberg, the nerves do
 not seem to consist of tubes.   Raspail has properly concluded, that
 the opinion of  Bogros and others, that they are hollow, and contain
 a fluid, is unsupported by facts, for although he admits, that Bogros
 succeeded in injecting the nerves with mercury, he thinks,  that the
 passage of the metal  along the  nerves was  owing  to its having
 forced its way by gravity.  Raspail found the nerve, under the mi-
  croscope, presenting a homogeneous  structure, without the  slightest
  trace  of solution of continuity.   Nor have we any reason for consi-
  dering the brain the organ of any ponderable  secretion.   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 regarding the hypothesis
  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  them  under  the  more modern  title;
£ Earle  firmly  believes  in the  existence  of  a circulation  in  the
  nervous system,—a view, which was for a long time adopted,—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  hypothesis of vibrations is ancient, but has been by no means
  as generally admitted as the last.  Among the moderns it has re-
   ceived  the  support of ('ondillac, Hartley, Blumenbach, and others;
   some supposing, that the nervous matter itself is thrown into vibra-
   tions ;  others, that  an invisible and subtile ether is  diffused  through
   it, which acts the sole or chief part.  As the latter is conceived, by 
80                 SENSIBILITY--SENSATIONS.

many to be the mode in which electricity is transmitted along con- *
ducting wires, it is not liable to the same objections as the former.
Simple  inspection, however, of a nerve at once exhibits that it is
incapable of being thrown into vibrations.  It is soft, never tense, al-
ways pressed upon in its course; and, as it consists of filaments des-
tined for very different functions,—sensation, volition,  respiratory,  -
motion, &c.—we cannot  conceive  how one of these filaments can
be thrown into vibration without the effect being extended to others,
and great confusion being thus induced.
  The last hypothesis is of later date, subsequent to  the discoveries
made in animal electricity.   The rapidity, with which sensation 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 proceeding to a part be
destroyed, and the  secretion, which ordinarily takes place  in the
part, be thus arrested, the secretion 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
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. Abernethy, 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 per-
formed  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 elec-
trical 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 con-
stantly going on. 
EXTERNAL SENSATIONS.
81
      Reil and  Prochaska are of opinion, that the nervous agency is
    generated through all the nervous system, and that every part de-
    rives sensation and motion from its own nerves.   Such likewise is
    the view of Broussais.  Gall, too, considers, that every sensation is
    effected in the organ  to  which the mind refers it.   We have satis-
    factorily shown,  however, 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 communication 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 excretions, may
    equally excite them.  Adelon has divided the external sensations into
    two orders—first, the senses, properly so called, by the  aid of which
    the mind acquires its. notion of external bodies and of their different
    qualities; and secondly, those sensations, which  are  still caused by
    the  contact of some  body, and  yet  afford no  information  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
    as the sole  regulators of the intellectual sphere of the individual.
    This we shall see is dependent upon another and still higher nervous
    organ,—the brain.
f      The external senses are generally considered to be  five  in num-
■:   ber; for, although others have been proposed, they may perhaps be
fr-   reduced to  some modification of these five,—tact or touch, taste,
    smell, hearing, and vision.   All these have some properties in com-
    mon.   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 con-
    sist of two parts;—the one, physical, which modifies the  action of the
    body, that causes the impression; the other, nervous or vital, whic*
    receives the impression, and conveys  it to the brain. In the eye and
    the car, we have better exemplifications of this distinction than in the
    other senses. The physical portion of the eye is a true optical in-
    strument, which modifies the light, before it impinges upon the retina.
    A similar modification is produced by the physical  portion of the
    ear on the sonorous vibrations, 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.
      vol.  i.                      11 
82             SENSIBILITY--EXTERNAL SENSATIONS-

  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-  j
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 nerves of
general sensibility.   All, however, seem intimately connected with  '
one of the nerves of general sensibility,—the fifth encephalic pair,—  j
and, in  the case of those senses  more  particularly, which  possess '
nerves  of  special sensibility, it is found, that they  are under thev"«
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 acquainted
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 movable in almost every direction.  The eye can be  <*<
turned towards objects in almost ail positions, by its own immediate
muscles.  The ear and the nose possess the least individual motion;
but the  last foiir, being seated in the head, are capable of being  as-  ;
sisted by the muscles adapted for its movement.
  All the senses  may be exercised passively or actively.   By direct-
ing the attention, we  can render the impression much more vivid;  4
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 plea-
sures 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
naade.  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 nume-
rous odorous characteristics of bodies; but, if the olfactory nerves be
constantly or too frequently stimulated by  excitants of this  or any- *■
other kind, dependence 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 sen- 
SENSE OF TACT OR TOUCH.
83
fj sations.  By corrugating the  eyebrows and approximating the eye-
  lids, 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 nos-
  trils, with the aid of the upper extremity.  Over the hearing we have
  less command, as regards its individual action: the upper extremity
  is here always called into service, when wre  desire 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 organ-
  . ization in these senses, but is another example of the influence of edu-
  cation.  The remaining senses are attentively  exerted to compensate
  for the privation, and become surprisingly delicate.

     We proceed to the consideration of the'separate senses, beginning
  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 touch.  In the
•  taste, the sapid body; in the smell, the odorous particle; in the hear-
  ing,  the sonorous vibration;  and in the sight, the  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 of tact or  touch.—palpation.

     The sense of tact or touch is the  general feeling  or sensibility,
Lt  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.  The sense of heat, for exam-
   ple, has  been separated 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 in 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 animal.
   It is nothing more  than tact, joined to muscular contraction and
   directed by volition.  So that, in the exercise of tact, we  may  be
  .esteemed passive; in that of touch active.
    % The organs, concerned in touch, execute other functions besides; 
84                 SENSIBILITY--SENSE OF TOUCH.                      j

and  in  this respect touch differs from the other senses.  Its chief §■
organ, however, is the skin; and hence it is necessary to inquire into  j
its structure, so far as is necessary  for our purpose.                   %

               Anatomy of the Skin, Hair,  Nails, fyc.
                                                                   1
   The upper classes of animals agree in  possessing an outer enve- u.i
lope or skin, by which the insensible perspiration passes;  a slight de-
gree  of absorbtion takes place ; the parts beneath are protected-;
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,  i
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 blister.
   The cuticle is probably a secretion from the true skin, which
concretes 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 said to be pierced  by  oblique pores for the  J
passage of hairs, and for the orifices of exhalant and absorbent ves-
sels.   Humboldt, however,  asserts,  that  he has never  seen these   ;
pores, even with a microscope which magnified 312,400 times.  It
is probable, that  this inorganic substance is placed  at the surface of
the body, not simply to protect the corpus papillare, but to prevenf^M
the  constant imbibition and transudation  that might take place dkkjj
no such envelope exist.  The cuticle exfoliates, in the form of scales,
from our heads; and,  in large pieces, from every part of the body,  •,
after certain cutaneous diseases.   According to  Raspail,  the  epi-
dermis is formed of a collection of vesicles deprived  of their contents,
closely applied together, dried, and thrown off in the form of branny
scales.  He regards it  as the outer layer of the corium.
   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 papilla?, 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 Eu-
ropean 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  uni-
versally admitted, and  scarcely concerns the present inquiry.
   3.  The corpus pajnllare is seated next below the rete mucosum.
It consists of a collection of small papilla?,  formed by the extremities 
ORGANS OF TOUCH.
S;j
i of nerves and  vessels,  which, after having  passed  through the co-
  rium beneatii,  are grouped in small  pencils or villi in a spongy,
 * erectile tissue.   These pencils arc disposed in pairs, and, when not
  in action, are  relaxed, but  become  erect when employed  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 some-
  times called  the papilla? 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.
      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 struc-
    tures  below by  cellular
    membrane;  and  this,
    with the layers external
    to it, forms the common
    integument.   In certain parts  of the body, and in animals more par-
    ticularly, the cutis  vera is adherent to muscular fibres; inserted
    more or less  obliquely, as at 6, Fig.  16. 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,  it  raises the feathers.  In man, it can hardly
    be said to exist. -Some muscles, however, execute a similar func-
    tion.   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
Fig. 16.
1. Cuticle.
2. Rete mucosum.
3. Corpus papillare.
4. Cutis vera.
5. Cellular {membrane.
C. Panniculus carnosus. 
86                .-.EX.MBILITY — M..N4E OF TOUCH.

where the  surface  is exposed  to  friction.  We  can  generally see %j
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 here-
after.  At present,  it is sufficient to remark, that they differ materi-
ally 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 covering, and
a central part, called the medulla or pith.  When we take hold of a
hair by the base, with the thumb and fore finger, 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 it  offers considerable resistance.  It is, there-
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  dependent—the hairs  being mechani-
cally entangled  together, and retained in that state  by the inequali-
ties on their surface.  Observers have, however, frequently  failed 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 having been  exhibited by the microscope, and, ^f
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
be owing  to the production of an acid in the system, which acts
upon  the colouring matter.   The explanation is purely hypotheti- 
ORGANS OF TOUCH.
87
'  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
  induced is identical with that which  occurs naturally to every indi-
  vidual, sooner or later.  Lepelletier  ascribes the change of colour
  to two very different causes.—First, owing to defective secretion
  of the colouring fluid, without any privation of nutrition.  In  this
  case, the hairs may live and  retain  their hold, as  we  observe in
  young individuals :—and secondly, the canals, which convey the fluid
  into  the hair may be obliterated, as in old age.  The same cause,
  acting on the nutritious vessels of the bulb, produces, successively,
  privation of colour, death and loss of these epidermoid productions.
  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
  porcupine, this seems to be the case, the pith being manifestly white,
  and  the horny covering coloured.
     The exact relations between the cuticle, the rete mucosum and the
  hair arc not known.   It is  not determined, whether the layers are
  simply perforated by the hair  in  its  passage  outwards, or whether
  they furnish it coats as it proceeds along.   There is often, however,
  an intimate relationship observed between the colour of the hair and
  that of the  rete  mucosum.  The fair complexion is accompanied
  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  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 nature.   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, ivhiskers, mustachios, eyebrows, eye- 
88                SENSIBILITY—SENSE OF TOUCH.                     9

lashes, &c.   In many animals it is long and straight; in others crisp-" "■
ed, when it is called icoot.  If stiff, it is termed a bristle; if inflexible,. M
a spine.                                                            a
   The hairs are entirely insensible, and, excepting in  their bulbous  "1
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   -1
known circumstance, may,  howrever, 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  k J,
of the opinion  of Dr. Bostock;—misled, apparently,  by  erroneous
reports  concerning  the  plica polonica; but Baron  Larrey has satis-  4
factorily shown, that the affection is confined.to the bulbs, and that   |
the hairs themselves continue totally devoid of sensibility.             H
   It is difficult to assign a plausible use for the hair.   That of the   n
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^ 9
the chin and  upper lip  of the male sex only,  set  our ingenuity at    g
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 ?u   y
Many physiologists regard certain parts, which exist in one animal,    |
apparently  without  function, but  which  answer useful purposes in
another,—as vestiges to  indicate the harmony, which reigns  through   J
nature's works.   The useless nipple on  the breast of one sex might   a
be regarded in this light; but the tufts of hair on various parts can-
not, in any way, be assimilated to the hairy coating, that  envelopes   1
the bodies of  animals, and is, in them, manifestly intended as a pro-    1
tection against cold.                                                  ;
   There is another  class of bodies,  connected with  the skin, and   ^1
analogous in nature to the last described,—the nails.  These serve a    ]
useful purpose in touch,  and consequently require notice here. i>(
   In the system of M. De Blainville, they constitute a  subdivision of
the hairs, which he distinguishes into simple and compound—simple, t  3j
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 together 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,*u  Jj
&c.  All these, like the hair, grow from roots, and are  considered to    j
be analogous in their physical and  vital properties.   Meckel, and De
Blainville are, indeed, of opinion, that the teeth are of the same class, ; ^M
and that they  belong, originally, to the skin of the mouth. The latter  ^m
zoologist, who  has  been distinguished  for  his  labours in  natural   J
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 
PHYSIOLOGY OF TOUCH.
89
being, in his view, bulbs analogous to those of the hair, but consider-
ably modified, so as to adapt them to the extremely delicate func-
tions they have to execute !

  For physiological purposes 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 proper-
ties, as to be, with propriety, termed dermoid.   If we trace the skin
into the  various outlets, we find, that a continuous, soft, velvety
membrane exists through their whole extent;  and, if the channel
have two outlets, as in the case of the alimentary canal, this mem-
brane, 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 ab-
sorption, which takes  place from  the  intestinal  mucous membrane,
as external.   They cannot, howTever, 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
apparatuses.   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
the teeth to be so, in correspondence with the  phantasies of Meckel,
and De Blainville.
  The analogy between the skin and mucous membranes is farther
shown, by the fact, that if we invert the polypus, the mucous mem-
brane gradually assumes the characters  of the skin, and the same
circumstance is observed  in  habitual descents of the rectum  and
uterus.

                 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  sub-
stance, 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
  vor. i.                         12 
90
SENSIBILITY--SENSE OF TOUCH.
the skin be cut, the sense becomes  destroyed.   In  the  exercise 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 papilla?  are grouped, pro- '
bably  aids them in their appreciation of bodies ; and the epidermis
modifies 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 recorded instances of great
resistance to heat have been caused by unusual thickness, and com-
pactness of cuticle, together with  a certain degree of insensibility of
the skin.   The latter may be an important element  in the explana-
tion, but some of the feats, executed by persons of the character
alluded to, could hardly have been influenced by the former,  as the
resistance seemed almost equally  great in the delicately organized
mucous membranes.  A Madame  Girandelli,—who exhibited in
Great Britain, many years ago,—was not only in the habit of  draw-
ing a box with a dozen lighted candles along her arm, and of putting
her naked foot upon melted lead, but of dropping melted sealing-
wax  upon  her  tongue,  and  impressing it with a seal, without  ap-
pearing to experience the slightest uneasiness ; and, some years ago,
(1832,) a man of the name of Chabert excited in this country, the
surprise,  which  followed his  exhibitions in London  a year or two
previously, and which  gained  him  the  appellation  of  the " Fire
King."  In addition to  the  experiments performed by  Madame
Girandelli, Chabert  swallowed  forty grains of phosphorus, washed
his fingers in melted lead, and drank  boiling Florence oil  with per-
fect impunity.  In the case of the phosphorus he professed to take
an antidote, and doubtless did so.   It is probable, also,  that agents
were used by him to deaden the painful impressions ordinarily pro-
duced by hot  bodies, when applied  to the  surface.   A  solution of
borax or alum, spread upon the skin  is said to exert a powerful ef-
fect of this kind; but, in addition to the use of  such agents, there
must be a degree of insensibility about the corpus papillare,  other-
wise it is difficult to understand why these hot substances did not in-
jure 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 per-
sons swallow fluids, at a temperature, which would excite the most
uneasy sensations in others.  In this,  habit has unquestionably much
to do. 
PHYSIOLOGY OF TOUCH.
91
   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  indi-
 cated by itching of the glans  penis.  A similar exemplification is
 offered during the passage of a gall-stone through the ductus com-
 munis choledochus;—the duct formed by the union of a canal  pro-
 ceeding 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 vio-
 lent irritation  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;
 it 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 subtile 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
 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 exhibit, ceteris paribus,
 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
 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 
92
SENSIBILITY--SENSE OF TOUCH.
them, the sensations experienced may be very different.   Hence the
difficulty, which 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 a chamber.   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, which 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, it con-
ducts  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 caloric from the  atmosphere, and experience the sensa-
tion 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 only as high 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 thi9*
part of Virginia  is about bbh or 56°; that the thermometer  varies
from 5^° 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 there
to experience  constantly the  sensation of cold.   This  we should
unquestionably 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 genera-
tion of heat is interesting and important, but it  does not  materially
concern us here.
   Yet, accustomed as the body is to give off caloric, there is a tem-
perature, which, clothed as we are, does not communicate to  us the
sensation  of cold, although  we  may  still  be disengaging heat to
some extent.   This temperature may perhaps be  fixed  somewhere
between 70°  and  80°, in the climate of the middle portions of the 
PHYSIOLOGY OF TOUCH.
93
United States.  So much, however, are our sensations in this respect
dependent  upon  the  temperature,  which  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  confortable when the thermometer rose to zero,  and
conversely.
  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
stationary, our sensations on descending to it in winter and in sum-
mer 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  tra-
veller, who  had ascended, would  feel correspondently cool.  An
experiment, often performed in the chemical lecture-room, although
strictly physiological, exhibits 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  dependant, 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,  calorification 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
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
provided for that purpose. 
94
SENSIBILITY--SENSE OF TOUCH.
   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 us temperature, shape, consistence, vVc.
 An  opinion has,  indeed,  been advanced, that  this  sense  is  best
 adapted for proving our own existence, as every time that two por-
 tions of the body  come into contact, two impressions  are conveyed
 to the brain, whilst if we touch an extraneous body we have but one.
   The tact of the mucous membranes is extremely delicate.  The
 great sensibility of the lips, tongue, conjunctiva, Schneiderian mem-
 brane, lining membrane of the trachea  and urethra is familiar to all.
 Excessive pain is produced in them by the contact  of extraneous
 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 re-
 petitions the sensation will become scarcely disagreeable.
   To appreciate accurately the  shape and  size of objects, 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
 direction.  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, indeed,
 and Galen term it the instrument of instruments.   The chief supe-
 riority of the  hand consists in the size  and strength of the thumb,
 which stands  out from the fingers and can be brought in opposition
 to them, so as to enable us to grasp bodies, and to  execute various
 mechanical processes under the guidance of the intellect.   So  im-
 portant an organ was the thumb esteemed  by Albinus,  that he called
 it a lesser hand assisting the larger—umanus parva majori adjutrix,"
 and its construction has been considered worthy of  forming the sub-
ject of one of the ' Bridgewater Treatises'—' on the power, wisdom,
 and goodness  of God, as manifested in the creation,'—a task assign-
 ed to Sir Charles Bell.
  In  addition to the  advantages referred  to, the hand is furnished
 with  a highly sensible  integument.  The papillae  are largely  de-
 veloped, especially at the extremities of the fingers, where they are
 ranged in concentric circles, and rest upon a spongy tissue, by many
 physiologists considered to be erectile, and, if not,  serving as a
 cushion.   At  the  posterior extremity of the fingers,  the nails  are
 situated, which support  the pulps of the fingers behind, and render
 the contact with bodies  more immediate.   This happy organization
 of the soft parts of the hand alone concerns the sense of touch di-
 rectly. The other advantages, which it possesses, relate to the power
 of applying it under the guidance of volition. 
PHYSIOLOGY OF TOUCH.
95
  Of the mode in which touch is effected it is not necessary to treat.
Beim'- nothing more than tact, exerted by an appropriate instrument,
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 pre-eminence in the universe—his intelligence,
in short—to the hand.  Anaxagoras asserted, and Helvetius revived
the idea, "that man is  the wisest of animals because  he possesses
hands."  The notion has been embraced, and expanded  by Condillac,
Buffon, and many modern physiologists and metaphysicians. Buffon,
in particular, assigned so much  importance to the touch, that he be-
lieved  the cause, why one person  has  more intellect 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 meta-
physicians 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 delicate 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 devoid 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 pencil between her head and  neck.   All her motions
were, in fact, confined  to the tongue and Ups, and to the museles of
the neck.
   Magendie, in  the second 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.   Within the  last few years, a Miss Ho-
neywell, born without  arms, has travelled about this country.   She
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, flow- 
 90                >ENsU!lLlTY--SENSE OF TOUCH.

 ers, &c.  She also writes, draws, and executes 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 regulating—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 re-
 ceives only the impression of an emanation from the body;  and, in
 that of audition,  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 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 distinction,
 made by Spurzheim and others, of the functions of the  senses  into
 immediate  and mediate.  Each sense has its  immediate  function,
 which it possesses exclusively ; for which, in other words, no other
 can be substituted.   The touch instructs  us regarding temperature;
 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, consist-
ing in the impressions they furnish to the mind, and by aid of which
it acquires its notions of bodies.   The  essential difference  between
these two sets of  functions is,—that the  mediate can be effected by
several  senses at  once.   Vision, olfaction,  and audition, participate 
PHYSIOLOGY OF TOUCH.
97
in judging of distances, as well as touch;  the sight instructs  us re-
garding 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 re-
marks, already made, have proved the inaccuracy of this opinion.
The  farther examination of it will be resumed under  the subject  of
vision. The senses are, in truth, of mutual assistance.  If the touch
falls  into error, as in the case of inaccurate appreciation of tempera-
ture, the  sight, aided by appropriate instruments, dispels it.   If the
crossed fingers  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 satisfac-
torily opposed this, by showing, that our notion of the existence  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 prerogative
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  instinctive 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 sen-
sation  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, indeed, nu-
merous  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 acutcness.  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-
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
  VOL. I.                      13 
f)H                 SENSIBILITY—sEN<E OF TASTE.

his own case, could distinguish between samples of wopllen cloth of
equal quality but of different colours.  The black appeared to him
among the roughest and hardest; to this  succeeded dark blue and   j
dark  brown, which he could not,  however, distinguish from each  'V
other.   The colours of cotton and silk stuff he was  unable to dis-  -J
criminate, and he propeily 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 dis-
criminating colours must be in the inequalities  of surface produced   i
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 discrimina-
tion.
  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 antennas 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, flying through
intricate 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   »i
supplied with  nerves,  which seem to  proceed  from the second  m
branch of the fifth pair, and are lost in the substance of the bristles. • j
In an experiment,  which Mr. Broughton made on a kitten, he  found' [ m
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  M
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. IL—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
the organ  of taste; and as that organ is, at the same  time, capable 
                         ORGANS OF TASTE.                      »»

 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 perceptions
 occasioned.  In some parts we experience the sensation of a pointed
 body without savour;  and in others a metallic taste is manifested.
 Pathological cases, too, exhibit, that the sense of taste may be lost,
 whilst the general sensibility remains,—and conversely.  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 imme-
 diate 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 knowr 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 papilla:; 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
absorbent  vessels, united  by  means of a  spongy  erectile  tissue.
Great confusion exists among anatomists in their descriptions of the
papilla) 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 called 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 
100
;ENSimLITY--SENSE OF TASTE.
and  resemble the mushroom—whence  their  name,—are  spreaa
about, here and there, upon the surface of the organ.   These papillae.
of taste must be distinguished from a third set, the papilla capitatas>\
which are mucous follicles, and of course accomplish^ a very differ-
ent function.
Fig. 17.
  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,
several branches  of  the  su-
perior,  filaments  from   the
spheno-palatine and naso pala-
tine  ganglions,  the  lingual
branch of the fifth pair,  the
whole of the  ninth pair  or
great hypo-glossus,  and  the
glosso-pharyngeal.   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.
 titcs of many anatomists, erroneously named, as they are not formed
 like the papillae, and as we have said, execute a very different office.
 They are  mucous 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  ccecum  of Mor-
 gagni.   (See Fig. 17.)   The fluids, exhaled from the  mucous mem-
 brane of the mouth, and the secretion of the different salivary glands
 likewise aid in gustation ;  but they are more concerned in masti-
 cation and insalivation, and will require notice under another head.
  Foramen of Morgagni.
  Fungiform papilla:.
  Conical papillce.
  Papilla capitatm.
  Epiglottis.
They are the papilla capi-
                          Of Savours.

  Before proceeding to explain the physiology of gustation, it will
be necessary to inquire  briefly into the nature of bodies, connected 
OF SAVOURS.
101
with their  sapidity, or, in other words, into savours, which are  the
cause of sapidity.
   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 inte-
 grant 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
 suggested 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 is exemplified by the sulphates and nitrates;  and that,  in
 the action of acids on the tongue and mouth, we witness a state  of
 whiteness and  constriction,  indicative of a first degree of combina-
  tion.   All these circumstances, however,  admit of a  more philoso-
  phical  explanation.   There  are unquestionably many substances,
  which do combine chemically,—not  with a nervous fluid,  of  whose
  existence we know nothing,—but with the mucus of  the mouth, and
  the sapidity  resulting from such  combination is appreciated  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 evi-
  dence that such powers are  existent.  Vegetable infusions or solutions
  aflbrd us strong examples  of this kind,—of which syrup may  be
  taken as the most familiar.   The effect of solution is easily intelli-
  gible ;  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 
 102               SENSIIllI.ITV--SENSE OF TVSTE.

 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 organs of taste arc as dry as the corn they
 select from a mass of equally arid substances, are probably  able to
 appreciate savours.   The taste,"produced by touching  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 tin ids, and
 when once produced, the nerve of taste  is  compelled  to appreciate
 the savour developed in the same manner as it does, in cases of mor-
 bid alterations of the secretion of the mucous membrane, when, it
 is well known, that a  body, possessing considerable and peculiar
 sapidity, may fail to impress the nerves altogether, or may do so inac-
 curately. 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  mecha-
 nical, and supposed to be produced by vibration of their nerves.
   The savours, met with  in the three kingdoms of nature, are innu-
 merable.  Each body has its owfi, by which it is  distinguished: but
 few instances occur  in which  any two can be said to  be identical. *
 This  is the great source of difficulty, when  we attempt to  throw' "*J
 them  into classes, as has been done by many physiologists.  Of these
 classifications, the one by Linnaeus is the  best known.   It will eluci-
 date  the  unsatisfactory character of the whole: he  divided sapid
 bodies, into  sicca, aquosa, viscosa, salsa, acida, slypticd, dulcia, pin-  ^
guia,  amara, acria, et nauseosa.  lie gives also examples of  mixed
 savours—the  acido-acria, acido-amara, amaro-acria, amaro-acerba,
 amaro-dulcia, dulci-styptica,  dulci-acida, dulci-acria,  and acrivis-
 cida ; and remarks, that the majority are antitheses to each other,
 two and two, as the dulcia and acria;  the pinguia and styptica)
 the viscosa and salsa ; and the aquosa and sicca.  Boerhaave agafn
 divides them into primary and  compound; the former including the
 sour,  sweet, bitter, saline, acrid, alkaline, vinous, spirituous, aromaticf^-^
 and acerb;—the latter resulting from the  union of some of the pri-
mary savours. There is, however, no accordance amongst physiolo-
gists  regarding those that should be esteemed primary, and those
that are  secondary and compound;  although  the division appeanf-  ■{
to be  fairly admissible.    The  acerb, for example—which is con-1  *
sidered primary by Boerhaave—is by others,  with more propriety,
classed among the secondary  or compound, and believed to consist    ,
of a combination of the acrid  and acid.   Still we understand suffi-
ciently well the character of  the acid, acrid, bitter, acerb, sweet, &c.;
but when, in common language, we  have to depict  other savours, 
OF SAVOURS.
103
wc are frequently compelled to take some well  known substance as
the standard of comparison.
  According to Adelon, the only distinction, which we  can make
antpngst them, is,—into the agreeable and disagreeable.   Yet of the
unsatisfactory nature of this classification  he himself adduces nu-
merous  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: the
southern planter is well aware, that  this is the case with his tobacco,
unless the operation  of worming be performed in due season.   The
old adage, that " one man's meat is  another man's poison," is meta-
phorically 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  sho rttime 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 O#os 2iX<piov, or laserpitium, is
 supposed to have been the assafcetida.   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, especial-
 ly if accompanied with the chick, is highly esteemed by the Siamese.
 In civilized countries, we find game, in a putrescent state, eaten as
 a luxury: this to those unaccustomed to it, requires a true education.
 The same may be said of the pickled olive, and of several cheeses
 —the  frontage de Gruyere, for example—so much esteemed 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 
104
SENSIBILITY--SENSE OF TASTE. '
a general  rule this  is true,  but  there  are  many signal 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
the utility of the  various  layers of which the mucous membrane of
the mouth consists.   In order that taste  may be satisfactorily exe-
cuted, it is necessary that this  membrane  should be in a state of
integrity;  for 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 mas-
tication and insalivation, by which solid bodies are divided into minute
portions, dissolved where soluble, and brought successively in contact
with the organ of taste.  The gustatory nerves thus receive the im-
pression, and by the same agents  the impression is transmitted to the
brain.  These nerves go to the formation of the papilla), 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 erection.   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 experience^; but
if we touch one of the papillae with the point of the brush;,and, at
the same time,  use 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, which
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 'Aglossostomographie? gives the case of a child,
six years of age,  who lost her tongue in small-pox and yet could 
PHYSIOLOGY OF TASTE.
105
 speak, spit, chew, swallow and taste.  De Jussieu exhibited  to  the
 Jicademie 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 blindfold, could distinguish be-
 tween 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 of the Germans—is sometimes felt in the whole mouth;
 at  others, in a part only; and is probably owing to the papillae
 having imbibed the  savour,—for the substances producing this effect
 belong principally to  the class of aromatics.   This imbibition fre-
 quently 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 glossopharyngeal.  An interesting question arises—
 which of these is  the  nerve of taste; or  are more  than one, or 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 denied 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 motion for the tongue;
the lingual branch of the fifth, a nerve having a posterior root,  as
the nerve of taste; and the glossopharyngeal as the nerve by which
  VOL. i.                         14 
106
SENSIBILITY--SENSE OF TASTE.
the tongue is associated with the pharynx in the function of degluti-
tion.  Bellingeri considers this nerve to  give the complete organic
and involuntary character to the tongue.   In this it is aided by the
branches  of the fifth pair and of the pneumogastric.  The  hypo-
glossal he regards as the  nerve of the voluntary motions of the or-
gan  for articulate speech and modulated sound in  singing—an in-
ference, which has seemed to be confirmed by the fact, that in fishes
(pisces muii) it is wanting.  It is likewise maintained, that the fifth is
the first encephalic nerve, which 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 would seem to settle the question
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 recognizing 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 function,
 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 sensibili-
 ty—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 sensi-
 bility.
   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
 proceed, 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 developement
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, whea 
PHYSIOLOGY OF TASTE.
107
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: on the
contrary, it is  classed with olfaction as  corporeal.
   To  appreciate a savour accurately, the sapid substance must re-
main for some time in the 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 extract all its  sweets.   How different, too, is  the  con-
sent of the auxiliary organs under  these two circumstances.   Whilst
a  luscious  body augments the secretion of the salivary glands—or
causes the mouth " to water," as it has been called,—projecting the
saliva, at times, to a distance of some feet from the mouth, and dis-
posing every  part to approach and mingle with it;  a  nauseous
substance produces constriction of every secretory organ, and this
effect  extends 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, cceteris 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 favourite
article of diet, we find that the relish is blunted as the stomach be-
comes 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,
cdunt ut vomant."
   Among animals wre  see great  diversities in this sense.   Whilst
none possess the refined taste of man,  there are many,  which are
capable, by taste or smell, of knowing those  plants, that are nutritive,
from those that are noxious to them;  and  it  is very unusual for us to
find that an animal has died from eating  those which are unquestiona-*
ble 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,  containing plants, all  of
which  are ranked by us as poisons, and which are poisonous to a ma-
jority  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 dependent 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 
108
SENSIBILITY--SENSE OF SMELL.
 be closed  or opened at pleasure; and, in addition, it  ordinarily re-
 quires the assistance of the upper  extremity, to  convey the sapid
 substance  to  the  mouth.  The sense can, therefore, be exercised
 either passively or actively; and, by  cultivation, it is capable of being
 largely developed.   The spirit taster to extensive commercial estab-
 lishments 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 these " tasters," 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 con-
 tact with every part of the membrane, and of course  impresses no t
 only the lingual branch, but the other ramifications of the fifth pair.
   The gourmet of the French—somewhat more elevated in the scale
 than our ordinary epicure—prides  himself  upon his discrimination
 of the nicest shades of difference and of  excellence in the  materials
 set before  him.  Many gourmets profess to be able to pronounce, 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:—" sape-
 vano dire gustando li tordi s'erano domestici d pur  selvaggi, e se
 maschi 6 purfemmine."  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 caught.  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 con-
 tinual annoyances  and  discomforts, which  the less favoured  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 nasal
 cavities, and is called the Schneiderian or pituitary.  It resembles
 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 membrane lines
 the whole  of the bony cavities called the nasal fossce, which are con- 
ORGANS of smell.
109
stantly 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 purpose of collect-
ing the odorous particles.  This capital is called the nose.  The es-
sential 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 superior 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. 18*, where figures 7 and 10  represent
the superior  and inferior spongy  bones respectively, 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." 
110
SENSITILITY — SENSE OK SMELL


           Fig. 18.
Transverse vertical seeion near the middle of the Nasal fossa;, seen from behind.
   1. Os frontis deprived of dura mater.
   2.  Do. covered by the dura mater.
  5 5. Anterior part of the cribriform plate of the
       ethmoid bone.
   6. Vertical plate of the ethmoid.
   7. Os spongiosum superius-
8 8 8. Ethmoid cells.
   II. Orbitar plate of the ethmoid bone.
10 10. Os spongiosum inferius.
     11  Vomer.
     12. Upper ma\illary bone.
   It 14. Anterior part of the maxillary sinus.
15  & 16. The fibrous and the mucous linings of
          the sinus.
     Ir1  Palatine arch.
     20. Teeth.
     20. Probe passed through  the ductus ad
          nasum.
     28. Orifice of the maxillary sinus.
   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, sphenoidal
ethmoidal,—the last being sometimes termed ethmoidal cells. 
ORGANS OF SMELL.


     Fig. 19.
a. Frontal sinus—b. Ethmoidal cells—c. Sphenoidal sinus—d Nasal fossa:—c. 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. It resembles 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 num-
ber of  vessels and nerves.  The sinuses are lined by a prolongation,
apparently, of the same membrane;  differing, however, in some re-
spects  from the other.  The whole of this membrane  is the seat of
the secretion of the nasal mucus, which, doubtless, performs a part
in olfaction as  important as the secretion from the mucous mem-
brane 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 sec 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,
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 Gall, and with pro- 
112
SENSIBILITY--1
SENSE OF SMELL.
 bability, referring them, like every other nerve of sense, to the me-
 dulla oblongata.   Beclard affirms, that in  a hydrocephalic patient,
 where a part of the brain had been destroyed by disease, he actually
 detected this origin.
   The  nerve proceeds directly forwards, (See Fig.  12,) 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 fossa;, 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 ab-
 sorption, the papillae; whilst others, as Scarpa, not having been able
 to trace them thither, have been of opinion, that the filaments inter-
 lace 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, wc
 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 in-
 ferius, on the inner surface of the middle spongy bone, or in any of
 the sinuses.
   Besides the first pair of nerves, the pituitary membrane 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  spheno-palatine  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 descntoW.
 by H. Cloquet  under the  name naso-palatine, and which he con-
 ceives 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 receives,
 likewise, the  superfluous tears by means of the ductus ad  nasum,—
 a duct passing from the inner canthus of the eye, and opening into
 the nasal fossae below the lower spongy bone.  The  constant evapo-
 ration, which must take place from the membrane, owing to the pas-
 sage of the air  during respiration, requires  that the secretion should
 be continuous and copious, otherwise the membrane would become
 dry.
  The nasal  fossae communicate externally by means of the nostrils,
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 vibrissa—whose function, it is  conceived, may be to sift, as 
OF ODOURS.
113
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 physi-
cal and nervous part of the apparatus than in  either of those we have
considered;—the nose proper forming the essential physical portion;
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 particu-
lar 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 aban-
doned, because no general  or common characters were  observable
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-
 Ijropriate  agents, as when we subject them to infusion  and  distil-
 ation.
   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,  by infusion and by distilla-
tion.   The fact, however,  has been directly proved by  an experi-
ment 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 1   By most writers on this subject it has been considered
to he dependent  upon the solvent action of caloric on the body.  The
opinion, that all bodies are odorous, is as old as Theophrastus, and it
is one, which it  is very difficult not to embrace, if we  add—provi-
ded they are subjected to the appropriate agents  for disengaging the
odorous particles; and the probability is, that the reason we esteem
particular bodies inodorous is, that our olfactory nerves are not or-
ganized with sufficient delicacy  to enable  us to distinguish  their
odorous properties.   Heat assists the escape of odorous particles from
   VOL. i.                      15 
114              SENSIBILITY--SENSE OF SMELL.
                                                                  si
a variety of bodies, and hence it has been maintained, that every   j
body  which is volatile must be odorous.  Adelon asserts, that this is   -J
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.
H. Cloquet  refers to the case of a  celebrated Parisian physician,   -
who was subject to violent attacks of hemicrania or megrim, and  jjl
who was dreadfully tormented, during one  of the  paroxysms, by
the smell of copper, exhaled from a pin that had been dropped in    j
the bed!                                                      •  iaJ
  Caloric seems to be only one of the causes of the disengagement.M
of odours.  Some  are  retained by so feeble a degree of affinity, -*H
that they  appear to  be  exhaled equally at all temperatures.  Light
influences their escape materially, in particular cases;—some plants
giving off their fragrance during the day, others perfuming the air
only at night.  Dampness, too, in many cases, assists their escape—
hence the fragrance of a garden after a  summer's  showrer and the
smell afforded by all argillaceous substances, when breathed upon—    J
a fact, the knowledge of which is of considerable importance to the    •
chemist.
  Lastly, substances, which appear to us entirely devoid of odour,
may exhale a strong one, when rubbed together.  All these circum-
stances tend greatly to prove, that every substance is possessed of odo-    \
rous 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 diffusibility in the atmosphere.  Some extend to a
great distance, whilst others are confined  to a small  compass.   The
odours of many flowers are so delicate as not to be appreciated, 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 exhibit 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 odo-
rous molecules during the whole  of this period.  Haller kept some 
OF ODOURS.
115
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 hy^TTs*4eootn °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
—seeing 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 per-
fumer consists in fixing and preserving them in  the most agreeable
and  convenient vehicles.  Yet, it was  at one  time  strenuously de-
nied, that they could be conducted through water; and, as a natural
consequence of this view, that fishes could smell.  Dumeril, for  ex-
ample, 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 en-
tertained by few.  We have seen, that odours can be  retained 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, few  anglers, who  have  used their oil of rhodium, or  other
attractive bait,  will be disposed to give up the results of  their  expe-
rience, without stronger grounds than  any that have 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 one, 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, how-
ever, have attempted to specify the precise  chemical composition,
that renders a body odorous.   The sensations  are not the most  fa-
vourable occasions for exhibiting chemical agency; and, in this par-
ticular 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 appre-
ciated ; and we may, in vain, look for  chemical action  in 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 
116
SENSIBILITY—SENSE OF SMELL.
varied; and each substance, as a general  principle, has its own, by
which it is distinguished.  Numerous attempts have been made  to
group them, but all are unsatisfactory.
  The classification,  proposed by Linnaeus, was—into Odores aro-
matici, as those of the flowers of the pink, bay leaves,  &c; 0. fra-
grantes, as those of the lily, jessamine, &c; 0. ambrosiaci, as those
of amber, musk, &c; 0. alliacei, as those of garlic, assafcetida, &c;
0. hircini, (like that of the goat,) as those of the Orchis  hircina, Che-
nopodium vulvaria, &c;  O. tetri, or  repulsive  or  uirous, as those of
the greater part of the  family solanea;  and  lastly, 0. nauseosi, as
that of the flowers of the veratrum, &c.   A  simple glance  at this
division 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, which 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;—Lorry 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, in
the seeds of  the Abelmoschus, 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 mineral sub-
stances ;—as in certain preparations of  gold, and in sorrj^    hs  of
which tea-pots are formed in  China and Japan.
   The odour of garlic,  again, is found not only in that vegetable,
but in assafcetida; 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, which 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
 suaveolentes, 0. medii, and O.faetores.   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.
   Assafcetida, we have seen, was employed by the  ancients as a
 condiment;  and although  with us it has the name devil's dung, it is
 by many of the Asiatics called the food  of the gods.   We find, too,
 certain  animals that are  almost enravished by particular odours.
 The cat, for example, if the  catmint—Nepeta cataria—or the root
 of the valerian—Valeriana officinalis—be placed in its way.   These 
OF ODOURS.
117
differences, like those in  the  appreciation of savours by animals,
must be referred to minute and inappreciable organization.
  Odours have been  considered to be  possessed of medicinal and
even of poisonous properties.   Some individuals, whose peculiarity
of constitution renders them very liable to the action of ipecacuanha
or jalap, will  experience  the  emetic effects of the former, or the
cathartic qualities of the latter, by merely smelling them for a short
time, and the majority of individuals, by pounding jalap or rhubarb
for  a long period,  will find themselves more or less affected.  By
emelling strong alcohol for a considerable time, 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 constant
application of this sense to the discrimination  of teas,  in the Eng-
lish 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 alf these cases, in which  we see medicinal or poisonous effects
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 account-
ed for by the  circumstance of the minute particles of the medicinal
or poisonous substance being diffused in the atmosphere and coming
into contact with the mucous  membranes, from which  they are ab-
sorbed, and in this manner enter the circulation.
  Odours have, likewise, been considered to possess nutritive proper-
ties ; and this chiefly, perhaps, from the effect  known to be pro-
duced by savory smells upon  the appetite.   It is not probable, that
absorption 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 mate-
rially, 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.
  This learned Prelate published a work  in  1638, entitled, " The
discovery of a New World, or  a Discourse tending to prove, that His
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 
118
SRNSITlIUTY--SENSE OF SMELL.
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, a learned contemporary of the Bishop, affords an amus-
ing instance of litigation, arising  from this  supposed  nourishing
character of  odours.   A poor  man  being very hungry,  staid so
long in a cook's shop, who was dishing up the 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 hav-
ing had any;  and  the  controversy was referred to the  decision 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
empty dishes, and that the cook should" be recompensed with the jing-
ling of the  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 nutri-
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  body 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 open-
ing into the trachea  of animals, and  thus  preventing the inspired
air from  passing through the nasal fossae, smell was not effected;
and that dogs, which were  the  subjects of  the experiment, readily
ate food they had previously refused.   These  experiments  were re-
peated 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 wrhy, on the contrary, we arrest the respi-
ration, or make it pass entirely through the mouth, when disagree-
able.  Still odours  are occasionally  so diffusible and  expansible,
that they will reach the olfactory membrane, and wTe are compelled
to shut them off by calling in the aid  of the upper extremity.  The
air being the ordinary medium for the conveyance of odorous mole-
cules, we can understand why the organ of smell should form a part
of the air passages.
   The use of the nose itself is to direct the air, charged wTith 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 expand-
ed or contracted.   The uses we  have  assigned to the  nose are de-
monstrated by the fact, that they, whose noses are deformed—espe- 
PHYSIOLOGY OF OLFACTION.
119
cially 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 resto-
ration 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 con-
firmation.
  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  experiments
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.
   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  sub-
stance, 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.  Des- 
 120              SENSIBILITY--SENSE OF SMELL.

 champs, the younger, also relates a 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 sinus
 or antrum of Highmore, produced no olfactory sensation whatever.
   All these facts would 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 function;
 but, doubtless, offer secondary advantages  of no little importance.
   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 deli-
 cacy of smell, as  in the dog and elephant.   It has already been  re-
 marked, that the ancients believed the olfactory nerves to be canals
 for conveying away the pituita or phlegm from the brain.  Diemer-
 broeck, 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
 distributed 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  experi-
 ments, he had observed with astonishment, that after he had removed
 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 olfactory
 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 
PHYSIOLOGY OF OLFACTION.
121
division, the pituitary membrane not only preserved its general sen-
sibility; 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 sensi-
bility; 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 infer-
ring, that the olfactory  nerve does not preside over the general
sensibility of the nose; that it has, at the most, but a special sensi-
bility 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  spe-
cial sensibility be comprised in the same nerve in the sense of smell,
as they are in that of taste;—in the fifth pair 1
  These experiments are highly interesting;  but they do not entirely
establish, that the fifth pair is the olfactory nerve. The numerous 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;  and that some of  them are
unquestionably supplied with nerves of special 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 olfac-
tory  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 substances, after the divi-
sion of the first pair ; but a source of fallacy might exist here, in dis-
criminating accurately between the general and special sensibility.
Some of the substances employed were better adapted for elicit-
ing the former than the latter;—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 func-
tion  is instinctive; requires no education ; and is exerted as soon as
the parts have attained  the necessary  degree of developement.  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 repugnant to 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  ani-
mals:  there  are many bodies,—those containing  prussic acid  for
  vol. i.                   16 
122               SENSIBILITY—SENSE OF SMELL.
example,—which are extremely pleasing by the odours they exhale,
and yet are most noxious to the human fra'me.   In the animal king-
dom, this sense is greatly depended upon,  and is rarely a fallacious
guide.   It enables animals to make the proper selection of the noxious
from the innocent—the alimentary from  that which is devoid  of
nutriment—the agreeable from  the  disagreeable; and this power
appears to be instinctive  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
where  they have been,—as an organ of gustation, by  which the ani-
mal tastes not only what it can touch and  seize, but even what is re-
mote, and cannot be attained;  and he esteems it a universal organ
of sensation, by which animals are soonest and  most  frequently  im-
pressed, and by which they act and determine, and recognize what-
ever is in accordance with, or in opposition to  their nature.  The
hound, amongst quadrupeds, affords us a familiar example of the ex-
treme  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.
   Until of  late it was almost universally believed, that many of the
birds of prey possess an astonishingly acute sense of smell.   Hum-
boldt relates, that in  Peru, Quito, and in the Province of Popayan,
when  they are desirous of taking the  gigantic Condor—the Vultur
gryphus, of Linnaeus—they kill a cow, or  horse,  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 dis-
tance 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!  The tur-
key buzzard of the United States is a bird  of this class, and it is sur-
prising to  see how soon they collect from  immense distances after 
                     PHYSIOLOGY OF OLFACTION.                 123

an animal has died in the forests.  The recent observations and ex-
periments of the  celebrated ornithologist—Audubon—have shown,
that this bird possesses the sense of smell in a less degree  than the
carnivorous  quadruped.  Audubon stuffed the  skin  of a deer with
hay, and after the whole  had become perfectly dry and  hard, he
placed it in an open field on its back, and in the attitude of a dead
animal.  In the course of a few minutes a vulture was observed fly-
ing  towards it.  It alighted near, and began  to  attack it, tearing
open the seams, and pulling out the hay; but finding that it could ob-
tain nothing there congenial to its taste, it took to flight.  It was found,
too, that when animals,  in an advanced  state of putridity, were
lightly covered over so as to prevent the vultures from seeing  them,
they remained undisturbed, and undiscovered, although the birds
repeatedly flew  over  them.   In  some  other  experiments it was
found, that birds  of prey were even attracted  by well executed
representations of dead animals, painted on canvass and exposed in
the fields,—and in other experiments, that young vultures,  enclosed
in a cage, exhibited no tokens  of their perceiving food, when it could
not be seen by them, however near to them it was brought.
  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  execution of
most of the few offices they have to perform during their transient
existence.  Occasionally, however, they are deceived by the resem-
blance 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 things being, in other re-
spects, equal, it may be fair to presume, that those, in which the olfac-
tory membrane is most extensive, possess the sense of smell most ex-
quisitely.  It is curious, however, that animals, which have the sense
of smell in the highest degree, are  those that feed on the most fetid
substances.   The dog, for instance, riots in putridity;  and the  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 are generally 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 incentive, by ejecting the putrid con-
tents of his stomach upon his possessor.
  One inference may, perhaps, be drawn from this penchant of ani-
mals with the most exquisite olfactories for putrid substances;—that
the taste of the epicure for game, kept until it has  attained the re-
quisite fumet, is not so unnatural as it might at first sight appear.
  Like  the senses  already described, that of smell is, to a certain 
124
SENSIBILITY--SENSE OF SMELL.
 extent, under the influence of volition;—in other words, it can be
 exerted actively, and passively.  Its  active exercise—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 muscles
 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 re-
 ception of disagreeable odours; and, if necessary, can prevent their
 ingress altogether, by compressing the  nostrils with the upper ex-
 tremity.
   Lastly, like the other senses, the smell is capable of great improve-
 ment by education.  The perfumer arrives, by  habit, at an accurate ■
 discrimination of the nicest shades of odours;  and the chemist and
 the apothecary emplby it constantly to aid them in distinguishing bo-
 dies 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 ac-
 customed 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-i
 vian Indians in the middle of the night, can distinguish the different
 races by their smell,—whether they are European, 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 in his 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. 
ORGAN OF HEARING.                  125
         Sect. IV.—of the sense of hearing or audition.

  Audition makes known  to us the peculiar vibrations of sonorous
bodies, which constitute sounds.  It differs from the senses, which 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, and 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. 
126
SENSIBILITY--SENSE OF HEARING.


            Fig. 20.
1. The pavilion.
3. Meatus auditorius extemus
3. Membrana tympani,
4. Malleus,      \
5. Incus.        /
(i. Stapes,
  ()s  orbiculare
  between the in-
  cus and stapes.
small bones of the ear.
 7. Cavity of the tympanum.
 8. Eustachian tube.
 9. Meatus auditorius ititernus.
10. 11. 12. The labyrinth.
10. Vestibule.
11. 11. 11. Semicircular canals.
32. The cochlea.
13. Stapedius muscle.
   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
navicular is 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. 
ORGAN OF HEARING.
127
  On the different eminences, some muscular fibres are perceptible,
which it is not necessary for our purpose to distinguish; for 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
be extremely unimportant.
  Numerous  vascular and nervous ramifications are distributed on
the pavilion.  It is attached to the head by different ligaments, call-
ed—from their situation or attachments—zygomato-auricular or an-
terior  auricular:—temporo-auricular  or superior  auricular,  and
mastoido-auricular or posterior auricular;  all of which terminate
on the  convex part of the concha.  Three  muscles, in animals at
least, are attached to the ear, so  as  to  move the pavilion.  These
occupy the same position as the ligaments described, and have simi-
lar 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  extemus extends from the  inner extremity
of the  concha to the  membrana tympan.  In the adult  it is  about an
inch long;  narrower in its middle than  at  the  extremities; longer
inferior ly 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 sur-
face of the   membrana  tympani.  Beneath  this  skin,  numerous
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 the alarm, in cases  where in-
 sects 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: and 
128
SENSIBILITY-
--SENSE OF HEARING.
even were it able to clear this obstacle, insuperable impediments ex-
ist 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, inap-
propriate.  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, arid 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 being the  membrane proper.  On its inner side is
distributed the nerve, called  chorda tympani, and its centre affords
attachment 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 ifcis ge-
nerally esteemed  to be devoid of fibres, vessels, and nerves.   Sir
Everard Home, however, in the Philosophical Transactions, for the
year 1800, and in the third volume 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,
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  not contractile  like  muscles,  are  distinctly
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
the same degree of contractility.
  Again, Ruysch, Sir Everard Home, and  Sir Charles Bell affirm,
that the membrana tympani is very vascular,—Sir Everard assert-
ing, 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 of it is
probably referable to some having directed their  attention to  the 
ORGAN OF HEARING.
120
membrane proper; others to the membrane with its dermoid cover-
ings, 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 or vesti-
bularis, situated  vertically, and forming a communication between
the middle  and the internal ear.   It is  closed by a membrane, con-
sisting, like the membrana tympani, of three layers,  to which is at-
tached the base of the stapes,—the other extremity of the chain that
stretches across the cavity.   Immediately below the fo&amen  ovale
is the bony projection, called the promontory;  and beneath  this
again, a second opening, called the foramen rotundum or  cochleare
or fenestra rotunda or cochlearis, which forms a communication be-
tween 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 communication 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 it produces a similar effect upon the mem-
branes  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.   Bellingeri thinks, that the fifth pair  regulates
altogether the involuntary motions of the internal ear.
  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 inward, 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
     vol. i.                    17 
130
SENSIBILITY--SENSE OF HEARING.
and ragged  canal, with numerous cells  contained  in  the  mastoid
process.0  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 hearing 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
foramen 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
comprises 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
wh ch the filaments of the auditory nerve reach the  labyrinth.   Ex-
ternally, it communicates with the cavity of the tympanum by the
foramen ovale.  Posteriorly, it opens into the  semicircular canals
by five foramina; and,  anteriorly, by a single foramen,  into the
internal scala  of the cochlea.  There is, also,  posteriorly and in-
feriorly, near the common orifice  of the two vertical semicircular
canals, the opening of a small, bony duct, which terminates inter-
nally at the  posterior surface of the petrous portion of the temporal
bone.  This duct is called the aquceductus 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 consti-
tuted 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, limacon  and schneke.  It is the most intricate part  of the
organ of hearing,  and  does  not, by any means, admit of  easy de- 
ORGAN OF HEARING.
131
script ion.  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 scala 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 communicates
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 hegins, which proceeds towards
the posterior surface of the pars  petrosa on which it opens.   It is
the aquaductus cochlea.
   The cochlea does  not exist in all animals that hear.  It is not,
therefore, 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 extremely
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 and vitrine
auditive,  which,  under particular circumstances, can reflow into the
aquseductus vestibuli and  aquaeductus cochleae.  This fluid  is  con-
tained in all the  cavities of the internal ear.
   It is in these, likewise, that the auditory or  acoustic nerve is distri-
buted.   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 ven-
tricle.  From thence it passes  obliquely outwards, forwards, 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 pro-
ceeds, giving off filaments  to different parts of the  middle 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 audi-
torv nerve attain the labyrinth.  These are distributed  to the  vesti* 
132
SENSIBILITY--SENSE OF HEARING.
bule, semicircular canals, and cochlea;  and terminate, by very deli-
cate ramifications, in the tissue  and at the surface of the membrane,
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 hear-
ing 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 po-
sition of its molecules is produced.  These, by virtue of their elas-
ticity, 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 oscil-
lations is greater  in todies 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 composition, 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 or-
der 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 sin-
gularly exhibited in the Chinese gong, the sound of which will  con-
tinue 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, by virtue of its elasticity, admirably
  * Lamarck supposes the existence in the atmosphere of a vibrative fluid, of great sub-
tilty, which penetrates the  globe invisibly as well as the bodies on its surface: and
Geoffroy St. Ililarie affirms, that sound "is a matter resulting from the combination of
the external air with  the polarized air of the sonorous body !"—but these are topics
that belong to works on higher physics. 
OF SOUND.
133
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 pump, and exhaust the air, the sound
will become gradually more and  more faint, and when the air is ex-
hausted will not be heard at all.  For the same reason a pistol fired
on the  top of the HimSla  mountains gives a  much feebler report
than in the valleys beneath.   Sympathetic sounds afford  additional
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 vibra-
tion, the string, that is in unison with the tone produced, will vibrate;
and  a wine-glass  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 direction,
whilst the aqueous  proceed only horizontally.  In this propagation
from stratum to stratum a portion of the sound  is necessarily lost;
so that the loudest sounds  are heard only within certain 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 upwards
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 communicating 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 calcula-
 tion.  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 report.
 Considering the light then to  have reached the eye instantaneously,
 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 calcu-
 late 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 
134
SENSIBILTY--SENSE OF HEARING.
thirty seconds, the cloud is at the distance of thirty times eleven hun-
dred and forty-two feet, or of six miles and a half.
  This velocity is the same for all kinds of sounds.   Biot found, 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 succes-
sion;  so that their velocity must have been uniform.
  When the aerial oscillations meet with a resisting body  of a re-
gular surface, as A B, 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. 21.                 as  at C,  will refer  the
                                        sound to a distance as far
                                        behind 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
                                        that proceed  along  the
                                        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 sono-
rous undulations impinge be favourably disposed, these echoes may
be very numerous.
  The utility of the ear trumpet, and of the 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 inser-
vient to audition on similar principles.  The ear trumpet is a tube,
narrow at one extremity, so as to enter the concha; and expanded
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  expand-
ed 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 com-
mon conversation, may be able to enjoy it.  A sheet of paper, fold-
ed 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
E 
OF SOUND.
135
much stronger vibration than air.  When they struck two  stones
together under water, a shock  was given  to  the  ear, which was
almost insupportable.  The former philosopher found by experiment,
that sound, after travelling above a mile through water, loses but lit-
tle of its intensity.  According to Chladni, the  velocity of sound in
water is about 4900 feet in a second, or between four and five times
as great as in air.
   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 inaudible 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 dis-
tance.  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 communica-
tion  of sound through solids, has lately given rise to a  valuable sug-
 gestion for  the discrimination  of the 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 aber-
 ration, 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 auscultation.   The direct
 application  of the ear  to the chest is, however, frequently inadmis-
 sible.  In these cases  Laennec used a hollow  cylinder,  called a
 stethoscope, one end of which  he applied to the chest—the other to the
 ear.  This  plan he  termed  mediate auscultation.  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 hundred and forty yards in length, was heard two seconds and
 b. half sooner through the sides of the pipe than through the air;  but
 the sound did  not extend so far.  Ice conveys sound even better than
 water; for if cannon  be fired  from a distant post—a frozen river
 intervening—each flash is followed by two distinct reports,  the  first
 conveyed hy the ice,—the second by the air.
    It has been already observed, that the vibrations of the air, caused
 by a sonorous body, are capable of exciting corresponding  or sym-
 pathetic 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 
13G
SENSIBILITY--SENSE OF HEARING.
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
arrangements, 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 structures,
which are thrown into oscillations, whenever the ear receives 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 musical
string; the sound of which becomes weaker as the extent of the os-
cillations 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
more  slowly.  The latter is  called grace, when compared with the
former.
  The gravest sound, that the ear can appreciate, is  ordinarily con-
sidered  to result from thirty-two vibrations  per second; the most
acute, from eight thousand one hundred  and ninety-two vibrations,
according to some;—twelve thousand, according to  others.   Some
well devised experiments, 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 per-
formed in equal times, a simple  and uniform  sensation will be pro-
duced on the auditory nerve, and one musical tone  will be  heard.
But if the vibrations be various and irregular, they will fall  irregu-
larly on the  organ of hearing, and will excite a harsh impression, 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 har-
mony  or concord.  This arises from  the agreement of the vibrations
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 another, the
second vibration of the latter will strike upon the ear  at the same in-
stant  as the first vibration of the former. This is the eoncord or 
PHYSIOLOGY OF AUDITION.
137
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 vibration of the latter, pro-
ducing the harmony called a fifth.   There are other tones, which,
although they  cannot be struck together 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, sounded in succession.
   There is another quality of sound, which  the French call timbre.
By some  of the translators  of the works of the  French physiolo-
gists, this  word has been inaccurately rendered  note.   It is  essen-
tially  different from note or tone, and  is  peculiar.  By English
philosophers it is termed the quality of sound.  It  is this quality that
enables us to recognize  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 conjectures, that it is
owing  to the series of harmonic sounds forming part of every appre-
ciable  sound.  When any sonorous body is made to vibrate,  a dis-
tinct sound is heard, which is the fundamental; but, if attention be
paid, others  will  be heard at the same time. -  These are called har-
monics.
   It is  not improbable but that the timbre or quality  may be depen-
dent  as well upon  the  nature of the sonorous body,  as  upon the
greater or less number of harmonics, that  accompany the funda-
mental sound.

                     Physiology  of Audition.

   In tracing the progress of the  sonorous vibrations  to the internal
ear, we shall follow the order of parts described  in the anatomical
sketch  of  the auditory apparatus;—commencing  with  the  external
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, by most physiolo-
gists, has been regarded as a  kind of ear trumpet, for 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 particu-
lar 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 sonorous ray,
   vol.  i.                     18 
138
SENSIBILITY
—SENSE OF HEARING.
  which falls upon the pavilion,  is ultimately directed  towards the
  meatus auditorius externus.  Simple  inspection of the pavilion will
  show that this cannot be universally true.  Some part of the anthe-
  lix is, in  almost  every individual, more prominent than 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, asserts,
  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 fa-
  vourable to audition, and is more inservient to the expression than to
  the hearing of the animal.  M.  Itard's view is doubtless too exclu-
  sive.  The pavilion may have but little agency as an ear trumpet,
  but it must have  some.   The  concha, being the expanded extremity
  of the meatus auditorius, must receive more sonorous vibrations than
  could  be admitted by the meatus itself.  These are reflected towards
  the membrani tympani, and reach that expansion in a state of con-
  centration—but to no great extent, it is true.   In this wray, and per-
  haps in that suggested  by M. Savart, the pavilion is useful in audi-
  tion.  That gentleman  is of opinion,  that the whole of the external *
  ear, the elasticity of which he considers to be capable of slight modi-
  fication by the action of its proper muscles,  is an apparatus for re-
  peating sonorous vibrations, and  transmitting  them along  its  own
  parietes  to the membrane of the tympanum. According to this view,
  the different inequalities of surface in the pavilion admit of explana-
  tion.   When a membrane  is stretched  in a  direction  parallel  to  a
  sonorous surface, the oscillations, impressed upon it, are most mark-
  ed ;  and, accordingly, as sounds impinge upon the pavilion from va-
  rious 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
  audition; 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 vibrations
  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 bodies.
  This is perhaps the cause of its tortuous character in all animals.  If
  too tortuous, the  sense of hearing becomes impaired,—the sonorous
  oscillations  not  being  properly directed towards the  membrane.
  Baron Larrey has published some  cases of deafness produced in this
  manner, which were  removed by  wearing an artificial concha and
*y?oeatus, 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 material for entrapping 
PHVSIOLOGV OF AUDITION.
139
insects in the  slough  formed by  it, or for destroying them by its
poisonous influence.  It is probable, however, that the most impor-
tant function of the cerumen is to keep the lining membrane of the
meatus in a physical condition, adapted 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 Sa-
vart would seem to show, that this membrane is thrown into vibra-
tions chiefly by the air contained in the meatus.  He made a small
truncated cone of pasteboard, and closed the smaller extremity 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 opposite 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 possessed
of other  functions.  Dumas, for example, conceived it  to be com-
posed 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  contrary,
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 vibra-
tions, 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 ap-
preciating tones, which amount to about eight octaves.
  Bichat thought, that the degree of tension of the  membrane  cor-
responded 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 tension.
  Savart, on  the other hand, from the fact, that every membrane
vibrates with  more difficulty, and less extensively, according to its 
 140              SENSIBILITY--SENSE OF HEARING.

 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 physiolo
 gists in  the case of acute, according to others,  in that of gr-ave,
 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 em-
 power 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 impressions."
   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 inquire
 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 oe 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 knowledge^
 of the precise effect on audition of such tension or relaxation.      ""rt.
   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, Flourens, -
 and others, in which the hearing continued ; and, in certain cases of
 deafness, the membrane is  actually punctured  for the purpose of
 restoring the hearing.
^  The communication of sonorous oscillations from the mehibrana
 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-
 vity of the tympanum;  2dly, by the chain of bones  to the membrane 
PHYSIOLOGY OF AUDITION.
141
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, aqd 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 oscillations to come in con-
tact with a larger surface ; or by the plates, which  compose them,
being thrown into vibration.   It has been  conceived, too, that they
may serve as a diverticulum for the air in the middle ear, when sub-
jected  by the membrana tympani to unusual compression.
  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 labyrinth, which he describes,  as the liquor of Cotunnius can
readily reflow  into the aqueducts of the vestibule and cochlea.  The
principal use  of these canals would  seem,  indeed,  to  be, to form
diverticula for the liquor, when it receives the aerial  impulses.
   Sir  ('. Bell cites the case, often quoted from Riolan, of an indivi-
dual, who  was  deaf from  birth, and  who  was restored to hearing 
142              SENSIBILITY--SENSE OF HEARING.
                                                                  i
by accidentally rupturing the membrana tympani, and breaking the
ossicles 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 internal ?ear through the air in the cavity of the tympanum,
and, notwithstanding the charge of " absolute confusion  of ideas,"
adduced against such individuals as Scarpa, Magendie, Adelon, and
others, who believe that the  foramen rotundum receives  the  undu-
lations of  the air, we must confess, that the idea  of the  communi-
cation of  vibrations through that medium, as  well as through the   1;
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-  M
brana tympani,  or to stretch the membranes to which the extremi    11
ties of the chain are attached.  Both these offices  are probably exe-   1
cuted by them,  the malleus receiving the vibrations from  the  mem-   -n
brana tympani,  and conveying them to the incus,—the incus to the os    ?
orbiculare,—the os orbiculare to the stapes,  and the  stapes to the    j
membrane of the foramen ovale by which  they are transmitted to    i
the liquor of Cotunnius.  Savart conceives, that  the chain  of ossicles    *
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, with-
out deafness being produced, provided the membrane of the foramen    t
ovale remains entire, and the parts within the labyrinth retain their <*■
integrity.   If, in the removal of the  stapes by ulceration or other-
wise, the membrane of the foramen were to  be ruptured, the liquor of   »
Cotunnius would of course escape, and partial or total deafness be    \
the result.  In  some experiments, instituted  by Flourens on pigeons,    -i
he found, that the removal of the malleus  and incus did not  have    *
much effect upon the hearing; but when the stapes  was taken away
it was greatly diminished, and  still more so when the membranes of
the fenestra ovalis and fenestra rotunda were destroyed.
  The Eustachian  tube is an important part of the auditory appa-   *
ratus, and an invariable accompaniment of the membrana tympani,
in animals.  Without the tube, the membrane would  be  devoid of
function.    Pathology shows  us, in the clearest manner, that its in-
tegrity 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, con-
nected 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 aper- 
PHYSIOLOGY OF AUDITION.
143
  ture 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 membrana  tympani at one end
  of the cylinder, and on the membrane of the foramen ovale at the
  other, as would be produced on the parchments of the ordinary drum
  by the closure of its lateral aperture.  We can, in this way, account
  for the temporary deafness, which accompanies severe  cases of in-
  flammation of the throat: the swelling obstructs 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, exhibits 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 be-
  comes 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  sonorous body is put in contact with the teeth, that
  the sound is appreciated.  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 properly
  remarked, however, that this may  be merely an act of expression ;
  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 meatus, 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 
144              SENSIBILITY--sENSB OK HEARING.                     '

foramen ovale and foramen rotundum resemble the membrana tyin-  j
pani in their physical characteristics ; and, when thrown into vibra-
tion, communicate the impression to the liquor of Cotunnius,  which
fills the cavities of the internal ear.  By this medium the vibrations
are conducted to the auditory nerve, which conveys the impression
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, with-
out 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  a
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    j
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 conjee-   ■]
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 as 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
a better 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 sernicular canals have  been compared to organ pipes,
adapted for producing  numerous tones; and  Dr. Young supposed
them to be " very  capable of  assisting in the estimation  of the 
PHYSIOLOGY OF AUDITION.
145
 acuteness or pitch of a sound, by receiving its impression at their
 opposite ends;  and occasioning  a  recurrence of similar effects  at
 different points of their length, according to the different character
 of the sound;  while the greater or less pressure of the stapes must
 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 knowledge of the
 precise functions of either vestibule, cochlea, or semicircular 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 distinctly
 audible; and Ingrassias relates the case of a person, who  had be-
 come  deaf in consequence of obstruction of the meatus auditorius
 externus, and yet could hear the sound  of a guitar, by placing the
 handle between his teeth,  or by making a communication between
 his teeth and the instrument by a metallic or other rod.  The physi-
 cian has recourse to  a plan  of this kind  for detecting  whether  a
 case of  deafness be dependent upon obstructed Eustachian tube—
 upon some affection of the meatus auditorius externus—or upon insen-
 sibility 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 may necessarily
 be one of a hopeless character.  If, on the other hand, the sound be
 perceived, the attention of the  physician may 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 impervious,
 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.
   Professor Mojon, of Geneva, is of opinion, that the cranium serves
 as an harmonic case, or drum,  which communicates its"vibrations to
the auditory organs.  Numerous observations have induced him to
 infer, that the cranium is by no means passive in  the  perception of
 sounds, and that differences in the thickness of its walls  may have
considerable influence in determining the degree of acuteness of the
faculty.
   Lastly—as regards the precise nerve of hearing. In this sense we
have the distinction between the nerve of general, and  that of special
sensibility, more clearly observed.   The experiments  of  Magendie
   vol.  i."                       19 
146
SENSIBILITY--SENSE OF HEARING.
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 ex-
hibiting any general sensibility, and that  it is inservient only to the
sense of hearing.   The  same experiments  demonstrate, 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 experiments of Flourens, to which allusion has been made, led
him to infer, that the rupture of the cochlea was of less consequence
than that of the  semicircular canals.   Laceration  of the  nerve, dis-
tributed to  the  vestibule,  enfeebled  the  hearing,  and its total de-
struction was followed by irreparable deafness. For these, and other
reasons, furnished  by comparative anatomy, Lepelletier infers, that,
in the higher organisms,  the vestibule and its nerve constitute the es-
sential organ of impression, the other parts being superadded to
perfect the  apparatus.

   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 sense
—that it is  instinctive, requires no education, and is exerted as soon
as the parts have attained  the necessary degree of developement.
   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  it that we  are indirectly indebted
for  the  use of verbal  language—the happiest   of  all inventions
—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 ultimately
 effected in  the brain,  " That it," (the power of  distinguishing 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  remembered,
 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 them-
 selves, or of their relations to each other may, to the mere  eye, be
 so minute,  as never to  be discovered by dissection."  Many phy-
 siologists of eminence have regarded the  complex internal ear as the 
PHYSIOLOGY OF AUDITION.
147
seat of the faculty;  some looking to the cochlea; others  to  the
semicircular canals, but few 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 melody 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
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 membrane,
like the movable bridge  of  the monochord, adjusting it to the vibra-
tions required to  be produced;" and  he  adds,  " the  difference be-
tween a musical ear and one which is too imperfect to  distinguish
the different notes  in music, will  appear  to arise entirely from the
greater or less nicety with  which the muscle of the malleus 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- 
148
SENSIBILITY--«KN>K OF HEARING.
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 Astley 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 cir-
cumference of the membrane could  be  discovered, with a circular
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; "he
played well on the flute, and had frequently borne a part in a con-
cert; and he sung with  much taste and perfectly in tune."
  But, 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 deli-
cate 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 ani-
mals between the power and  character of their music, and the con-
dition of their auditory sense.   We are compelled then to admit, that
the faculties of music and speech are dependent upon the organiza-
tion of  the brain;  that  they require  the ear as a secondary instru-
ment ; but  that their degree of perfection is  by no means in propor-
tion to the delicacy of the sense of hearing.  In these opinions, Gall,
Broussais,  Adelon,  and other distinguished  physiologists,  concur. 
PHYSIOLOGY OF AUDITION
149
" Speech," says Broussais, "is heard and repeated by all men, who
are not deprived of the auditory sense, because they are all endowed
with cerebral organization, fit to procure for them distinct ideas on
the subject.   Music, when viewed as a mere noise, is also heard  by
every one; but it furnishes ideas,  sufficiently clear to be reproduced
and communicated  by those individuals  only, whose frames are  or-
ganized 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."

   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 evidences
 of their wide separation. Whilst the professed musician is frequently
 devoid of all poetical talent, many excellent poets have no musical
 ear.  Neither does the power of discriminating musical tones indi-
 cate that the possessor is favoured with the finer sensibilities  of the
 mind; nor the want of it prove their deficiency.  It has been a com-
 mon remark, that, amongst professed musicians, the intellectual mani-
 festations 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 moved with concord of sweet sounds," alike  distinguished
  as philosophers and philanthropists.
    The defect, in these cases, differs probably in an essential manner,
 from one to which attention has been drawn by the late Dr. Wollas-
  ton, in the Philosophical Transactions, for 1820.   In that communi-
  cation he describes many curious facts, regarding, what he terms, a
  peculiarity in certain ears, which seem to have no defect in the gene- 
 105              SENSIBILITY--SENSE OF HEARING.

 ral  capacity of receiving  sound, or in the perception 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 consti-
 tuted.  Thus, according to Wollaston, certain  persons  cannot hear
 the  chirp of the grasshopper;  others the cry of the bat; and he re-
 fers 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 would, at first sight, appear to 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 vibra-
 tions, that are performed with great rapidity, not being responded to
 by the parts of  the  organ  destined  for  this purpose;  and, con-
 sequently, never  reaching  the auditory  nerve.  Researches, how-
 ever, of Savart—one of the most dexterous and  ingenious experi-
 menters of the day—seem  to  show, that the defective appreciation
 of acute sounds, in such cases, is  not owing to their acuteness, but
 to their feebleness; that, if  the sound  can  be  made  sufficiently in-
 tense, the ear is capable of  hearing a note of upwards of forty thou-
 sand 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 judg-
 ment  of the distance of bodies.   This we  do  by attending  to the
 loudness of the sound; for  we instinctively lay  it down as  a princi-
 ple, 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 numerous
 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 circum-
 stances, 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  com-
 pleted by the appearance of the military band on  the stage, allow-
 ing its soul-inspiring strains to  vibrate freely in the air. In like man-
 ner we are deceived by the ventriloquist.  He is aware of  the  law,
 that guides us in  our estimation of distance, and, by skilfully modi-
 fying 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 Physiologie 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 injec-
 tions thrown into the cavity of the tympanum through the  pharvn- 
                    PHYSIOLOGY OF AUDITION.                  151

geal extremity of the Eustachian tube, one of the most remarkable
points was, his difficulty in acquiring a knowledge of the position 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 em-
ploying both.  Still we are often deceived even under these last cir-
cumstances, 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 by the ear.   In the  Belisar of Zeune,
the case of a blind man is cited from Diderot;  who, guided  by the
direction of the voice, struck his brother, in a quarrel, on the fore-
head, with a missile, which brought him to the ground.
  If the sonorous vibrations before reaching the ear are deflected
from their course we are liable  to  deception, mistaking  the echo
often for the direct or radiant sound.
  The  ideas 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
indirectly produced will  necessarily be modified by the different re-
flections or echoes, that may  be excited.   By attending to these
circumstances—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
intensity 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 inter-
vening  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 
 152                SENSIBILITY--SENSE OF SIGHT.

 experience,  without which  we should be completely at a loss; and
 to execute a very  rapid, but often  a very complicated  intellectual
 operation.

   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
 example, the advantage be limited to the better direction given to
 the ear, as regards the sonorous  body, and to the avoiding of all
 distraction,  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
 extrinsic 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
 reception of the  impression, and the brain for its  appreciation.  All
 these points  are insusceptible of direct observation, and experiment,
 and 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 edu-
 cation 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 in-
 audible to one brought up in the din of the busy world.
   The blind, for  reasons  more than  once assigned, afford examples
 of extreme  delicacy of this  as  well as  of their  other  remaining
 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
 organization, 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 accom-
 plished.

           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
 subtile, 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 
OF LIGHT.
153
 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 sim-
 plicity ; 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
 admits the  light.  It is  in  this simple state, that M. de Blainville
 assimilates it to a  bulb of hair, modified for the new function it has
 to 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 tt  the laws of optics—the latter
 being  a production  or expansion  of the nervous system, for the
 reception of the  impression of light, and for conveying such impres-
 sion to the proper part of the encephalon.  There is, besides, attach-
 ed to the organ,  a  number  of  accessory 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 accessory or-
 gans,  which serve to lodge, move, protect, and lubricate it.  The
 description  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 phos-
 phorescent 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 extremely
minute particles, emanating from luminous  bodies; the other—that
  vol. i.                         20 
154
SENSIBILITY--SENSE OF SIGHT.
of Descartes, Hook, Iluygens, Euler, and others,—that it is a subtile,
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 vibrations affect the ear.  It
is  not for us to discuss  this question of higher physics.  We may
merely remark, that difficulties attend both hypotheses.  According
to that of Descartes, it is not easy to explain, why an opaque body
should prevent the undulations from reaching the eye,—or the change
of direction, which the light experiences in passing from one medium
into another; whilst, according  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  extreme delicacy, is insufficient to dis-
turb the  equilibrium.  To the hypothesis of Newton it has also been
objected, that the particles, being reflected by thousands of bodies,
and in innumerable directions, 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  impres-    i
sion of a luminous object remains upon the  retina for the sixth part
of a second.   Admitting it, however, to impress the eye for the
s^o-th part, three hundred particles, per second, would be sufficient
to excite a constant 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 se-
cond, 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 Romer, Cassini, and other astronomers, it has been calcu-
 lated, that the light of the sun is eight minutes and thirteen seconds
 in  its passage from that luminary to the earth.  The distance be-
 tween the earth and sun is  thirty-three millions of leagues, so  that
 the velocity of light is  sixty-seveii thousand leagues, or two hun-
 dred thousand miles per second; in other words, in  the  lapse of  a
 single second it could pass between Washington and Albany—sup- 
OF light.
155
   posing 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 y^th part of a second.  Inconceivable as this
   velocity is, it is far surpassed by that of the attractive power exerted
   between the heavenly bodies.  " I have ascertained," says La Place,
   "that between the  heavenly bodies all attractions are transmitted
   with a velocity, which, if it be not  infinite, surpasses several  thou-
   sand times the velocity of light; and we know that the light of the
   moon reaches the earth in less than two seconds."  An annotator on
   the works  of this distinguished mathematician is  more definite,
   affirming, "that the gravific fluid  passes over  one million of the
   earth's semi-diameters  in a  minute  of time."  Its  velocity is  eight
   millions of times greater than that of light.
      A series of  particles, succeeding  each other in  a straight line,  is
   called  a ray of light.   The light which proceeds from a  radiant
   point, forms diverging cones, which would be prolonged indefinitely
   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, af-
   terwards, 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  case,  as  in every other, diminishes  according to the
   square of the  distance from the luminous body.  According to this
a 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 calo-
   ric—in much  greater intensity; whilst the more distant  luminaries
   can receive 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: it 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. 
150
SENSIBILITY--SENSE OF SIGHT.
Fig. 22.
  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 per-
pendicular to the surface of the medium at  the point of incidence, is
exactly equal to that  made  by the  reflected ray with  the same per-
pendicular.
  Suppose I J, (Fig.
22.)  to represent a
plate of polished me-
tal, or of glass,  ren-
dered  opaque  by a
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 K C; that  j
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 be-
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 ne- *
cessary 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
B C K, or angle of incidence,  must  be equal to the angle of reflection,
A C K.   In this case, again,  the object will not appear 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 prin-
ciples  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
 
OF LIGHT.
157
  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 emergence.  Instead
  of considering the medium I J opaque, let  us  regard it as transpa-
  rent.  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 con-
  tinues its course through the medium without  experiencing any mo-
  dification, and  emerges in the same  straight  line.   Hence, a body
  at L, will appear in  its true direction  and distance  to  an observer
  at K looking directly downwards 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 direction C H, it  is refracted, at the
  point of immersion, in the direction C F—that  is,  towards the  per-
  pendicular 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/row the perpendicular.  The cause of this difference in
   the  deflections, produced  by different media, is not easy of expla-
   nation.  The fact,  alone, is  known to us, that  bodies refract light
   differently according to their densities and nature.  If the light pro-
   ceeds 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  rarer medium, it is  refracted from the perpendicular.
   The ray A C passed from a rarer medium,—the air,—into a denser,
   I J—water:  it was refracted in the direction C F, towards the  per-
«  pcndicular 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 tro-
   phies, by his prognostic, in the  then  infant state  of chemistry, that
   water and the diamond would be found to contain combustible ingre-
   dients.  The diamond or brilliant is one of  the most refractive  of
   known substances, and this is  one of the sources of its" brilliancy.
   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,
     fives  rise to numerous optical illusions.  The ray proceeding from
     ', in the bent course F C A, will impinge on an eye at A;  and the 
158
SENSIBILITY--SENSE OF SIGHT.
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 per-
ceptible to an eye in the water at F, in the direction OOF; whilst
one at A would  be distinctly visible; the ray from it  proceeding in
the direction A C F, but appearing to come straight to the eye in
the direction OCF.
   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, what-
ever may be its  shape:—in all cases, the sine of the angle of refrac-
tion holding the same ratio to the  sine of the angle of incidence,
whatever may be the incidence.  The angle of incidence is the  an-
gle formed by the incident ray with a perpendicular raised from the
point of  immersion; the angle  of refraction, that formed by the re-
fracted portion of the ray with the same perpendicular.  In Fig. 22,
A C K  is the angle of incidence of the ray A C; 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  arrange-
ment.  The perpendiculars to the surface may approach or recede
from each other; and if this be the case the refracted rays will  ap-
proach 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 entering
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 thickness 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 interval  be-
tween the direct ray and the ray A C F after its emergence is that
between  G and H.
   If the  surfaces of the diaphanous body are plane, but inclined to-
                                             wards each  other,
                    Fig. 23.                  as  in the common
                        ■n*                H prism, the  refrac-
                                             tion,   experienced
                                             by  the   ray  on
                                             emerging,  instead
                                             of  correcting that
                                             experienced during
             C       -^            •---       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
 
OF LIGHT.
159
two  refractions.   The  ray A B, Fig. 23, after impinging upon the
side D L of the prism, at B, instead of continuing its course in the
direction B J, is refracted towards the perpendicular C B F; the me-
dium being denser than air; and on emerging into the rarer medium,
instead of continuing its course in the direction G 1, it is refracted in
the line G H or from the perpendicular K J.
  Again, if the surfaces of the medium be convex, the  rays are so
situated, after refraction, as to converge  behind the refracting body
                                         into a point called the
                 Fig 24.                focus, which is nearer to
              \^                       the medium the less the
                 \^  C   y^-'         divergence of the rays,
                _^S^^C             or  in other words, the
         ^-^^^Z-^^^^^^       more distant the lumi-
 A **^^^Z2^:Jpjl ^S^^13  nous object. Fig. 24 ex-
         '^y^^^Z^^^P^^Z['^       hibits a  pencil of rays,
                   Js^v"--..   "'"       proceeding  from a ra-
                 y"'   D    "*■*•           diant point at  A, and
                                         meeting at a  focus at
 B; the dotted lines being 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. 25,
 the luminous rays, proceeding from a radiant point as at A, are ren-
 dered so divergent, that if we look for a focus here it must be ante-
 rior to the medium or at G.

                            Fig. 25.
  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 
1(J0                SENMLILITY—SENSE OF MG11T.

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 arc
composed of two segments of a  sphere.  The medium in Fig.  21 is
a double convex lens; that in Fig. 25, 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.

                            Fig. 26.
              White.
  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
whitened 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
direction 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 pass-
ed 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. 
OF LIGHT.
161
   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 yellow.  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 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 ivhite colour'; 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 ac-
counting for the ignotum per ignotius.
   Two other  points require a  brief notice, being  intimately con-
cerned in vision;—the  aberration of sphericity, and the aberration of
rcfrangibility.
   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
rays do not, however, meet in this focus.  The rays  that are nearest
the axis, It" F of the lens, Fig. 27, 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 It',
R",  and R",
are brought to
a  focus  at  F,
whilst the rays
R L, and 11""
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 diversity of focal
  vol.  i.                      21
 
162                sENMHILITY--SENSE OF SIGHT.

distances  is  called  the  spherical aberration,  or the  aberration of
sphericity: the distance / F is the longitudinal spherical aberration;
and B A the lateral spherical aberration, of the lens.  This aberra-
tion  is  the  source of confusion in  common lenses;  and, as it is
dependant upon  the  shape of the lens,  it has  been  obviated, by
forming these  instruments of such degrees  of curvature, that the
rays,  falling 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 inconvenience  is  obviated by  employing  lenses of a  small
number of  degrees, or  by interposing an opaque body—called, by
the opticians, a diaphragm—anterior to the lens,  so that the rays of
light  can only impinge upon the central part,  and  consequently
be refracted to  the  same  focus.   This diaphragm  is present in
all telescopes,  and occupies  the situation of the curves D and D'
in Fig. 27, so as only to  admit the rays R', and 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,
constituting the solar spectrum, are unequally refrangible,—the red
being the least, the violet the most  so; hence  the cause of their
dispersion 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 coloured.  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  it has
been attempted to be obviated by glasses, which  have  been termed,
in consequence, achromatic.  These  are made by combining  trans-
parent bodies of different dispersive powers,  in such sort, that they
may  compensate  each  other, and thus  the object be  seen  in its
proper colours, notwithstanding the refraction.  Dr. Blair found, for
                   p.  2H                   example, that by en-
                                            closing   muriate of
                                            antimony,  B E, ber
                   AJt!p                    tween  two  convex
                                            lenses  of  crown
                                            glass, A D and C F,
                                            the parallel rays R,
                                           PR and  R  were re-
                                            fracted  to  a   single
                                            focus at  P without
                                            the slightest trace of
                                            secondary   colour.
                                            Newton was of opi-
                                            nion, that  the  light,
in traversing a  refracting medium, always experiences a dispersion
 
ORGAN OF VISION.                  *   163
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 in-
struments have  been formed on the principles above mentioned; so
ns to greatly diminish the inconveniences sustained from the use of
common lenses; although, still, not perfectly achromatic.   The in-
convenience 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 constituted 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
offices, which are admirably performed by the eye—the most per-
fect of all optical  instruments. 
164                SENSIBILITY--SENSE OF SIGHT.

                             Fig. 29.
a. Aqueous humour.—6. Cornea.—c. Iris.—d- Lens.—e. Ciliary processes.—/. Vitreous humour.—    -S
                 g. Optic nerve.—h. i. Muscles above and below.                     1
  Every telescope consists, in part,  of a tube, which always com-
prises pieces, capable of readily entering into each other.  Within   TJ
this cylinder are several glasses or lenses, placed in succession from  '-r--lj
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 purpose
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 coloured black, to absorb the oblique rays, which    '*
are not  inservient to vision, and thus to prevent them from causing,   •'
confusion.                                                        <  V*
   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 humour.
Lastly, in the interior of the  eye, near the anterior surface  of the
crystalline lens, is a  diaphragm—the iris, having an aperture in its
centre—the pupil.  These different parts will demand a more detail-
ed notice. 
ORGAN OF VISION.
165
   1. Coats of the eye, &c—The sclerotic is the outermost coat.  It
is  that which gives shape to the organ, and which constitutes the
white of the eye.   It is of a dense, resisting, fibrous nature, belong-
                                            ing  to  what Chaus-
                                            sier  calls the albugi-
                                            neous tissue. Behind,
                                            it is penetrated by the
                                            optic nerve; and be-
                                            fore,  the  cornea  is
                                            dovetailed into it.  It
                                            has,  by  some  anato-
                                            mists, been consider-
                                            ed a  prolongation  of
                                            the  dura mater,  ac-
                                            companying  the  op-
                                            tic nerve; whilst the
                                            choroid  has  been re-
                                            garded  as an  exten-
                                            sion of the pia  mater,
                                            and  the retina, of the
                                            pulp   of  the  nerve.
 a. 1ns— 6. White of the eye.-P. riica semilunaris.—CCaruncuIa \ne  SClerotlC  IS the
lacbrynialis.—S S S. Supercilimn.—'I'. Under surface of upper eye- place of  insertion for
lid.—t. Under surface of lower eyelid.—p. Punctuin lachrymale in r
the tarsus of each eyelid.
the various muscles that move the eyeball, and is manifestly intended
for the protection 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 laminae 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 pigmentum
nigrum.   In some  cases, as in the albino, this substance, which is
exhaled  from the choroid, is light-coloured, approximating to white.
Leopold Gmelin conceives,  that it approaches 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 Ruyschiana appear.  This  spot is termed
the tapetum.  It is met with only in quadrupeds. 
166
SENSIBILITY--SENSE OF SIGHT.
   The retina is the last  coat, if we except a highly delicate serous
 membrane,—lately  discovered  by Mr.  Jacobs, Demonstrator of   j
 Anatomy in Trinity College  Dublin, and  called after  him Tunica   <j
 Jacobi,—which is interposed between  the retina and choroid  coat.   '4
 Mr. George H. Fielding, of Hull, has also recently affirmed, that im-
 mediately behind the  retina, and  in  connexion with it, there is  a
 peculiar membrane, separable into distinct layers from the choroid,   ',
 and supplied with blood-vessels, which he proposes to name mem-
 brana versicolor.  He  presumes, that  it receives the  vibrations of   '
 light, and communicates them to the retina.  The eyes, used for ex-
 periment, were those of the ox and the  sheep.  The retina lines the
 choroid;  and  is a soft, thin, pulpy, and grayish membrane, formed   j
 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 distributed;—a structure more  consistent with analogy. On   I
 its inner surface, it is in contact with the membrane of the vitreous
 humour, but they are not adherent.  Anteriorly, it terminates  near   j
 the anterior  extremity of the choroid, forming a kind of ring, from   i
 which an extremely delicate lamina is  given off  This is reflected   \
 upon the ciliary processes, dips  into the intervals separating them,   J
 and, according to  some anatomists, passes  forward as far as the   j
 crystalline.   About a sixth of an inch on the outside of the optic   1
 nerve, and in the direction of the axis of the eye, or of a line drawn   1
 perpendicularly through the centre of the cornea, is a yellow  spot,   i
 about a line  in extent, surrounded by several folds, and having a
 foramen in its  centre.   These are the limbus luteus, and foramen'-^S^
 centrale of Sommering.                                         " '^^
   The retina receives  many blood-vessels, which proceed from the   j
 central artery of the retina, or of Zinn.  This vessel—it is important ■-.VJj
 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 refract-
 ing bodies, are either transparent membranes, or fluids contained in
 capsules, which give them a fixed  shape.   These parts  are the cor-
 nea, 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 larger.   It was,  for a long time, considered to be a prolongation    "J
 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 com-
 posed of several thin laminae in super-position, which have been com-
pared to horn, and hence the name of the membrane.  Like the cor-
neous tissue  in general, it possesses neither blood-vessels nor nerves.
In animals, the  density  and convexity of the  cornea vary with the 
ORGAN OF VISION.
167
media in which they exist, and with the condition of the other re-
fractive 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 posterioi—the latter being
the  small interval between the hinder surface of the iris, and the an-
terior surface of the crystalline.   Sir David Brewster erroneously
asserts that the posterior chamber contains the crystalline and  vitre-
ous  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 hu-
mour has a proper membrane, which secretes it, or whether it is not
an  exhalation from the vessels of the iris and  ciliary processes.
Itibes, indeed, derives it from the  vitreous  humour.   However se-
creted, 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 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 little greater.   According to
Berzelius, it is composed of water 98.10; a little albumen, muriates,
and lactates 1.15; soda, with  a substance soluble in water, 0.75. 
168
SENSIBILITY--:>E\>E OF SIGHT.


          Fis. 31.
                    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 2$
   lines thick at its centre.  It is situated between the aqueous and vitre-
   ous humours, and  at about one-third of the antero-posterior diame-
   ter of the organ.  A depression, at the anterior surface of the vitre-
   ous humour, receives it,"and   a reflection of the  proper membran&H
   of this humour passes over it.
     The crystalline is  surrounded by its capsule, the interior of which
   is bathed by a slightly viscid and transparent secretion, called liquor
v  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
■A 
OKG \.\  OF VISION.
169
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. \ oung.
Its muscularity  is, however, by no means established, although 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 consequence of 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 specifie 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 communi-
cate freely with each other, and are well represented in Fig 31.
  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 goudronne, 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-
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
  vol. i.                        22 
170                SENSIBILITY--SENSE OF SIGHT.

the eye.   Edwards, of Paris, affirms, 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 humour, and is
reflected over its anterior surface; and the fourth is the proper tissue
of the iris.  Magendie asserts  that the most recent anatomical in-
vestigations prove  the membrane to be muscular; and to be com-
posed of two sets of fibres;—the outermost radiating; whose office
is to dilate the pupil; the  innermost circular and concentric, for the
purpose  of contracting it.  The  arrangement  of these fibres is re-
                           presented in Figs. 32 and 33; the former
                           of which  is  an internal  view  of the
                           human iris, magnified three diameters;
                           and  the latter, an  external view, exhi-
                           biting the  surface  to  consist essentially
                           of a plexus of blood-vessels;  both  are
                           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-
tum. 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 vasculo-
membranous appendages  arise, which appear to be prolongations of
the anterior margin of  the  choroid, turning inwards towards the
margin of the crystalline  lens, and terminating  abruptly, without be-
ing attached to that body.  They are the ciliary processes.
Fig. 32.
Fig. 33.
 
OriGAV OF VISION.
171
  These beautiful appendages  are from sixty to eighty in number;
and resemble the  disk of a radiated flower.  On their posterior  sur-
face 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 processes have been esteemed  nervous; by others, muscular,
glandular, and vascular.  Sir Everard Home asserts, on the authority
of microscopic observations  by Mr. Bauer, that  between the  pro-
cesses are bundl§s of muscular fibres of considerable length; which
originate all around from the capsule of the vitreous humour, pass
forward over the edge of the lens, are  attached  firmly to  its cap-
sule, and there terminate.  They are  unconnected with the ciliary
processes, or iris, and he conceives that their contraction will  pull
the lens towards the retina.  In appearance they resemble the cho-
roid, 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 ante-
rior 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 thalami, 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 substance, situated be-
tween the point of junction of the  nerve of each side and the emi-
nentiae mamillares,—called the tuber cinereum.  Proceeding forward
towards the eye, the nerves approach, and form a  junction at the
sella turcica, or on the upper surface of the sphenoid bone.   Ante-
rior to this point, they diverge, each passing through the optic fora-
men to the corresponding eye ; piercing the sclerotic and choroid at
a point about one-tenth of an inch from the 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  iunction 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 
172          *     SENSIBILITY--SEN^F. OF SIGHT.
the left.  Anatomical investigations have  hitherto left the question
unsettled, whilst pathology appears to have furnished proofs on both
sides.  Thus, where the  right eye has  been lost for a considerable
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 pass-
ing  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 touching  at all; and yet without any
disturbance of  vision.  It is not necessary, however, to  adduce the
numerous cases that have been published  in favour 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,  Cheselden,  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.
   Sommering—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, Berard, Pravaz, Gall and Spurz-
heim, Cuvier, Serres, and others, embrace  this opinion for the pur-
pose 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 arrangement in the horse, in the
nerves when subjected to appropriate maceration.
   These views are, however, opposed by the  direct experiments of
Magendie.   He divided, in  a rabbit, the right optic nerve, behind
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- 
AC( E-m>RY ORGAN=> OF VISION.
173
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 de-
cussate 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
Size of pupil diminished by magnifying power of cornea
     to             .      .       •       •       •    0.25 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
      cenlrale of Sommering     .       .       .       .        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°
                                                      120°
Field of vision below a horizontal line   .       .    70° \
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.

                       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-
■v 
174         4     SENSIBILITY--SENSE OF SIGHT.

tions  for  which  they are destined.  They are, in the first  place,
securely 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 proceed
to the eye or its appendages.   The base of the orbits is not directly
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. 29, 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,  which is not  occupied by the optic nerve,
being 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  augmented, so  as  to  cause
the eye to  start from  its socket;  constituting the  disease called
exophthalmos.
   The  parts,  however,   that  are  more  immediately  reckoned
amongst the protectors of the organ—the tutamina oculi—are the
eyebrows,  eyelids, and the  lachrymal apparatus.
  The  eyebrows or supercilia,  (Fig. 30, S S S.) 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
subaceous follicles, situated at the root of each hair—and of muscles '*
to move them, namely, the frontal portion of the occipito-frontalis, ^
(A A. Fig. 34;) the upper edge of the orbicularis  palpebrarum, C;
and the corrugator supercilii, B.
  The palpebra 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
below it,  and  therefore  improperly  termed, by  Haller,  ^Equator '
oculi.   By the separation  of the eyelids, we judge, but inaccurately, '.A
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
conversely.
    ■■*■ 
ACCESSORY ORGANS OF VISION.


          Fig. 34.
175
A A. The frontalis muscle.
B B. Corrugator supercilii.
C C Orbicularis palpebrarum.
  D. Levator labii superioris absque nasi.
  E. Compressor naris.
  F. Levator labii proprius.
  G. Levator an^uli oris.
  H. Zygomaticiis.
 K. Orbicularis oris.
 L. Depressor alae nasi.
 M. Nasalis labii superioris.
 N. Triangularis oris.
 O. Ouadratus menti.
P V. Levatores menti.
 Q,. Buccinator.
 R. Platysma myoidea.
 S. 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 up-
wards ;  on  the lower  downwards, as in Fig. 30.  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- 
176
SENSIBILITY--6E.NSK OK SIGHT.
  ment, the  skin  of which  is very  delicate and semi-transparent,
  yielding  readily to the  motions of the eyelids, and  having nume-
  rous transverse folds.   The.cellular tissue, beneath the skin, is very
  loose, and, under particular circumstances, is 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 orbicularus  palpebrarum,  (C C.
  Fig.  34.) in the lower eyelid; in the upper, by the same muscle
  and the levator palpebra superioris, (Fig. 35,15) 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 tunica
  conjunctiva, or tunica adnata; so named 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 dis-
  pute is of no moment.   At its outer surface, a humour is constantly
  exhaled, which keeps it  moist, and facilitates the motions  of the eye-
  lids over the eyeball. Its loose state also favours these motions. Both
  eyelids 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-
f junctiva,  (Fig 30, 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 
ACCESSORY ORGANS OF VISION.
177
lower.   In the sun-fish—tetraodon  mola—the  eyelid  is  single  and
circular, with a perforation in the centre, which can  be contracteo
or enlarged, according to circumstances.  In many animals, again,
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. 30, 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. 35.
I. Globe of the eye.
2. 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.
C. Inner origin of do. from an aponeurosis.
7. Aponeurosis common to it and the rectus in-
   ferior ami rectus internus.
VOL. I.
23
 8. Rectus superior.
 9. Posterior extremity of do.
10. Rectus inferior.
11 11 11. Obliquus superior.
12. Trochlea.
13. Obliquus inferior.
14. Rectus internus.
15. Levator palpebrse superiors-
 16. Upper eyelid. 
178
SENSIBILITY--SENSE OF SIGHT.
  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-
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 lachrymal groove, pass
under the eyeball,  and  are inserted between the entrance of the
optic nerve and insertion of the abductor oculi, and opposite the in-
sertion 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-musctlar,  to the abductor.
   Lastly,  the  office of tu.tuniina 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
lubricates the  surface of the eye,  and  keeps  it  in the necessary
degree of humidity  for  the proper  performance  of  its functions.
It is a beautifully  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  lachry-
malis, 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
                               part  of  the  orbit.  It is  an oval
                               bodyr 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 Fourcroy and
                               Vauquelin, of water,  mucus,  mu-
                               riate of  soda,  soda,  phosphate  of
                               lime, and  phosphate  of soda,  and
                               their taste is manifestly  saltish, al-
Fig. 36.
 abed. The lachrymal canals.
   a a. The puncta lachrymals
efg h i. Tlw lachrymal duct.
    k l. The lachrymal gland. 
PHYSIOLOGY OF VISION.                  179
 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,
 whitish humour, to fulfil a similar office with the  secretion of  the
 meibomian follicles.   It completes the circle formed by the meibo-
 mian glands around the eyelids. (See Fig. 30.)
   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. 30 & 36,) 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 in
 the substance of the eyelids, between  the orbicularis palpebrarum
 and tunica conjunctiva. These open, as represented in Fig. 36, 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
 fossa?.
   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  lachry-
 mal sac; arises from  the posterior superior part of the os unguis;
 and, after  having advanced a quarter of an inch, bifurcates; one
fork being inserted along each lachrymal duct, and terminating at or
 near the punctum.   It is probable, that  the function of this muscle is
 to keep the puncta properly directed 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  con-
 traction, the cavity of the lachrymal sac, and thus producing a ten-
 dency  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 apocry-
 phal.

                      Physiology of Vision.

   The preceding anatomical sketch will enable the reader to com-
 prehend this important organ in action.  In describing the office ex-
 ecuted by its  various  components, we shall follow the order there 
180                  SENSIBILITY--SENSE OF SIGHT.

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.
  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. 37.
  It is obvious, that the rays, which fall upon the transparent cornea
can alone be inservient to vision.  Those, which  impinge upon the
sclerotica, are reflected;  as well as a part of those that fall upon the
cornea, giving occasion, 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 below, by the free edge of the eyelids.
  . Again, the whole of the light, that enters the cornea, does not im-
pinge upon the retina.  A portion falls upon the iris, and is reflected
back  to  the eye, in  such manner as  to give us  the notion of the
colour of the organ.  It is, consequently,  the light, which passes
through the pupil, that can alone attain the retina.
  If we  suppose a luminous cone to proceed from the radiant point
B,  Fig.  37, directly in  the prolongation  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 re-
ferred to, pass through the humours without undergoing deflection,
and will  fall upon the  retina at  b.  This, however, is not  the  case
with the  other rays composing the cone.  They do not fall perpen-
dicularly upon the cornea, and are, consequently, variously  refracted 
PHYSIOLOGY OF VISION.
181
in their passage through the cornea, aqueous  humour, crystalline,
and vitreous humour; 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.
			CRYSTALLINE LENS.				Vitreous Humour.
	«~, Aqueous Cornea. un Humour.		Capsule.	Outer Layers.	Centre.	Mean.	
HawkBbee -Jurin - -Roclion Young - -Chossat 1 HrewBter -	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
  A 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. 24.)  In pro-
ceeding  through the aqueous humour, little variation  will be pro-
duced, as the densities of it and the cornea differ but little: the latter
is slightly more  refractive, according to the table, and therefore the
tendency, that exists, will be to render the  ray  less convergent.
This convergence gives occasion to  the entrance of a greater'num-
ber  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 impinging on
the  surface of the crystalline, which possesses a much  higher re-
fractive  power than the cornea  or  aqueous humour; in the ratio
of 1.384 to 1.336.  From this cause, and from  the convexity of the
anterior surface of the lens, the ray is rendered still more convergent
or approaches still more the axis of  the cone.   It is probable, how-
ever, that even here, some of the light is  reflected back, and goes
towards the formation of the image in the eye, and 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  emerges into  a medium possessing
less refractive power; and, therefore, is deflected from the perpen-
dicular.   The shape, however, of the posterior surface of the lens  so
modifies  the perpendiculars, as to occasion such a degree  of con-
vergence, that the oblique ray  meets the axis at a  focus on the re- 
182
. K.NSIB1LITY
--SENSE OF SIGHT.
tina. (See Figs. 24 and 37.)  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 A  B C,
Fig. 37, 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 g b 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 retina;
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 of  an erect object is excited in the mind 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 two  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
the 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.   As, however,
the oblique ray has to pass through the cornea and aqueous humour,
before it impinges  on the crystalline, it undergoes  considerable de-
flection, and consequently  it  is not accurate to represent it, as pur-
suing a straight course through the  different humours, in its way to
the retina.  The  main deflection—as in the  case of the rays D t s,
and E t r, Fig. 37—occurs  at the entrance of the rays  into the
cornea.
  That  an inverted representation  of  external objects is formed
within the eye, is in accordance w ith 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. 37, with the object, ABC  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  con- 
PHYSIOLOGY OF VISION.
183
centrating 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
consists in removing the Lns through an opening, made in the lower
part of the cornea,  the aqueous humour escapes but is subsequently
regenerated.  If,  however, too much  pressure be  exerted  on the
baTl, 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.
   Experiments have also been instituted  on this subject, the results
of which  are even  more satisfactory than the facts just mentioned.
These  have  been of different kinds.  Some experimenters  have
formed artificial eyes of glass, to represent the cornea  and  crystal-
line, with water in place of the  aqueous and vitreous humours.
Another mode has been to place the eye  of an ox or sheep in a hole
in the  shutter of a dark  chamber, having previously 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 nearly transparent; and, direct-
 ing 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 artificial retina in an  inverted
 position; the image being clearly defined, and with  all the colours of
 the original.  Yet how minute must these  representations be in the"
 living eye; and how  accurate the mental appreciation, seeing that
 each  impression from  myriads of luminous  points  is transmitted by
 the retina to the  encephalon, and perceived with unerring certainty !
    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  evacuated,  the
  image seemed  to  occupy a greater space on the retina, and  to  be 
184
SENSIBILITY--SENSE OF SIGHT.
less distinct and luminous, and the removal of the cornea was attend-
ed with similar results.
  When the crystalline was  either  depressed  or extracted, as in
the operation for cataract, the image was still  formed at the bot-
tom 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 order
to have the object depicted with distinctness on  the retina, that the
eye should accommodate  itself to  the  distance at which  the  ob-
jects 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
inquire into the offices executed by the separate parts, that enter into
its composition, where they have not already engaged attention.
  We have shown, that the cornea, aqueous humour, crystalline, and
vitreous humour are 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;  of, in other  words,
that the rays, impinging upon the retina, are not decomposed into
their  constituent colours,—an inconvenience which appertains to
the  common  lens.    (Fig.  27.)   The eye  is strictly achromatic;
and it has been an object of earnest inquiry amongst philosophers, to
determine  how  the  aberration of refrangibility is corrected in it
Euler,  first perhaps, asserted, that  this is owing to the different
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. 28.)   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, again, have placed it in the crys-
talline, 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 
PHYSIOLOGY OF VISION.
185
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-
mon refracting telescope, and therefore imperceptible.  Uncertainty
still rests on this subject;  and it cannot be removed until the disper-
sive 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 per-
fectly achromatic, and that, in this respect, it exceeds any instrument
of  human construction.   The views of Euler are the most probable;
and the  effect  doubtless is much aided by the ins or diaphragm,
which prevents the rays from falling upon the margins of the lens,
where, by the  surfaces meeting  at an angle, the aberration must
necessarily be 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 the  pigmentum
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 cover-
ing.   In the albinos or white animals, in which the pigment is want-
 ing, 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 unimpair-
 ed; and hence the  albinos of our species have  been called 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  least exposed to  the scorching 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, also.
    The use of  the shining spot on the outside of the optic nerves, in
 the eyes of quadrupeds, called the tapetum, has been an interesting
 theme of speculation, and has given rise to  much ingenious, and to
 not a little ridiculous, hypothesis amongst naturalists.  The absence
    vol. i.                     24 
186                SENSIBILITY--SENSE OF SIGHT.
                                   »
of *the black pigment necessarily occasions the reflection of a por-
tion 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 to  the in-
tensity of vision.   Another view has  been, that the  reflected  rays
may pass outwards through the retina without exciting any action,
to be thrown on the object in  order to increase the distinctness 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 phi-
losophical  acumen, and physiological accuracy, thinks it not pro-
bable, that both surfaces of the retina  are equally adapted for re-
ceiving impressions of external objects, and  is of opinion, 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 pig-
mentum  nigrum is wholly wanting; and that it is only necessary 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 presumes, 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 re-
flecting more and  more of the rays according as the pigment is re-
moved from its surface.
   The views of M. Desmoulins are the most satisfactory of any that
have been propounded, and  they are corroborated  by the  experi-
ments of Gruithuisen, Esser  and Tiedemann, which  show, that the
phenomenon never occurs when the light is totally excluded. Gruit-
huisen observed it  in the dead as well as in the living  animal. Tiede-
mann perceived it in a cat, which had  been decapitated for  twenty
hours, and it did not cease until the humours had become turbid. The
views of these observers impress us the more forcibly, when we com-
pare 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 impress-
ed 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 retina.  Biot
has remarked, that this diaphragm is situated  in the eye precisely at 
PHYSIOLOGY OF VISION.                    187
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 ins, have been
very discrepant, and that some esteem it  to be essentially vascular
and nervous, the vessels and nerves being distributed on an erectile
tissue.   The partisans of each opinion  explain the  motions of the
iris differently.  They who admit it  to consist of muscular  fibres
affirm,  that the pupil is contracted  by the action of the circular
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 turges-
cence similar to what occurs in erectile parts in general, and dilata-
tion 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  emotion  being
excited; 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 influence,
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 noctur-
nal 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
immediately contracted, and  continued  so, as  long as the effort
was maintained.
    Many experiments have been made to discover the nerve, which
presides over  the movements  of the iris.  These experiments have
(lemonst rated, 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 immovable 
188
SENSIBILITY—SENSE OF SIGHT.
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
induces  immobility  of the pupil.   The  same effect  is produced,
according to Mr. Herbert  Mayo, by dividing the third  pair; and,
according  to  Desmoulins,  in the  eagle, whose  iris is  extremely
movable, the third pair is the only nerve distributed to the organ.
   The general remark, made by Broussais, on the organs that com-
bine voluntary and  involuntary functions, is applicable here;—that
they will be found to possess both cerebral  and ganglionic nerves.
Accordingly, Magendie conjectures, that those of the ciliary nerves,
which proceed from the ophthalmic ganglion, preside over the dila-
tation of-the pupil,  or are the  nerves of involuntary action;  and
that those, which arise from the nasal branch of the fifth pair,  pre-
side over the contraction of the pupil.   We might thus understand
why, in apoplexy,  epilepsy,  &c, the  pupil should be immovably
dilated.  All volition and every cerebral phenomenon are abolished
by the attack; the  nerve of the fifth pair, therefore, loses its influ-
ence;  and  the  iris  is given up  to the  agency  of the  ganglionic
nerves or nerves of involuntary  action, proceeding from the ophthal-
mic ganglion.
   Mr. John Walker, of Manchester, England, considers the iris a
third, or internal eyelid, exhibiting the same  phenomena  of opening
and shutting, and the same sensibility to light  and other stimuli as
the true  eyelids.  The two sets of fibres, of which the iris is com-
posed, correspond, in his view, to the orbicularis  palpebrarum,  and
the levator palpebrae superioris.  The motions of the iris he con-
ceives to be regulated by the ophthalmic ganglion—the branch of the
fifth pair probably  giving  it the power of contracting, whilst its
dilating  property is attributable  to the third pair.
   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; and
the obscurity is not  diminished by  a remark of Bellingeri.  The iris
he observes,   derives  its  nerves  from  the ophthalmic ganglion,
which is formed by the fifth in conjunction with the third pair, and
its involuntary motions, he thinks, are regulated by the fifth pair.  In
those instances, in which  the motions  of the  iris  have been found
dependent  on  the  will, Bellingeri argues, that  the ciliary nerves
received no branches from the  fifth—a fact, which has been proved
by dissection,  as well  as  by the circumstance,  that in the parrot,
the  owl, and  the  ray  genus among  fishes—in  which the iris  is
under the will  of the animal—there is no ophthalmic ganglion.
   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  con- 
PHYSIOLOGY OF VISION.
189
trary,  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  disease  to judge of the
deirrec of insensibility.
  We shall presently inquire into the effect of contraction or dilata-
tion of the pupil on distinct vision; and show, that they are actions
for accommodating the eye to vision at different distances.
  We may  conclude, then, that the iris is one of the  most im-
portant parts of the  visual apparatus;  and that its functions are
multiple:—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 aber-
ration 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 regard-
ing 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
motion of the iris, others  to vary the  distance of the crystalline  from
the retina.  Jacobson  makes  them  dilate  the apertures, which  he
conceives to exist in the canalgoudronne, so as to cause the admis-
sion of a portion of  the  aqueous humour into the canal, and thus to
change the situation of  the  crystalline.   Others believe,  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 sen-
sibility 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 
190
SENSIBILITY--SENSE OF SIGHT.
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 interior of the eyeball; and thus to
allow 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 in birds of prey, has already  been  referred to, under the sense
of smell.  (Page 122.) It was there stated, that the strange facts re-
garding the condor, vulture, turkey-buzzard, &c, which meet in num-
bers 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 inconceivably sensible to its  special irritant must this mem-
brane 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 proper  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! 
PHYSIOLOGY OF VISION.
191
  If pressure be made on the eyeball, behind the cornea so as to af-
fect the retina, concentric  luminous circles will be seen, opposite to
the part on which the pressure is applied; and,  if the  pressure be
continued  for  twenty or thirty seconds,  a broad  undefined  light,
which increases in intensity every moment, rises immediately before
the eye.   If the eyelids be open, and light be present, on the repeti-
tion of the last experiment, a dense cloud  arises, instead of the broad
undefined  light, and  the eye becomes, in a few   seconds, perfectly
blind, but, in the course  of three or four  seconds  after the finger is
removed, the cloud appears to roll  away from before the eye.   From
this, it seems, that sensations of light may be produced by mechanical
pressure made on the retina, in  other words, the retina becomes
phosphorescent by pressure.  The same  thing, too, is observed if a
sudden blow be  given on the eye, or if  we place a piece  of  zinc
under the upper lip, and a piece' of copper above the eye.   A flash
of light is seen, produced, doubtless, by the galvanic fluid impressing
directly, or indirectly the optic nerve.  The same thing occurs in
the act of sneezing, and  in forcing air violently through the nostrils.
On repeating  the experiment of pressing  the eyeball,  Sir David
Brewster observed, that when a gentle pressure was first applied, so
as  to  compress  slightly the  fine pulpy substance of  the  retina,
a circular  spot of colourless light  was  produced, though the eye
was in total darkness, and had not been  exposed  to light  for many
hours; but if light be now admitted to the eye, the compressed part
of the retina is found to be more sensible to the light than any other
part, and consequently it appears more luminous.   If the pressure be
increased, beyond the point mentioned above, the circular  part  of
light  gradually becomes darker,  and, at length,  black, and is sur-
rounded  with a bright ring of light.  By augmenting the pressure
still more,  a luminous spot appears in the middle  of the central dark
one, and another luminous  spot diametrically opposite, and  beneath
the point of pressure.  Now, considering  the eye,  says Sir David, as
an elastic sphere, filled with incompressible fluids, it is obvious, that
a ring of fluids will rise round the  point depressed by the finger, and
that the eyeball will protrude all around  the point of pressure, and
consequently the retina, at the protruded  part,  will be  compressed
by the outward  pressure of the contained  fluid, while the retina on
each side,—that is, under the point of pressure, and beyond  the pro-
truded part,—will be drawn towards the protruded part or dilated.
 Hence the part under the finger, which was originally compressed,
 is now dilated, the adjacent parts are compressed, and the more re-
 mote parts, immediately without this dilated also.   " Now," continues
 Sir David in his " Letters on Natural Magic"—"  we have observed,
 that when the eye is, under these circumstances, exposed to  light,
there is a bright luminous circle shading off externally and internally
 into total  darkness.   We are led therefore to the important con-
 clusions, that  when  the retina is compressed in total darkness it
 gives out light; that when it is compressed, when  exposed to  light, 
192
SENSIBILITY--SENSE OF SIGHT.
its sensibility to light is increased;  and that, when it is dilated under
exposure *to light, it  becomes  absolutely blind, or insensible to all
luminous impressions."

  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 in-
quire into the  various interesting and important phenomena exhibited
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 towards
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 pro-
tection is afforded by  the instantaneous  occlusion  of the eyelids, on
the anticipation of danger to the ball.   The incessant nictation like-
wise  spreads  the lachrymal secretion over  the surface of the con-
junctiva, and cleanses it; whilst the movement, at the same time,
probably excites the gland to augmented secretion.
  The chief part of the movement of nictation is performed by the
upper eyelid;  the difference in the action of the  eyelids being esti-
mated, by some physiologists, as four to one.   Under ordinary cir-
cumstances, according  to Adelon, it is the levator palpebral supe-
rioris, which,  by its contraction or  relaxation, opens or  closes the
eye; the orbicularis palpebrarum not acting.  If  the levator be con-
tracted, 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 ex-
traordinary  cases, and under the influence of volition; whilst the
closure of the  eye, during sleep,  is  dependent upon simple relaxation
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  orbicularis muscle, which acts 
PHYSIOLOGY OF VISION.
193
whilst the others rest.  If the opening of the eye were wholly de-
pendent upon the action of the levator palpebra) supenons 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  function;  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  influence
chiefly of the portio dura  of the seventh pair, or facial  nerve:—one
of the respiratory nerves of Sir Charles Bell's  system—the respira-
tory of the face.   When this nerve is cut, nictation is completely ar-
rested; and when the nerve of the fifth pair, also distributed to these
parts,  is divided, it ceases likewise, but less  thoroughly; a  very
vivid  light exciting it, but  only at considerable intervals, and imper-
fectly.
  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, by their approximation, can  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;
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, pro-
bably, 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 frequently
had occasion to speak—Sir Charles Bell.   The arrangement  of the
four straight muscles, and especially their  names, sufficiently indi-
cate the direction in which they are capable of moving the  organ,
when acting singly.  If any two of them  contract together, the eye-
ball will, of course, be moved in the-direction of the diagonal, be-
tween the two forces;  and if each muscle contracts rapidly after the
other, the organ will execute  a movement of circumduction.  The
oblique muscles are antagonists to each other, and roll the  eye in op-
posite directions; the superior oblique directing the pupil downwards
and outwards; the inferior upwards and  inwards.   But as the dif-
ferent straight  muscles  are capable of carrying the  eye in these
directions, were we to regard the two sets of muscles as possessing
analogous functions, the oblique would appear  to be superfluous.
   vol. i.                      25 
194
SENSIBILITY--SENSE OF SIGHT.
  This, along with other reasons,  attracted the attention  of  Sir
Charles Bell to the subject; and the result of his experiments and re-
flections was:—that the straight muscles are concerned in the mo-
tions 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 this happens at the approach of, and during sleep: and when-
ever insensibility occurs, from  any cause, as  in faintness, or on the
approach of  dissolution;  and that turning up of the eyeball, which
we have been accustomed to regard  as the expression of agony, is
but the  indication of a state of incipient  or total insensibility.
  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 eye-
lid, 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
protection of the eye;  to the clearing of the  eyeball of everything
that could obscure  vision, and perhaps, as Sir Charles Bell presumes,
to procure the discharge  from the  ducts  of the  lachrymal gland.
During sleep, when the closure of the eyes is prolonged, the trans-
parent 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 was  there stated, that
the superior oblique muscle receives  one  whole pair of nerves:—the
fourth.   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 ex-
pression, as in bodily pain, and  in mental agony,—in which the ac-
tion of the direct muscles seems, for a time, to be  suspended,—he was
led to consider the fourth pair  as  a nerve of  expression—a  respira-
tory nerve; and, hence,  intimately connected with the facial nerve
of the seventh pair, which, as has  already been  remarked, is the
great nervous agent in the twinkling of the eyelids.  Anatomical ex-
amination confirmed this view;—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 up-
wards 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 su- 
PHY SI0L0GY OF VISION.
195
perior oblique only; the lesser oblique receives none of its ramifica-
tions. 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 func-
tion of the former, when acting singly, is to carry the eye upwards
and outwards; and, when the action of its antagonist  is  abolished,
this is more clearly manifested. Sir Charles found, that the effect of
dividing the superior oblique was to cause  the eye to roll more forci-
bly 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 anomalous:—
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 up-
wards!   In addition to this, too, as Mayo has observed, the distri-
bution of the muscular nerves of the eye is not such as to allow of our
opposing the straight muscles to the oblique, and one cogent reason
is, that the third pair of nerves supplies half of each class.
   We have still, therefore, much to learn regarding this subject, into
which so much interest, and, at the same time, so much uncertainly
has been infused.  The views of Sir Charles, regarding  the functions
of the two sets of muscles  on certain  optical  phenomena 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, they 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 differ-
ence 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 anteriorly 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  sur-
face of the eye, whence they are  partly absorbed, and the rest  per-
haps being evaporated.   Under extraordinary circumstances, how-
ever, the gland  increases its secretion  so  much, that the tears not
only pass freely through the lachrymal ducts into the nose, but  flow 
196
SENSIBILITY--SENSE OF SIGHT.
over the lower eyelid.   The epiphora or watery eye, caused by  ob-
struction of these ducts, also proves that a certain quantity of the
secretion must always be passing into the puncta.  The physical ar-
rangement of the eyelids  and  tunica conjunctiva is 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, by acting like a layer of oil on the margin of a vessel
filled with  water. A similar function has been assigned to the secre-
tion of the caruncula lachrymalis.   Both these fluids, however,  are
probably inservient to other ends.  They are readily miscible with
water; become consequently dissolved in the tears, and, with the as-
sistance of the fluid secreted by the tunica conjunctiva, aid the move-
ments of the eyelids  over  the  ball of the eye, and keep the tarsal
margins  and their appendages in the condition requisite 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
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
cases in the human body, which admit of satisfactory explanation *
on the physical principles of capillary attraction.   In vegetables, the
whole of the circulation of their juices has been thus accounted  for.
If we twist together several threads of yarn, moisten them, and put
one extremity of the roll into a vessel of water, allowing 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  twentieth part of an inch in
diameter, which is  called  capillary, and  place it so as to touch the
surface of wrater, 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 extremity of a capillary tube, which receives the fluid of 
                       PHENOMENA OF VISION.                 ^'

the lachrymal  gland and conveys it to  the  nose, the punctum being
properly directed  towards the eyeball by the tensor tarsi muscle ol

  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-
rt.  As the conjunctiva lines the eyelids, 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
insignificant.
   Ther 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
 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 in-
 terior  surface of the  iris.   The  crystalline and vitreous humour
 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 separated 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; in-
 asmuch as when the branches of the nerve proceeding to the eye-
 lids  were simply divided, or when the lachrymal gland was taken
 away, the opacity did not supervene.

                       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, which  re- 
198
SENSIBILITY--SENSE OF SIGHT.
ceives the impressions of luminous rays, whence  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,  I 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."
  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 directing
the rays to the insensible point  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 concealed
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
retina 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 conclusion
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  probable,
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.  Thilaye, that it falls upon the
yellow spot of Sdmmering,  can only be explained by  presuming him 
PHENOMENA OF VISION.                   199
to have been 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
central 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
becomes 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 proportion.  The estimate of Lecat, 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
direction.   Simple experiment, with two wafers placed upon a door
at 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, except
at the base of  the optic nerve, where the choroid is alone absent, 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,  entertained  the
opinion, that  the retina  receives the impression of the h>ht in a
secondary way, and through the choroid  coat as an intermediate
organ: that  by the light striking  the choroid  coat, that membrane is
agitated, and  this agitation is communicated  to the retina.  The
views  of De  La Hire  are  embraced by Brewster,  in hisrecent
treatise on optics, as  well as  by numerous other philosophers.
   The opinions of Mariotte have  now few supporters.   The remarks
already made  regarding the optic nerve; the effect of diseases of
the retina, of the nefve itself, and of its thalami, compel us to regard
its expansion as the seat of vision: and  if we were  even to admit
with Mariotte, that the insensible portion is really a  part of the medul-
lary  matter  of the nerve,  and not a blood-vessel existing  there, we
could still satisfactorily account for the phenomenon by the  anoma-
lous circumstances in which  the nervous part of the organ is there
Placed.  The choroid coat,  of great importance  in thf Lction! is 
200
SENSIBILITY--SENSE OF -SIGHT.
absent; as well as the pigmentum nigrum;  and hence we ought not
to be surprised, that the function  is  imperfectly executed;  we say
imperfectly,  for the  experiment with the candles exhibits, that the
part is not really insensible 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 retina,
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  circum-
stances, no difference is perceived  between the parts  of the retina
over which the vessels  creep, and the  remainder of its extent.  We
can, however, by an experiment described by  J.  G.  Steinbuch, in
his Beitrag zur Physiologie  der Sinne, published at
Nurnberg, in 1811, exhibit, that under particular circumstances 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 directed straight for-
ward,) 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 ramifications  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, corre-
sponding 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.  37.
   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 believed,
that originally, we do see them so inverted; but that the  sense of
touch apprizes us of our error, and enables  us to correct it at so 
PHENOMENA OF VISION.
201
early a period, and so effectually, that wc are afterwards not aware
of the process.  Berkeley again asserted, that the position of objects
is always judged of, by comparing them with our own; and that, as
we see ourselves inverted, external bodies 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 position 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 the}- have imagined a
true  picture to be formed on the retina, which is regarded by  the
mind, and therefore see^uiverted.  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-
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.  37,  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 still  seen in the same
direction as when it was viewed by the  whole cone  of rays proceed-
ing from B.  If we look, again, beneath the card, in a similar man-
ner, so as to  see the object by the lowermost ray of the  cone, the
radiant point will be equally seen in the same direction. 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 perpen-
dicular to the retina;  and, as the  surface 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 visible point."
   The point  o, Fig. 37, is, in Sir David's view, this centre of visible
direction.  Where  a luminous cone proceeds in the direction of the
axis  of the eye, the centre of visible direction will  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 o,  and  the same  thing, he conceives, will apply to
every other  pencil  of rays.  Thus, the rays from  D and E, which
fall upon the cornea at /, will be refracted so as to impinge upon the
   vol. i.                       26 
 202               SENSIBILITY--SENSE OF SIGHT.

 retina at s and r respectively, and D and,R will be seen in the direc-
 tion of lines drawn from these points to the centre of visible direc-
 tion, o.
   This  " law of visible direction," laid down by Sir David Brew-
• ster, removes at once, he  thinks,  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 visible 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.
   The views of Sir David are embraced by Mr. Mayo, who con- "*
 siders them confirmed by the fact—to  which  reference has already   j
 been made—that any pressure, made  upon  the  retina through  the
 eyeball, causes a spectrum to be  seen in a direction  opposite to the
 point  compressed,  as  well  as  by  the following experiments of
 Schemers.
   If the head of a pin, strongly illuminated, be viewed with one eye
 at a distance of four inches, that is, within the common limit of dis-  ^
 tinct vision, the object is seen large and  imperfectly defined, the   <
 outermost  cone  of rays, which enters  the pupil  from each point,
 being too divergent to  be collected to a focus on the retina.   If a
 card, pierced with a pinhole, be now interposed between the eye and
 the object,  the latter may be seen  distinctly defined through the pin-
 hole, by means of rays that have entered the pupil nearly parallel,
 with a slightly divergent tendency.  But the object may be seen by
 rays passing  either through the upper  or  lower part, the right or
 left side, or the centre of the pupil. Upon shifting the card for this pur-
pose the object appears to move in an opposite direction. Or, if three
pinholes be made, one in the centre, and one at either side, the ob-   ;
ject appears tripled; and  if  one  of the  side  holes be closed,  the
opposite of the three objects disappears: if, for example, the  left hand
pinhole be  closed, the right object disappears.
  Again, if the head of a pin, strongly illuminated, be  viewed at the
distance of eighteen inches, its outline is distinct and clear:  the rays,
passing from each point of the object, are brought tea point on  the
retina, but  these rays reach  the retina  at different angles, and, by
interposing a card perforated with a single pinhole, the object may
be seen by rays, which enter the upper part,  or the lower part, or
the centre  of the  pupil.   No change, however, in the visual place
of the object occurs in this instance, as the  card is shifted; nor is
the image multiplied,  when seen through  several pinholes in  the
card.
  The last experiment, says Mr. Mayo, proves, that the  angle at
which'rays of light fall upon the retina, does  not affect our  notion of
the  place  of objects, and,  taken  with the  preceding,  establishes
as an  inductive law, that  the retina is so constituted, that, hmvever
exerted, each point of it sees in one direction only, that direction being 
PHENOMENA OF VISION.
203
a line vertical to it; or, that in every instance of visio *^V°™\\f
an object  is seen in the direction of a line vertical, to the point of  the
retina upon which the rays proceeding from it are collected.
  A certain  intensity of light is necessary, in order that  the retina
may be duly impressed,  and this varies in different animals;  some
of which, as we have seen, are capable of exercising  the  functlon
of vision  in the night, and have hence been termed nocturnal. Q In
man, the  degree of light, necessary for distinct vision, varies ace  rd-
ing 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  anything, 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 im-
pression produced by the introduction of lights into a room, where
the company have  been previously sitting in comparative 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.
   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; and 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 phenomena of
 vision.   If flic eye be directed,  for a time, to a white wafer, laid 
204              SENSIBILITY--SENSE OF SIGHT.

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  in-
tense, when compared with the previous deficiency.
   It is on this, that the whole theory of  accidental colours, as they
are called, rests.  When the eye has been, for some time, regarding
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 :—
       Colour of (lie             Acc;dental colour, or colour of the
         wafer.                    ocular spectrum.
       Red      .     .    .     Bluish-green.
       Orange   .     .    ,     Blue.
        Yellow    .     .    .     Indigo.
        Green    .     ,    .     Violet, with  a little red.
       Blue      .     .    .     Orange red.
       Indigo    .     .    .     Orange yellow.
        Violet     .     .    .     Yellow green. •
       Black     .     •    •     White.
        White    .     .    .     Black.
   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 oppo-
site colours.
   It will  follow, from  what  has
been  said, that if the  primary  co-
lour, or that to which the  eye  has Black f|SQ|     BSS3 f m»its
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.
 
OBLIQUE VISION.
205
The accidental  colour, in  other words, is what  the  primitives co-
lour requires  to make it white light.  The primitive and^accidental
colours are, therefore, complements of each other; and  hence acci-
dental colours have also been called complementary colours,   lhey
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 toe
spectrum will remain visible for a long time after the cause has
been  removed.   Such  appear  to  be the  views of  Drs.  .berriar,
Hibbert, and Alderson—the chief writers, in modern times, on ap-
paritions.  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 hallucina-
tions 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 retina,  or
 in  the direction of the axis of the eye; we always, therefore, in our
 examination of minute  objects, endeavour to cause  the rays from
 them to impress this part of the retina;—the distinctness of the im-
 pression  diminishing directly as the distance from the central fo-
 ramen 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 re-
 tina, 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 eve 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 reap-
  pear,  and  again vanish.  When the  object, seen obliquely, is lu-
  minous, as a  candle, it never vanishes  entirely,  unless  its light is
  much weakened, by being placed at a great distance;  but it swells,
  and contracts, and is encircled with a  nebulous halo; the luminous
  impressions extending themselves to adjacent parts of  the retina
  not directly influenced by the  light itself. 
206
SENSIIULU'Y--SENSE OF SIGHT.
   From these, and other experiments of a similar character, detailed
 in his Treatise of Optics, Sir  David infers, that  oblique or indirect
 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 cannot, 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  neigh-
 bourhood of a large  one,  will  often become very conspicuous, so as
 to bear a  certain illumination, and yet it will entirely disappear, 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 account  for
 the phenomenon, by supposing, that the lateral  portions of the  re-
 tina, being less fatigued by strong light, and less exhausted by per-
 petual attention,  are probably more  sensible  to faint impressions  ^
 than the  central  ones; and  the  suggestion carries with  it an air of
 verisimilitude.
   Sir  David Brewster, however—from the result developed by  his
 experiments, that, " in the case of indirect vision, a  luminous  object
 does not vanish,  but is seen indistinctly and produces an enlarged
 image on the  retina, beside that which  is produced by the defect
 of convergency  in the  pencils,"—concludes somewhat  mystically,
 " that  a  star,  seen  indirectly, will  affect  a  large  portion of the
 retina  frpm 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 appre-  -j
 ciated: in the  next place , the image  must be distinct or sharp;  in
 other words, the  luminous rays,  that  form it, must converge  accu-
 rately to a focus on the retina : lastly, the image must be  sufficiently
 illuminated.  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
 consequently invisible.
   An object may be so small,  that the eye  cannot  distinguish  it;
 because the image, formed on the retina, is  too minute.   To remedy
 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 
LIMITS OF VISION.
207
this imperfection of the sense, minute bodies may be viewed through
a small hole in a  piece  of paper or card, or with  the  instrument
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 converged
into a focus upon that membrane,  so  that a sharp and distinct  im-
pression is received.   The iris is, in this  way, useful in effecting
distinct vision;  the  most  divergent rays  being—by its contracting
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 the visual power must differ
greatly in  individuals.   Some eyes are much more capable of minute
inspection 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  the eye than
common ; in the  presbyopic or long-sighted, more distant.  The iris,
here again, plays an important part, by its action in shutting off the
the most diverging rays, as above  described.
   There is also a limit  beyond which objects are no longer visible.
This is owing to the light from the object becoming absorbed before
it  reaches the retina, or so feeble as not to make the necessary im-
pression.  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 a darker.  A distant object may also be imperceptible,
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  presbyopic;  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 dis-
tance, at which the ocular cone  arrives at a focus behind the lens,
is always m 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  ens-  the  focus will be more remote behind it, and the
contrary   If this occurs in  the human eye it must necessarily  fol-
low;—either that it is not necessary, that  an object be impressed 
208                SENSIBILITY—SENSE OF SIGHT.

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
almost  universal reception,  and has given  rise to many ingenious
speculations; whilst the third has been seriously urged of late years    i
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 possessed    ]
by the  eye of accommodating itself  to distances.  It is a subject,    s
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:—First.
That the cornea or lens must recede from, or approach the retina,    /
according to the focal distance, precisely  as we adapt our tele-    -
scopes,  by lengthening or shortening the tube.  Secondly. If we sup-
pose the retina  to  be stationary the lens must experience a change
in its refractive powers, by an alteration of its shape or density; or,    *
Thirdly. 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   j
upon an alteration in the antero-posterior diameter of the organ, or
on the relative position of the humours and retina, has been strongly    jj
supported by many able physiologists.   Blumenbach was of opinion,   ^
and his  views seem to have been embraced by Dr.  Hosack, that the
four straight muscles of the eye, by compressing the eyeball, cause    |
a protrusion of the cornea, and thus an increase in the  length of the    ?
axis.  Dr. Monro  believed,  that  the  iris,  recti muscles, 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 around 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.  Porter-
field, 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 mus-
cular fibres, which 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 ?•• 
ADAPTATION OF THE EYE TO DISTANCES.
209
Dr. Knox, that the annulus albus, or the part which unites the choroid
and sclerotic coats, is muscular, and  the chief agent in  this  adjust-
ment; 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  his  eye, and at the same
time forced in  upon the ball the ring of a  key, so as to cause a very
accurately 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 were modified, that the spot, caused  by the
pressure, would  be  altered in shape and dimensions; but no  such
effect occurred; 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.
   Sir Everard Home, again, asserts, that  all the ingenuity of  the dis-
tinguished  mechanician, Ramsden, was unable to  decide, whether^
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, that
many animals are incapable of altering the shape of the eyeball, by
the muscles at least.  The cetacea and the ray, amongst fishes,—
and  the lizard  amongst reptiles, have the sclerotica so inflexible as to
render any variation in it impossible.
   With regard to many of the particular views that have been men-
tioned, they are mere " cobwebs  of the brain," and unworthy of se-
rious argument.  In the action of the orbicularis  palpebrarum, as
suggested  by Dr. Monro, there  is,  however, something so  plausible,
that many persons have been misled  by it.
   lie made a  set of experiments to show, that this muscle, by com-
pressing the eyeball, causes the cornea to protrude, and thus  enables
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 exer-
tion to read, he found he could see  the letters distinctly.  But 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 pro-
duced 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
   vol. i.                      27 
210                SENSIBILITY--SENSE OK SIGHT.

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 cen-
tre indicates rather a cellular structure, the cells being filled  with
transparent matter of various degrees of concentration; and an ex-
amination 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 differ-
ence 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  affirmatively; Porter-
field, Young, and Travers, negatively.
   Magendie, as we have seen, considers  the great use of the crys-
talline  to  be:—to increase  the  brightness and  sharpness of the
image by diminishing its size.   Mr. Travers again,  regards adjust-
ment as a change of figure  in the lens;  not, however, from a con-
tractile power in the part itself, but in consequence  of the  lamellas,
of which it is composed, sliding over each  other,  when  acted  upon
by external pressure ; while  upon the  removal  of this pressure, its
elastic  nature restores it to its former sphericity.   The  iris is con-
ceived to be the agent  in this  process;  the pupillary 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 refrac-
tive power.
   3.  One  of the causes, to  which the faculty of  seeing at different
distances has been ascribed,  is the contraction and dilatation of the
pupil.  It  has been already observed, that when we look at near
objects, the  pupil contracts, so that the most divergent  rays do not
penetrate the pupil, and the vision is distinct.  Hence it has been
conceived probable—by De  La  Hire,  Haller, and others—that the
adjustment of the eye to various distances, within the limits of dis-
tinct vision, may be effected by this mechanism, in  the  same  man-
ner 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 ob-
jects, 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 
ADAPTATION OF THE EYE TO DISTANCES.
211
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 certain
limits at least, than of either of the other supposed methods of adjust-
ment;  and,  accordingly, the majority of  opticians  of the present
day embrace this view of the subject; but without being able to ex-
plain satisfactorily the change in the interior of the  eye effected by
its movements.   " It seems  difficult," says Sir David Brewster—the
latest writer on this subject, "to  avoid the conclusion,  that the
power of adjustment depends on  the mechanism, which contracts
and dilates the pupil; and as this  adjustment is  independent of the
variation of its aperture, it must be effected by the parts in  imme-
diate 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  re-
moved from the retina by the contraction of the pupil."   The con-
clusion, drawn by Sir David, does  not, however, impress us with
the same degree of certainty.
  Pouillet, in his lectures before the Faculte des Sciences of Paris, ex-
plains the matter with no little confidence, by the  double  effect  of
the crystalline being composed 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 remainder becomes greater and greater,  until the
most central portion has the shape  of  a  sphere.   Hence,  he  re-
marks, 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 arrangement, he says, enables us to see at  all  distances, inas-
much 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 parts; 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  inconve-
nience of the aberration of sphericity must result; as when  the pupil
is dilated, the rays must pass through the more marginal, as well  as
through  the  central parts of the  lens.  Pouillet himself is aware of
this difficulty,  but  he does not dispose  of it  philosophically.  " It 
212
SENSIBILITY--SEN'sE OF SIGHT.
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; \\ >r, 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 it 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,
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  at-
tempted 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  accommodation from the  contraction of the pupil in viewing
near objects, effected in the mode already explained.   If the accom-
modation existed to  any material extent, it is difficult to understand,
why trifling cases of short  or long-sightedness  should not  be rec-
tified.   Sir  Charles Bell conceives, " that  the mechanism of  the eye
has  not  so great a power of adapting the eye to various distances
as is generally imagined, and  that much of the effect attributed  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  attended to." " The mind,"
he adds, "not the eye, harmonizes with the state of sensation, bright-
ening 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 ob-
jects.  It cannot be an adaptation of the eye, but an accommodation
and association of the mind with the state of the impression."
  The view, which we have expressed upon the subject, is strikingly
confirmed 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, 
SHORT AND LONG-SIGHTEDNESS.
213
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 eve, by the intimate composition of the refractive bo-
dies: as the aberration of sphericity probably is? Yet, if this be the
case, how admirable must be the construction of such an instrument!
how far surpassing any effort of human ingenuity! an instrument ca-
pable 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 m dif-
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 constituting
myopy or short-sightedness, and presbyopy or long-sightedness.
  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. 39.             power in the transparent parts of
                                 the organ;  or to  too great  a
                                 depth of the humours; or it may
                                 be caused by unusual convexity
                                 of the  cornea or crystalline; or
                                 from the retina being too distant
                                 from 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.  39.)  To  see them distinctly, they must be
placed close to the  eye, in  order that the rays may  fall more diver-
gently,  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
sec well without spectacles, when others of the .same age may find
them essential.  It is probable, however, that this is, in many cases
at least, a vulgar error;  as we have  known different myopic sexage-
narians, who have not experienced the slightest improvement by the
p ogress of age.
   The  presbyope, presbytic 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
 
214
SENSIBILITY--SENSE OF SIGHT.
                                   the transparent parts of the eye;
              Fig. 40.              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. 40.)
   This  defect, which is experienced more or less by most  people,
 after middle age, is palliated. by the use of convex glasses, which
 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 arbitrarily
 numbered to suit different periods of life, but each person should se-
 lect 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 atten-
 tion 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  minute
 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 exemption
 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
 
SINGLE VISION.                        215
thus become instructed of its error, a habit of rectification is attain-
ed, 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 motions 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 retina.   This, we 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 direct-
ed to any particular point,—the eyeballs move together, 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 1
Can we suppose, for example, that the young calf sees two mothers,
and that it is by an intellectual process, that it knows there  is only
one?
   The truth is, as we have already observed, the encephalon is com-
pelled 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 exists.  This  oc-
curs 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 as-
sociations is broken in upon, and hence double vision results.  The
proper explanation, however, of this diplopia of the drunkard 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  irregularly exe-
cuted.  The voluntary muscles of the  eye  partake of this  vacilla-
tion and do not  move in harmony, so that the impressions are not
made on corresponding points of the retina, and double vision neces-
sarily results.
  Another hypothesis  has been, that although a separate impression
is made upon each retma,-in consequence^ the union of the optic
ne.es, 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 
21fi               SENSIBILITY---->K.\*F. OF SIC.IIT.

was generally received.  Still more recently, Dr. Wollaston has sup*
posed the consentaneous motion of the eyes to be connected with   '
the partial union of the optic nerves.  The anatomical and physio-
logical facts, relating to the union and decussation of the optic nerves,  '|
have already engaged us.   By a reference to that subject it will be  1
found, that a true decussation takes place between them; that each
eye has, notwithstanding, its distinct nerve, from origin to termina-  M
tion; and that no such semi-decussation, as  that contended for by   '
Dr. Wollaston,  exists.  These facts are  unfavourable to this hy-   \
pothesis of amalgamation of impressions; and, besides, if we pres3  M
slightly on the eye, we have a double impression, although the rela-  H
tion of the optic nerves to  each other is the  same; and, moreover,  m
the same explanation ought to apply to audition, in which we have
two distinct impressions, but only a single perception:—yet no one  I
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  function.  In
active vision, he asserts,  we always employ one eye  only,—some-
times 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   i
such is the case  in man.   He remarks farther, that in many  cases   j
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 
SIMPLE VISION.
217
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
Physique of' the  Faculte de Mtdecine of Paris, by M. Magendie, in
the presence of M. Thillaye  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 corre-
sponding 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 retina?, vision is
double. This is merely stating the physical  circumstances, necessary
for single vision; and farther we cannot proceed, without entering
the regions of conjecture.
VOL. I.
28 
218                 SENSIBILITY--SENSE OF SIGHT.


                             Fig. 41.
  In  Fig. 41, 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
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 retinas are not, as  Dr.  Arnott has
asserted, equidistant, and in similar directions from the centres of the
retinas.  They are in similar directions, but not  equidistant, as will
be obvious from the figure.  Let us suppose the axes directed 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 previously
stated, not be as distinct as the star A; but we know from expe-
rience, 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  being neces-
sarily 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 the
lines  D e Fig. 42,  to be the  optic axes of  the eyeballs  A  and B 
DOUBLE  VISION.
219
respectively; the object  at  D will,  of course, be seen single; 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 crys-
talline in each eye, impinge upon the retinas on the outer side of the
axes; and  are,  therefore, not  on  corresponding points.  In like
manner, the rays, from a more distant  object,  at E, will impinge on
the inner side of the axes, and double vision will be the consequence.
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 finger, the ob-
ject 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.
                           Fig. 42.
.13
#E
from
If, from any cause, as from a tumour pressing upon one eyeball
>m a morbid debi htv of the mi»nlp. ™ aJL /____.  eveu.ui,
debility of the  muscles, or from a want of
corre- 
220
SENSIBILITY--SEN^E OF SIGHT.
spondence in the sensibility of the two retinas, 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
resumes its proper direction;  a fact,  which  disproves  the  idea of
De La Hire and  others, that  the cause of strabismus  or squinting
is a  difference of sensibility  in  the corresponding  points of the
retinas, and that the discordance in the  movements of the  organs
occurs, in order that the images may still fall  upon  points of the
retinas, 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, which 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 labdur  :
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 correspond-
ence between  the retinae, or in inequality of the foci, it is irremedi-
able.
   It would appear, then, that,  in confirmed squinting, one eye only
is used, and that vision is single,—that the inclination of one eye in-
wards may be so great as to deprive  it of function, or so slight as to
allow the organ to receive rays from the same  object as its fellow;
but, in either case, it would seem, that they, who  squint habitually,
neglect the impressions on the distorted eye, and see with but one.
   We have  said, that the eyeball of the imperfect eye is drawn 
MULTIPLE VISION WITH ONE EYE.
221
  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 ap-
  plies his classification of the muscles  of the eye to an explanation
  of the same fact.  He asserts, that the recti muscles of the eyeball
  are in activity during attention to the impression  on the retina,—
  but that, when the attention  is withdrawn, the straight  muscles are
  relieved, and the eyeball is given up to the  influence of the oblique
  muscles, the state of equilibrium between  which exists, when the eye-
  ball 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, in time, wanders about, so  as  to  produce
  squinting at the pleasure of the individual.  In these cases, the eyes
  become of unequal power, so that one  only can be employed where
  distinct vision is  required.
     So far  our remarks have been directed to double vision, where
  both eyes are employed.
     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  being
  closed—and within the point  of distinct vision, so that the bright
  light of a  lamp  or from a window shall fall upon  the  object, in 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 explained, and
  elucidated at considerable length.  The elaborate  character 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. 
222
SENSIBILITY--SENSE OF SIGHT.
   At first sight, it  might seem, that this  phenomenon should be
 referred to the diffraction or inflection, which the light experiences   I
 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  Philosophical
 Transactions, explains,  on  the  same principle, a  very  curious
 optical appearance, noticed  by Mr. Hopkinson, in which, by the in-
 flection of light, caused by the threads of a  silk handkerchief, 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   '4
 not coloured.                                                       j
   Dr. Jurin considers  the phenomena to be caused by fits  of easy   j
 refraction  and  reflection of  light.   Newton demonstrated, that   ''
 the rays of light are not, in  all parts  of their  progress, in the same
 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 trans-
 mitted by refraction,  or to be reflected by the surface of a transpa-
 rent  medium,—he called their fits of easy refraction, and fits of easy
 reflection; and he showed, that these  fits succeed  each  other alter-
 nately 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 to-
 lerable  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 pre-
 sents  alternately to the line of its motion an attractive and a  repul-
 sive pole, in virtue of which it will be refracted,  if the attractive
 pole be nearest any  refracting surface on  which it falls,  and re-
 flected, if the repulsive pole be nearest the surface.
   A less scientific notion of the hypothesis has also been suggested,
__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 presumes, 
MULTIPLE VISION WITH ONE EYE.
223
Fig. 43.
that the light,  in
passing through the
humours of the eye,
experiences,  these
fits  of easy refrac-
tion  and easy  re-
flection.  This will
be  understood  by
the  marginal   fi-
gure,   Fig.   43.
From the point A,
suppose a number
of rays of light to
proceed and to im-
pinge,  with differ-
ent 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 A B C; so that we may presume, that
all  the  rays, which fall upon the  parts of the medium B C, corre-
sponding 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
fo5us at D.   Now, if all the bundles of rays, transmitted through the
surface B C, be accurately collected into a focus, no other conse-
quence  will arise  from the  other bundles of rays having been re-
flected 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 dis-
tinct vision, we have  only  a single impres-
sion 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 represented  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  men-
tioned, should be formed upon the retina; but
how is it, that the objects seen preserve their
linear  form '.   Suppose a b, Fig. 44, to be a
luminous cone, which in a  fit  of easy  re-
fraction, has impinged upon  the retina: and
A  B, b a,  the concentric circles,  corres-
ponding to the  rays, that have been reflected.
It is obvious  that every point of the ob-
ject will be the  centre of so many concentric (i
Fig. 44.
 
224
SENSIBILITY--SENSE OF SIGHT.
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  parallel to them: and
if the light from the luminous point be strong enough to form  more
lucid  rings than are- represented  in  Fig.  44, and the breadth  of
those rings be not too minute to be perceived,  we may have the ap-
pearance of five, seven, or more lucid  lines, separated by parallel
dark lines.

  We proceed now to consider the advantages, which  the mind de-
rives 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 co-
lour.   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  developement.   Yet, occasionally, we
meet with singular  cases, in which  the eye appears to be totally in-
sensible to certain colours, although capable of performing the  most
delicate functions of vision.
  Sir David Brewster,—in his  recent Treatise  on Optics, in his Let-
ters on Natural Magic, and in the  article on Optics in the Library
of Useful Knowledge, which is evidently an  emanation  from the
same  mind,—has collected several  of  these  cases from  various
sources.
  A shoemaker, of the name of Harris, at Allonby, in Cumberland,
could  only distinguish black and white;  and, whilst a child, could
not discriminate the  cherries on a  tree from  the leaves, except by
their shape and size.  Two of  his brothers were almost equally de-
fective.  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 sisters,
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  Transactions
of the Royal Society of Edinburgh, by Mr. Harvey,  of Plymouth, re-
garded the solar spectrum as consisting only of yellow and light  blue;
and he could distinguish, with certainty, only yellow, ivhite 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. 
INSENSIBILITY OF THE EYE TO COLOURS.
225
On one occasion he repaired an article 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  ob-
servation, 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 capable 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 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 perform-
ing 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 nature.
"In the sense of vision," says Dr. Brown, "there is a  species of de-
fect very analogous to the want  of musical ear,—a  defect, which
consists in  the difficulty, or rather the incapacity, of distinguishing
some colours from each  other—and colours, which, to general  ob-
servers, seem of a very opposite kind.   As the want of musical  ear
implies  no  general  defect of mere quickness of hearing,  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 absolutely unsuccessful, have been made to explain the
apparent contusion of colours by certain peculiarities of the external
organ of sight."
   Mi. 'Dalton^ who believes the  affection to be seated in the physical
part ol  the organ, has endeavoured  to explain his own case, by sup-
posing  that the vitreous humour is blue, and  therefore  absorbs a
great portion of the red and  other  least refrangible rays; and  Sir
David Brewster,  in the  Library of Useful Knoivledge,  appears to
   vol. i.                        29 
226
SENSIBILITY--SENSE OF SIGHT.
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 contain-
ed in his more recent Treatise on Optics, it is probably no longer
considered by him to be satisfactory.
  The defect in question  has alwrays 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 apprecia-
tion, 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, ex-
ercises its function perfectly, as regards the form and position of ob-
jects, 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 deficiency is in the
part  of  the  brain, whither the impression is conveyed, and where
perception is effected, which is incapable of accurately 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  direction,
position, magnitude, distance, surface, and motion of bodies.  Meta-
physicians have differed greatly in their views on  this  subject; the
majority believing, that, without the sense of touch, the  eye is  inca-
pable of forming any  accurate judgment  on  these  points; others,
that the sense of touch is no farther necessary than as an auxiliary;
and that a correct appreciation  could be  formed by sight alone.
The  few remarks,  that  may  be necessary on this  subject, will be
deferred, until the physical  and other circumstances, which 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.  When-
ever, therefore, the luminous cone meets  with reflection or refrac-
tion, before reaching the eye, the retina conveys erroneous informa-
tion to the sensorium, and  we experience an optical illusion.
  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 
APPRECIATION OF DISTANCES.              227
size, the intensity of Ught,  shade and  colour, the convergence of
the axes of the eyes, the size or position  of intervening objects, &c.
   Porterfield enumerates six methods, which are employed in appre-
ciating 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  distinctly at
different distances; 5, the direction  of their axes; and 6, the inter-
position of objects.
   Dr. Brown reduces them to three—1,  the difference of the  affec-
tions of the optic nerve; 2,  the different affections of the muscles,
employed  in varying the refracting power of each eye,  according
to the distance of objects, and in producing that particular inclina-
tion 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 considering a part
of one compound  perception."
  Lastly, Dr. Arnott, in his " Elements of Physics," enumerates four
modes by which this is effected—1. The  space and place, occupied
by objects in the  field of view, measured by what  is termed the
visual angle.  2.  The intensity of light,  shade, and colour.  3. The
divergence of the rays of  light—and 4. The convergence of the
axes of the eyes. This enumeration may be adopted, with  some
slight modifications.   The circumstances, in our opinion to be con-
sidered, are:—
  1.  The visual angle, or that formed by two
Fig. 45.
                                             lines, which shave
                                              the extremities of
                                              an object, and cross
                                              at the centre of the
                                              crystalline; so that
                                              the  visual  angle,
                                              subtended  by the
                                              object, as a d,  Fig.
                                              45, is exactly equal
                                              to that subtended
                                              by its image i u on
 u  •     r      i •  n       ,    .,   ,            tne 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 magnitude, the difference would be
accurately  indicated by the difference 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  iu and  io.  The cross ce
however, which is twice the size of bd, subtends  the same visual
angle, and  is alike represented 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, 
 228              SENMBILITY--SEN>E OF SIGHT.

 conversely, we cannot judge accurately of their  distances, without
 being aware of their magnitudes.
   A man on  horseback, when near us, subtends a certain visua.
 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   I
 subtend as large a visual angle as  the planet Jupiter, which is one
 thousand two hundred and eighty-one times  bigger than this earth,
 and is eighty-six thousand 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  1
 persists in spite of our being aware of the mathematical accuracy,  1
 with  which it has  been determined,  that the former is ninety-six
 millions of miles from us, and the latter only twro hundred and forty  |
 thousand.                                                         ■
   The visual  angle, again, subtended  by an object, differs greatly
 according to the position of the object.  A sphere has the same ap-
 pearance or bulk, when held  at  a certain  distance from  the eye,
 whatever may be the position in which it is viewed; and, accord-
 ingly, 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 obvious, that if any such  object be held in a sloping position to-
 wards 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
 appearance is what  is called foreshortening; and it  may be eluci-
 dated by the following figure.  Suppose a man to be standing on a
 level plain, with his eye at c, looking down on the plain.  The por-
 tion of the surface a d, which  is  next to him, will be seen without
 any foreshortening;  but  if
 we suppose him to regard                Fig. 46.
 successively  the  portions  ~        e
 d f f g,  and g  b of the
plain, the  angle, subtended
by  each portion,  will di-
minish ; so that if the an-
gle a  c d be  45°, d c f ■<■        a,       f       sr       o
will be 18°; / c g  8°, and so on; until,  at length, the obliquity will
 
APPRECIATION OF DISTANCES.
229
be  so
cause
un
though
      crreat, that the angle becomes inappreciable.   This  is  the
   ;c why, if we look obliquely upon a long avenue of trees, we are
nable to see  the intervals between the farthest  in  the  series; al-
       that between the  nearest to  us may be  readily distin-
  In all paintings, of animals especially, the principle of foreshorten-
ing has to be rigidly attended to: and it is owing  to a neglect of
this, that we see such  numerous distorted  representations—ot the
human figure particularly.
   It has been already stated, that objects appear smaller according
to their distance; hence, the houses of a street, or the trees of an
                                        avenue, that are nearest to
                Figm  47.                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 sufficient-
                                        ly  prolonged,  they would
                                        appear to  meet in a point,
                                        as  in  Fig. 47.   The art
                                        which  traces objects, with
                                        their various degrees of ap-
                                        parent  diminution on ac-
 count 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 dis-
 tance of the body, from which it emanates;  so that it is only one-
 fourth as powerful when doubly distant, one  sixteenth when  quad-
 ruply distant, and  so on.  This  fact  is early recognized; 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 luminous 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.

   * A delightful season in the southern and western parts of North  America, generally
 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 con-
 dition 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 objections  to it. 
230
SENSIBILITY--SENSE OF SIGHT.
   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 por-
 tion only of that, which has to pass through the dense heterogeneous
 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 ap-
 pear larger at rising and setting.
   The shade of bodies keeps pace with their intensity of light; and,
 accordingly, the shadows of objects near  us, are strongly defined;—
 wdiilst in the  distance  they become confused,  and the light altogether
 so faint, that the eye at last sees an extent of distant blue mountain
 or plain; "appearing  bluish," says Dr. Arnott, "because the  trans-
 parent 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, Dr. Arnott  probably la-
 bours under  misapprehension.   Within a very few miles from the
 whole of this extensive chain, as well  as  from a distance, the blue
 tinge is perceptible, especially when the air is dense and clear, soon
 after the sun has descended behind it;  so that the name is as appro-
 priate in the vicinity as it was when "the  discoverer's eye was bent
 on it 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 dis-
 tinguish 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 per-
 ceptible;  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 foreground
 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 mode-
rate distance from  us,  we  so direct the eyes, that if the axes  were
 prolonged they would  meet at the object, as  at  D. Fig. 42.  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 
APPRECIATION OF DISTANCES.
231
of iudging, to a certain extent, of near distances.  A definite mus-
cular effort is required for each particular case; and the difference
in the volition necessary to effect it enables the brain to discrimi-
nate, precisely in the same manner as it judges of the height ol  a
body, by the  muscular action, required to carry the axis from  one
extremity of the object to the other.
   We have the most satisfactory evidence, that such convergence
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 occa-
 sionally never regained; notwithstanding every endeavour to train
 the remaining organ.
   It need scarcely be said, that  the  convergence  of the axes is no
 guide to us in estimating objects, which are 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  esti-
 mating  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 an unvaried  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
  comparison.   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 ob-
  jects that are on the same level with us, than when they are either
  much  above or much below us. 
232              SENSIBILITY--SENSE OF SIGHT.

  The size and distance of a man on  horseback are easily recog-
nized 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: —

                                  " 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.  Halfway 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 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 ab-
sence of intervening bodies; and still more perhaps to 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, unsurrounded by objects to
enable us to form  an accurate judgment, it would appear to be much
shorter than when erect, on the principles 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 compare 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 be-
comes 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,  al-
though 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 
APPRECIATION OF MOTION.                 233
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 oc-
cupy sixty degrees  in his field of view, and he might see from be-
tween the houses many broad constellations 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 instancej
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 con-
vergence of the axes of the eyes—and 4thly, by the interposition 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 inca-
pable of  perceiving  it;—as in the case of a shot  fired from a  gun,
especially when near us.  But if it be projected from  a distance, 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 for some time before they fall, in the  darkness of night; and af-
ford objects  for interesting speculation regarding their  probable des-
tination.
  To form an accurate estimation 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
arc receding from us.                                          y
  If at a distance, and the visual angle between the extreme points
of observation be very small, the motion of an object will hkewSe
appear extremely slow;  hence  the-difference between a  carrTage
Hashing past  us  m the street, and the same  object viewed from^a
30 
234              SENSIBILITY--SENSE OF SIGHT.

lofty column.   A balloon may be moving along at the rate of nearly
one hundred miles per hour; yet, except for its gradual diminution
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 re-
volves 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 arc
at a yet greater distance from the earth.
   These are cases in which the body  moves with excessive velocity,
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 ob-
served, 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 instinctive  or  '
dependent upon an  original " law of the constitution," and totally  i
independent of any knowledge gained through  the medium of the  j
external senses.  It has already been remarked, that metaphysicians
may be considered as divided into  those, who believe 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.                                                  m
   Of the precise condition of the visual perception,  during early  in-  i
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
yet having received a sufficient degree of assistance from touch, or
from want of the necessary developement 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, which 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- 
APPRECIATION OF DISTANCES, ETC.
235
vations  on the celebrated case  described  by  Cheselden in  his

 "ThHubject of this was a young  gentleman, who was born blind,
or lost his sight so early, that he  had no  remembrance of ever
bavin" seen, and was "couched," so says Cheselden,  "between
thirte?n and fourteen years of age."   Magendie affirms, that  there
is every reason to believe, that the  operation was not that tor cata-
ract, but consisted in the incision of the pupillary membrane. It need
hardly be  remarked, that Cheselden must be the  best possible  au-
thority on this subject.
  "VVhen  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 left  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 anything, 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
Chesclden's, which has  always appeared to  us  too  poetical, was
 laid before the Royal Society of London,  in  1826, by Mr.JVard-
 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 affect-
 ed 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. 
236               SENSIBILITY--SENSE OF SIGHT.

  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   I
exclaimed, " What is that large thing that has passed by us l"  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 out  to  the hour of twelve and
smiled.   Her  brother asked her if she  saw anything  more; she
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  I
again, when she playfully pulled it off, and asked,  " What is that ?"  1
On the thirteenth day, she walked out with her brother in the streets  m
of London, when she distinctly distinguished the street from the  1
foot pavement,  and  stepped from one  to  the other, like  a person  1
accustomed to the use of her eyes."  " Eighteen days after the last
operation," says Mr. Wardrop, " I attempted to ascertain, by a few  J
experiments, her precise notions of the colour, size and forms, posi-" JS
tion, motions and distances of external objects.  As she  could only   (
see with one  eye, nothing could be ascertained respecting the  ques-fc^
tion of double vision.   She evidently saw the difference of  colours;
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 onlyM
distinguished them at once from one another, but gave a decidediW
preference to some colours, liking yellow most, and then pale  pink.  J
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 di«-$B
tinguished a large  from a small object, when  they were 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 
                                                           237
                APPRECIATION OF DISTANCES, ETC.

really were, and not inverted.(!!)   She could also ff ^ ^jj*0^
 or when a glass of water  was  placed on the table before her on
broaching her hand near  it, it  was moved quickly to a greater
Knee  upon which she immediately said, • You move it; you take
W ThVseemed to have the greatest difficulty nii finding ^out
 he  d^ancc  of any object;  for, when an object was held close to
her eye, she wouk/search for it by stretching her hand far beyond
its position, while on other occasions die groped close to  her own
 face for a thintr far remote  from her.                          .
  We have given the particulars of this case at some length, mas-
 niuch as thf;  are regarded  by Dr.  Bostock-and «gP™*££
 Mr. Wardrop himself-as strikingly confirmatory  of those  ofChe-
 selden, than which we  cannot imagine ^y*^fim°ronft^X "'
 It wil  have been  noticed, that, from the  yery first.after he re-
 ccn™ n  of sight, she formed an imperfect judgment of objects, and
 ^cn of distance's, although she was devoid of the  elements neces-
 sary for arriving at an accurate estimate of the latter-the sight ol
 both eyes.   Tllis  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  more  easily and accurately with their assistance, espe-
 cially with 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 I  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 obtaining an imperfect  knowledge
  of distance, shape, &c.  must,  therefore,  be trifling; although  an
  accurate acquaintance may  demand numerous,  and  careful com-
   Karisons.  This  first  degree of knowledge is  probably  obtained,
   y 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 eyebaJJs  harmonize instinctively in 
238
SENSIBILITY--SENSE OF SIGHT.
their parallel motions;  but the convergence requires an effort of voli-
tion, 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 judg-
ing more correctly of  objects, that are somewhat more remote, and
where less convergence, and, consequently,  less muscular  effort is
necessary.
   The numerous optical illusions,  which, we have been compelled
to describe, in the progress of the preceding remarks, will render it
necessary to refer to but few under this head.
   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  caused by
mirrors.  A ray of light, K C, Fig. 22, falling upon a plane mirror,
I J, is reflected back in the same line ; but, as we have seen, the ob-
ject 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 ob-
ject B will appear to be at  H, in the  prolpngation 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, as A B, Fig.
48, be reflected  to  an eye at F,
and that from the lower part of c\ ""'"■......
the object meet the other  at this  ""!
point.   To  an  eye so placed,   j
the object  will  appear magni-   j
fied, and seem to be at C U, or D ;...--*"*
in the prolongation of the rays
which fall upon the cornea.
   If the mirror, as  in Fig. 49, 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 accu-
rate miniature 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. 22, in the
pool of  water, I J, does not proceed into the air in the  direction F
C O, 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
Fig. 48.
Fig. 49.
 
OPTICAL ILLUSIONS.
239
 at /; the pool will, consequently, appear shallower than it really is,
 by the space at which/ is situated above the bottom.
   Wo can  now  understand, why rivers should appear shallower
 than  they really are, when viewed obliquely;  and why the lower
 end of a pole, immersed in water, should, when seen obliquely, ap-
 pear 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 cor-
 rected.  Those birds, too, that live upon the inhabitants of the wa-
 ter, will have to learn, from experience, to obviate  the  optical illu-
 sion ; or to descend perpendicularly upon their prey, in which direc-
 tion, as we have seen, no refraction takes  place.   Similar remarks
 apply to the fish that leap out of the streams to catch objects in the
 air. The Chatodon rostratus, about six or eight inches long, frequents
 the sea-shores in the East Indies: when it observes a fly, sitting on
 the plants that grow in shallow water, it swims to  the  distance  of
 five or six feet, and then, with surprising dexterity, ejects out of its
 tubular mouth a  single  drop of water, which  never fails to strike
 the fly into  the sea,  where it soon becomes its prey.  Hommel—a
 Dutch governor—put some of these fish into a tub of water, and
 then pinned a fly on a stick within their reach.  He daily saw  the
 fish shoot at the fly, and, with such dexterity, that they never failed
 to hit their mark.  Pallas describes the Siana Jaculatrix  as secur-.
 ing flies by a similar contrivance.
   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 modifying the sphere of vision.  If the lens be double con-
 vex, the body, seen through it, appears larger than it is, from the illu-
 sion so often referred to, that we always refer the object in the di-
 rection of the line, that impinges upon the retina.   The  object, con-
 sequently, appears to be greatly augmented.  (See Fig. 28.) For the
 same reasons an object seems smaller to an eye at A, Fig. 25, when
 viewed through a  double concave lens.
   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

  An impression of light continues to affect the retina for the  sixth
 part (M. D'Arcy says the seventh part,) of a second.  If, therefore,
 a hve coal be whirled round in a circle, six or seven times in a  se-
 cond, it will seem to be a continuous circle of fire.   It is  owing to
 this circumstance,  that meteors  seem to form a line of b>ht— as in
 lie ease  of the falling star,-and that the same impre sfon is  con"
veyed by a skyrocket ,n its course through the air  We have  an
elucidation of this fact in the instrument or toy-called, by Dr Pari
the rt««,«,/T-which consists of a circle?cut out of a card and
hiving two sJken strings attached to opposite points of its dfameten 
240               SENSIBILITY—SENSE OF SIGHT.

by twisting these with the finger and thumb the card may be twirled
round with considerable velocity.   On one side of the card an ob-
ject is drawn—such as  a chariot—and on the other, the charioteer.
If the card be twirled round six or seven times in a second  the cha-
rioteer will be  seen in the chariot; the  duration 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 optical 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 opticafcr-
rors, which we are habitually incurring.

  To conclude,—the sense of sight differs materially in the  scale of
animals: in few is  the  organization more perfect or the  function
better executed than in  man.  Situated at the  upper and  anterior
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 ani-
mals ; and it is very movable, and under the domination of a mus-
cular apparatus of admirable arrangement.   Still, it  is  not  as deli-
cately 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.                                          ,,j
  Like  the other  senses, it can be exerted actively and  passivelyj£j
hence the  difference between  simply seeing and looking.   In tneii
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 ac-
curate 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
worker 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,  J
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, which have been considered, constitute so many
special nervous systems, each concerned in its appropriate function; 
ADDITIONAL SENSES.
541
and, although conveying ideas  of the  external world to .the:  brain,
and connected with that organ, to a certain extent independent ot it.
  The generality of physiologists  admit only these five; but some
have suggested  "others, differing, in general, however, from the five,
in havinc?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 es-
teemed a peculiar .variety of tact  in the mucous membrane of the
aenital organs;—differing  from  ordinary tact in those parts, by re-
quiring in both  sexes a special  condition of the  membrane; and, m
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,
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 in the lungs; but all these are more properly internal
 sensations.
   The German physiologists have suggested another  sense, which
 they   term  coznasthesis,  gemein gefiihi, or  common feeling,
 1 e  b e n s g e f ii h 1, 1 e b e n s s i n n, individual i t a t s s i n n, and
 sclbstgefuhl. *  Tins  is not seated in any particular part of the
 body, but over  the whole system, and hence termed  gemein, or
 common.   It is indicated by  the 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, belongs the involuntary
 shuddering, glow, or chilliness, experienced  under similar circum-
 stances.  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 possess
  other senses than the five  we have  mentioned.  Of this we can
  have no positive evidence.  We are  devoid of all  means of judg-
  UI& of their sensations; and if we  meet with an  additional organ,

       * " Feeling of life, seme of life, sense of individuality, and self.feeling."
    VOL. i.                     31 
242                SENSIBILITY--\DDITlONAL SENSES.

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,    j
 which is presumed to preside over this faculty.  This  is, however,
 in all probability, a cerebral faculty, and may fall under  considera-
 tion 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    I
 dentes incisores, when such are present, but they exist in animals   |
 also that are destitute of teeth.  They are termed ossa intermax.il-    i
 laria,  ossa incisoria, and  ossa  labialia, and are  situated,  as their  $■
 names import, at the  anterior part of the jaw, and between the ossa   .<
 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,   xlccordingly, 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    t
 imaginary.

    Adelon, it was remarked, makes  two divisions of the external   .
 sensations :—those that convey information to  the mind; and those   f
 that do not.   The former have engaged attention; the latter will  "i
 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,  . 1
 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 of  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 produced.   When   .
 It arises extraneously, it can generally  be readily 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 
INTERNAL SENSATIONS.
243
the part, it is called tingling.   This kind of purring also often occurs
without the presence of itching.
   Tickline or tifiliation is always caused by the contact of some ex-
traneous  substance, and  is  therefore a  true external sensation.
Although occurring in the skin, and in the commencement or termi-
nation °of the mucous membranes, all parts are not equally suscep-
tible  of it: and some—as the lining membrane of the genital organs,
—arc onlv, 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 con-
vulsions, and even death.  Lecat terms it an hermaphroditic  sensa-
tion, inasmuch as, on the one hand, it excites laughter; and,  on the
other, is insupportable ;  and, consequently, appears to be intermedi-
ate 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 everything
that  can be, in  any manner, inservient to  our necessities.   Such
necessities  have,  however, to be  suggested to the mind, before if
reacts through the aid of the organs  of prehension or otherwise, on
external  bodies, and this is accomplished  by the agency of  the in-
ternal or organic sensations.
   Without  the intervention of any external  cause, every organ of
the body is capable of transmitting to the brain a numberof different
impressions, many  of which  impel the organ to acts, that  are ne-
cessary not only for the preservation of the individual and of the
species, but also for the perfect developement of the faculties.   Such
are the sensations of hungef 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 fasces;  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
arc often obscure, but sometimes  very acute.  Amongst these are 
244            SENSIBILITY--INTERNAL SENSATIONS.

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 intellectual labours.
   The last species succeed to the action of organs, especially when
such action has been too long  continued:  hence the inward  feeling
offatigue, 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 on the part
to which the sensation is referred;  an action of perception, accom-
plished 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 first, or the mode in which the impression is effected, and the
character of the impression itself, are much  more obscure.  In the
external 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 interna]  sensations or  sentiments,^
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 interna] sensations.
   They  differ,  in other respects,  from  the external  sensations.
Whilst the latter  may be entirely passive,  or  be rendered active by
volition,  without either action  being the  cause of particular pleasure
or inconvenience, the former  are but little influenced by volition.
Constituting the wants—the instinctive desires—which impel to acts,
that are  necessary for the preservation and full developement 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
that  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  compelled  to 
MORBID SENSATIONS.
245
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 were entirely neglected, until of comparatively late years:  but
attention has been attracted to them chiefly by the  labours of Caba-
nis and of Destutt-Tracy, and they now form subjects for interesting
speculation with the metaphysician.
  The morbid  sensations belong  more particularly to  pathology:
a brief notice of them will consequently be all that  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  a 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  impressions,
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 dif-
ference  between the  pain caused by a burn, and that  by a cutting
instrument;  and the immense variety of pains  to which the human
frame is subject,  the  attentive study  of  whichns so indispensable to
the pathologist. 
246
SENSIBILITY--MENTAL FACULTIES.
   So much for the sensations.  These we have seen are innume-
rable, 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, and 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.

   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
other hand, consist, as we  have seen, of the numerous wants and
appetites, necessary for the preservation of the individual and of the
species.   In addition  to these, man possesses another series of facul-
ties, which influence  his character  and disposition,  and  direct his
social existence:—these are the affective or emotive faculties, 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, at one time,
universal, and hence the appellation metaphysician, applied to such
as were considered to proceed in their investigations of those sub-
jects beyond what was physical, material, or corporeal.
   There is no subject, which has given occasion to so much excite-
ment and controversy, as that of the connexion of the mental facul-
ties  with the encephalon.   "It has unfortunately  happened," says
Dr. Bostock, " 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 interwoven with  our accustomed associations, on topics
connected with morals and religion, as to render  it doubtful, on some
occasions,  how  far we oughjt to attempt  their  removal:  but if this
concession 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 
MENTAL FACULTIES.                   247
to be conducted;  and in such a spirit will  the few remarks,  which
we have to make, be offered.
  The chief opinions, which 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, perception
is imperfect;  where the organization  is sound  and  vigorous, per-
ception 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  gene-
rality of physiologists,  and is most consistent with  reason and ana-
logy;  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 which 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 matter 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 form 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
afi  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 affected 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
is a poet, another a  mathematician; or one is 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
according 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, 
248
SENSIBILITY--MENTAL FACULTIES.
 that they are the exclusive product of the mind or immaterial prin-
 ciple.   An immaterial or spiritual principle ought to be  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 modifica-
 tions are impressed by varying organization—of the brain in par-
 ticular.
   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   1
 likewise.                                                          ^
   The brain, again, must be in a state of  integrity, otherwise the  j
 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 organ
 be more permanently disordered, as by the pressure of an exostosis
 or of a tumour, or by some alteration in its structure or functions—  1
 less appreciable in its nature—insanity, in some of its forms, may be   ,
 the result. '                                                        '
   In serious accidents to the encephalon, we observe the importance   *
 of the cerebral organ to the proper exercise of the mental faculties   (
 most clearly evinced.   A  man falls from a height, and fractures his
 skull.   The consequence of this is depression of  a portion of bone,
 which exerts a degree of compression upon the brain; or extravasa- "^
 tion of blood from some of the encephalic vessels, attended with simi-   i
 lar results.  From  the  moment of the infliction of the  injury, the i ^j
 whole of the mental and moral manifestations are suspended, and do
 not return until the compressing cause is removed, 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,  .1
 that pressure upon the brain completely deprived her of all conscious-
 ness, which was not restored until the pressure was removed.  A simi-
 lar case is related  by Lepelletier, de la  Sarthe.  A patient of a Dr.
 Pierquien had an extensive caries of the os frontis, with a perforation
 of the  bone, which exposed the  brain  covered by its membranes.
 When  she slept  soundly the organ sank down: when she dreamed,
 or spoke with feeling, a turgescence and marked oscillations were
 perceptible; when  the  brain was pressed upon she stopped  in the
 middle of a sentence or of a word, and when the pressure was re- 
MENTAL FACULTIES.
249
moved, she resumed the conversation, without any recollection of the
experiment to which she had been subjected.
  We notice, however, an important difference in the effect, accord-
ing to the suddenness or tardiness with  which the pressure is pro-
duced.  Whilst a sudden compression suspends the intellectual and
moral manifestations for a time, slow pressure, produced by the gra-
dual formation of a tumour, may exist  without  exhibiting,  in any
manner, the evidences of its presence.   Accordingly, the anatomist
is sometimes surprised to discover such morbid formations in the
brains of those who have never laboured under any mental aberra-
tion.
  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  portions, may exist and pass on to a fatal ter-
mination, leaving these faculties almost wholly unimpaired.  Such is
proverbially the case with phthisis pulmonalis, the subject of which
may be flattering himself with  hopes never to be realized,  and devis-
ing 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 different.
Much may depend upon education;  but it may, we think, be laid
down as an incontrovertible position, that there is an original differ-
ence 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 does not  exceed
thirteen, or is not greater than in the child one year old.
  It was an  ancient observation, that a large  developement  of the
anterior and superior parts of the head is a characteristic of genius;
and, accordingly, we find, that all the statues of the sages  and heroes
of antiquity are represented with high and prominent foreheads.  In
the older poets, we  meet with  many evidences, that the height of the
forehead was regarded as an index of the intellectual or moral cha-
racter of the individual—Thus, Shakspeare:

                        " We shall lose our time,
           And all be turn'd to barnacles, or to apes,
           With foreheads villanous low."
                                Caliban,  in * Tempest.'—Act iv.

And again:—
           Ay, but her forehead's low, and mine's as high."
                         Julia, in the ' Two Gentlemen of Verona.''—Act iv.

  The relation between the size of the head and the mental manifes-
tations has,  indeed, interwoven itself into our  ordinary modes  of
speech. 
250              SENSIBILITY--MENTAL FACULTIES.
  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 re-
sults, and in which the largely developed  organ may be greatly de-
ficient.   Size is only one of the elements of the activity of an organ.
  The difference between the moral of the male and female is signal;
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 de-
veloped in the female, whose forehead is, therefore, as a general rule,
smaller; whilst the posterior parts are larger than in the male.  In
the system of Gall, 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 feel-
ings, 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
state of the encephalon is as various.   The anatomist notices, a mani-
fest difference between its organization in  the infant and in the adult.
or the aged.   Like the other organs of the body, it is gradually de-
veloped until the middle  period  of life; after which it  decays along
with the rest of the frame.   Our acquaintance with the minute or-
ganization 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 able to appreciate 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 mania
or delirium probably never occurs, without the physical condition of
the brain having undergone some change, directly or indirectly.  It
is true, that, on careful examination of the brains  of the insane, it has
often happened that no morbid appearance has presented itself; but
the same thing has been observed  on inspecting those,  who  have
died of apoplexy or paralysis, in which cases, not a doubt is enter-
tained that the cause is seated in the encephalon,  and that it consists
in a physical alteration of its tissue.   These are  a few of the cases,
which make us sensible of the limited nature of our powers of ob-
servation.   They  by no  means encourage, in the most sceptical, the
belief, that the  tissue of the organ is  not implicated.  The investiga-
tions of the morbid anatomist consequently afford us  but few data,
on which to form our opinions on this subject.
  The effect of intoxicating substances must be  mainly exerted  on
the brain.  When taken  in moderation, we find all the faculties ex-
cited ;  but, if pushed too far, the intellectual and moral  manifesta- 
MENTAL FACULTIES.
251
tions  become  perverted.  This  can only be through the action of
those substances upon the cerebral organ.  We can thus understand,
how regimen may cause important  modifications in the brain.   Cli-
mate has probably a similar influence: 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  animal
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 which 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  notion,
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 assumes the
simple original character, which has laid the foundation for  one of
the divisions of  Sir Charles Bell's system; and, although it is im-
possible to change places with the  animal, we have  the strongest  M
reasons for believing, that their sensibility diminishes as we descend;
and that the feeling, expressed by the poet, that the beetle, 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.
Redi  removed the whole of the brain from a common land tortoise:
the eyes closed to open no more, the animal walked as before, but,
as it were, groping  its way for want of  vision.   It lived  nearly six
months after.  All have noticed the independence of 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 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 rabbit; and
when the tail was laid hold of, the headless neck  bent itself quickly
round as if to strike him.
  The instances of a similar kind, which 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- 
252
SENSIBILITY--MEN TAL FACULTIES.
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,—rthat 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 combined
so  as to moderate and temper each other.  Modern physiologists
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 appa-
ratus of organs predominates, the effect of such predominance may
be exerted over the whole economy.  In the description of the tem-
peraments, in different authors, we find a particular character of in-
tellectual and  moral faculties assigned to each.  The man of the
sanguine temperament is  described as of ready conception, retentive
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,  ambitious, and
self-willed; whilst the lymphatic  bestows feeble  passions, cold ima-
gination, tendency to idleness; and the melancholic disposes to dul-
ness 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-
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: this, he suggests, it does probably by impressing them with a
character of energy or of languor, but without, in  any respect, re-
gulating the intefiectual sphere of the individual;  and it may be  re-
garded  as one of the media of connexion between the mind and the
body.
  Bichat, again,  maintained, that whilst  the encephalon is evidently
the seat of the intellectual  functions,  the organic nervous system, 
MENTAL FACULTIES.
253
and, consequently, the different organs of nutrition, which are sup-
plied  from this system,  are  the seat  of the  emotions or passions.
That distinguished  physiologist, than  whom, as Corvisart wrote to
the First Consul, in  announcing his death,  lipersonne en si peu de
temps n'a fait tant de choses et aussi Men," 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 or 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
are 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 *~ -^oress 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 or long head;"
and we say that the possessor has " much or little brain."   On the   9
other hand,  if we are desirous of depicting the passions, the hand is
carried to the region of  the stomach or heart; and the possessor of
benevolent or uncharitable  sentiments is said to have a good or bad
heart."  Bichat properly adds, that this idea is not novel, inasmuch
as the ancients conceived  the  seat of the  passions to be in the epi-
gastric 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 ranges the passions, are involuntary,
and consequently uninfluenced by education, education can  have no
influence over the passions, and the  disposition is consequently inca-
pable of modification.
   The answer of  Gall  and  Adelon to the views of Bichat appears
to us irrefragable.  How can we  conceive that viscera, whose func-
tions 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
essentially nervous organs.
   Again, when  an injury befalls the brain,* and'the  intellectual
faculties are perverted or suspended by it, the same thing happens to
the affective faculties;  and if the viscera fulfil the high office assigned
to them, why  are not the  passions manifested from  the earliest
1 nfancy, a period when the viscera are in existence and very active ? 
254
SENSIBILITY--MENTAL FACULTIES.
 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 re-
 marks, 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, by7 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 im-
 pressed with the most prominent effect  of the passion—the feeling
 accompanying it—and  this is  the cause of the  gesture and the de-
 scriptive 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
 they  are irresistible, and  cannot be modified by education, falls to
 the ground.  His  notion  was, that the nutritive organs  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, conceives, that the passions
 can  be  fomented and  increased by attention,  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 persons, whose habitual  indulgence  of the
 lowest passions and  propensities had rendered them outcasts from
 society, having become restored to their proper place in the com-
 munity by exerting the  due control over their  vicious inclinations
 and habits?   We can 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
 repression.
  Lastly. Many physiologists, we have  seen, have  considered the
 brain as a grfeat 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;  and they conceive, that a necessary connexion
exists between these two orders of parts.
  The supporters of these opinions ascribe the differences, observed
in the intellectual and  moral  faculties  of different individuals, as 
MENTAL FACULTIES.
255
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  s'chdbl 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, 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 priusfuerit in sensu;"
and they adopt, as an elucidation of their doctrine,  the  ingenious
idea  of Condillac—of a statue, devoid of all sensation, which is
made to receive each of the five senses in succession; and which,
he attempts to show, from the received impressions,  can develope
the different intellectual and moral  faculties.   All  these, he affirms,
are derived from the impressions made on the external senses; and
he considers, that  the whole of human  consciousness is  mere sen-
sation variously transformed.
  The views of Condillac have been largely embraced, with more   #
or less modification; and, at the present day, many metaphysicians
believe, that the impressions of the senses are the necessary and
exclusive materials of all the intellectual 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 re-
ception 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  '
external senses, such a being  must not  only  be defective  in  the
nerves which, in the perfect animal, are destined to convey the im-
pressions to the brain, but probably 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,—
particulary those portions that  are especially concerned in the func-
tion of thought,—being  properly organized, it  appears to us, that
certain mental  or moral  manifestations  ought to  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 
 250             SENSIBILITY--MENTAL FACULTIES.

 this period,  and which are doubtless dependent  upon encephalic
 organization.  In this assumed case, then, a  certain  degree of
 mental action might exist;  and, under the supposition of a properly
 organized  brain, ideas—limited,  it is  true, in consequence of the
 privation of the  ordinary inlets  of knowledge—might be formed;
 and memory, imagination, and judgment, be compatible within cer-
 tain limits.
   The 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 are overwhelming.  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 supe-
 riority 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_jj
 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 mental  developement;  and  that its  place
 may be supplied, to a great extent, by the proper exercise of others.
   The deaf and dumb, being deprived of the advantages of spoken
 language, are compelled to have  recourse to the only kind available
 to them—that addressed to the eye.  In this typical way, by a well-
 devised system of instruction, they can be  taught to preserve their
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 
MENTAL FACULTIES.
257
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  senses of touch, smell  and taste;  yet even here we
have the strongest evidence of independent intellect.
   One of. the most striking cases of this kind is that of the Scottish
boy Mitchell, the object of much  interest to Spurzheim and to Du-
gald Stewart, both of whom have described his case in their writings.
It is 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 partia]  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 tympanum of both ears was per-
forated, but without any advantage. In his fourteenth year, the ope-
ration  for cataract was performed on the right eye, after which he
recognized more readily the presence of external objects, but never
made  use  of his sight to become acquainted with the qualities of
bodies.  Before, and after, this period, red, white, and  yellow par-
ticularly attracted his attention.  The senses, by which he judged of
external bodies, were those of touch  and smell.  His desire to be-
come  acquainted with  objects was signal.  He  examined every-
thing he met with, and every action indicated reflection.   In his in-
fancy,  he smelt at every one who approached him, and their odour
determined his affection or aversion. He always recognized his own
clothes by their smell, and refused to wear those which  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, gathering round, smooth stones, laying
them  in a circle, and placing  himself  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 distin-
guish 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  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  signifi-
cation 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 an 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 different emotions—of hatred, passion, malice, and the
  vol. 1.                      33 
258              SENSIBILITY--MENTAL FACULTIES.

kindlier feelings.   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 metaphysi-
cian, but it is not so elucidative as it would have been had the priva-
tion of the senses in question been total.
  There is, at present,  in the  American Asylurn 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 Hartford,
and was born in that town in June, 1807; so that she is now, (1835,)
twenty-eight years old.   At four years of age, she was seized with
typhus fever; was taken sick on the evening of Monday, November
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 shq was unconscious of
her misfortune, appearing to think, that a long night had come upon
the world; and often said, "It 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 hen   At length,  in passing
a window, she felt the sun shining warm upon her hand, and points
ed with delight to indicate  that the sun shone.   From the Januar "
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.   Even now, the intervention of a-day of fasting or thanks-
giving will confuse her reckoning, and some time elapses before she
gets right.
  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 
                      MENTAL FACULTIES.                    *ov
                                    *
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."
   An equally extraordinary example is cited by Dr.  Abercrombie,
from the Medical Journals of recent date.   A gentleman in France
is asserted to have  lost every sense except the feeling of one side  of
his face; yet his family acquired a method of holding communication
with  him, by tracing characters upon the  part, which  retained  its
sensation.
   How  strongly do these  cases demonstrate  the  independence
 of the organ of intellect;  requiring, indeed, the  external  senses
 for  its perfect developement, 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
 incapable of  any understanding, as wanting all those senses which
 furnish the human mind with ideas." But if he groiv 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
 competent as witnesses, provided  they evince sufficient understand-
 ing,  and to be liable to punishment for a breach of the criminal laws.
   ('abanis embraces the views of Condillac  regarding  the exter-
 nal senses; but he thinks, that the impressions from these are insuffi-
 cient to constitute the mattricl of the mental and moral manifesta-
 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 exter- 
 260             SENSIBILITY--MENTAL FACULTIES.

 nal 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?  (Jan 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 select a branch
 of the cytisus from 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 manifesta-
 tions, according to sex, temperament,  climate, state of  health or
 disease,  regimen, &c. cannot  be  referable to the senses, as they re-
 main the same ; and that, consequently, we must look  elsewhere 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 or-
 ganic movements in the process of this secretion, are  the  materials
 of the new desires, which appear at that age.  These impressions
 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 intel-
 lect,  the internal impressions are the  materials of what are called in-
 stincts; and, as the organs of  internal life, whence the internal  im-
 pressions 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.
   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 developement
of the testicles, 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  faets demonstrate, that
the condition of the uterus has much influence  on the mental and
moral manifestations  of the female.  For example, the  period of 
MENTAL FACULTIES.
201
the developement 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  mental and
moral faculties,  observed in  these different cases.   ThirUly.  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 xhe con-
trary; hence the  expressions  melancholy'*  and hypochondriasis,^
assigned  to  the  state of 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, he  says, to  the abdominal
 viscera.
   Hence, Cabanis concludes, it is evident,  that  the  abdominal or-
 gans are to  the  brain the source of fortuitous and anormal impres-
 sions, which  excite it to irregular acts; and  is it not, he asks, pro-
vable, 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 may be indispensable
 to the production of the mental  and moral faculties 1
   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  impressions,
 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 there is a ratio between the duration and
 intensity of the intellectual results and the kind of impressions, which
 have constituted the materials of them.  All the mental and moral
 acts, for instance, that are derived from  impressions  engendered
 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 impressions  are
 the materials.   They are powerful  and constant.  Lastly; the acts
 of the intellect  arc  more transient, because they emanate from  the
•*  From /utKas, black, and ;£oxj», bile.   -f Disease of the bypochondres. 
202              SENSIBILITY--MENTAL FACULTIES.

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 manifestations must
be placed, not only the encephalon and the external senses, but the
different  organs of the body, which furnish the different internal im-
pressions.
  The influence of the external senses on  the intellectual and moral
developement has already  been  canvassed : 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, as we
have seen, by Cabanis, in consequence of the external senses appear-
ing to him insufficient to explain all the phenomena.
  By Gall, Adelon, and others, however, all these cases are considered"
explicable, by the varying condition  of the brain itself.   In the foe-
tus 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 manifestations
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 developement 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-
velopement 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  developements  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 developement 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
the cerebellum; and as the most intimate connexion and dependence
must exist between the encephalic and the external apparatus, it is not
surprising, that the removal of the latter should prevent the deve-
lopement 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 developement
has already taken place, and  the  cerebellum is in a  condition for
fulfilling  the function.  The continuance of the instinct, under  such 
PHYSIOLOGY OF THE MENTAL AND MORAL ACTS.
203
circumstances, Adelon conceives to be strong  evidence against the
existence of such internal impressions.
  The influence which Cabanis has ascribed to the uterus in females,
and to the abdominal organs in the melancholic and hypochondriac,
are esteemed to belong to that excited by the temperament, 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 facul-
ties.   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  well 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 fre-
quently executed without the participation of  the  mind, and even in
its absence—inasmuch as it is not  confined  to beings possessed 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 a 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 their pro-
duction.   Such study is the basis of a particular science—metaphy-
sics, ideology or philosophy.  Apart from  organization, this  subject
does not belong to  physiology;  but as some of the points of  classifi-
 cation, &c. are concerned in  questions that will fall under consider-
 ation, it may be well  to give a short sketch of the  chief objects of
 metaphysical inquiry; which are, indeed, intimately connected in
 many of their bearings,—as commonly treated of by the  metaphysi-
 cian,—with our  subject.  Broussais has considered, that metaphysics
 and  physiology  should be kept distinct;  and that all the investiga-
t 
201             SENSIBILITY—MENTAL FACULTIES.

tions of the metaphysician should be confined to the ideal.   "I wish
metaphysicians, since they so style themselves,"1 he remarks  some-
what splenetically, "would never treat of physiology;  that they
would only occupy themselves with ideas as ideas, and not as modi-
fications 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 inquire whether
there are innate ideas, or whether they come through the medium of
the senses; that they would not undertake to  follow their develope-
ments 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 pre-
vailing diseases, &c. but then they should avail themselves of the
experience of physiologists  and  physicians."   A more appropriate
recommendation would  have  been, that the  metaphysician should
make a point of becoming acquainted with physiological 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 bodies sur-
rounding us: the latter comprising our  internal  feelings,  our  appe-
tites, desires, and  affections, by which we are excited to establish
a relation with the beings around  us:—the two  sets of  acts respec-
tively embracing the  qualities of the mind and of the heart.
   If we attend to the different modes in which the intellectual mani-
festations are evinced in our  own persons, we shall find that there
are several operations, which differ essentially from each other. Wc
are conscious of the  difference between perceiving  an impression;
made upon one of the external senses, which  constitutes perception,
and the recalling of such impression to the mind,—which is the  act
of memory; as well as the distinction between feeling  the relations,
which connect  one thing to another, constituting judgment;  and the
tendency to  act in any direction, which we  call will.  The  con-,
sciousness of these various mental acts has induced philosophers  to
admit the plurality of the intellectual acts, and to endeavour to re-
duce them  all to certain  primary faculties; in  other words, to facul-
ties, which  are fundamental or elementary; and which, by their com-
bination, give rise to other and more complex manifestations.  To
this analytical  method  they have  been  led by the fact,  that these
different acts, which they have esteemed elementary, exhibit great
variety in their degrees of activity; that one,  for example,  may be
mpressed with  a character  of great energy—as the memory— 
            I'HYSlOLOUY OF THE MENTAL AND MORAL ACTS.         205

 whilst another, as the judgment, may be singularly feeble,—and con-
 versely.
   Broussais, indeed, conceives, that without the memory we cannot
 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
 memory.  Hence  the loss of this faculty, he says, necessarily occa-
 sions that of judgment, and reduces man to a state of imbecility.
   To  a  certain extent this  is doubtless true.   Total privation of
 memory 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 metaphysi-
 cians; some admitting will, imagination, understanding and sensi-
 bility; others  sensibility, imagination, memory, and reason; others
 will, intelligence, and memory; others, again, imagination,  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 constituent faculties
 in the intellect:—sensation,  attention, comparison, judgment, reflec-
 tion, imagination, and reason. Sensation he defines the faculty of the
 mind,  which  affords the  perception  of any sensitive impression.
 Attention, the faculty of sensation, applied exclusively to a determi-
 nate object; being, as  the word imports, the tension  of  the mind
 upon a particular object.  Comparison, the faculty of sensation  ap-
 plied  to two objects at once.   Judgment, the faculty by which  the
 mind perceives the connexions, that exist between the objects com-
 pared.  Reason, the faculty of running through a succession of judg-
 ments, which  are  connected with, and deduced  from, each other.
 Reflection, as the word indicates, the faculty by which the mind  re-
 turns upon itself, upon its own products, to prove their correctness,
and to subject them again to its power:—and imagination, to which
Condillac attaches memory, the faculty possessed by the mind of re-
producing at will the different 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-
   vol. i.                        34 
200
SENSIBILITY--MENTAL FACULTIES.
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 rea-
son; 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 this first sensation successively transformed.
   The  doctrine  of Condillac,  abstractly considered,  has already
engaged attention.  The  division of the faculties, which, he con-
ceives, by their aggregation, form the  intellect, is  simple and inge-
nious, and appears to be more easily referable to physiological prin-
ciples  than  that of other  metaphysicians; accordingly, it  has been
embraced, with more or less modification, by certain physiological
writers.
   The power of  reflection, according to Broussais, is the character-
istic of the human intellect; and to reflect is to  feel.  Man not only
feels the stimulation produced by external organs, and by the move-
ments  of his own organs, which constitutes sensation or perception,
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 I, (moi,) and
says, i" am; and,  viewing  himself in  action, says, /  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.
Consequently,  to judge is  only to feel.  Hence,  he  concludes, " sen-
sation, reflection, and judgment, are absolutely synonymous, and pre-
sent to the physiologist  nothing more  than the same phenomenon.
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 reflection.   Conse-
quently, when we consider it in a physiological point of view, we
can only discover in it the faculty of feeling ourselves, and of per-
ceiving that we feel ourselves."
  Some of the later  French metaphysicians have proposed certain
modifications  in the system of Condillac. M. De La  Romiguiere,, 
CLASSIFICATION OF THE MENTAL FACUTIES.
207
for  instance,  denies that sensation  is  the original faculty, and he
derives all from attention.  The mind, he remarks, is passive during
the  reception  of sensation, and  does not commence action  until di-
rected to some object, or until it attends.   According to him, the in-
tellect 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.  Ac-
cording 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 imagination,
both of which enter into the judgment.
  The division of M. Destutt-Tracy is embraced by Magendie  in
his  Precis Elementaire 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,  memory,
imagination,  and reason.  Brown reduces all the intellectual states to
simple suggestion  and relative suggestion, comprising, in the former,
conception, memory, and  imagination,—in the latter, judgment, rea-
son, abstraction,  and  taste.  Abercrombie  considers  the mental
operations to be chiefly referable to four heads;—memory, abstraction,
imagination,  and  reason  or judgment; 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, Dide-
rot, 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 considerable for us
to hope, that this  will ever be effected by metaphysical inquiry. We
must, therefore, look  to physiological investigation, if not with well
founded—with the only—hopes, we can entertain, for the elucidation
of the subject; and we shall find presently, that  the minds of meta-
physical 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
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 intellect, at  birth, 
268
SENSIBILITY--MENTAL FACULTIES.
is  a tabula rasa, and that the mind has to acquire and form all the
ideas it possesses from impressions made on the senses.               I
   The truth includes  probably both these propositions—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 facilities, affections, passions, are  com-   '
prehended 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, which 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,—of pain, when  'M
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^ i
of will  or desires.   Condillac is  one of those. Every sensational
he observes, has the character of pleasure or pain, none  being in-
different: as soon, therefore, as a sensation is experienced, the mind
is excited to act.  This tendency is at first but slightly marked, and
is only an uneasiness (malaise:) but it soon increases, becomes rest-   t
lessness or inquietude; in other words, a difficulty experienced by
the mind of remaining in  the same situation.  This gradually be-
comes desire, torment, passion, and finally will, excited to the execu-
tion of some act.
   Many  moralists have endeavoured, by ultimate analysis, to derive
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, parental,  and  conjugal love, which
* From palior, I suffer, 
CLASSIFICATION OF THE MENTAL FACULTIES.
209
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,   ine
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, ac-
cording to  their use  or  abuse; such as ambition, which  may be a
laudable emulation  or insatiable passion, according to its extent and
direction.                      .,.,,.     .     .    ,        u
   A^u'n,  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 for his own preserva-
tion as  well as for 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
 iucluding  appetites, desires, and  affections, the latter  self-love and
 the moral faculty;  all of which Brown comprises  under emotions,
 immediate, retrospective, or prospective ;—and  lastly, Abercrombie
 refers all the principles,  which constitute the moral feelings, to  the
 following heads:  1. The desires,the affections and self-love; 2. The
 will; 3.  The  moral principle, and  4. The moral  relation  of man
 towards  the Deity.
    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
  fundamental faculties they may each have a special organ concern-
  ed in  their production,  as  each of the external senses has  an organ
  concerned in its production.  According to  this view, the  cerebral
  organization  of animals ought to differ according to their psychology:
  where one is simple the other should be so likewise. 
270
SENSIBILITY--MENTAL FACULTIES.
   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  he 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,
or its kennel; if, in short, he possesses  faculties which animals do
not,—religious and moral  feelings,  with all  those 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 existence,  and specially intended to live  in society-  Hence it
was necessary that he  should not only have an intellect sufficiently
extensive 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
conduct as to maintain with facility his  mortal connexions, and to
deserve the future life to which he is called."
   But if the intellectual sphere be  regulated by the cerebral deve-
lopement, 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 al-
though he is unquestionably the most intelligent of beings. The weight
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 esti-
mated by Sommering  at from two pounds three  ounces, to three 
RATIO OF THE ENCEPHALON.
271
pounds three ounces and three quarters; and  that of the elephant,
according to Haller, weighs from seven to ten pounds.  This, con-
sequently, overthrows  the  proposition; and, besides, in certain in-
sects with very minute brains, as the bee and the ant, we meet with
evidences of singular intelligence.  The proposition was therefore
modified, and it was laid down, that the larger the encephalon, com-
pared 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,  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 pro-
perly observed  by Mr. Lawrence, that it cannot be a very satisfac-
torv mode of proceeding to compare the body, of which the weight
varies so considerably, according to  illness, emaciation, or embon-
point, with the  brain,  which  is effected by none of these  circum-
stances, 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 150 by one compara-
tive anatomist, and as 1 to 82 by another;  that of the dog as 1 to
305 by one, and as one to 47 by another, &c.
   The  following table, taken chiefly from Haller  and  Cuvier, exhi-
bits the proportion, which the encephalon  bears to  the  rest of the
body, in man and certain animals.
Child, 6 years old    ...   ^5
Adult........tV
Gibbon.......-grs-
Sapajous, from ...   ^\ to ^2-
Apes......xV t0 2V
Baboons.....T£r t0 tV
Lemurs.....tz l0 e\
Bat (vespertilio)  ....   T'?
Mole........-jV
Be;ir........jes
Hedgehog......ret
Fox........2^5
Wolf........**T
Beaver.......-giff
Hare........■$$?
Rabbit.....rb t0 rh
Rat........-fa
Mouse.......xj
Wild  boar......-g-fa
Domestic do.   .   .  .   TT^ to -jig
Elephant.......•§%?
Stag........2-b
Roebuck (young) ....   -^
Sheep.....tst to rb
Ox.......Thri0*h
Calf........2H
Horse    .....T£„ to 4fo
Ass........T54
Dolphin  .  .   .   3V' io> <rV ih
Eagle........?h
Goose.......-3^0
Cock........sV
Canary bird......-^
Humming bird.....TXT
Turtle.......s^Vff
Tortoise.......^^
Fr°g........TT¥
Shark........^J^
£ike........tAi
CarP........TB-5
Wrisberg and Sommering proposed another point of comparison, 
272             SENSIBILITY--MENTAL FACULTIES.

—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 ani-
mal 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 ex-
pected 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  oblongata.
The first is essentially the organ of intellect;  and the most striking
character of the human brain is  the large developement of the cere-
bral hemispheres,  of which we  have no parallel in the animal king-
dom.  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 G^V or 8T\2T to 1; in the horse, 4| to 1 ; in
the cow,  5|^4 to 1;  in the  dog, Gf\ to 1; in the cat, 4-^ to 1; in
the mole, 3f to 1; and in the mouse,  Of 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 various 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  developement 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,.ano\ the  amount  of  the  facial
angle.  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
horizontal line and  its point  of union  with  the facial line are not
uniform in all the figures  given by Camper: sometimes it is made to
pass through the meatus auditorius externus, but it often falls far
below 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 
FACIAL LINE AND ANGLE.
273
of the cranium; and, as we
descend from man, the angle
becomes less and  less, until
it is finally lost; the cranium
and face being, in  most  rep-
tiles  and fish, completely on
a level.  The marginal figure
exhibits  the  difference   be-
tween the facial  angle of
those-of European descent,
and that of the negro.   By
covering with the finger the
parts  below the nose alter-
nately, we have the counte-
nance of the white or of the
negro, in wjjich  the facial
angle differs as much as 10°,
or 15°.   Figure 51 exhibits
the facial line and angle of
the ourang-outang.   Those
animals that have  the snout
long,  and the  facial angle
consequently  small,  have
been  proverbially  esteemed
foolish,—such as  the snipe,
stork, crane,  &c.; whilst superior intelligence is ascribed to those
Fig. 51.
  580
in which the angle is more largely de-
veloped—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 be-
tween 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 ele-
phant has received a name in the Malay
language, indicating an opinion, that he
is possessed of reason.   The following
table  exhibits the  facial  angle in  man
and certain  animals, taken by  a line
drawn  parallel to  the floor of the nos-
trils, and meeting another, drawn  from
the  greatest prominence of the alveoli of the upper jaw to the promi-
nence of the forehead.
  vol. i.                      35
 
274
SENSIBILITY--MENTAL FACULTIES.
Man  .  .  05° to 85° and more.
Sapajou.......05°
Ourang-outang .   .  . 50° or 58°
Gucnon.......57°
Mandril.....30°  to 42°
Coati........28°
Pole cat.......31°
Pug dog.......35°
Mastiff.......11°
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 ne-
gro, 70°, not many degrees above  the  ourang-outang.   It is found,
however, that the skulls of different nations, and of individuals of the
same nation,  may agree in  the facial angle, whilst mere may be
striking distinctions in the shape of the cranium and face, in the air
and character of the whole head, as well as  in the particular fea-
tures;  the inclination of the facial line being obviously more depen-
dent on the  prominence of the upper jaw and frontal sinuses than on
the general form of the head.  The  ancients had 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, altl.< >ugh  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 ani-
mals.   One  line  is  drawn from the posterior margin of the foramen
magnum of  the occipital bone to the  inferior margin of the  orbit,
and the other from the top of the head to the  space between the oc- 
DIFFERENCES IN THE SKULLS OF MAN AND ANIMALS.
275
cipital 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 necessarily be
thrown farther forward, and the angle be thus rendered much more
acute.'  Blumenbach says, that Daubenton's method may be adapted
to measure the degrees of comparison betwixt man and brutes, but
not the varieties of  national character;  for  he found it different in
the skulls of two Turks, and of three Ethiopians.
   Blumenbach found  the methods of both Camper and Daubenton
insufficient to  indicate the varieties in the  national  and  individual
character.   He, accordingly, describes  a new  method,—which he
calls  the norma verticalis,—in  the  " Decas Collectionis  sua 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 comparative
dimensions of the two bones in one direction.   It does not indicate
the depth of the maxillary bone or of the os frontis, or their compa-
rative 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 Eu-
ropean ;  in  the  negro, one-fifth, and in the Sapajou, one-half.  In
the Mandril, the two areas are equal; and, in  proportion  as  we de-
scend 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  ruminant
animals double; in  the horse, quadruple, &c.; so that the intelligence

   * 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 an-
other 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. 
276
SENSIBILITV—MENTAL FACULTIES.
of the animal is said to be greater or less, as the preponderance of
the area of the face over that of the skull diminishes or increases.
   The truth, according to Sir Charles Bell, is, that the great differ-
ence  between the bones of the cranium and face in the European
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 Montaigne
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 manifestations; although
Gall includes, also, the cerebellum.  It has already been remarked,
that no animal equals man in the developement of the cerebral hemi-
spheres.  In the ape, they are less prominent; and below  it in the
scale of creation, they become less and less; the middle lobes are
less arched downwards; and the posterior lobes are  ultimately want-
ing, 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 ence-
phalon, with the view  of detecting their functions; endeavouring,
as much as possible, not to implicate any part except the one which
was the subject of investigation; 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 eerebral hemispheres uninjured, the animal was deprived of some
other faculties,—that of moving, for instance,—but retained its con-
sciousness, and the exercise of all its senses.
   M. Desmoulins, in  his observations  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 
GALL'S CRANIOLOGICAL SYSTEM.
277
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
fcelus and in 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 Cer-
veau et sur  celles de chacune de ses Parties, are,  1st, That the in-
tellectual and moral faculties are innate. 2dly, That their exercise
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 are appetites, 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
  Esychology  of man,—require that the  physiological student should
  ave 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, io 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
which  has  been  since  transferred  to his Physiologie  de VHomme;
both being abridgments of the Analyse d'un cours du Dr. Gall, pub-
lished by him in 1808. 
278              SENSIBILITY--MEXTAL FACULTIES.

  The foundation of this doctrine is, that the brain  is not a single
organ, but is composed of as  many  nervous systems as there arc
primary  and original faculties  of the mind.   Tu  the  view of Gall,
the brain is a group 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 developement, the  animal has, in its
moral sphere, a greater or less number of, or  more or less  active,
faculties.
  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-'*ij
tics 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   r
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- .^j§
tual and moral faculties are multiple.   This every one admits.  Each,
consequently, ought to have its special organ;  and 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
or more active, UkU 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 
OALL'S CRANIOLOGICAL SYSTEM.
279
 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 developement and
 decay. Kthly, 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
 it is readily explicable under  the doctrine of 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 exiting 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—groups  of special nervous sys-
 tems, 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 erroneous:
  he has adduced the opinions of numerous writers who preceded 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
•  germs of many discoveries and speculations, thought that the first or
  anterior ventricle of the brain, was the ventricle of common sense;
  because from it, according to him, the nerves of the five senses
  branched  off.   The second  ventricle, connected by a minute open-
  ing with the first, he fixed upon as the seat of imagination, judgment,
  and reflection ; and the third ventricle, as  a store-house into which
  the  conceptions of the mind, digested  in the second ventricle, were
  transmitted for retention and accumulation;  in other  words, he re- 
280
SENSIBILITY--MENTAL FACULTIES.
garded it as the seat of memory.  Bernard Gordon, in a work writ-
ten in  1290, gives nearly the same account  of the brain.  It  con-
tains, 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 and images, received by the several
senses.  In the posterior part of the first ventricle, he places phan-
tasia:  and in the anterior  part of the second, imaginaliva:  in  the
posterior part of  the middle 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,—
                              imaginatio, cogitatio, and memoria,—
                              each of which  has a  special organ
                               engaged in its production.
                                 For many  centuries  it was  be-
                              lieved, that the cerebrum was  the
                              jorgan  of perception,  and the  cere-
                               bellum that of memory.
                                 Albert the Great, in the thirteenth
                               century, sketched a head on which
                               he represented the seat of the differ-.
                               ent intellectual faculties.  In the fore-
                               head  and first ventricle  he placed '
                              common sense and imagination: in
                              the  second, intelligence and judg-
                              ment:  and in the third, memory and
                              the motive force.
                                The head in the margin (Fig. 52)
                              is from an old sketch contained in
                              the Book Rarities, of the University
                              of Cambridge.
                                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 ven-
                              tricle that of memory.
                                In 1491, Peter Montagnana pub-
                              lished an engraving, in which were
                              represented the seat of  the sensus '
                              communis, a cellula imaginativa, cel-
                              lula estimativa sen cogitativa, a cellu-
                              la memorativa, and a  cellula ration-
                              alis. A head, by Ludovico Dolci exhi-
                              bits a similar arrangement. (Fig. 53.)
                                The  celebrated Dr.  Thomas Wil-
                              lis, in 1081, asserted, that the corpora
 
gall's craniological system.
281
    striata are the seat of perception; the medullary part of the  brain
    that of memory and imagination:  the  corpus callosum that of re-
    faction : 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, had  been long in-
    dulged by anatomists  and philosophers.  The views of Gall are re-
    suscitations of the old; but resembling them little more than in idea.
    Those of the older philosophers were the merest  phantasies, unsup- ,
    ported by the slightest observation; the speculations of the modern
    phvsiologist have  certainly been the result of long and careful inves-
    tigation, and of the deepest meditation.  Whilst, therefore, we may
    jiistly discard the  former, the latter are worthy of rigid and unpre-
    judiced examination.
--....  Admitting, with Gall, the  idea of the  plurality of organs in  the
|F? brain, the inquiry  would next be,—how many special nervous  sys-
    tems are there in the human brain, and what  are  the  primary intel-
    lectual and moral faculties over which they preside ?  This Gall  has
'   ' attempted.  To attain this double object, he had two courses to adopt;
^fyeither, first of all, to indicate anatomically the nervous systems 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 facul-
^.-./ties, and afterwards to assign to each an organ or particular seat in
    the brain.   The first course was  impracticable*  The cerebral  or-
    gans are not distinct, isolated in the brain;  and, if they were, simple
|fc / inspection could not inform  us of the faculty over which  they pre-
Kj^pide; any more than the appearance of a nerve of sense could exhibit
 „'  the kind of sensation for which it is destined.   It was, only, there-
    fore, by observing the faculties, that he could arrive at a specifica-
lly  tion of the cerebral organs.   But here, again, a source of difficulty
t   arose. How many primary intellectual and moral faculties are there
    in man?  and, what are they?  The classifications of the mental  phi-
P • losophers, differing, as we have seen they do, so intrinsically and es-
f'  sentially from each other, could lead him to no conclusion. He first,
    however, followed the notions on which they appeared to be in ac-
    cordance ; and endeavoured to find particular organs for  the facul-
    ties 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 mathematician,  he carefully examined
>   the heads of such as presented these predominant qualities, and en-
►   ' deavoured to  discover in them  such  parts  of the  brain as were
    more prominent than usual,  and which might be considered as  spe-
    cial nervous systems,—the  organs of these faculties.  After multi-
    tudinous empirical researches  on living individuals; on a  collection
       vol. i.                          30 
282               SENSIBILITY--MENTAL FACULTIES.

of crania, and on casts made for the purpose, attending particularly
to the heads of such as had one of their faculties predominant, and
who were, as he remarks, geniuses 6n one point.—to  the  maniac,
and the monomaniac;—after a sedulous  study, likewise, of the heads
of animals, comparing especially those, that have  a particular fa-
culty, with such as have it not—in order to see if there did not ex-
ist in the  brain of the former some part which 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 or-
gans ;  and, in their psychology, as 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 ©f a
function is the developement 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 co- £
vering it, that Gall attempts, in the living subject, to appreciate the
state of the  brain.—Now, 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 con- •
volutions are the final expansions of the  cerebrum:  if we trace back
the original  fasciculi, which, by  their expansions,  form the hemi-
spheres 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 convolutions.  Lastly, to a certain extent,  the  era- $
nium is moulded to the brain;  and participates in  all the changes, *
which the latter undergoes' at different periods of life, and in disease.
For example, during 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 con-
tain the brain, has fitted the one to the  other; and this so accurately,
that its internal surface exhibits sinuosities, corresponding to the ves-
sels that creep on the surface of the  brain; and digitations, corre-  *
sponding to the cerebral  convolutions.  The brain, in fact, rigidly >
regulates the ossification of  the  cranium; and  when, in  the  pro-
gress of life, the  brain augments, the capacity of the cranium is aug-
mented likewise; not by the effect of  mechanical pressure,  but ow-
ing 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 happens to the portions of the skull that invest them. The
forehead, for example, begins to  be developed  after the age of four 
GALL'S CRANI0L0GICAL SYSTEM.
283
months:  but the inferior occipital fossae do not increase in propor-
tion until the period of puberty.
  When the brain, again,  fades  and wastes  m  advanced Hie, tne
cavity of the cranium contracts, and its ossification takes 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 for-
mer; restricted in the latter.  Lastly, in cases of mania, the cranium
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  organs 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 era-
nioscopy: though, strictly speaking, it is hy cranioscopy that we ac-
quire  a knowledge of  craniology;  the art of prejudging  the intellec-
tual and moral aptitudes of man and animals, from an examination
of the cranium.  It is, of course, limited in its application.   Gall ad-
mits,  that it is not available in  old age; "owing to  the physiological
fact before stated;—that the external table of the skull is  no longer
modified by the changes, that happen to the brain; and  he acknow-
ledges, that its employment is always difficult, and liable  to numer-
ous 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 corresponding develope-
ment of the brain.   In this respect, craniology presents more difficul-
ties 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 longitudinal sinus, and from the
possible separation of the hemispheres at the median  line.   The dif-
ficulty is, of course, extremely great in  appreciating the parts  of the
brain, that are situated behind the eyes; and craniology must  be en- 
284              SENSIBILITY—MENTAL FACULTIES.

tirely 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 developement of the portion of the brain which is its organ, he
goes so far as to particularize, in this developement, 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, which seem to
 be very different, on account of the difference  between station in ani-
 mals and  man; and of the greater or less number of systems, that
 compose their brain.
   The cerebral organs, enumerated by Gall, with the corresponding
 faculties, are as  follows;—the numbers corresponding with  those of
 the accompanying engravings.
Seated in the cerebellum.  It is ma-
  nifested at the surface of the cra-
  nium by two round protuberances,
  one on each  side of the nape of
  the neck.
1.  Instinct of generation, of (
  reproduction;  amativeness.
  Instinct of propagation; ve-
  nereal instinct.           -<
(German.) Zeugungstrieb,
  Fortpfl an zungstrie'b,
  Geschlechtstrieb.
2.  Love of progeny; philo-pro- f
 ,genitiveness.              J Indicated at the external  occipital
(G.) Jungenliebe,   Kin-]   protuberance.
  derliebe.                (^
                            C About the  middle of the  posterior
3.  Attachment, friendship.  .<   margin of the parietal bone; ante-
(G.) Freundschaftsinn.   I   rior to the last.
4  Instinct of defending^ self f    .
  and property; love of strife  Seated a little above the ears; in front
  and combat; combatiyeness ;<   of the last, and towards the mas-
  courage.                     toid angle of the parietal bone.
(G.) Muth, Raufsinn.    (^
  Z a n k s i n n.              C Greatly developed in all the carni-
5.  Carnivorous instinct; incli- j   vorous animals;  forms a promi-
  nation  to murder; destruc-J   nence at the posterior and superior
  tiveness; cruelty.           j   part of the squamous surface  of
(G.) W u r g s i n n,  Mord-    the temporal bone, above the mas-
  sinn.                     ^  toid process. 
iTiANIOI.OlICAL  DIVISION  of  CALL.
Vagt 284
flfi 
 
gall's craniological system.
285
0. Cunning; finesse; address; (Ahoye  the meatus  auditorius ex-
  secreticencss.              >   ternus, upon the sphenoidal angle
                         ' |   of the parietal bones.
■<
Anterior  to  that  of  cunning, of
  which it seems to be a prolonga-
  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.
(G.)  List, Schlauhe
  K 1 u g h e i t.
7. Desire  of property; provi
  dent instinct; cupidity; in
  clination to robbery; acqui
  sitiveness.
(G.) Eigenthumssinn
  Hang  zu  stehlen,
  Einsammlungssinn,
  D i e b s i n n.             V.
8. Pride;  haughtiness;  love (
  of authority; elevation.     | Behind the  top of the head,  at the
(G\) Stolz,   Hochmuth,<>   extremity of the sagittal suture,
  Ho hens inn,   IIerrsch-|   and on the parietal bones.
  s u c h t.                 L
9.  Vanity; ambition;  love  o/fSituated at  the side of the last, near
  glory.                   J   the posterior internal angle of the
(G.) E , t e 1 k e 11,  R u h m-*S       -^ boneg#
  sucht, Ehrgeiz.     ^  r
10. Circumspection;foresight.
(G.) Behutsamkeit, Vor-
  sicht,  Vorsichtigkeit.
11.  Memory of  things; me-
  mory of facts;  sense  of
  things;  educability; perfec-
  tibility ; docility.
(G.) Sachgedachtniss,
  Erziehungsfahig:
  keit,  Sachsinn.
Corresponds to the parietal protu-
  berances.
Situated at the root of the nose, be-
  tween the two eyebrows, and  a
  little above them.
12. Sense of locality; sense of
  the  relation of space;  me-
  mory of places.
(G.)   Ortsinn,
  s i n n.
R a u m-
13.  Memory of persons; sense
  of persons.
(G.) Personensinn.
r 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 organ of me-
   mory of things.

 At the inner angle of the orbit.
r   j          r f 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
                i^   make the eye prominent.
14.  Sense
  names;  verbal memory.    \
(G.) W o rt g e d a c h t n i s s,»
  Namensinn. 
280
SENSIBILITY—MENTAL FACULTIES.
15.  Sense of spoken language; f

  TalTuSt""'"^' SiUdy°f) Als° ■* tho top of the orbit, between
                           "S   the preceding  and  that  of the
                               knowledge of colour.
(G.)  Spr achforschungs-
  sinn,      Wortsinn,
  Sprachsinn.
10.  Sense of the relations of
  colour;  talent  of painting.
(G.) Farbensinn.
17.  Sense of the relations of
  tones;  musical talent.
(G,) T o n s i n n.
18.  Sense of the relations of
  numbers; mathematics.
(G.) Zahlensinn.
19.  Sense of mechanics; sense
  of  construction;  talent of
  architecture; industry.   <
                     Bau-
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, and behind the organs
  of music and numbers.
21.  Metaphysical    penetra-
  tion ;  depth of mind.
(G.) Metaphysischer*
  T ie fsinn.


22.  Wit.
(G.) Witz.
(G.) K u n s t s i n n,
  sinn.
20.  Comparative sagacity.   C At the middle and anterior part of^
(G.) Vergleichender <   the frontal bone, above that of the *
  Scharfsinn.          (   memory of things.
                           fin  part,  confounded  with the  pre-
                               ceding.  Indicated,  at  the outer
                               side of this last,  by two  protu-j
                               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-
                           c   ded into two halves by the coronal
                           '    suture.
                           r
23. Poetical talent.
(G.) Dichtergeist.

24. Goodness;   benevolence;
  mildness; compassion; sen-
  sibility ;  moral sense; con-
  science; bonhommie.
(G.)   Gutmuthigkeit,
  Mitleiden, moralis-
  cher  Sinn, Gewissen.
25.- Imitation; mimicry.
{G.) Nachahmungssinn.
20.  God  and religwn; theo- C M ^ top ofthe fronta, bone and
                          ^   at  the  superior angles of the  pa-
Indicated by an  oblong prominence
  above the organ  of comparative
  sagacity; almost at the frontal su-
  ture.
At the outer side of the last.
  sophy.
(G.)  Theosophisches*
Sinn.
I
rietal bones. 
SPURZHEIM's CRAN10L0GICAL SYSTEM.
287
27. Firmness; constancy; per- rThe     of ^ head; at the anterior
   sererance; obstirvacy.       I    and »     elevated part of the pa-
(GOStctigkeit, Fester^    rietal bones.
   Sinn.                     ^.
   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  publica-
tions, has added some other faculties, so as to  make the whole num-
ber thirty-five;  but they have not been embraced by Gall in his most
recent publication,  whence many of these details are taken.  The
following are  the  organs admitted by Spurzheim:—the  numbers
correspond with those of the accompanying figures.
     «       Fig. 54.                         Fig. 55.
Fig. 50.
ORGAN OF
 1. Amativcness.
 2. Philoprogeuitiveness.
 3. Inhabitiveness.
 4. Adhesiveness or At-
   tachment.
 5. Combativeness.
 6. Destrucliveness.^
 7. Constructiveness.
 8. Acquisitiveness.
 9. Secretiveness.
10. Self-esteem.
11. Love of Approbation.
12. Cautiousness.
13. Benevolence.
14. Veneration.
15. Firmness.
16. Conscientiousness or
   Justice.
17. Hope.
Marvellousness.
Wit.
Ideality.
Imitation.
Individuality.
Form.
Size.
Weight  and  Resist-
ance.
Colour.
Locality.
Numeration.
Order.
Eventuality.
Time.
Melody or Tunc.
Language.
Comparison.
Causality. 
288
SENSIBILITY--:
MENTAL FACULTIES.
   On the situation of the different cerebral organs, Gall remarks,—
 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 infe-
 rior, 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, which form the fore-
 head.  2dly. The more indispensable a faculty,  and the more  im-
 portant to the animal economy, the nearer is its organ to the median
 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 si-
 tuated 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 developement and decrease, and
 does not, in  this  respect, coincide with the other  faculties; when it  j
 can be exerted alone,  be  diseased alone, continue sound alone, or .-J
 be  transmitted alone from parent to child, &c.  Lastly, he points 4|
 out the part of the brain, which he considers  to be its organ, found-
 ing his decision on numerous empirical observations of the brains of
 men and  animals', that have  possessed, or been  devoid of, the  fa- "^
 culty and organ in question ;  or have had  them in unequal degrees':J|
 of developement.                                                 '*
   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
 purpo'se 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 primary and fun-
 damental, for it is  independent of all external influence.  It does not
make its  appearance until puberty, and it disappears long before
other faculties.   In many animals it returns 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 instinct. It may be either alone 
GALL'S CRANI0L0O1CAL SYSTEM.
289
   active,  amidst  the  languor of other faculties, or it may be alone
   languishing.  Lastly, it cannot be referred to the genital organs, for
   it has been observed in children, whose organs have not been deve-
   loped; 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, ac-
   cording to  Gall, the cerebellum.   His reasons for this belief are the
   following.  1st.  In  the series  of animals a cerebellum exists  only
   in those, which 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-
L.  ists between the cerebellum and the external genital  organs.  If the
   latter are extirpated at an early age, the developement of the cere-
fc  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
li"  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 othei
   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, who are 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 data, Gall concludes, that the qgtebcllum 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
   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.
     Hut Gall does not restrict himself to  the physiological applications
   of his system.6 lie  endeavours, likewise, to explain the differences,
     vol. i.     \ ,                37 
290
SENSIHILITY--MENTAL FACULTIES.
that exist between him and other philosophers.   He altogether re-
jects 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 himself
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
expression, 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 de-
sires as faculties; but there is only one will, which is the product of
the imultaneous 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, memoryAidgment 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,
and totally  defective upon another.  The memory  of  tones, for
instance, is  not ihe same  as that  of  language; and he, who pos-
seses 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 
GALL'S  CRANIOLOGICAL  SYSTEM.
291
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 ex-
cited 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 into action, and, according to the
degree 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 facul-
ties.  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,  expresses only the
modifications, the primary  faculties may present, according to the
mode  in which the external and  internal influences affect them.
Some  of these  modes  are  common to all the faculties, as those of
pleasure and pain.  Every faculty may be the occasion  of the one
or the other.   Other affections are special to  some faculties; as
pretension, which, he says, is an affection of pride:  and repentance
an affection of the moral sense.  Finally, these affections are simple
or compound: simple when they only bear upon one faculty, 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 modi-
fications of a single faculty, and the  combination of several, give
rise  to many sentiments, that are  apparently  different.   For  in-
stance, the  primary faculty of vanity  begets  coquetry^ emulation,
and  love of  glory.  That of self-defence  gjves  rise 'to temerity,
courage, a quarreling spirit, and fear.   Contempt is the product of
a combination of the faculties of pride and of the moral sense, &c.
  Lastly, as  regards their  psychological differences, Gall  divides
all men into five classes.  First.  Those  in whom all the faculties
of humanity predominate; and in whom,  consequently, organization
renders the developement of the mind  and the practice  of virtue
easy.   Secondly.  Those in whom  the  organs of the animal facul- 
292
SENMBILITY-
--MENTAL FACULTIES.
tics 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  predominant.
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 arc
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 develope-
ment and activity, seeing that each of the faculties, 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, independently of the differ-
ences in their cerebral  organization, which gives rise to their dis-
positions, 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."
   " 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 more 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
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-
velopement  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." 
GALL'S CANI0L0G1CAL SYSTEM.
293
  It is impossible  for us to enter, at length, into the various facts
and hypotheses developed in the preceding exposition.   The  great
points of doctrine, and the system of Gall, are:—First. That the brain
consists of a plurality of organs, each engaged in a separate, distinct
0fljce _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 less developement of the part;
and, Thirdhj. That, by observation of the  skull, we may  be enabled
to detect the protuberance, produced by such cerebral developement,
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 ol
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  organs may not be sufficiently extensive to enable us to designate
them.  Of the innate character of several  of the faculties, described
by  Gall, it is scarcely possible for  us to  admit a-doubt.   Take, for
instance, the instincts of generation and of love of progeny.  With-
out  the existence of these instincts, every animal species would soon
be extinct.  It is fair, then, to presume, that these instincts, or innate
faculties, have encephalic  organs,  specially concerned in their pro-
duction.  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 physiologists; by Broussais,
Foville and Pincl-Grandchamp,  Rolando,  Flourens, Desmoulins, and
others; and,  not only by argument, but  by that  which must ulti-
mately test the validity  of the doctrines of the phrenologist—direct
experiment.   The views of these gentlemen, regarding the influence
of the cerebellum, will be given under the  head of muscular motion.
  t  >ne of the greatest objections that has been brought  against the
system of Call is the independence in it  of the different faculties
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 function of the frame ;  and
with which it  is so important,  for the pathologist  particularly, to
be acquainted. 
294
SENSIBILITY-
'--MENTAL FACULTIES.
  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
developement 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 func-
tion is restricted to the brain proper.  Gall and his followers include
the cerebellum.   Yet we meet with cases,  which appear to  militate
strongly against this notion.   Hernia of the brain is one of these: in
this, owing to a wound of the  cranium and dura mater, a portion of
the cerebral substance may protrude and be removed;  yet the indi-
vidual may do well;  and to all appearance retain his faculties unim-
paired.  This is explained by the craniologist, by presuming, that as
the fibres of the brain are vertical, their extremities have alone been
removed, and a sufficient amount of fibres has remained for the ex-
ecution of the function;  and he  farther entrenches himself in the
difficulty  of  observing accurately, in these cases, whether the facul-
ties are really in their pristine integrity.   He  asserts, that it is fre-
quently extremely difficult to prove the existence of mental  aberra-
tion ; that the precise line of demarcation between reason and un-
soundness 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 re-
ply to questions put  to  him, and  to have  consciousness, the moral
sense is esteemed to be free, and  in a state of  integrity.
  It must, however, be admitted,  that the explanation of the cranio-
logist on  these topics is feeble  and  unsatisfactory.  It is, of course,
gratuitously  assuming, that observation in  such  cases has been in-
sufficient ; and if he finds, that the fact in question militates  against
the faith he has embraced, he is too apt to deny its authenticity alto-
gether.  With all the candour, which Gall possessed, this failing is
too perceptible in his writings.
  Again, in many of the cases of severe injury of the brain, which
are on record, but  one hemisphere was  implicated; and, accord-
ingly, the impunity of the intellectual and moral manifestations has
been ascribed to the cerebrum being a double organ;  so that, al-
though one hemisphere may have been injured, the other, containing
similar organs, may have been capable of carrying on the function?
as one eye can still 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 pre-
served their faculties entire.  These Gall explains, by affirming, 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 slowly,  and the pressure is moderate, the 
                  gall's cra.mological system.               ^Ji>

organ may be so habituated to it as to be able to continue its func-

  Lastlv, some  experiments of Duverney have been adduced as ob-
jections'to the view of Gall.  These consisted in removing the whole
of the brains of pigeons;  yet no change seemed to  be produced 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;  for,
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,  in others, the comparative immunity attendant upon in-
jury to all appearance equally grave.  Pressure, of whatever nature,
seems to be  more detrimental than any other variety of mechanical
mischief; 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  in-
strument, may be  entirely consistent with the  existence  of perfect
consciousness.
  The doctrine, that, by observation of the skull, we may be able to
detect the protuberance produced by the cerebral organs of the dif-
ferent 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; that, by cra-
nioscopy, 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 cere-
bral faculties, even if we  grant,  that  separate organs can be detect-
ed 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 topographi-
cal division  of the skull, which  he has proposed, can hardly be re-
garded  otherwise than premature, to say the least of it;  and the re-
mark of course applies a fortiori to that of Spurzheim.
   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, which 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  Call," 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 
 296              SENSIBILITY—MENTAL faculties.

 the moment engaged, they amused themselves in view ing the va-
 rious efforts of his skill.  Dr. Gall was requested to say. from the
 organs exhibited  in a certain bust, what was the predominant pro-
 pensity  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  mathematician.
 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 phrenologist, whose oracular
 dicta too often draw down  ridicule not only upon the empiric him-
 self, 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 ignorant
 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 Perkhas;—

             " 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, haa
 vaccination every where exhibited itself!           4
   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 phre-
 nologist.   It is now, however, we believe, generally admitted by the
 liberal  and scientific, that  if we are to attain a farther knowledge
 of the mental condition of man, it must be by a combination of sound
 psychological and physiological observation and deduction.  It is
 time, indeed, that such a union should be effected, and  that the un-
 disguised and inveterate hostility, which exists between certainof the
professors of these interesting departments of anthropology, 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 Folic,—" 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 
SEAT OF THE MIND.
297
  That they have no means of affording the explanations they promise.
  3dly.  That they are the dupes of the words they employ in dissert-
  ing on incomprehensible things.  4thly. That the  physiologist alone
  can speak authoritatively on the origin of our ideas and knowledge;
  and 5thly. That men, who are  strangers to the  science of animal
  organization, should confine themselves to the  study of the instinc-
  tive 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 subservience;
  some  part in  which the mind exclusively  resides;—for such was
  probably  the meaning of the  researches of the older physiologists
  into the seat of the soul.  It is certain, that it is seated in the en-
  cephalon, 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 of the encephalon, which holds the others
  in subordination.   He  thinks, that each cerebral  organ, in turn, di-
  rects  the action of the others, according as it is, at the time, in a
fc state  of greater excitation.  On the other hand, different physiolo-
| gists admit  of a central cerebral part, which they assert to be the
i  seat of the moi, or mind.  They differ, however, regarding the pre-
  cise situation of its domicile.  At one time, the notion prevailed, that
-  the seat of perception is not in the brain itself, 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.  13, at the posterior part of the third
  ventricle, and, consequently,  at  the base of the  brain.  Being se-
1  curely lodged, it was  conjectured by that philosopher,  that it must
  be  inservient to some important purpose;  and,  upon  little better
  grounds, he supposed, that the soul is resident there.  The conjec-
  ture 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 matter.  This sand was supposed to
  be an extraneous substance, which 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 esta-
  blished, 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  cerebellum;
  Summering in the fluid of the ventricles; and the greater part of
  physiologists in the point, where the sensations are received and vo-
    vol. i.                      38 
298              SENSIBILITY--MENTAL FACULTIES.

Ution sets out; the two functions, which, together, compose the senso-
rial 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 concerned. 
MUSCULAR MOTION.
299
                 OF MUSCULAR MOTION,

        ESPECIALLY OF LOCOMOTILITY OR VOLUNTARY MOTION.

  The functions, which 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 neces-
sary 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 vo-
luntary motion comprise the whole of the life  of relation.  Magen-
die  includes the voice and movements under the  same head;  but
there is convenience  in separating them, and  in  treating the func-
tions of locomotility, and of 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, there-
fore, 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 them have been of a microscopic  character, they are
highly discrepant.  A few of  these  speculations will exhibit  this
truth.
  Leeuwcnhoek 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, 
300                     MUSCULAR MOTION.

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 supposed 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 -g\th part of the diameter of the red globules of
the blood in thickness;  and MM. Prevost and  Dumas, from the  re-
sult  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, Heis-
ter,  Cowper, Vieussens, Mascagni,  Prochaska,  Borelli, John Ber-
nouilli, &c. believing the filaments to be hollow; 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 substance or
marrow;—the shape of these vesicles being, according to the former,
rhomboidal,—according to the latter spheroidal.   Deidier conceived
it to be a fasciculus, composed of an artery, vein,  and lymphatic, en-
veloped  by a nervous membrane, and held together by nervous fila-
ments :—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 ob-
servers,  but of  a polyhedral shape; and that they  are generally
flattened, or thicker in one direction 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, always 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  cannot be  traced
into  the substance of the  fibre.  Mr. Bauer and  MM. Prevost and
Dumas,  again, differ essentially  from the observers already men-
tioned.   Mr. Bauer found, that the muscular fibre was composed
of a series of  globules,  arranged in straight lines;  the size  of
the globule being ^oWtn Part °'  an mcn m diameter; and lastly,
Raspail  considers that  the  intimate  structure  of the muscular 
M0T0RY APPARATUS.
301
 tissue, when it  is in its most simple state, consists  of a bundle of
 cylinders, intimately agglutinated together, and  disposed, in a very
 loose spiral form, around the ideal axis of the group.   These tubes
 are filled with a substance not wholly miscible with water, and may
 be regarded as elongated vesicles, united  at  each  end to other
 vesicles of a similar character.
   When a muscular fibre  is seen through an  ordinary microscope,
 it appears to be composed of longitudinal filaments,  each consisting
 of a string- of globules, about ff7Wn of an inch in diameter.  " But
 with a better instrument," says  Mr. Mayo, " such  as  that, which
 Mr. Lister  possesses, the  delusion vanishes, and the parallel lines,
 which  traverse  the fibre, appear perfectly clean and  even.   Mr.
 Lister  politely gave me an opportunity  of examining  this  appear-
 ance, which was discovered by himself and Dr. Hodgkin."
   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 them to
 move readily upon  each  other,  and preserves them in situ.  The
 fibres are not the same at the extremities, as they are at the middle.
 The latter only consist of the proper muscular tissue;  the extremi-
 ties 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 membrane, which
 surrounds every fibre, becomes freed  from the muscular 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 contract, the whole
 force is exerted upon it.   This arrangement will explain the close
 union which 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.   The fibres of the
 muscle were supposed by  him  to be continuous  with  those of the 
302
MUSCULAR MOTION.
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 vital agents.   M M.  Dumas and
Prevost, however, affirm, that  the  microscope shows,  that neither
the one nor the other terminates in the  muscle. The vessels merely
traverse the  organs;  the  arteries terminating  in corresponding1
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 elaboration
to be exerted upon it, before it can become so.   A similar distribu-
tion they assign to the  nerves.  All the branches they  assert, enter
the  muscle in a direction perpendicular to that of the  fibres com-
posing it;  and their final ramifications, instead of terminating in the
muscular fibres, surround them loopwise and return to the trunk that
furnished them, or anastomose with some neighbouring trunk.  In
their view, each nervous filament, distributed to the muscles, sets
out from the anterior column of the spinal  marrow, forming part of
a nervous  trunk, turns  round one or more  muscular fibres, and re-
turns 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 disw
tributed to them, as it may  be  removed  by repeated washing ar  _
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 is extravasated from
the vessels; by others, it is  presumed, with more  probability per-
haps, to be  still contained  in  the vessels.  Bichat conceived, that
the colour is dependent  upon  some  foreign substance 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 appear to corre-
spond with the quantity of red blood circulating through their ves-
sels.  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 addi-
tional evidence, that their colour is dependant upon the blood they
receive, which is found to diminish or increase in quantity, accord-
ing to the degree of inactivity or exertion.
  The muscles  differ,  like  the primary fibre, at their extremities
and centre; the former being composed of condensed cellular mem- 
MOTORY APPARATUS.
303
brane, the latter of the muscular or fibrous tissue.  The centre of a
muscle is usually called its venter or  belly, and the cellular texture
at the extremities is variously termed;—the part, from which it
appears to arise, 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 the albugineous tissue,
(if we adopt Chaussier's nomenclature,) assumes a round form, so
as to constitute a cord or tendon, is called 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.
 
304
MUSCULAR  MOTION.
  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. 59 is a representation of a double penniform muscle.  Muscles
may, also, be complicated: that is, with one belly,  and several ten-
dons, having the fibres variously inserted into them, or having seve-
ral bellies with the tendons interlaced.

                            Fig. 59.
• They are, again, partitioned into the long, broad, and short.   The,
long muscles are situated chiefly on the limbs, and are concerned in
locomotion.   The  broad  generally form the parietes of  cavities;
they are not so much enveloped  as the  long muscles by strong fi-
brous aponeuroses or fasciae, owing to their being obviously less liable
to displacement; and the short muscles are situated 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 ana-
tomists ;  some describing several  distinct muscles under one name;
and others dividing into many what ought to belong  to one.  Ac-
cording 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, ammo-
nia and lime, carbonate of lime, muriate, phosphate, and lactate of
soda; and, according to Fourcroy and Vauquelin, sulphur and po-
tassa are present.   The great constituents of the pure muscular tis-
sue are,—fibrine, and probably osmazome;—the gelatine, 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 con-
stituents :—Fibrine, albumen, osmazome, fat,  substances capable of
passing to the state of gelatine, acid (lactic,) and different salts.  It
must be borne in mind, as Raspail has properly remarked, that these
are  the results of the  analysis of  the muscle, as we meet with it
The analysis of the muscular fibre  has yet to  be  accomplished.  In
this, too, and every analogous case, the analysis only affords us evi- 
MOTORY APPARATUS.                    305
     dence of the  constituents  of the  dead animal  matter;  and  some
     of the products may even have been formed by the new affinities,
     resulting  from the operations 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 conversion,
     under particular circumstances, to which it may be  well to  advert.
     When, about  the  latter part of the last century, it was determined,
     for purposes of salubrity, to remove  the bodies from the church-yard of
^    Les Innocens at Paris—which had been the cemetery for a consider-
£'.   able 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 opening the  ground, to re-
     move the  prodigious collection of dead bodies, they were found to be
     strangely  altered in their nature and appearance.  What had con-
     stituted the soft parts of the body  was converted into  an unctuous
     matter, of a gray colour, and of a  peculiar, 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 hundred to  fifteen hundred bodies,—and accord-
fr    ing 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, which 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 cime-
     tieres, which was found to be a saponaceous compound, consisting of
     ammonia, united to  adipocire,—a  substance, as its  name imports,
     possessing 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.
i       It was afterwards discovered, that the conversion of muscular flesh
5.   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   is not  the only  interest  attached to this sub-
    stance.  It has been invoked in a court of justice, for  the purpose
    of enabling some judgment to be formed  regarding the period that
    a body may have been immersed in the water.  It is  probable that
•   this must differ greatly according to various circumstances;—the time
    that has elapsed between the  death of the individual,  and the period
    of immersion; the conditions of the fluid as to rest or motion,  tem-
    perature, &.r.; and the temperature of the atmosphere; so that any
    attempt to fix a period for such  conversion must be  liable to much
    inconclusiveness.   Yet the opinion  of a medical practitioner, on this
      vol. i.                      39 
306                    MUSCULAR MOTION.
subject, has been the foundation of a juridical decision.  At the lent
assizes, holden at Warwick, England, in the year 1805, the  follow-
ing case came before the court.  A gentleman, who was insolvent,
left his home, with the intention,—as was presumed from his previous
conduct and conversation,—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
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 subject, 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 k
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 accordingly 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 gene-
 ral shape.  The principal  functions they fulfil are,—to form defen-
 sive cavities for the most  important  organs of the body—the ence-
phalon, spinal marrow, &c.—and to act as so many levers for trans-
mitting the weight of the body to the soil, and for the different loco-
motive 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 rule, within the body;  his
skeleton is, consequently, said to be internal.   In the  Crustacea, the
testaceous mollusca, and in certain insects, the skeleton  is external,
the whole of the soft parts  being  contained within it.  The lobster
and crab are familiar  instances 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 con-
siderable variation from this average. A skeleton of an Irish giant,
in the museum of  the Royal College of Surgeons of London, mea-
sures eight feet four inches.  On the  other hand, Bebe, the dwarf of 
MOTORY  APPARATUS.
307
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 moveable:—in the hands and feet for example, and
in the spine.  The flat or broad bones form the parietes of cavities,
and they aid materially in the movements and attitudes, by affording
an extensive surface for the attachment of muscles.  The long bones
arc  chiefly intended for locomotion, and are  met with only in  the
extremities.  The shape of the body or shaft, and of the extremities,
merits attention.   The shaft or middle 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 diminishes the obliquity of the inser-
tion of the tendons, passing over them, into the bones.   In their in-
terior  is a medullary canal or cavity, which contains  the medulla,
marrow, or pith:—a secretion, whose office will be a theme for after
inquiry.   One great advantage of this  canal  is, that it makes  the
bone a hollow cylinder, and thus diminishes its weight.  On many
of the bones, prominences and  cavities are perceptible.  The emi-
nences 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 ligament, and furnished with a  synovial
membrane, which lubricates them, and facilitates the play of the ten-
dons, for the passage of which they are destined.
  The mechanical structure of bone is a  laminated  frame-work,
incrusted  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 essen-
tially composed of two substances:—the one a cartilaginous basis or
parenchyma, giving form  to the part,—the other a peculiar  earthy
matter, deposited  in this basis, and communicating to it its hardness.
These two  constituents can be readily demonstrated; the first, by
digesting the bone in dilute muriatic acid, which dissolves the earthy
part, without acting on the animal matter;  and the second, by burn-
ing the bone, until all the animal  matter  is  consumed, whilst  the
earthy part is left untouched.
  If wc 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 
308
MUSCULAR MOTION.
Fig. 60.
 condensation.  These are,—the hard or compact substance, the spon-
 gy 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 extremities
 of the long bone, and in almost the whole of the short bones.  In it,
 the laminae are less close, and have a cancellated appearance,—the
 cellules bearing  the name of  cancelli.  The reticulated substance is
 a still looser formation; the laminae being situated at a considerable
 distance, and the space between  filled up with a series of membra-
 nous cells, which lodge the marrow.  The marginal figures represent
 a longitudinal section of the os femoris, and os humeri,  in which this
 arrangement is well exhibited.
    We have seen the advantages of the  ex-
 panded 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 advan-
 tages, which would otherwise  have accrued;
 whilst, if the shaft of the bone, exposed, as it is,
 to  external violence, had consisted of the spongy
 tissue only, it would not have been able to of-
 fer the necessary resistance.   It  is, therefore,
 formed  almost entirely of the compact tissue;
 so  that a section of one inch in height, taken
 frorn  the body of the bone, will not  differ  es-
 sentially 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 cir-
 cumference, the  contrary 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 suggested  by a
 distinguished individual of this country, to whom  surgical 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 demon-
 stration, 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 middle ball of the series, a ball made of the
 
MOTORY APPARATUS.
309
cellular structure of bone, we find that almost the whole of the mo-
mentum is lost in this osseous 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 human
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.   Fourcroy and
Vauquelin did not  detect any fluoric acid, but they found oxides of
iron and  manganese, silica, and albumen.  Hatchett  detected, also,
a small quantity of sulphate of lime.
  The bones are enveloped by a dense  fibrous  membrane, termed,
in the abstract, periosteum: but assuming different names accord-
ing to the part it covers.  On the  skull, it is called pericranium :
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 and from the bone, and to assist in its
formation; for we find, that  if the  periosteum be removed from a
bone, it  becomes  dead  at the surface previously covered by the
membrane, 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 gene-
rally 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 contained in the
cells, formed by the spongy substance, and in the areolae of the com-
pact substance.  This is called the oi7 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 longitudinal 
310
MUSCULAR MOTION.
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 al-
ways 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.
   In the following Table  of the  Bones, the numbers on the  left hand
correspond with those of the accompanying plates of the skeleton.


                      TABLE OF THE BONES.
Bones of the.
   Head.
Bones of the
  Trunk.
Bones of the Cranium or Skull,<
I Bones of the Face,
lDenles or Teeth,

 Bone of the Tongue,

„Bones of the Ear,  -




 Vertebra,


[Sacrum, -
\Os Cqccygis, -

I The  Thorax, ■
1. Frontal,
2. Parietal,  -
5. Occipital, -
3. Temporal, -
  Ethmoid, -
4. Sphenoid, -
7. Superior Maxillary,
6. Malar or check,
  Nasal,
  Lachrymal,
  Palatine, -
  Inferior Spongy,
  Vomer,
8. Inferior Maxillary,
  Incisores, -
  Cuspidati, -
  Molares,  -
  Ilyoid,
  Malleus,  -
  Incus,
  Orbiculare,
  Stapes,
HOW MANY.
       1
       2
       1
       2
       1
       1
       2
       2
       2
       2
       2
       2
       1
       1
       8
       4
   -   20
       1
       2
       2
       2
       2
9.10.11. Cervical
113.
Dorsal,
Lumbar,
  Atlas and )
10. Dentata, S
Ifi
14. Sternum,
   ir t>m  S 15. True ribs, and
   1 o. Ribs '
i-
The Pelvis,
25.
          S 15. True ribs, and ) at
          ) J 6. False ribs,    <
28. Innominatum, comprising
   29. Ilium,  30. Ischium, and
   31. Pubis, 
MOTORY APPARATUS.
311
' The Shoulder, ■
 The Arm,
I The Forearm, -
5 17. Clavicle,
} 18. S
Boxes of the
  upper
 extremity.
' Carpus or
 Wrist,
22.<
The Hand,*



The Thigh,
The Le^,
'23. Metcarpus,
J24. Phalanges,
   Scapula,
19. Humerus, -
21. Ulna,
20. Radius,   -
   Naviculare,
   Lunare,
   Cuneiforme,
   Orbiculare,
   Trapezium,
   Trapezoides,
   Magnum,
   Unciforme,
Bones of the
   lower
 extremity.
. The Fool, 38.
'Tarsus or
v Ankle or   36.
jlnstcp,

/3fl. Metatarsus,
 40. Phalanges,
 32. Femur,
 33. Patella,   -
1 34. Tibia,
1 35. Fibula,
' 37. Os Calcis, -
    Astragalus,
    Cuboidcs, -
    Naviculare,
    Cuneiforme,
Total,
  2
  2
  2
  2
  2
  2
  2
  2
  2
  2
  2
  2
  2
 10
 28
  2
  2
  2
  2
  2
  2
  2
  2
  6
 10
 28

240
  The  bones  are connected by  means of articulations or joints,
which differ materially from each other.   To all  the varieties,
technical  names  are  appropriated,  wrhich  form  a  difficult 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  pre-
vails  at the present day, all  the  articulations being  separable into
two classes:—the immovable  or synarthroses:  and the movable or
diarthroses.
  The  synarthroses arc 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, schindylesis,
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 fossa?
from each other.
  The  movable  articulations  comprise  two  orders:—the  amphiar-
throses, in which the two bones are  intimately united by  an inter-
mediate substance, of a soft and flexible character—as  in the junc-
tion of the vertebrae with each other, and the  diarthroses, properly so
called.  The last admit of three subdivisions—the enarthroses or ball 
312
MUSCULAR MOTION.
 and  socket joints;—the condyloid,  in which, owing to the head
 being oval, the movements are not as easv in all directions as where
 the head is  spherical; and the ginglymoid or ginglymus, in which
 the motion can occur only in one  direction as in a hinge.  The
 farther subdivision of the joints belongs more  to anatomy than phy-
 siology.
   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 move
 easily upon each other, and may have some influence in deadening
 shocks, and defending the bones, which it covers.  The arrange-
 ment 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 centre, and be-
 comes thicker towards the circumference;  and on 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, by the  French anato-
 mists, are 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 bones; and
 loose, when the joint admits of much motion.  In this way, the arti-
 culation 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 resistance
 preserving the bones in situ; and by their suppleness admitting 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 membrane
 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 secreted,
 and its chief properties and uses, will  be the subject of future in-
 quiry.
   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, may thus
protect the joints to which they belong;  and, accordingly, it  is as-
serted, that they are  met with in the joints, which 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 suggests, is more
specious;—that they  may favour the extent of motion, and prevent
displacement. 
SEAT OF VOLITION, ETC.
313
     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, as that  of the shoulder, which, as regards their os-
   seous arrangement, ought to be very liable to displacement.

                    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  propagated
   along the nerves to the  muscles, which are excited by it to contrac-
   tion.  The encephalon, spinal marrow, nerves, and muscles, are, there-
   fore, 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 concerned
   with muscular  motion,  it was judged  advisable to defer its  consi-
   deration 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  apoplectic
   pressure on some part of it;—or if it be deprived of its functions 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 exerted, and vo-
   luntary  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 sti»
   mulus to activity.
     That an emanation from the encephalon is necessary  is likewise
   proved  by the effect  of tying, cutting, compressing, or stupefying
   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  pro-
   duced ;  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 spinalis,
   we abolish all muscular motion, notwithstanding the brain may  will,
   and the muscles  be  in a  state  of physical integrity; because we
   have destroyed the parts whence  the nerves proceed.  In like man-
   ner, 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.
     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 spontaneous motion;  and in
     vol. 1.                      40 
314                     MUSCULAR MOTION.

writing, dancing, speaking, singing, "&c. we have indisputable evi-
dence of its direction by the intellect.
   It is not so clear, that the seat of volition is entirely restricted to
the encephalon.  There are many  actions  of the yet  living 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 perceptibly when in
utero, but at birth.   Without referring to the lower  classes of ani-
mals, which, as we have already had  occasion to remark, execute
voluntary motions for a long time after they  have been  bisected,
every one must have noticed the motions of decapitated fowls, which
will continue,  for a time, 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
also  recorded of  men walking  a few  steps  after  decapitation,
striking  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 pre-
sented themselves for testing this question;  but no zealous N a t u r-
f o r s c h e r appears to have been present to record them.  Similar
opportunities have likewise occurred,  under the operations  of the
guillotine.
   Legallois, in some experiments, which he instituted,  for  the pur-
pose 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 impossibility 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  system  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 
SEAT OF VOLITION, ETC.
315
 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
 thut, in the encephalon alone, volition  is produced.  His arguments
 on this point, however, are not characterized by that ingenuousness
 and freedom from sophism, for which his physiological disquisitions
 are  generally distinguished.
   "First of all," he  observes, "the  fact of 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 regular  and ordained?   And, supposing them to be so,
 may not this have arisen from  the conformation of the parts,  or
 from habits  contracted  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 may,
 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;
 —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 something
 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 voli-
 tion may, perhaps, extend over the whole of the cerebro-spinal axis.
 This conclusion, of course, applies only to  the higher classes  of ani-
 mals; 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  < >f brain have been lost, owing  to accidents, (in one case
 the author knew nineteen tea-spoonfuls,j with equal immunity, as re-
 gards 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 encepha-
lon.  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 
316
MUSCULAR MOTION.
fixed  upon the  cerebral lobes.   Animals, from which these were
removed, were thrown into a sleepy, lethargic  condition; were de-
void of sensation  and spontaneous motion, and moved only when
provoked.
  On the other hand, Magendie affirms, that the cerebral hemispheres
may be cut deeply in different parts of their upper surface, without
any evident alteration in the movements.  Even their total removal,
if it did not implicate the  corpora striata, 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, de-
tailed, were observed on quadrupeds, and particularly on dogs, cats,
rabbits, Guinea-pigs, hedge-hogs, and squirrels.  In birds, the re-
moval  or  destruction of the hemispheres—the optic  tubercles re-
maining untouched—was often followed  by the state of stupor and
immobility, described by Rolando and Flourens; but, in numerous
cases, the  birds ran, leaped, and swam, after  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  appear to be
affected.
   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; but as regards
the mammalia, reptiles, and fish,—at least such of them as were the
subjects of his experiments,—his conclusion is applicable.
   Of the nature of the action of the brain,  in producing volition, we
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 re-
gulates 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, intestines,
blood-vessels, &c.  All the involuntary  muscles equally require a
stimulus to excite  them into action; but,  as  their name imports, they
are removed from the influence of volition,  and instead of receiving
their  nerves directly from the  brain or spinal marrow,—as the or-
gans  of voluntary motion do,—they are supplied  from the organic
nervous system, or the  system  of the great  sympathetic.  In cer- 
SEAT OF VOLITION, ETC.
317
tain  diseased conditions, we find, that all  the  voluntary  muscles
assume involuntary motions; but this is owing to the ordinary voli-
tion being interfered with, and to some direct or indirect 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 muscles, we have a common
example in the convulsions of children; and  one 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 affected
by the will; but they contract on irritating  the part of  the  spinal
marrow, from which the nerves 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 percep-
tion is effected in the brain;  so, in muscular motion, volition  is the
act of the encephalon, and the nervous influx corresponds to the act
of impression.
   With regard to the seat of this nervous centre  of muscular con-
traction, much discrepancy has  arisen amongst recent  physiolo-
gists.   It manifestly, 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 ence-
phalon.
   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 power  was slight; and conversely.  Impressed
with the  resemblance  between the cerebellum of  birds and the
galvanic; apparatus of the torpedo;  and taking into consideration
the lamellated structure  of the cerebellum, which, according to him,
resembles a voltaic  pile; and the results of  his experiments,  which
showed, that the movements diminished  in proportion to the injury
done to the cerebellum, Rolando drew the inference,  that this
part of  the  encephalon  is an  electro-motive apparatus, for the
secretion of a fluid analogous to the galvanic.  This fluid is, accord- 
318
MUSCULAR MOTION.
ing to him, transmitted along the nerves to the muscles, 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 was held  to it; and he properly remarks,
that a single positive fact of this kind is  worth all the negative
facts that could  be adduced.   He farther  observes,  that  there
could be no doubt of the entire removal  of  the brain in  his experi-
ments.
   These  experiments of  Magendie  are equally  adverse to  the
hypothesis of  Flourens, that the cerebellum  is the regulator or
balancer of the movements.
   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 system  of locomotion."
It is manifest, however, that the encephalon  must participate  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 disease of the ence-
phalon ;  yet, as  has been remarked, there  is  some reason for be-
lieving, that, in  the upper classes of animals, an obscure  volition
may be exercised for a time, even when the encephalon is separated
from the body,  It need  scarcely be said, that we are as ignorant
of the character of this influx, as we are of that of the nervous phe-
nomena 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 appear to be
the corpora striati, the thalami nervorum opticorum, at their lower
part; the crura cerebri, the pons varolii, the peduncles of the cere-
bellum, the lateral parts of the medulla oblongata, and the anterior
column  of the medulla spinalis.  This  is proved by direct experi-
ment, as will  be seen presently; and, 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 
SEAT OF VOLITION, ETC.
319
an encephalic character,—we find  motion almost lost, and yet the
sensibility 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 tracts ; the anterior for motion;
the posterior for sensibility; and the two are kept  separate  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 attract-
ed 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
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 group of organs which-
ever 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 encepha-
lon.  In this view they conceive themselves  supported by the dis-
covery 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 functions.
Professor Adelon remarks, that Willis professed a similar notion.
and that he considered the cerebral lobes to be the point of depar-
ture  for the movements, and  the cerebellum the seat of sensibility.
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 reflec-
tion : and the cerebellum, the source of the motive spirits."  Willis,
in truth, regarded the  cerebellum as supplying animal spirits to the
 nerves of involuntary functions, as  the heart, intestinal canal, &c. 
320
MUSCULAR MOTION.
  The opinions of Foville and Pinel Grand-Champ are subverted by
the experiments of Rolando, Flourens. and Magendie, which show,
that sensation continues, notwithstanding serious injury, and even
entire removal of the cerebellum.
  By other physiologists, the two functions have been assigned  re-
spectively 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 Treviranus, 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, as  MM. Foville and  Pinel Grand-Champ have  re-
versed 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 special
seat of these functions.  A part of the discrepancy, in the results of
the experiments, must be ascribed to organic  differences in the ani-
mals, which were the subjects of the experiments.  This was striking-
ly exemplified  in  those, instituted by Magendie, which  have been
described.
   Similar  contrariety exists  in the experiments and hypotheses,  re-
garding the particular parts of the encephalon, that are concerned
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 with-
out any knowledge of those of Rolando, affirmed it to be  the regula-
tor 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, al-
though possessing all  its sensations, could it fly from the danger it
saw menacing it.   The same view has  been advocated by Bouil-
laud, who has detailed eighteen experiments, in which he cauterized
the cerebellum, and found that, in all, the functions of equilibration
and progression were disordered.
  The experiments of  Magendie, on this subject, are pregnant with
important novelty.   We have already referred to those that concern
the cerebral hemispheres and cerebellum, as the  encephalic organs
of the general movements, in the mode suggested by Rolando and
Flourens, and others.  He affirms, in  addition, "that there exist, in
the brain, four spontaneous impulses or forces, which are situated at 
                      SEAT OF THE MOTIVK FORCES.                J*!

   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 rotation."   The first of these im-
   pulses he fixes in the cerebellum and medulla oblongata; the second
   iti the corpora striata;  and the  third and  fourth in  each of the pe-
   duncles of the cerebellum.
      1. Forward Impulse.—It has  often been observed by those who
   have made experiments on the  cerebellum, that injuries of that or-
   gan cause  the animals  to recoil, manifestly against their will.  Ma-
   gendie asserts, that he  has frequently seen animals, wounded in the
   cerebellum, make an attempt to advance, but be immediately com-
(;  pelled 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 cerebella he thrust pins, constant-
   ly 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 ani-
   mals to go forward.
      Magendie thinks it  not  improbable  but that this force exists in
 [j  man;  and  he  states, that Dr.  Laurent, of Versailles,  exhibited to
   him, and to the Academie Royale de Medecine, 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, con-
   sequently,  exposed to  serious  falls  and  bruises.   This force,  he
   affirms, only exists in the mammalia and in birds;—certain fish and
   reptiles, on which he experimented, appearing  to be unaffected by
)  the entire loss of the cerebellum.
 I    2. Backward Impulse.—When the corpora  striata are removed,
 r-. Magendie found that the animal darted forward with great rapidity;
 J and, if stopped, still maintained  the attitude of running.   This was
 \  particularly remarked in young  rabbits; the animal appearing to be
   impelled forward by an inward  and irresistible power;  and passing
 \  over obstacles without noticing them.  These effects 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 re-
   moved, it remained master  of its-movements, and directed them in
 y  different ways; stopping when it chose; but, immediately after the
 , i  abstraction of  the other, all regulating power over  the  motions ap-
 ,/ peared to cease, and it  was irresistibly impelled forwards.
 f.,   In the disease of the  horse, called, by the French, immobility, the
f  animal  is  often capable of walking, trotting, and galloping forward
   with  rapidity; but he  does not back;  and frequently it is imprac-
v  ticablc  to arrest his progressive motion.  Magendie asserts,  that he
 i  has opened several horses which died in this condition ;  and that  he
 I"  found, in all, a collection of fluid in the lateral ventricles, which had
     vol.  i.                         41 
322
MUSCULAR MOTION.
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 the case 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
forwards or backwards until stopped by some obstacle.  In this case,
however, the patient got well; and accordingly there was no oppor- **
tunity for investigating the encephalic cause.  M. Itard, also, de-
scribes two cases, in which the patients were impelled, in paroxysms,
to run straight forward, without the  power of changing their course,
even when  a river or precipice was immediately before 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 in-
quiry.   The subject of it was, also,  irresistibly impelled to  constant
motion.  " At the time of the greatest stupor," says M. Piedagnel, y
 "he  suddenly  arose;  walked about in an  agitated 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  permit.   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, seve-
ral 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 depressed 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 peduncles of the cerebellum— A
the crura cerebelli—be divided in a living animal, it immediately be-  \
gins to turn round, as  if impelled by some considerable force.   The
rotation or  circumgyration is made in the direction of the divided
peduncle; and, at times, with such rapidity, that the animal makes
as many as sixty revolutions in a minute.  The same kind of effectas  •
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. 13,)
but the movement is more  rapid,  the  nearer the  section is to the
origin of the peduncles; in other words, to  their  point of junction
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- 
SEAT OF THE MOTIVE FORCES.                323
   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: 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 ana-
   tomy  of the brain, and  must have had unusual opportunities for ob-
   servation at the Hospital La Pitie, 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 effusion
   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 was
   to the  left, and conversely; 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
jf  one peduncle, when the animal immediately rolled in one direction;
   but on cutting the other, or the one on the opposite side,  the  move-
   ment 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-                F'g- 61.
<   ducing any  other.    The
   marginal figure of the  base
   of  the brain, will explain,
   more directly, the impulses
-.'   described by that physiolo-
   gist.   The corpora  striata
   are situated in  each hemi-
   sphere, but  their  united
   impulses may be represented
   by the arrow A; the  im-
   pulse, seated in the cerebel-
   lum, by the arrow B; and
   those  in each  peduncle of
   the cerebellum,  p p,  by the
   arrows ('  and D respec-
   tively.   When the impulse
   backwards  is  from  any
   cause destroyed, the animal
   is given up to the forward
 
324
MUSCULAR MOTION.
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 control.
   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
oblongata, 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.
   Pathology has, likewise, indicated the brain as the seat of different
bodily movements.  Diseases of the encephalon have been found not
only  to cause irregular movements or  convulsions, but, also, para-
lysis  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
encephalic  cause  of the  affection is found in the opposite  hemi-
sphere.  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 number, perhaps, have  referred it to the corpora pyrami-
dalia.  These, the  researches of Gall  and  Spurzheim  had pointed
out, as decussating  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 decussate—of the  corpora  olivaria  for example—or of the
corpora  pyramidalia,  which do.  Serres, however, affirms, that
affections of the cerebellum, pons varolii, and the tubercula quadri-
gemina, exert their effects upon the opposite side of the body; and
he supports 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
ventricle; 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, 
SEAT OF THE MOTIVE FORCES.                 325
   was equally devoid of perceptible influence on the general move-
   ments; and to cause paralysis of one-half the body, it was neces-
   sarv io divide the half of the medulla oblongata, and then the cor-
   responding 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 determi-
   nations 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 induced
   some  physiologists to proceed still farther  in their  location  of the
   encephalic organs of muscular motion ; and to attempt some expla-
   nation of paraplegia, or of those cases, in which one-half the body,
   under the  transverse bisection, is paralyzed.   MM. Serres, Foville,
   and Pinel Grand-Champ assert, that the anterior radiated portion  of
   the corpora striata presides over the movements of the lower limbsj
   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 1708,  Sauce-
>.  rotte presented a prize memoir to the  Academie Roy ale de Chirurgie,
   of Paris, in which a similar view was expressed.  He  had con-
h  eluded, from experiments, that affections  of the anterior parts  of
   the encephalon paralyzed the lower  limbs, whilst those  of the poste-
   rior parts  paralyzed the upper.   M. Chopart,—in  a prize essay,
   crowned in 1709, and contained in the same volume with the last-—
   the fourth of the  Prix de V Academic Roy ale de Chirurgie—refers  to
   the  result of some experiments by M. Petit, of Namur, which ap-
   peared 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  Academie Royale de
   Medecine, of Paris, in 1820.  They were attended with like  results.
   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 extre-
   mities 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 extremities, 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 j notion has  been attempted to be deduced from pathological
   facts.   Foville places  it  in the cornu ammonis and  temporal lobe;
   and Bouillaud in the anterior lobe of the brain, in the medullary 
326
MUSCULAR MOTION.
substance; the cineritious being concerned, he conceives, in the in-
tellectual 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 compa-
 rative anatomy and  physiology  as might  have  been anticipated.
 The  greatest source  of discrepancy, indeed, between his  experi-
 ments and those of M M. Rolando and Flourens, appears to have
 arisen in the employment of different animals.  Where the same ani-
 mals were the subjects of the vivisections, the results were in accord-
 ance.  The  experiments demand  careful repetition, accompanied^ »*
 by watchful  and assiduous observation of pathological phenomena;
 and,  until this is effected, we can, perhaps, scarcely feel justified in
 deducing, from all these experiments and investigations, more than
the  general propositions, regarding the  influence of the cerebro-
 spinal axis on muscular motion, which we have already enunciated. J|
   The nerves, it has been shown, are  the  agents for  conducting j|
 the locomotive  influence to the muscles.  At one time, it was uni-'
 versally believed, that the  same nerve  conveys both sensation and
 volition ; but  the pathological cases, that not unfrequently occurred,
 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
 mainly indebted to Sir Charles Bell and Magendie, have  satisfied   j
the  most  sceptical,  that  there  are separate nerves  for  the two   i
functions, although they may be enveloped in the same neurilemma,
or nervous sheath; or, in other  words, may constitute the same   J
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 anterior column,
and  the  nerves  connected  with  it, are inservient  to muscular
motion ; whilst a third column intervenes, which, in the opinion  of
Sir Charles Bell, is the source  of all the  respiratory nerves 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. 
SEAT OF THE MOTIVE FORCES.
327
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, 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 prolon-
gations, as the crura  cerebri,  corpora pyramidalia, the  anterior
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
nxdulla spinalis, and the nerves connected with it, preside over the
movements of extension:  he infers, in other words, that there is an
antagonism between these sets of nerves.
   The  prima facie  evidence is  against  the accuracy of Belhn-
geri's experiments.   The weight  of authority in  opposition to him
is,  in  the first place, preponderant;  and  in the  second place,
it seems highly  improbable, that distinct nerves should be  em-
ployed  for  the same kind  of muscular  action.    Moreover, in
some  experiments  'on the  frog, Professor  Muller  of Bonn,  has
established the correctness  of  the  views of Bell.  It  seems,  that
the  different  physiologists,  who  engaged  in  the  inquiry before
he did, employed warm-blooded  animals in their experiments,  and
he imagines, that the  pain, resulting from the necessarily extensive
wounds, may have had such an effect on the  nervous system as to
rtfodify, and perhaps even counteract, the results.   Muller employed
the frog,  whose  sensibility  is less  acute,  and its tenacity of life
greater.  If the spinal marrow of  this animal be exposed, and the
posterior roots of the  nerves of the lower extremities be  cut, not the
least  motion is perceptible  when  the divided roots  are excited by
mechanical means, or by galvanism.   But if the anterior  roots be
touched, the most active movements  are instantly observed.   The
movements may also  be excited by the galvanic pile.  These expe-
riments, Muller remarks, are  so readily made,  and the evidence
they  afford is so palpable, that they leave no doubt as to the correct-
ness of the views of Sir Charles Bell.

   In  the ordinary cases of the action  of a  voluntary  muscle, the
nei'vous 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  contraction.
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; 
328
MUSCULAR MOTION.
and  Dumas  carried it still higher.  It must, of course-, be propor-
tionate  to  the  length  of the  fibres,—being greater the longer the
fibres.  It has,  also, been a subject of experiment and of speculation,
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 a jar of water, with which a baro-
metrical tube was connected; and when the muscles were made to
contract strongly,  the level of the water in  the  tube was raised.
Glisson, however, from the same experiment,  deduced opposite
conclusions: Swammerdam  and  Ermann  appear to  be of  his
opinion, and Sir  Gilbert Blane, Mr.  Mayo,  Barzellotti and  MM.
Dumas and Prevost, during the most careful experiments, could  see
no variation in  the  level of the  fluid;  and, consequently, 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,  the neck of which was drawn out into a fine tube; then, by
means  of a wire,  introduced into the vessel, he irritated the tail of  a
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 : their specific gravity was pre-
cisely the same.
   The  experiment of Barzellotti was the following.—He suspended,,
in a  glass vessel,  the posterior  half of a frog, rilled  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 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  forcibly closed,
and some men  possess the power of producing sonorous vibrations
by striking the  contracted biceps  with a metallic rod.             .^
   It has been  a  matter of dispute, whether the quantity of bloodfj
circulating in a muscle,  is 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 supposition
with his idea, that  the absolute size of the  muscle is augmented 
CONTRACTION OF MUSCLES.
329
    during contraction.  The truth is, we have  no evidence, that the
    colour of a muscle, or the quantity of blood circulating in it, is at all
    altered  during contraction.  Bichat, who adopted the opinion, that
    the blood is forced out during this state, relies chiefly upon the fact,
    known to every one, that, in the operation  of blood-letting from the
    arm, the flow of blood is augmented, by working the muscles; but
    the additional quantity, expelled 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 con-
    traction.
      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 aponeu-
    roses, 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 evidence in favour
    of this view  is extremely feeble and unsatisfactory.  The arrange-
    ment 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 muscles to bend,
    but also  to extend it; and, accordingly, when it has been bent, and it
    becomes necessary to extend it, the flexor muscles are relaxed and
    rest, whilst the extensors are thrown into  action.   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
    condition, 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
    extenlleaV^d; by returning upon themselves,  they become active
    agents of expirationTtSQding to restore the chest to its  unexpanded
    state.                       "• —
     The production of the  phenomena o( muscular contraction is, so
    far as we know, unlike  any physical process  with  which  we  are
    acquainted.   It has, therefore,  been  considered essentially organic
     vol. i.                       42 
330
MUSCULAR MOTION.
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 elementary fibre,—it
 is obvious, that the explanation  is  defective, inasmuch as we have
 still to look to the cause, which produces  this  mechanical influence.
 Again, how are we to  account, under  this hypothesis, for the sur-
 prising  efforts of strength executed by muscles?  The mechanical
 influx of animal  or other spirits—granting for a moment their ex-
 istence—might develope a certain  degree of force; but how can
 we conceive  them able, as in  the case of the muscles inserted
 into the foot,  to develope  such a force as to project the  body
 from the ground 1  In  all these cases,  a new and  occult force is
 generated in the brain; and this,  by acting on the muscular  fibre,
 is the grand, efficient  cause of the contraction.  Moreover,  what
an inconceivable  amount of  fluids would be  necessary to produce
the contraction of the  various muscles, which are constantly in ac-
tion ; 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 pro-
portion as it is more exercised.  These phantasies  are  too abortive
to require comment.
   When chemical  hypotheses were in fashion in medicine, physio-
logy 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 opinions of
this kind;  some ascribing the effervescence to a union of the  ner-
vous fluid with the arterial blood; others to a union of the particles
of the muscular fibre with the nervous fluid;  and others,  to the dis-
engagement  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 ab-
surdities of this  period—so prolific in physicallobjcu^i^^Mea^"
cine has generally  kept pace with   phyjic^Hriawhere the latter
science has  been  dark  anderjb^fff^j^ the former  has been so
likewise.  In physiology^^htsis especially apparent;  most of the
natural philosophers  of eminence having applied  their   doctrines
in physics to  the explanation of the different functions of the human 
CONTRACTION OF MUSCLES.
331
 frame.   Newton,  Leibnitz,  and  Descartes,  were  all  speculative

 I,hK1tscovery of electricity gave  occasion to its application to
 the&cW^n;  a»d *  ^imagined,  that the  fibres  of.the
 musde might be disposed in  such a manner as to form a kind ot
 bauerv  Xble of producing contraction by its  explosions;  and
 afte^L discovery of galvanic electricity, Valli  attempted to ex-
 ptn muscular  coltractfon, by supposing,  that the muscles have an
 arrangement similar to that of the galvanic pile.         relebrated
   Haller endeavoured to resolve  the  problem by his celebrated
 doctrine of irritability,  which will engage  atten 10n  hereaftei;
 He conceived, that the muscles possess  what he calls  a ™™^
 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 volUion  This, it  is  manifest, affords us no new light cm  titaj
 mysterious process.   It is, in fact, cutting the gordian  kno j.  We
 should still have to explain the precise mode of action of this vis

 '"The hypothesis of Prochaska is entirely futile.  He gratuitously
 presumes, as we have seen, that the minute ramifications ot the ar-
 teries are everywhere connected with the ultimate  muscular  fila-
 ments,  twining around  them, and crossing  them in  ^directions.
 When these vessels are rendered turgid by an influx  of blood,—-by
 passing among  the filaments, he conceives they must bend the latter
 into a serpentine shape, and  thus diminish their length, and that ot
 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 thick-
 ness exactly what it loses in length—that this may be owing to the
 muscle being composed of particles of an oblong shape; and that
 when the muscle is contracted, the long diameter of  the particle is
  removed from  a perpendicular to a transverse direction.  But the
 same objection applies to this  as to other hypotheses on the subject;
 that  it is entirely gratuitous—resting  on no  anatomical  support
  whatever.
    There are two views which may be esteemed as the most preva-
  lent at  the present day; the one, which considers muscular contrac-
  tion to be a kind of combustion; the  latter, that  it is produced by
  electricity. The former, which was originally propounded by Gir-
  tanncr, and zealously embraced  by Beddoes, who was more  cele-
  brated for his enthusiasm than for the solidity of his judgment, has
—iiuw  0*01' JLjV'MppHitrTi   This hypothesis  supposes, that muscular
  contractiond^peTnTS;-4]Don  the combustion  of the  combustible ele-
  ments of the muscle, bydrOg§n^_carbon, and azote, by the oxygen of
  the arterial blood;—the combustion 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 physio- 
332                     MUSCULAR MOTION.

logical speculators.  Of course, we have neither direct nor analogi-
cal 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 afford the  elements.  The  idea is as unfounded as
numerous others  that have been  entertained, and is worthy only of
particular  notice, from  its being professed  in one of the few works,
which we possess, on physiological science.
   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 exam-
ples on record of the analogous  effects produced  by the physical
and by the vital fluid on the phenomena under consideration.
   It has been long known, that when nerves and muscles are exposed
in a living animal, and brought into contact, contractions or convul-
sions occur in the muscles.  Galvani was the first to point this out.
He  decapitated a living  frog, removed the fore-paws, and  quickly
skinned it.  The spine was divided, so as to leave the spinal marrow
communicating only with the hind extremities by means of the lum-
bar nerves.   He then took, in one hand, one of the thighs of the ani-
mal, and the vertebral column in  the other, and bent the limb until
the crural muscles touched the lumbar  nerves.  At the  moment of
contact, the muscles were strongly convulsed.  The experiment was
repeated by Volta, Aldini, Pfaff, Humboldt and  others, and with
like results.  Aldini observed convulsions in the muscles by the con-
tact of those organs with nerves, not only in the same frog, but also
in two  different frogs.  He  adds, that he remarked them when he
put the nerves of a frog in connexion with  the  muscular  flesh of an
ox recently killed. Humboldt made numerous experiments of this
kind  on frogs.  He found convulsions supervene when he  placed
upon a dry plate of glass a posterior extremity whose crural nerves
had been exposed, and touched the nerves and the muscles with a
piece of raw muscular flesh, insulated at the extremity of a stick of
sealing-wax.  Convulsions likewise occurred, when, instead of one
piece of flesh, he  used three different pieces to form the chain, one
of which touched the nerve, the  other the thigh, and the third the
two others.  The experiments were repeated by Ritter with similar
results, but they were only found to succeed, when  the  frogs were
in full vital activity, especially in spring after pairing; when the ani-
mal was of sufficient size, and" its preparation for the experiment had
been rapidly effected.
  From all these experiments it  may be inferred, that parts of an
animal  may form galvanic chains, and  produce a galvanic effect,
which, independently of any mechanical excitation^rnj^y.^i^-ri^eTo"
the contraction of muscles.   This excitafion^jr^el^ctricity in chains
of animal parts, M. Tiedemann  thitfefought not  to be  esteemed a
vital act.   Its effects onlys**4TR^contractions excited in the  muscles
—are dependent on^tfre vital  condition of  the muscles and nerves.
He considers^thsttthe electricity, excited in chains of heterogeneous 
CONTRACTION OF  MUSCLES.                 333
animal parts, may be  modified and augmented by the organic or
livine forces; and that, moreover, in  certain animals, organs exist,
the arrangement of which  is such as to excite electricity  during
their vital  action—as in the different  kinds of electrical fishes;  but
in some experiments, instituted by M. Edwards, the same effects, as
those above  referred to, were produced by touching a denuded nerve
with  a slender rod of silver, copper, zinc, lead, iron, gold, tin, or
platina, and  drawing it along the nerve for the space of from a quar-
ter to a third of an inch.  He  took care to  employ metals of  the
greatest purity, and as they were furnished him by the assayers ot
the mint.  But  it was not even  necessary, that the rod  should be
metallic: he succeeded with glass or  horn.  All these metals, how-
ever, did not produce  equally vigorous contractions.  Iron and zinc
were far less effective than the others, but no  accurate scale could
be formed of their respective powers.
   Much  difference is  found to exist,  when  electricity is employed,
according as the nerve is insulated or not; for as the muscular fibre
is a good conductor of electricity, if the nerve be not insulated, the
electricity is communicated to both nerve and muscle, and its effect
is consequently diminished.  It became,  therefore, interesting to M.
Edwards to discover, whether any difference would be observable,
when one metal only was  used, according as the nerve was insu-
 lated or  not.  In the  experiments above referred  to, the nerve was
 insulated  by passing a strip of oiled silk beneath it.  A comparison
 was  now instituted between an  animal thus prepared, and another
 whose nerves instead of being insulated, rested on the subjacent flesh.
 lie made use of small rods, with which he easily excited contrac-
 tions, when he  drew them from  above to below, along the denuded
 portion of nerve which was supported by the oiled silk, but he was
 unable to excite them, when he passed the rod along the nerve of
 the other animal which was not insulated.  His experiments were then
 made on two  nerves of the same animal, and he  found that after
 having vainly attempted to produce contractions by the contact of a
 nerve resting upon muscle, they could still  be induced if the oiled
 silk were had recourse to, and he was able to command their alter-
 nate appearance and  disappearance, by using a non-conductor or a
 conductor for the support of the  nerve.
   Somewhat surprised at these results, M.  Edwards was stimulated
 to the investigation,—whether some degree of contraction might not
 1m: excited by touching the uninsulated nerve, and, having remarked,
 that contractions were most constantly produced in the insulated
 nerve, by a quick and  light touch, he adopted this  method on an
 animal wfrtfS&Iierye^was not insulated, and frequently obtained slight
 contractions.   AlTlns -experiments on this subject seemed to prove,
 that, ca-teris paribus, the  musc"tfi3£^contractions,  produced by the
 contact of a solid body with a nerve, are much less considerable, or
 even wholly wanting, when the  nerve, in place of-being insulated is
 in communication with a good conductor, and it would seem to fol- 
334
MUSCULAR MOTION.
low, as a legitimate conclusion, that these contractions are dependent
on electricity;  facts, which it is well to bear in mind, in all experi-
ments on animals where feeble electrical influences are employed.
  Galvanic  electricity, we shall see hereafter, is one of the great
tests of muscular irritability, and is capable of occasioning contrac-
tion, for some time after the death of the animal, as well as of main-
taining, 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 pheno-
menon.   Much discrepancy has, however, arisen amongst the par-
tisans of this opinion, regarding  its modus operandi.  Rolando, we
have seen, assimilates the cerebellum to an electro-motive apparatus.
which furnishes  the fluid, that excites the muscles to contraction.
Some have compared 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 amongst
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 of the nerves really terminate  in the muscle; but that the final
ramifications 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 return-
ing 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 occurred 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 the small nervous filaments enter or pass from the  muscles.
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, accord-
ing to the lawlaid down by Ampere, that two currents attract each
other when they  move in the  same  direction.   The livingjmasde*_
are,  consequently, regarded by them as gahanqmet^^fSiT^i-
nometers  of an extremely sensible  knjd#j^J* account of the very
minute distance and tenuityof^jifcrTiervous filaments.
  They, moreover^afjifffiithat,  by anatomical arrangement,  the
nerve is fixedin^lTemuscle in the very position required for  the
proper pejfeflnance of its function;  and they esteem the fatty mat- 
CONTRACTION OF MUSCLES.
335
tcr, which envelopes the  nervous fibres, and which was discovered
by Vauquelin, as a means of insulation, to prevent the electric fluid
from passing from one of the fibres to the other.
  Soon after hearing of Ampere's discovery of the  attraction  of
electrical currents, it occurred to Dr. Roget, that it might be possi-
ble to render the attraction between the successive and  parallel turns
of heliacal or spiral wires very sensible, if the wires were sufficiently
flexible and  elastic: and, with the assistance  of Mr. Faraday,  his
conjecture was put to the test of experiment, in the laboratory  of
the Royal Institution of London.  A slender harpsichord-wire bent
into a  helix, being placed in  the voltaic circuit,  instantly  shortened
itself whenever the electric stream was sent through it: but recover-
ed its former dimensions the moment the current was intermitted.
From this experiment it was supposed, that possibly some analogy
might  hereafter be found to  exist between the phenomenon and the
contraction of muscular fibres.
  The views of Prevost and Dumas have been altogether  denied by
M. Raspail,  inasmuch as it is impossible, he says, to distinguish, by
the best miscroscope, the ultimate  muscular  fibre from  the small
nervous fibrils by which  those gentlemen consider  them to be  sur-
rounded loopwise.  He  farther affirms, that the  zig-zag form is the
necessary result of the method in which they performed their expe-
riments, and  is produced by  the muscular fibre adhering to the glass
on which it was placed.   His own idea, founded on numerous ob-
servations, is, that the contraction of the fibre in length is always
occasioned by its extension in breadth under the  influence of the
vital principle.  Independently, however, of Raspail's objection, the
circumstance, that, in this mode of viewing the  subject, the muscle
itself is passive, and the nerve alone active, is a  weighty stumbling-
block in the  way of the views of both MM.  Prevost  and Dumas,
and Dr. Roget.
  With regard to the hypothesis, which ascribes muscular contrac-
tility to the chemical  composition of the fibre, or that  which main-
tains,  that the property is dependent upon the mechanical structure
of the fibre, they are undeserving of citation, notwithstanding the
respectability of the individuals, who have written and experimented
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 de-
veloped.
   But  not only is  it necessary, that the muscle shall possess a proper
physical organization, it  must, likewise, be endowed with one, that
js essei^u1i#r^i2lirin otncr words, with  irritability.  The cause  of
the ordinary contractiefi-ef^riuscles is, doubtless, the nervous influx,
but if we alter the condition  of"the ffiuscle, 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 becomes fatigued, 
336
MUSCULAR MOTION.
notwithstanding volition may regularly direct  the nervous  influx 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 interesting of
the many experiments  that have been  made  on the  bodies of cri-
minals recently deceased,  for the purpose of exhibiting  the effeets
of galvanism on muscular irritability, 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 gal-
lows  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 per-
fectly 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 glutacus 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, connected
with  one end  of a galvanic battery, of two  hundred and seventy
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  convulsive
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 vio-
lence, as  nearly to overturn one of the assistants, who  in vain at-
tempted 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 respirajjojj^jj^g^n^tantly
contracted,  but with less force  thanjaa^xnected. "Satisfied,"
says  Dr.  Ure, "from amo\e^j^^r\ZQ on  the living  body, that
more  powerful effecj£_-€oiTbe  produced in galvanic excitation, by
leaving  the  exta^nB communicating rods in close contact  with the
parts  to be-operated on, while  the electric chain or circuit is com- 
CONTRACTION OF MUSCLES.
337
 pleted, 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 im-
 mersed in the last cell of the opposite pole, 1 had immediate recourse
 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 inter-
 ruption, 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 representation of a Fuscli  or a Kean."  At  this period, se-
 veral of the spectators were forced to leave the room from terror or
 sipkness, 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 prevent it.
 When the  one rod  was applied to  a slight incision in the tip of the
 forefinger, the fist  being previously  clenched,  that  finger was in-
 stantly 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.   The experiments  of Dr. Ure have been  several
 times repeated, in this country, on the bodies of criminals,  and with
 analogous results.
   What important  reflections are  suggested  by the perusal  of such
 cases! The strict resemblance between the galvanic and the nervous
 fluids, and the absorbing idea,  to the  philanthropist, that galvanism
 may be  found  successful in resuscitating  the apparently dead, in
^as^^vfiSr^Cil]01'  means would  probably fail!   Unfortunately  it
 can rarely bnpppTT^^  the  means will be at hand, and can, conse-
 quently, be available.  It niTr^™"over, be borne in mind,  that, in
 the case just  narrated, many of the elkets were produced,  two hours
 after respiration had been finally arrested.
   An experiment,  described by Dr. George  Fordyce,  signally ex-
     VOL. I.                        l3 
338                     MUSCULAR MOTION.

hibits the power of the contractility, which is resident in the 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 mechanical 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 account for the phe-
nomena of muscular contractions: we are compelled to infer, that
a new force must always be 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 might have led to a different result.  Ac-
cording 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  moment for  the
husband to show that the child was born alive: and the law author-
ities have, with singular infelicity, attempted to define 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, indeed, is the strongest evi-
dence of its being born alive, but it  is not the only evidence."  Ac-
cording 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, and 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,  al-
though, when immersed in  a warm bath, immediately after birth, it
did  not "cry or move, or show any symptoms of life;" yet, accord-
ing 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, that 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 thepaj£jyJ*g^ pre.~
viously and recently formed part of a hving^^n;

  *It need scarcely be said, that the deafifeftib cry at the moment of birth the same as
other children.  The natural cry is  effected by them as well as by the infant that pos-
sesses all its senses.^ It is the acquired voice, alone, which they are incapable of at-
tain ing. 
CONTRACTION OF MUSCLES.
339
    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 nervous
  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 maintains, that the re-
  laxation of the  muscle is produced by  a nervous action the reverse
  of that which occasions its contraction;  the will relaxing the mus-
  cles as well as  contracting them.   The  muscle is the  only part sus-
  ceptible of contraction.  The tendon conveys the  force, developed
  by it, passively 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 or  Bewegungssinn
  or muscular sense of Gruithuisen, Lenhossek, Brown, Bell, and other
  writers. It appears to be an internal sensation, produced by the mus-
  cle  pressing on the  sensible  parts surrounding it;  which parts con-
  vey the sensation to the brain.
    It is by this muscular sense that the brain learns to adapt the effort
  to the effect to be produced.  Without it no precision could  exist in
  the movements of the muscles, and every manual effort—whether of
  the artist or the mechanic—would be confused and disorderly.  The
  step, too, would be unsteady and insecure.  " In chewing our food,"
  says Dr. A. Combe, "in turning the eyes  towards an object looked at,
  in raising the  hand to the mouth, and, in fact, in  every variety of
  muscular movement which we perform, we are guided by the mus-
  cular sense in proportioning the effect to  the resistance to be  over-
  come ;  and where this harmony is destroyed by disease, the extent
  of the service rendered us becomes more apparent.  The shajve  of
  the arm and hand which we see in drunkards, and  their consequent
  incapability of carrying the morsel directly to the mouth, are exam-
  ples of what would be of daily occurrence, unless we  were directed
  and assisted by a muscular sense."
    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 motions; and is ac-
  curately regulated so as to raise a weight of  one  pound or of one
  hundred.   Again, we notice astonishing efforts of strength  in  those
^Jliat are labouring, at the time, under strong  cerebral  excitement;
" under*rn^nPTS*i«£L:delirium, &c.   In such cases, the delicate mus-
  cles of the fem3?M&«ap^le of contracting with a force far trans-
  cending that of the healthyfcak--. The  power of muscular contrac-
  tion is, therefore, in a compound  ratio  *.vith the strength of the  or-
  ganization of the muscle, and the degree ot  excitation of the brain.
  Where both are considerable, the feats of strength surpass beliet,
  and where both are small, the results are insignificant. 
340                     MUSCULAR MOTION.

  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 leaping.
Rudolphi asserts, that he has seen  a horse, which fractured its under-
ja.w by biting a piece of iron.
  We have  a number  of feats of surprising strength on record:
several of which are contained in the 'Letters on Natural Magic'
by Sir  David Brewster: of these, the  cases of John Charles Van
Eckeberg, who travelled through Europe under the  appellation of
Samson, and of Thomas Topham, are the most authentic and extra-
ordinary.  Dr. Desaguliers saw Topham, by the strength of his fin-
gers,  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,
Having 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 to-
gether 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 on his right
hand, he struck upon his bare left arm, between 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 circumference, 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 roll-
ing-stone, eight  hundred 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 witness-
ing the inferiority, in  strength,  of the aborigines to the white
settlers.
   Peron  took  with him, in his  voyage round jhe^^errrtTwmp of
Regnier's dynamometers, which indicates^Jbg'*£cj^ve force of men
and animals.  He directed his  attejjii**fto  the  strength of the arms
and  of the loins, making.^ on several individuals of different
nations;  viz. twelve  natives of Van Diemen's land, seventeen of
New  IMUvso1; fifty-six of the  island of Timor, seventeen French- 
         FORCE AND DURATION OF MUSCULAR CONTRACTION.        341

men, belonging to the expedition,  and fourteen Englishmen in the
colony of New  South Wales.  The following  was the mean result.

                                                STRENGTH
                                       .------------A------------
                                       Of the arms,     Of the loins,
                                      kilogrammes.f    myriagrammes.
1. Van Diemen's land,    -    -    -     50.6
2. New Holland,     ....     50.8     -     -    10.2
3. Timor,.....58.7     -     -    116
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
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 re-
spect  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 developement 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, whieh 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 hundred
pounds.   Topham lifted eight hundred.
  JThe daily work of a horse is estimated  to be equal to that of five
or SJY ihpIN^
  In the duration  of  |r'jj"£cl"ar contraction, wTe  notice considerable
difference between thatoFSh^voluntary and  of the  involuntary

  * The approximate  value of a kilogramme is  about  i'.vo pounds avoirdupois:—
of a mynagramme about twenty. 
342
MUSCULAR MOTION.
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 muscular
action appears absolute;—relaxation being followed by contraction,
in every  organ, from  the commencement of life until  its  final ces-
sation.  The  intermission has, indeed,  by many physiologists, been
held to prevail—to a slight extent only, it  is true—during, what we
are  in the habit of considering, continuous, muscular contraction.
In proof  of this, they cite the fact, that when we put the tip of the
finger into the meatus auditorius externus, we hear a kind of buzzing
or humming, which does not occur when an  inert body  is intro-
duced.  There are, however, other actions going on in the finger,
besides this  of muscular contraction;  and it might, with as much
propriety, be  referred to the noise made by the progression of fluids
in the vessels, as to the oscillations of muscular contraction and re-
laxation.   We know not, in truth, whence the sound  immediately
proceeds.
   In the velocity of muscular contraction,  much difference also ex-
ists, according to the stimulus which sets it in action.  If we apply
galvanism to  a muscle, we find the contractions at first exceedingly
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 en-
tirely by  the will.   We  have, in various classes of the animal king-
dom, remarkable instances of this velocity.   The motions of the
racer, of the grayhound, of a practised  runner, of the fingers in play-
ing 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 cases, it must
be reo-ulated  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 cer-
tain birds—which can, with facility, wheel round and^-jfij the
most rapid racer in circles of immense  diam^jff^^j wjtn tnat 0f
numerous  small insects, which accomjpaijk^u^  when we travel with
great rapidity—even against jhe_j*HSd—with apparent facility.
  It has frequently  excited surprise, how the  migratory birds can
support themselyes'sb long upon the wing,  as to  reach the country 
                VELOCITY OF MUSCULAR CONTRACTION.            343

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 hun-
dred and fifty miles an hour; and that one  hundred miles per  hour
is certainly not  beyond a fair computation for the continuance 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 common crow, at nearly twenty-five miles an
hour.   Spallanzani 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 from Fontainbleau,  and was,  in  twenty-four hours after-
wards, 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 seventy-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 Fifeshire,
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 be greatly dependant upon habit.  Nothing  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,
         ]£tice never fails to confer, in any one of those varieties
of:muscuiar^onfr^i°»'?  In running, leaping, wrestling,  dancing,
or any other motioiTof*^ body, one person  can  execute with
facility, what  another,  witli>f}Hal!y^ favourable  original  powers,
cannot effect, because he has not previously and frequently  made
the attempt.  Prize-fighting affords an instance ot  tfcjs kind of mus- 
344
MUSCULAR CONTRACTION.
 cular velocity and  precision, acquired by habit;—the practised
 boxer being able to inflict his blow and return his arm to the guard
 so quickly, as almost to elude the sight.   By considering the  mus-
 cular motions, employed in  transporting  the  body  of the  fleetest
 horse, Haller  has concluded, that the elevation  of the leg must have
 been performed in ^th part  of a second.   lie 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,  pro-
 nounced fifteen hundred letters in a minute; and, as the relaxation
 of  a muscle occupies  as much  time as  its contraction, the  con-
 traction of a muscle,  in pronouncing one of these  letters, must  have
 been executed in 7oWtn 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  pro-
 nunciation of  this letter, be estimated at ten, the muscles, concerned
 in it, must have contracted, in Haller's experiment, in T^^th part
 a minute.
   It has been the opinion of many physiologists and metaphysicians,
 that, only within certain limits of velocity, is muscular contraction
 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 and remote.  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 attending 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 mean-
 ing, that is to  be  conveyed by them.  In learning music, we begin
 by  imitating particular motions of the fingers, but  at length the fin-
 gers 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 brought for-
 ward, it is difficult to conceive how the effect can be produced with-
 out the agency of volition;—obscure it is  true, but still_i^T-S^UonT""
 The case of reading is often  assumed, as conhvjp*fiZ~^he view  that
invokes habit: yet, if a letter be inverted, \ye 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, 
MECHANICAL PRINCIPLES.
345
ought to exist, that an effort of volition is exerted on each note com-
posing 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.
  Before  passing to the examination of special movements, it will
be necessary to consider briefly a few elementary principles of me-
chanics, most of which are materially concerned  in every explana-
tion, and without some knowledge of which such explanations would,
of course, be obscure  or unintelligible.  Were we,  as Magendie
has remarked, to investigate narrowly every motion of the body, we
should find the applicability to them of almost all  the laws  of me-
chanics.
  If we take a rod of wood or metal, of uniform matter  throughout,
and support it at the middle, either like the beam of a balance,  or on
a pointed body, we  find, that7the 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 suspension,
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 gravity or of inertia.
  The centre of gravity, in a mass  of regular form and  uniform
              substance, as in the parallelograms, Figs. 62 and 63,
   Fig. 62.    is  easily determined, inasmuch as it  must necessarily
              occupy the centre c;  but  in bodies, that are irregular,
          I    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
     c'{       which the body rests, the more stable is the equili-
              brium.   In order that the figures 62 and 63 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
  ---->----1    lifted  in  the same degree.  In Fig. 62, the curve is
              nearly horizontal, owing to the narrowness  of the
  vol. i.                       44 
346
MUSCULAR MOTION.
base and the height of the  centre of
                   other hand, whose
Fig. 63.
                                      ravity.  In Fig. 63,  on the
                                      iase is broad and the centre
                   of gravity  low, the curve  rises considerably;
                   the resistance  to overturning  is consequently
                   nearly equal  to  the  whole weight of the body,
                   and the equilibrium necessarily firm.
                     The condition of equilibrium, of a body rest-
                   ing upon a plane, is  such, that a perpendicular,
                   let fall from the centre of gravity, shall fall
                   within the points by which it touches the plane.
                   This  perpendicular  is called the vertical line or
line of direction, being that in which it tends naturally to descend to
the earth;  and the space, comprised between the 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
                                             along a sloping road;
                                             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 c p falls
                                             considerably  within
                                             the base of sustenta-
                                             ' tion; and the centre
                                           x 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
 
MECHANICAL PRINCIPLES.
347
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 pro-
jected 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 latter, the
inertia of  motion.   The danger of attempting to  leap from  a car-
riage, 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.
  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 penetrate the most
solid substances.  If a man be running, and strike against another,
who is standing, 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, that is, resulting  from  the
                       composition  of  the  forces.   Let us sup-
                       pose two forces a T and b  T in Fig. 65,
                       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 draw-
ing 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 abt.  ,
 
348
MUSCULAR MOTION.
Fig. 67.
                     In the case,  assumed  in  Fig. 65, the forces
                   are equal.   If not so, the parallelogram may re-
                   sult as in Fig. 67; 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 66.
                     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. 65, which is capable of  acting in the
                   directions T a  and T b; it is  only necessary
                   to draw, from the point c,c a parallel to T b, and
                   cb  parallel to  Ta; and  the lines Ta and T b,
                                     cut off by  these, will be the
                                     forces into which it may be re-
                                     solved. The same applies to
                                     Figs. 66 and 67,  and to every
                                     other of the kind.
                                        Friction  is the  resistance
                                     necessary to be  overcome in
                                     making one body  slide  over
                                     another;  and  adhesion is the
                                     force, which unites two polish-
                                     ed bodies when applied to each
 other,—a force, which is measured by the perpendicular effort neces-
 sary for separating 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 another, it will be  always advantageous to make the surfaces
 polished, or to put a liquid between them.
   A beam or rod of any kind, resting at  one part on a prop or sup-
 port, which thus  becomes its centre of motion,  is a lever.   The ten
                                                inch beam, P. W,
                     Fig. 68.                    Fig. 68, is  a le-
                                                ver, of which F
                                                may be consider-
                                                ed  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 three points;—the fulcrum,
power, and  resistance; and, according to  the  relative position of
these points, the  lever is  said to  be of the first,  second, or  third
kind.
  In a lever  of the first kind, the fulcrum is between the resistance
and the power  as in  Fig. 68; F being the fulcrum on  which the
beam rests and turns; P, the power; and W, the weight  or resist-
ance.  We iiave  numerous familiar  examples  of this lever;—the
 
MECHANICAL PRINCIPLES.
349
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. 69, be-
tween the  power
P  and  the ful-                     Fig. 69.
crum F; the ful-
crum and  power                                _________mmrlP
occupying  each
one   extremity.
The rudder of a
ship,  a wheel- -^
barrow, and nut-crackers, are varieties of this kind of lever.
  In a  lever of the  third kind, the power P is between the re-
sistance  W,  and
the  fulcrum   F,                  Fig 70.
Fig. 70 ; the resist-
ance and  the ful-
crum    occupying
each  one  extre-
mity of the lever.
In  the   two  last
levers,  the weight  j^iiitiiiiiiiiiitiirilA
Wj
Wit
and   the   power x       P                            w
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 ex-
erted  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. 68, 69, and 70 ; 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 un-
equal  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. 
350
MUSCULAR MOTION.
  The arm of the power, in Fig. 68, 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 resistance,
in order that the two forces may be equilibrious.
  In the lever of the second kind, again, the proportion 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.
  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. 70, 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 resistance is moving
through the much more considerable space W w.
  The direction  in which the power is inserted in to  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 direction; and this part of the force is destroyed by the resist-
ance 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. 70, for example, the line of direction of the upper
weight isWw;;  that of the power P p; and 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  in that of the parts which it supports. 
              APPLICATION OF MECHANICAL PRINCIPLES.           351

  In different parts of the skeleton we find the three kinds of levers.
Each of the  vertebrae of the back  forms, with the one immediately
beneath it, a lever of the first kind; the fulcrum being  seated in the
middle of the under surface of the body of the vertebra.   The foot,
when we stand upon the toe, is a lever of the second kind; the ful-
crum 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 ankle
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, 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  consi-
derable force must be exerted  to raise an  inconsiderable  weight;—
that so far, consequently, mechanical 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 con-
comitants, 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  afterwards attempt to show  the advantages re-
sulting from these  and similar arrangements in  effecting the won-
derful, 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. 71, represent  the os humeri,
with  a weight W  at the elbow, to
be raised by the deltoid muscle D.            Fig. 71.
The fulcrum  F is necessarily, in
this case, in the shoulder joint; and
the muscle D is inserted much nearer
to the fulcrum than to the end of the
bone on which the  weight rests;
the arm of  the power P F, (sup-
posing, for a moment, that it is act-
ing at this part with every advan-
tage, 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 del-
toid being  inserted into the humerus about one-third down.  Now,
if we  raise  a weight of fifty-five pounds in this  wray, and add five
pounds for the weight of the limb, (which may be conceived to act
entirely at the end of the bone,) the powrer, 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.
 
352
MUSCULAR  MOTION.
Fig. 72.
A. the Scapula, B. the os humeri, C the deltoid.
  Figure 72, strikingly exhibits the disadvantages  of the deltoid, so
far as regards the place of its insertion into the lever; but many muscles
have insertions much less  favourable than the deltoid.  The biceps,
D, for example, in Fig. 73,—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 times
ten, or six hundred pounds to raise the weight.

                             Fig. 73.
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. 71,
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 
APPLICATION OF MECHANICAL PRINCIPLES.
353
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. 70,
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
Fig. 74.
 tendon, has great influence  on the
 power  developed by the muscles.
 There are but few straight muscles,
 in which  the fibres  have the same
 direction  as the  tendon.  Fig. 74
 will  exhibit  the loss  of power,
 which  the  fibres must  sustain  in
 proportion to the angle of insertion.
 The  fibre T J F would, of course,
 exert its whole force upon the ten-
sion, whilst the fibre  t  90°  would,
 by its contraction, merely displace
 the tendon. 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 calculated these proportions as fol-
 lows:—At an  angle of 30°, they  are as 100 to 87; at 45° as 100
 to 70; at 26° 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 disad-
 vantage 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 has to exert as  much force in resisting the
 bone which affords a fixed point at one  extremity, as in elevating
 the weight  at the other.  This estimate, if admitted, would elevate
 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 con-
 traction of the muscle.
   vol. i.                         45 
354
MUSCULAR MOTION.
  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 vertebra?, &c. augment the arm of the lever   *
and are  thus  inservient to a  like valuable purpose. The smoothness    ■■
of the  articular surfaces of bones,—tipped, as they are, with carti-    ]
lage, and the synovia, which lubricates the joints, by diminishing the
friction, also  augment the power, as well as  the  bursas mucosa-,
which are interposed wherever there is much pressure or friction.    ;
The trochleas  or pulleys  act only  in  directing the force, without
augmenting its amount; and the same may- be said of the bony ca-   :;i
nals and tendinous  sheaths,  by which  the tendons  of  the muscles,   .•!
especially those passing to the fingers  and toes, are kept in their yjm
proper course.                                                  ^3
   Still, it must be  admitted, that, as regards  the  effort  to be ex- .Jfl
erted by the muscles, it must, in  almost all cases, be much  greater "V)H
than the resistance it has to overcome.   The very fact  of the lever   £
of the  third  kind  being  that which  prevails  in  our movements   M
exhibits this.   The mere mechanician has conceived this to be an   J
unwise construction; and that there is a needless expense of force ;JB
for the attainment of a determinate end.   In all cases we find, that
the expense of power has been but little  regarded in the construe- jjS
tion of the  frame; nor is  it  necessary that it should have  been.-i'fjB
It must be recollected, that  the  contraction of  the muscle is  under ""73
the influence of volition, and that, within certain limits,  the force, to   M
be employed,  is regulated by  the influx sent by it into the muscles.  Jo|
The great object,  in the  formation  of the body, appears to have   q|
been;—to unite symmetry and convenience,  with the attainment of  <jj|
great  velocity and extent of motion,  so that, whilst  the power is   "^
moving through but 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  'ffl
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. 73, 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 con-
venient and symmetrical member into a cumbrous,  webbed  instru-
ment, badly adapted for the multitudinous  purposes  to  which it has
to be applied. 
APPLICATION OF MECHANICAL PRINCIPLES.
355
   The  same effect  results,  as  Sir  Charles  Bell  has remarked,
 from the course of  the
 tendons and their con-                  Fig. 75.
 finement  by  sheaths,
 strengthened  by  liga-
 ment.
   If the tendon A, Fig.
 75,  took the  shortest
 course  to its  termina-
 tion  at  B, it  would
 draw up the toe with
 more  force;  but  the
 toe  would lose its velo-
 city 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.
   Let  A B and C D, Figs.  76 and 77, be parts of two ribs, that
 are parallel, and
 will   continue                     Fig. 76.
i parallel till they
 are  brought  in
-contact  by the
 action   of  the
   aight  muscle
   F;  or by that
 of   the  oblique
 muscles F G and
 F  H.   Now, it
 is obvious,  that,
 when  the  point
 E comes in con-
 tact with F, the
 length,  of  the
  straight muscle
  E  F  must  be
  null; whilst that
  of   the  oblique
  muscles will only
  have  experienc-
  ed  a decurtation
  equal to G g and
  II  h,  Fig, 76;
  and to F g and
n_
llllllllllil[llll"R
"iiiiiill)
Fig. 77.
HDD 
356
MUSCULAR MOTION.
F h, Fig. 77.  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 extent.  We can, therefore, understand, why the intercostal
                                    muscles  pass  obliquely from
                                    one rib  to another,  as at  D
                                    and B  C, Fig. 78, instead  of
                                    in a direction perpendicular to
                                    the two ribs, as at A.
                                      There  are cases, however,
                                    in  which a  straight  muscle
                                    may pass between two parallel
                                    ribs, and carry them through
a given space, with less decurtation of fibres, than any oblique mus-
cle, which has the same  origin, but is inserted at a greater distance
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.
  Suppose A B and C D, Fig. 79, to be two parallel ribs, of which
                                                A B is  movable
                                                about A,  as  a
                                                centre; and sup-
                                 -3=E________   pose   it    to
Fig. 79.
brought,
 by
of
 be!
the
the
                                                action
                                                straight   muscle
                                                E  F, and of the
                                                oblique   muscles
                                              D E  G and  E H,
                                                into  the position
                                                Af.   The  points
of insertion of the muscles will now be at a, c, and  e, after having
traversed the spaces F a, G c, and H e.   If we, now, from the point
E, as a centre, describe the arcs c b 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 relative
position of any two bones, they, at the same time, change the direc-
tion 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 positions 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
which pass perpendicularly from one rib to the other, will act upon
each with equal  leverage, and each will  approach the other with 
APPLICATION OF MECHANICAL PRINCIPLES.
357
&
F
A
B
liiiinnHiMiiiii'fiiiiiiiiiiiiffityiJii:	.Miiiiin;i	iin	:i -imi'i.-	lllll , '|im> 1 h 1	
/ ^\					
illllliiiiiilllliiiiimiiiiiililllH'llillllniii	Miimi'imi'i1	'iiuii'	niiin.i n	'iLur'iiiiiniiri	
the same velocity; whilst those, which 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.                    Fig. 80.
80, to be two pa-
rallel  ribs, articu-
lated   with  the
spine  at A and C,
and that they are
equally  movable
on these centres
of motion.   Let
D B  represent  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, perpendiculars drawn  from the
centres of motion to the line of direction of the power.   These le-
vers,  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 lat-
ter approach the former,—in the ratio of C F to A C, or with three
times the velocity.
   In  all muscular motions, the levers of the power and of the resist-
ance are undergoing variation; so  that the degree of power, neces-
sary  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. 81, represent the os humeri; E  A the forearm; E
the elbow joint; W, a
weight or resistance,                  Fig. 81.
hung at the wrist, and
D the biceps muscle,
inserted at b, a tenth
of the distance down
the forearm.  It is ma-
nifest, that the force,
necessary for bending
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
 
358
MUSCULAR MOTION.
Fig. 82.
 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; it is 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 fore-
 arm 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 bi-
 ceps, in proportion as we  raise the arm,  the mechanical disadvan-
 tages 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 cen-
 tre itself is  often describing, at the same
 time, a curve.  In Fig. 82, let A B repre-
 sent the foot, B C the tibia, C D the thigh
 bone, and D E  the trunk; and let us sup-
 pose it is required to bring the body to the
 erect position B F; so that B C shall cor-
 respond 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 lat-   '
 ter, instead of describing  the curve D H,
 which it would do, were the centre of mo- E
 tion C fixed, proceeds along the curve D
 I;  the  point E, again, is subjected to  the
 like influence, and instead of describing the
 curve E K, which it would do if the cen-
 tre D were fixed, rises along E F..
   The  motions, produced  by the muscles,
 may be either simple or compound.  The
 simple muscles admit of variety;  some be-
 ing straight, composed of parallel fasciculi,
 others  reflected in their course, and others, again, are 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
 
ACTION OF SIMPLE AND COMPOUND  MUSCLES.
359
    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
j    brought to act on  the tendon, as in  the case of the deltoid, we find,
t    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-
f    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
m   insertion to  the point of reflection ; precisely as a rope, passing over
P   a pulley, raises the weight in a line  drawn from  the weight to the
f   pulley.
fe     The circular muscles, which have no precise  origin or insertion,
|jr~ are inservient to the contraction  of the apertures  around which they
K". are placed.
¥&■'  In executing the complex movements of any part of the frame, a
I*  combination of  the action of the different muscles,  attached to the
    part, generally occurs, rendering the  process one of a  complicated
m< character.  This, if no other cause existed, would render it extremely
w-- difficult to calculate the precise degree of force, which particular
mi; muscles,  alone  or  in combination,  are  capable  of  exerting.  The
}    mathematical physiologists made multifarious attempts in this direc-
h   tion; but their conclusions were most discrepant.  When we  bear
E" in mind, that the force,  capable of being exerted by any muscle, is .
 ■Edependent upon the proper organization of the muscle,  and likewise
 Eupon the degree of energy of the brain, it will be apparent, that  all
H&attempts  of this kind must be futile.  We can determine,  with nicety,
    the effect  of which the parts are capable, supposing  them inani-
•    mate  structures.   We can calculate  the  disadvantages,  caused
    by the insertion of the power near the fulcrum ;  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
i>'   that  mysterious  process, which generates a new force, and infuses
    it into the muscles, in  a  manner so unlike that in which the ordinary
o.' mechanical powers are exerted.  The  data, necessary for  such a
tj.   calculation, would be the precise influx from the brain,—the irrita-
    bility of the muscle,—the mechanical influences, dependent  on  the
    straight  or oblique direction of the fibres composing the muscle,
j    as regards the tendon,—the perpendicular or oblique direction  in
    which the tendon is attached to the  bone,—the particular variety of
if   lever,—the length of the arm of the power  and of that of the resist-
K  ance,—the  loss sustained from  friction, and  the diminution of such 
360
MUSCULAR MOTION.
loss caused  by the cartilages that tip the bones, and by the synovia,
&c.—data, which it is impossible to attain;  and hence the solution
of the problem is impracticable.
   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 distant muscles may be  concerned in  this fixation of
one  end of a  muscle, when it is excited to the developement of
plenary power, we will take the  case  of the deltoid.  This muscle
arises  from the scapula and  clavicle, and  is inserted into the  os
humeri; but the scapula and  clavicle, themselves, are not entirely
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 vertebra;  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 con-
tracted, 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 motion
may be partly regulated by the action of antagonist muscles.  Sup-
posing, 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 flexors of the head.  Hence, 
ATTITUDES.
361
    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 re-
    laxation ;  and, hence, this condition  has been invoked, as  affording
    evidence  of the comparative preponderance of particular antago-
    nizing muscles,—the flexors and extensors, for example.   In perfect
    sleep, when  no volition is exercised over the muscles, we find the
    body reposing in a state of semiflexion,—which seems  to show, that
    the flexor muscles have slightly the advantage  over the  extensors.
    Richerand,  in a memoir laid before the  Societe de Medecine of Paris,
    in 1799, assigned the following reasons for this preponderance.  First.
    The number of flexors is greater than that of extensors.   Secondly.
    The fibres, composing them, are more numerous and longer:—take,
    for examples, the  sartorius, gracilis, semi-tendinosus, semi-membra-
    nosus, and biceps, which  are  the flexors of the leg, and  the rectus
    and triceps cruris, which are its extensors.   Thirdly.  Their inser-
    tion 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  perpendicular; and Fifthly.
    Their arrangement is such, that the continuation 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 predominant; and,
i',   according to Adelon, experiments,  instituted  by Regnier with his
    dynamometer, make the extensors some kilogrammes  more power-
[    ful than the flexors.
      In our various attitudes, the movements of flexion certainly pre-
f"   vail largely; but as the power of contraction is regulated by volition,
  •  it is unnecessary to inquire, whether there be any physical predomi-
    nance in  the flexors over the extensors, as has been  attempted by
    Richerand.   We have already seen, that we can in no way attain a
    knowledge of the  degree of  force,  which  any  one muscle 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  classes—the
    active and the passive; the former, including those that  require a
    muscular  effort; 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.
I    The base  of sustentation—being  the space  comprised  between the 
362
MUSCULAR  MOTION.
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 sustenta-
tion, 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 imme-
diately falls forward.
  The head, which is  intimately united with the atlas or first verte-
bra of the neck, forms with  it a lever of the first kind, the fulcrum
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.
  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 seen by supporting a skull on the condyles; yet Mr.
Abernethy affirms, that" the condyles are placed so exactly parallel
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 prepon-
derate 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 vertebra]
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  inserted  perpendicularly into the  lever
or bone to be moved, which  is an advantage, and some  compensa-
tion 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 trans-
verse processes  of the vertebrae  and the occipital depressions are
larger; and, in addition, they have a strong ligament—the posterior
cervical or ligamentum  nucha—which  extends from  the  spinous
processes of the vertebras 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 for-
wards : the upper limbs; 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 for its 
ERECT ATTITUDE--ON BOTH FEET.
363
great firmness and solidity, which are readily appreciated, if we ex-
amine the  mode of junction  of the different vertebras,  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, to  support very heavy burdens,
in addition to the weight of the organs pressing upon it.
   The tendency of the spine to fall forward is resisted by the ex-
tensor muscles,  which fill the  vertebral fossae or gutters—the sacro-
lumbalis, longissimus dorsi, multifidus spinas, &c.  which pass  from
the sacrum to the lower  vertebras 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-
wards, and the resistance in the muscles attached to the spinous and
transverse processes.
   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         Fig. 83.
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 hori-
zontal.  We can, accordingly,  compre-
hend why fatigue should be  experienced
in the loins and  sacrum, when we  have
been, for  a long time,  in the erect atti- £ Kilr contain?'ihe  sptnai
tude                                       marrow.
                       • i  ,     11       c. Spinous process.
   It need scarcely be said, that the longer dd. Transverse processes.
and more horizontal the spinous processes, ee'  rllcu ating p,ocesses-
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 ilio-femoral articulations; the power  and resistance being
situated before and behind.
   The pelvis supports the weight of a part  of the abdominal vis-
cera ; and the sacrum that of the vertebral column, which, by rea-
son of its  shape, transmits the weight equally to the ossa femorum,
through the medium  of  the ossa ilii.  When the pelvis is, therefore,
in  equilibrium 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
 
364
MUSCULAR MOTION.
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, as well as muscles passing from the femur
to be inserted into the os pubis by the contraction of which the ex-
cess 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 the equilibrium of the  pelvis on the thigh
bones ; for the pelvis, instead of having a tendency to be depressed
posteriorly, would appear to bear forwards, inasmuch as the mus-
cles, that resist the  tendency  which  the spine itself has to bear for-
wards, have their fixed point on the pelvis;  and, consequently, exert
a considerable effort to draw it upwards.
   The strong glutasi muscles, which form the nates, and are inserted
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
the thigh bone, which, as represented in Fig.      Fig. 84.
84, B, joins the  shaft  of the bone  at  a consi-
derable angle.  The trochanters D and C are
for muscular attachments; and are,  of course,
advantageous to the muscles, which are insert-
ed 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 corre-
 sponds 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
 
ERECT ATTITUDE--ON BOTH FEET.
365
the strains produced by the wheel sinking with force into a rut or
other hollow. (See Fig. 64, and the plates of the skeleton.)
  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 equi-
librium.
  The tibia is the sole agent for 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
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 effect 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. 
366
MUSCULAR MOTION.
  Whatever diminishes  the base of sustentation, diminishes, in like
proportion, the stability of the erect attitude.  Hence the diificulty 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 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 na-
tives,  in consequence, habituate themselves to the use of stilts or
wTooden poles, the former of  which  are put  on  and off as regu-
larly 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.
  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 glutasi, the  gemelli, the tensor vaginas 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 provided with such a
fatty cushion  as  exists at the  sole of the foot, the  position becomes
painful and  the surface soon abraded.  These remarks 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 aug-
mented,—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 
MOVEMENTS.
367
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
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, which 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—partial  and  locomotive: the former simply changing  the re- 
368
MUSCULAR MOTION.
lative 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 with-
in the base of sustentation.   Accordingly, to produce this  effect, 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
whole  of the cervical vertebras 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 arises 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
vertebra dentata: 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 op-
posite 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  vertebras  composing it,
are capable of flexion, extension, lateral inclination, and circumduc-
tion.  These motions occur  in the fibro-cartilages between the ver-
tebras ;  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 invertebral substances or fibro-cartilages possess a remarkable
degree of elasticity.   They  yield somewhat, however, 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 as-
serts, that  the son  of one  of his most zealous collaborateurs,  M.
Gueneau de Montbeillard,—a young man of tall  stature,—lost an
inch and a  half  after having danced all night.  The loss  must be
partly ascribed to the condensation of the adipous tissue  beneath the
foot.
  During the flexion of  the spine, these cartilages  are depressed on 
MOVEMENTS.
369
    the side of the flexure, but they rise on the other;  and, by their
    elasticity, they are important agents in the restoration of the bodv
    to the erect position.   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 laminas.
    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 vertebras becomes modified.  If we bend forwards,
    it is thrown to the anterior  part of the body of the vertebras, 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-
    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 ver-
    tebra, and the arm of the  power being the distance  between  this
fj£k •boint 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 it is estimated by multiplying
    the single motion by the number of vertebras.  The result, however,
    can only be regarded  as approximate, as the. extent of motion, of
    which the different vertebras are capable, necessarily varies.
      The arrangement of the spinous processes of the vertebras—espe-
    cially 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 arrangement of the
    spine having been modified, in  early life,  by constant efforts of this
    kind,  until they are no longer obstacles to the movement.
     The motions of the vertebras are frequently united to those of the
    pelvis on the  thigh bones, so that they seem to be more extensive
    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
        vol. i.                    47 
370         MUSCULAR MOTION—LOCOMOTIVE MOVEMENTS.
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.
   Thus 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 different varieties of locomotion or progression.

                      LOCOMOTIVE MOVEMENTS.

                             Walking.

   Walking is a motion on a fixed surface, the centre of gravity be-
ing alternately moved by one of the extremities and sustained by 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 detach the foot
from the ground by the general decurtation of the limb. The flexion
of the limb is  succeeded  by its being carried forward; the heel is
then brought to the ground, and, successively, the whole of the  in-
                                 ferior surface of the foot.  If the
             Fig. 85.             bones of the leg were perpendicu-
                                 lar to  the part which first touches
                                 the ground, we should experience
                                 a 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 carried forward the corresponding side of
 the body.   As  yet, only one limb  has advanced.  The base ot sus-
 tentation has been modified, but there has been no progression.  Ihe
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 ol
 the trunk, and excites the  rotation of the pelvis on the head ot  tne
 thigh bone  first carried forward.   A succession of these  movements
 constitutes  walking; the essence of which consists in the heads ot
 the thigh bones forming fixed points, on which the pelvis  turns alter-
 nately, as upon a pivot, describing  arcs of circles, which are more
 extensive in proportion to  the size of the steps.
 
WALKING.
371
     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 towards
   the side opposite to that of the limb, whose movements are more ex-
   tensive.  Without the  aid of vision, it would be impracticable for
   us to make the arcs equal; or, in other words, to walk straight for-
   ward.
     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.
   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.
tf   • 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
■a. brought down to the ground.   The other limb follows.
K,  ; If we walk up hill, the fatigue is much augmented; because the
   flexion of the  limb, first carried forward,  has to  be more con-
   siderable ; 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 forwards,
   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.
   Fatigue  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 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 
372         MUSCULAR MOTION—LOCOMOTIVE MOVEMENTS.

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 elacticity.   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 sustentation is
enlarged by separating the legs so as to give a characteristic 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  re-
quired—by the use of a long  and heavy pole.

                             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 direct-
ly 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 suc-
ceeded by a quick  extension  ©f all the bent joints; so that the dif-
ferent parts of the body are rapidly elevated, with  a force surpass-
ing their own gravity, and to an extent dependant 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, which  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 82 will show, that whenever the body is bent in the posi-
tion  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. 
LEADING.
373
     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 forward  leap, in particular,  is greatly  dependant 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
   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
fe•*< separated from it, at the moment when the body leaves the soil.  By
El', being held firmly in this manner, they allow the muscles, that pass
lfe>Jrom the os humeri to the trunk, to exert a  degree of traction up-
   wards, and thus to assist the  extensors of the foo't in the projection
   of the body.  It is with  this  view,  that the ancients employed their
   «Xr?jps£,  (halteres or poisers) in  leaping; and  that 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 rapidly 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, neces-
   sarily 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  as Mr. Sharon Turner has remark-
   ed, in his  * Sacred History of the World,' exhibit muscular powers
   still more superior to those of the  greatest animals than  their com-
   parative minds.  He has given some amusing representations of this
   difference:—for example, Linnasus observes, that if an elephant were
   as strong in proportion  as a stag beetle, he would be able to tear up
   rocks and to level mountains.  A cock-chafer is, for its size, six times
   as strong as a horse.   The  flea and the locust leap two hundred
   times their own length, as if a man should leap three times as high
   as St. Paul's.  The cuckoo-spit frog-hopper will sometimes leap two 
374
MUSCULAR MOTION--LOCOMOTIVE MOVEMENT?.
or three yards, which is  more than two hundred and fifty times its
own length, as if a man should vault at once a quarter of a mile.
Mouffet relates, that an English mechanic  made a  golden chain as
long as a finger, with a lock and key, which was dragged by a flea:
and Latreille mentions  sc flea, of moderate size, dragging a silver
cannon on wheels, that was twenty-four times  its own weight.  This
cannon was charged with powder and fired, without the flea seeming
to be alarmed.

                            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
being raised  before the fore-foot touches the ground.  It is more
rapid than the quickest  walk, because the acquired velocity is pre-
served and increased, at each bound, by a new velocity.  Running,
therefore, 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 ad-
vanced,  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.

                           Swimming.

   Although  Magendie  affirms, that the human body is, in general,
specifically heavier than water, and that consequently, if left to itself
in a considerable quantity of that  fluid, it would  sink to its  lowest  '
portion,  the  question  respecting its  specific  gravity  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  Transactions,—seems to  have originally coin-
cided 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  circumstance connected with his own personal knowledge.
A young gentleman, thirteen years  of age,  little  acquainted with
swimming, fell overboard from  a vessel in a stormy sea; but having 
SWIMMING.
375
   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  precau-
   tion 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 Niagara, 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 captain  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 consider-
   ed 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 quar-
   ter 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, expecting that the canoe would come
   every moment to his  assistance.  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 cap-
   tain'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 bath-
   ing, 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  per-
   fectly 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 particularly 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
A 
376
MUSCULAR  MOTION--LOCOMOTIVE MOVEMENTS.
one inch at every inspiration, and sinking one inch at every expira-
tion ;  and also, that clothes give little additional weight in the water,
although, in stepping out of it, the case is quite otherwise.   He con-
cludes, therefore, if a person, could avoid struggling and  plunging,
that he  might remain in the posture described with safety.  That the
body is to a certain degree buoyant he  refers to the experience of
every one, who has ever attempted to reach the bottom of deep wa-
ter, the effort required sufficiently proving, that something resists our
sinking.
   The truth would appear to be, that there is only a slight difference
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 spe-
cific 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  esta-
blished than that no water gets into the stomach, except  what is acci-
dentally 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 absence
of water in these situations  has  been looked upon  as evidence,—
where a body has been found in the water,—that death had  not oc-
curred from drowning; and attention  has, consequently, been direct-
ed to other causes, which  might 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.
   AH these fallacious notions are dwelt upon in a case, deeply inte-
resting  to all jurists, medical and others;—that of Spencer Cowper,
Esq. a member of the English bar, who, with three other individuals,
was tried at the Hertford  Assizes, in  1699, for the murder of Mrs.
Sarah Stout.  The speeches of the  counsel, with the evidence 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 won-
dered at; for, in the first place, it is contrary to  nature, that any per-
sons,  that drown themselves, should float upon the water.   We have
sufficient 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 engage- 
SWIM.MINti.
377
ment, 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 gene-
ral 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 ren-
ders them buoyant, by the disengagement of air into the splanchnic
cavities.
  On the  same trial, Drs. Coatsworth, Burnet, Nailor, and Wood-
house 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
bo.  This conviction being acquired, no more than a common  share
of presence of mind would seem to be necessary to insure, that the
portion of the body, which is the great outlet of the respiratory or-
gans, 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;—proficiency
in this, as in everything else, being the  result of pratice.
   Swimming nearly resembles leaping, except that the effort in it
does not take place from a fixed surface.   Both the upper and  lower
oxtremities 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, the hands and feet being 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
bod}% and,  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
   vol. i.                       18 
378
MUSCULAR MOTION.
resembles the boat;  and the  upper and lower extremities 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 Dasdalus
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 flying, are;—the great weight of the
body, and the insufficient force, which the  muscles  are capable of
exerting.  It  is by no means impossible, however, that by some con-
trivance, 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.
   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 cause 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. 
MUSCULAR  MOTION.
379
  On the other hand, when we drag a weight after us, or attempt to
dislodge a stake 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

 ' Squeezing consists in laying  hold of the object, either between the
arms and body, or by the  fingers; and then forcibly contracting the
flpTrov 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, closing the glottis to  prevent the exit  ot
the air.                           t          j             c  ,
   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—the
scapula  and clavicle—are  themselves  movable.  The forearm  is,
likewise, susceptible of various movements on the arm, of which those
of pronation and supination  are  not the least important; whilst the
hand  possesses  every requisite for an  organ  of prehension.  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 sphe-
 rical bodies; to take  up any object; to lay a firm hold of whatever
 we  seize, and to execute the various  useful, and  ornamental pro-
 cesses 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  accurate  the  muscular con-
 traction, 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 oro-an of touch, the advantages of the upper extremity have
 already beeri depicted; and much of what was then said  applies to
 it as an organ  of prehension.  "In this  double respect," observes 
380
MUSCULAR MOTION.
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 remarked, he has,  in  his organization,
neither the offensive nor defensive arms, that arc 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 labour 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 ex-
tremity.  In short, whilst other animals find  everything 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
execute."

          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 address-
ed  to the  car, or the  phenomena of voice: and those that  are ap-
preciated by the senses of sight and touch, or the gestures.  Of these
we shall treat consecutively.

                          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 fossas.   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 fossas have been, or will have to
be, described  in other places.   The larynx, and its primary depen-
dencies, which are immediately concerned in  the production of voice,
will, therefore, alone engage us at present. 
EXPRESSION.
381
  The larynx is situated at the anterior part of the neck, and forms
the projection so perceptible in that of the adult male, called pomum
Adami.
  An attentive  examination of the various parts which compose the
larynx, 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 entertained on the 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 in-
ferior 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  cornua.
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 at-
 tachments—crico-arytenoid.  The  arrangement of this  articulation
 would appear  to  permit only of lateral movements of the arytenoid
 cartilages on the cricoid;  all motion  anteriorly or posteriorly, or in
 any other direction, being  impracticable.   The joint, consequently,
 is a lateral ginglymus.
   Three fibro-cartilages, likewise, form part of the constituents of
 the larynx.  These are—the epiglottis,  and two  small  bodies, that
 tip the arytenoid cartilages, and are met with only in man—the capi-
 tula  Santorini or the  supra-arytenoid cartilages  or the  capitula
 cartilaginum arytenoidarum.
   On examining the interior of the  larynx, we discover, 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 cartilage and epiglottis;
 posteriorly, by the  arytenoid cartilages; and, laterally,  by  two folds
 of  the  mucous  membrane,  C C,  Fig. 88,  which pass  from  the
 epiglottis  to each  arytenoid cartilage, and  are called  the superior
 ligaments of the glottis, and  the supeiior  vocal cords.   A  few lines
 below  this is a second cleft, also  oblong from before to behind,
  (1, Figure 87,) and of  a  triangular shape, the base   of  which 
382
EXPRESSION--VOleE.
is  behind.    It  is  bounded,  anteriorly, by the  thyroid cartilage;
posteriorly, by a muscle extending  from one arytenoid cartilage to
the other—the arytedoineus;  and,  laterally, 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. 87  ; and by B B, Fig. 88.


              Fig. 86.
Larynx seen externally.
           1. Os hyoides.
           2. Lesser cornu of do.
           3. Greater cornu of do.
           4. EUreniity of the Epiglottis.
           5. Hyothyroid membrane
           6. Thyroid Cartilage.
           7. Cricoid Cartilage.
           8. Trachea.


   Between these  two clefts  are the  sinuses or  ventricles of the

larynx, V V, Fig. 88.  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 
VOCAL APPARATUS.
383
Fig. 88.
Section of the Larynx.
                      and inferior apertures are perfectly 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
                      space between the inferior ligaments with the
                      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
 group exists  between  the epiglottis behind, and the os hyoides
 and thyroid cartilage before, which has been termed  the  epiglottic
 gland.  The uses of this body are not clear.  Magendie conceives,
 that it favours the frequent  slidings of the thyroid cartilage over the
.posterior surface of the os hyoides; that it keeps the epiglottis  sepa-
 rated above from this bone  ; and, at the same time, furnishes it a very
 elastic support, 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 margin  of  the thyroid.
 Magendie  affirms, that its  use is not, as generally imagined, to de-
 press  the thyroid on  the cricoid, but to elevate  the cricoid and ap-
 proximate it to the thyroid, and even to  make it pass slightly under
 its  inferior  margin.   2dly.  The  crico-arytenoidei postici, and  the
 crico-arytenoidei laterales; the former of which pass from the posterior
 surface of the  cricoid fo the base  of the arytenoid; and  the latter
 from the side  of the cricoid to the base of the arytenoid  cartilages.
 The use of these muscles is to carry the arytenoid cartilages back-
 wards, separating them at the same  time  from each  other.   3dly.
 The arytenoid muscle—of which there is one only.  It extends across
039999999� 
384                    EXPRESSION--VOICE.
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 muscles of the  larynx, as  its vibrations produce the vocal
sound.   It forms the lips of the glottis, and Magendie describes it as
constituting, also, " the inferior, superior,  and lateral parietes of the
ventricles of the larynx."  Generally, it is considered to  arise from
the posterior surface of the thyroid cartilage, and the ligament con-
necting it with the  cricoid, and  to be inserted into the anterior ed<*e
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 vestiges  of the glolto-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 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, 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. 86, 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, may throw certain
parts into vibration, and afterwards make its exit by the  vocal tube,
—that is, by the mouth and nasal fossas.
   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.
  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 
THEORY OV VOICE.
385
   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 fistulas 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 ary-
   tenoid 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  ac-
   cording  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.
„. 4 Paralysis of the intrinsic muscles of the larynx likewise produces
■Uiumbness; and this can be affected artificially.  Much discussion
   at one time prevailed, regarding the effect of tying or cutting  the
i   nerves distributed to these muscles.  The experiments of Haighton
t  induced  him to think,  that the recurrent branches of the par vagum
E' supply parts, which are essentially necessary to the formation of the
E voice; whilst the laryngeal  branches seemed to him to affect only
Kjts modulation or tone.  Subsequent  experiments have sufficiently
   sllown, that if both the recurrent nerves and the  superior laryngeal
   are divided, complete aphonia must result.  Magendie found, indeed,
   that, when both recurrents,—which, as  has been  remarked, are dis-
V  tributed to the thyro-arytenoid muscles,—are cut, the voice is usually
li  lost; whilst if one only be divided, the voice  is but half destroyed.
   He  noticed,  however, that several animals, in which  the recurrents
j   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 distribu-
   tion of the nerves of the larynx.   The recurrents being divided, the
   thyro-arytenoid muscles are no  longer capable of contracting, and
   hence aphonia results; but the arytenoid  muscle, which receives its
   nerves from  the  superior  laryngeal, still contracts,  and, during a
   strong expiration, 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 he.  in a state of contraction.
     Again, every part of the larynx, with the exception of the inferior
       vol. i.                      49 
386
EXPRESSION--VOICK.
ligaments, may be destroyed, and yet the voice may continue.  Bi-
chat 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,  destroyed
the glottis.   Lastly, when the larynx is exposed  in a living animal,   j
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 csscn-  " $
tial organs of voice.
   The deeply interesting,"but difficult problem now presents itself;—
 to determine the precise mechanism of the vibration of those liga-  ^|
 ments;  and what kind of instrument the vocal  organ must be re-  ,Jj
 garded.  The latter question, on which, it might be conceived, so  fc:
 much physical evidence  must exist, has been the topic of  much dis-  • t
 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 ,^jj
 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  can- ^s
 not be regarded  as  the body of the flute, but as a porte-vent to con-  ~
 vey the air to the glottis.   He was of  opinion, that the glottis  cor-
 responds 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 Blu-
 menbach, Sommering, Savart, &c.
    About the commencement of  the last century Dodart  laid before
 the Academie des Sciences  of Paris, three memoirs on the theory of
 the voice, in which he  considered the  larynx to be a wind instru-
 ment of the horn, and not of the  flute, kind; the inferior ligaments 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 Academie
 des Sciences maintained  that the larynx is a stringed instrument;—
 the sound resulting from the oscillation caused in what he called the
 corda vocales, or the inferior  ligaments of the larynx, by the air in

   * The flute here alluded to, ie the common flute or flute a bee, in which the embou-
 chure is at one extremity. 
TONE OF THE VOICE.
3s^
   expiration; and  a modification  of this view was professed by Dr.
   Young.
     At the present day, the majority of physiologists and natural phi-
   losophers 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 almost all are agreed, that it is produced by
   the  vibrations  of the  inferior ligaments of  the glottis.   Piorry, and
   Jadelot consider the glottis to be an instrument sui generis, eminent-
   ly vital, and which, of itself, executes the movements  necessary for
   the production of vocal sounds;  but all we  know, of the physiology
   of the production of the voice, is—that the expired air is sent  into
,   the larynx by the muscles of  expiration,—that the intrinsic muscles
   of the larynx give to  the inferior ligaments sufficient tension to di-
   vide 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
ti case of the voice, it is partly dependent upon the force with which
p£ the air is sent from the lungs, and  partly on the size of the larynx.
i  A strong, active person, with a capacious chest and prominent pomum
i  adami,—in other words, with a large larynx,—is of an organization
m  the most favourable for a strong  voice.  But if this same individual,
v  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,
'r   of the eunuch, or of the child.  This is greatly owing to his larynx
W..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,
[*'  which has supervened in the  lips of  the glottis.   As voice is com-
   monly 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, ceteris paribus, one-half its in-
   tensity.   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 calcu-
 <  late 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-
   gether with all the combinations  of which  they  are capable.  The
   muscles, proper to the five cartilages of the larynx,  are,  at least, 
388                    EXPRESSION--VOICE.

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 estimated to be capable of producing upwards of sixteen thousand
different 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
larynx, or the  muscles restricted in their attachments to itsfive 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
 degrees of force, velocity, &c. with  which they  may be brought
 into action.
   But these muscles  are not  the whole that  co-operate with the
 larynx, in the  production of the voice.  The diaphragm, the abdo-
 minal muscles,  the intercostals,  and all, that directly or indirectly  ; ij
act on the air, or on the parts to  which  the muscles of  the glottis  J
or os hyoides are attached,—in short,  all the muscles  that receive^
 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  move-
 ment  of which the vocal  apparatus  is directly  or indirectly  sus-
 ceptible.
   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-
 tions, 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 embou-
chure.  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 descent
or depression   of  the  larynx,  which shortened  the  body  of the
instrument—the trachea; whilst  the  grave  tone, he thought,  was 
                       TONE OF THE VOICE.                    380

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 descend-
ing in the case of acute tones,  and  rising in that of grave, the
reverse is the fact;  and, accordingly, what Galen calls the musical
tube,  in man,  is elongated in the formation of acute  tones, and
shortened in the  case  of grave,  which,  every flute-player knowrs,
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 diminish-
ed in  the former case  and augmented in the latter,  as  in  the  artifi-
cial instrument.
   In the theory of  Dodart, to which  allusion has  been made, the
jdjuman  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 chords were'stretched and shorten-
ed.  For grave tones, they were relaxed, and, consequently, longer.
 He was of opinion, that the  length of the vocal tube had no influ-
ence  on the tone.  Ferrein  supported  his theory  by experiments,
performed before  commissioners  appointed by the Academie  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 recognized—that, at the time of the produc-
 tion 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-
sion  and length  of the vocal cords;  and,  according as one-half,
 two-thirds,  or  four-fifths of each chord was made  to vibrate, the 
390
EXPRESSION--VOICE.
octave above, the fifth, or the third, or of the fundamental note was
obtained.   The  result was  the  same,  whether the  two  chords
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 "vo-   .j
cal cords" are not sufficiently dry, tense, or insulated, to execute vi-
brations,  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 academicians, who were pre-
 sent 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 the sounds, the vocal cords acted like the    j
reed.                                                              ,
   Of late years, several new views have been propounded  on this   *
subject, and chiefly by Cuvier, Dutrochet, Magendie,  Biot, Savart^H
&c.—men of the highest eminence in various departments of physi-    *
 cal science.
   Cuvier attributes  the variety of tones, in the first place, to the va-
ried 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    J
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-   ";j
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 \.H
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
the  glottis;  but its influence appears to be greatly limited to giving 
                       TONE OF THE VOICE.                    391

 it rotundity, volume, or the contrary, as will be seen hereafter; al-
 though 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 exter-
 nal 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 in-
 strument, 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
 eliciting, comprised only one octave: 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-arytenoid mus-
u cles  naturally draw them ; 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.
b-  In these experiments,Dutrochet saw the inferior ligaments vibrate;
  and  he concludes, that the tone of the voice  depends upon the num-
 ber  of vibrations of these ligaments in a given time, and that the
  number will necessarily vary considerably, as the dimensions of the
  ligaments,—that is, their length, and thickness,—and their elasticity
  are susceptible of incessant changes, by the  contraction of the thyro-
^ arytenoid muscle of which they are essentially composed,—the liga-
  ment, 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 impor-
  tant points.  Like him, they do not consider the human larynx to
  constitute  a stringed instrument.   They  regard it as a variety 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 cartilages,
  which admits of motion inward and outwards only, but they ask how
  the vocal cords can attain the length they would require for the pro-
  duction of grave tones;  and how these cords could elicit sounds of
  a volume so considerable as those of the human voice.  They  es-
  teem it, consequently, as a reed instrument—of such nature as to be
  capable of affording  very grave tones with a pipe of little  length;
  and  such that the  same tube, almost without varying its length, is 
392                    EXPRESSION--VOICE.

susceptible, not only of furnishing a certain series of sounds in har-
monic progression, but all the imaginable sounds and shades of
sounds, in the compass of the musical scale, which each voice em-
braces.
  In  the  reed  instrument,  comprising  the  clarionet,  hautboy,
bassoon,  &c. two parts are  distinguished,—the reed, and the tube   )
or body.  A reed  is  generally formed of one,  sometimes of two,   ]
thin  laminas,  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 produces and modifies the
sound.  If the lamina be long, the movements are extensive, slow,
and, consequently, give rise to grave sounds; a short lamina, on the
contrary, produces acute sounds,  because 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, 'J
—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, however, has no influence  upon the   j
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 basei£3
outwards.  If the cone be inverted, the sound  becomes  dull; but if  '■.
two similar cones are  applied, base to  base, and adjusted to a coni-   ?
cal tube, the sound  assumes rotundity and force, an effect, which has
not been accounted for by the natural  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 if generally becomes necessary to establish,   i,
beforehand,  an accordance between the  reed and the  body of the
instrument; and, when we are desirous of obtaining different 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 accordance has
the additional advantage of facilitating the production of any desired
note from the reed, by means of the lips.   The  influence of the tube
is very evident in the narrow instruments, as the clarionet and haut-
boy, 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
apply to the human vocal apparatus.   The lips of the glottis are the
reed and the thyro-arytenoid muscles render them fit for  vibrating. 
TONE OF THE VOILE.
393
 In his  experiments, made on living dogs, Magendie saw, that when
 grave  sounds were produced, the ligaments of the glottis  vibrated
 in their whole extent, and the expired air issued through the whole
 of the glottis.   In acute sound, on the other hand,  they  vibrated
 only at their posterior part, and the air passed out through the part
 only that vibrated,  the aperture being,  consequently, diminished;
 and, when the sounds  became very  acute,  the  ligaments  vibrated
 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 power producing almost all
 the  acute tones;  the voice, at the same  time, acquiring a degree
 of  habitual  graveness,  which  it  did  not previously  possess.
 The  influence of contraction  of the thyro-arytenoid muscles  on
 the tones, he considers,  are  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:—MM. Biot, and Magendie however  in-
 clude,  in their theory of the voice, the  action of the vocal tube, like-
 wise. 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  rela-
 tion with  the larynx,—and thus  of favouring the production of the
 numerous 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
 arrangement 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,
 shortened in the former case; elongated in the latter.  It experiences
 also a simultaneous change in  its width.   When  the larynx de-
 scends,—in other words, when the vocal tube is elongated, the thyroid
 cartilage  is depressed  and separated from the  os hyoides by the
 whole  height of the thyro-hyoid membrane.  By  this separation, the
 epiglottic  gland  is carried forwards, and lodged  in the concavity at
  vol. i.                       50 
394
EX PRESSION--VOICE.
the posterior surface of the os hyoides.  The gland drags after it the
epiglottis; 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, Ma (rendie
considers to be, to  isolate the inferior ligaments, so that the? 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 remedy
this inconvenience, Grenie found no 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, with-
out 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
laminas; 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 laminas; 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 its length, whilst in the laminas of the
larynx  the width varies.  Lastly, say they, in  musical instruments
reeds  are  never employed,  whose  movable laminas   can vary in
thickness and elasticity every moment, as is the case with the liga-
ments 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 re-
ferred the vocal organs to an instrument of the flute kind.
   The objections, which he makes to the doctrine, that likens it to a
reed instrument, are the following. 
TONE OF THE VOICE.
395
     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,
   according 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 withheld.
     Again, there is nothing in the sound of the voice, which resembles
   that of a reed, even of the best formation; and, lastly—he  remarks—
   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 lube situated above the glottis;
   and yet it cannot be  doubted, that these parts are  important 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 ex-
   ertion, 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 larynx
   is a reed instrument.  The sounds of the human voice have, indeed,
   he remarks,  a peculiar character, which no musical instrument can
f  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
V  for any of our instruments.   He conceives, that the production of the
£  yoice  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 susceptible of ren-
   dering sounds of a  particular  nature, and at the  same  time,  of a
   much more  grave character than the dimensions  would seem  to
   admit.
     In the  tube of a flute the column  of air, within, is  the sonorous
   body.   A sound is first produced at the embouchure of the instrument,
   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.
     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 one so little  variable in length, tones so different,
   and especially so grave, ran be produced. 
396
EXPRESSION--VOICE.
'"""""'«  ...........
ITfl'iiiit.l.l I .Uil......n1
  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. 89.
three-fourths of an inch in diameter, and a third of 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,               I
as A A, Fig. 90, when it is capable of producing               ;
all the sounds comprised  in an  extent of" from an   -^-;        JA
octave  and  a  half  to two  octaves.   M.  Savart      !         i
found, that, other things being equal, the diameter      !         j
of the apertures has an  appreciable  influence on      !-'"*'N-..J
the  acuteness or graveness  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  quality of the sounds; and if, in
the hemispherical whistle, Fig. 90, the plain plate was replaced by a
thin leaf of some extensible substance, as parchment, the sounds is-
sued more  readily,  and were, usually, more grave, full,  and agree-
able, than when they were formed of a more solid substance.
  It is an opinion, generally admitted, that  the material, which com-
poses an organ pipe, has  no influence on  the number of vibrations,
which the  column of air, contained in it,  is capable of executing.
This is true as  regards  long pipes; but, according to Savart, it is
not  so with the short, and the nature of the biseau* he conceives,
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,
  * The biseau or fanguette is the diaphragm, placed between the body of an organ
pipe and its foot. 
I'ONE OF THE VOICE.
397
formed of some elastic substance, as skin or parchment, and so ar-
ranged as to admit of being stretched at pleasure;  by gradually in-
creasing the tension of the membrane, at the same time that we in-
crease 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 different  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 con-
tain, and when  their degree of tension can be, moreover, varied, they
have such an influence on the number  of vibrations, that the  sound
it seems 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 musical 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, pyra-
midal, &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 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 liga-
ments.   These surround the upper aperture of the  instrument, and 
398
EXPRESSION —VOIC E.
 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.  I his sound acquires intensity, because the  waves, that
 constitute it,  are extended into the vocal tube situated above the
 arynx  and excite, in the column of air  filling it, a movement simi-
 lar 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, suscep-
 tible of varied tension; and the  mouth, by modifying the dimensions
 of the column of air  within  the vocal tube, exerts an influence on
 the number of vibrations which the column  is capable of experi-
 encing; whilst the lips can convert the channel at pleasure into an
 open or closed  conical tube.  Certain  sounds, Savart  affirms, are
 produced altogether in the ventricles of the larynx—those of pain
 and  the falsetto 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. 88, a striking
 analogy to the action of the bird-call; and, in this way, he explains
 the use of the superior ligaments C C, which are entirely overlooked
 in the different theories 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
 function.  Our notions on  this  point must  not, therefore, be  con-
 sidered definite.   Farther experiments are  necessary;  and, in all
 deductions from  them, great importance will have to be  attached to
 the-vital action of the  organs, especially of the intrinsic  muscles,
 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 
                         TIMBRE OF THE VOICE.                   399

   unexplained.   The same remark inapplicable 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
   female, is connected with the osseous  condition of these parts, and
   especially  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
E  may resemble each other in every other respect.
r    The  form  of the body  of  the instrument  has, also,  considerable
W  effect.   If it be conical, and wider  towards its outlet, as in the cla-
■*-■nonet, 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
K-'presence or  want  of teeth, &c. all of which  circumstances modify
f$ the voice considerably.   The first modification takes place, probably,
   in the  ventricles  of the larynx, in  which the voice requires more
   rotundity and expansion.
     By the  generality of physiologists, it is conceived, that the voice
   enters the  different nasal fossas, 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 fossas, the vocal sound becomes dis-
   agreeable  and nasal.   Simple experiment,  by holding the nose, ex-
   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
   fossas be pervious—the m and the n, and the ng,  for  example.  It
   would  seem that, under ordinary circumstances, the sound, after it 
400                    EXPRESSION'--VOICE*.

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 fossa?,
the voice becomes nasal.
   The fine, sharp voice prior to puberty is especially owing to the
narrowness of the glottis, to the shortness of the ligaments, and, ac- •
cording to Malgaigne, to want of developement of the nasal cavities.
At puberty the  size  of  the opening of the larynx is  doubled:  the
ligaments  enlarge, and the  meatuses of the nose are augmented.
The timbre now becomes raucous, dull and coarse, and for a time its
harmony is lost.   M. Bennati, himself an excellent theoretical  and
practical musician, whose voice marks three octaves, advises,  that
the  voice  should  not  be much  exerted during this  revolution.
He has known perseverance  in singing at this  time completely de-
stroy the voice in several instances.
   Not only does the  voice, when produced in the  larynx, pass  out
by the vocal tube, but it resounds along the tracheal and  bronchial   ;
tubes, giving rise to the resonance or thrill, which is audible in certain
parts of  the chest more especially, when the ear or the stethoscope  ''""
is  placed over  them;  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 stethoscope be  used.  In this case,  the voice will ap-
pear to pass directly through the tube to the ear, when the extremity: . .'<
of the instrument is applied over the vomica, so as to give rise to what"'  ''■■
Laennec terms pectoriloquy.  Adelon conceives, that this distribution  "j
of the  sound, along the trachea or porte-vent  and the lungs, may in-  •
duce 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, which 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 indivi-
duals,  capable  of not  only imitating  various kinds of birds, but the
timbres of different musical instruments; and the success which has
attended the personation of the different voices of public speakers, by
Matthews, 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 polyglottis or mocking bird, which is capable of imitating, 
                         •  VENTRILOQUISM.                     401

  not only the voices of other  birds, but  sounds of other character,
  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 engastrimism
  or ventriloquism.   Both these terms, by their derivation, indicate the
  views,  at  one time entertained, of its  physiology,  namely,  that the
  voice of the ventriloquist is made to resound in the abdomen,  in some
  inexplicable manner, so as to give rise  to the peculiarity it exhibits.
  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 great-
  est perfection, I was soon convinced, that the name  of ventriloquism
   is by no means applicable."—M. Richerand  was probably  the last
   remnant of the ancient vague hypothesis, and his views soon under-
   went a conversion.
     Another, equally unfounded notion, at one time entertained, was,
   that the  ventriloquist  possesses  a double  or triple larynx.  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
w,proceeding from  it.   We instinctively believe, that a loud  sound
E 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 mare
   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.  Mr. Dugald Stewart gives some striking  examples of
   this kind of illusion.  He mentions having seen a person,  who, by
   counterfeiting  the actions of a performer on the  violin, whilst he
   imitated the music by  his voice, riveted the eyes of the audience on
   the instrument, although every sound they  heard proceeded  from his
   own  mouth.   Mr. Savile Carey, who  imitated  the whistling of the
   wind through a narrow chink, told Mr. Stewart,  that he  had fre-
   quently practised the deception  in  the  corner of a  coffee-house, and
   that he seldom  failed  to  see some of the company rise to  examine
   the tightness of the windows, whilst others, more intent on the news-
   papers, contented themselves with putting on their  hats, and button-
   ing their coats.
     vol. i.                          5* 
 402                EXPRESSION--VOICE.

   It is to account for the mode in which this is effected, that  dif-
 ferent hypotheses have been, from time to time, entertained. Haller,
 Nollet,  Mayer, 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 ventrilo-
 quism to be  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  ex-
 piration, which is always preceded by a deep inspiration.  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, selecting 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.
 Gough, to be placed designedly by the ventriloquist on one or both
 sides of him.  A sufficient answer to this is, that the practised ven-
 triloquist is  careless  about the room, chosen 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 Austrian
 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 vibration.
 His object must evidently have been to mislead.
   In 1811, M. Lespagnol, a young physician, maintained a thesis
 on this  subject before the Faculte de Medecine of Paris, which may
 be regarded, as at least, an honest exposition of his beliel, 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 fossas.  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 difference, says Iiespagnol, 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, to permit this direct
sound only to pass to the ear,  to prevent the nasal sound from being 
                             VENTRILOQUISM.                     403

[    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 fossas;  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 determinate place,
    it  is owing  to the ventriloquist  attracting our  attention to it; the
    voice itself need only appear to proceed from a distance;  and this
    it does more or less, according as the pendulous veil  has  more  or
    less completely prevented the vocal sound from issuing by the nasal
    fossa.  The  ventriloquist, thus,  according to M. Lespagnol, makes
    the voice nearer or more remote  at pleasure, by raising or depress-
    ing the velum  palati.  He denies that  he  speaks with his mouth
    closed; and affirms, that he articulates, but to a trifling extent only.
       M. Comtc,  another ventriloquist,  and of  some  celebrity, who
    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
    the action of other parts of the apparatus; inspiration directing it
    into the thorax, where it resounds; and that both strength and flexi-
    bility are required  in the organ  to produce this effect.  This, how-
    ever, is no  explanation.   It is  now universally admitted,  that  the
r    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 apparatus, but the  particular action that produces it is not
    elucidated by  any of these attempted explanations  of the ventri-
    loquist.
* •      About twenty years ago, Dr. John Mason Good, in some lectures
$■   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 ca-
    pable of answering the  purpose, and  of supplying the place of the
(J£<Uftssociate 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, loo,  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 
404
EXPRESSION--VOICE.
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, who  yet
possessed  the faculty of speech.  To these we may add one other,
which excited unusual interest at the time,  and was examined under
circumstances, 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 Wickham
market, near Ipswich, in Suffolk, when only four years old, lost the
whole of her tongue, together with  the uvula, from a cancerous af-
fection; 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 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  individual.  The society, how-
ever,  were not satisfied, and they appointed  commissioners to in-
quire  into  the case, whose  report coincided minutely 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
articulation, but that it shares the function with the various parts that
compose the  vocal tube. In reality,  out  of the twenty-four  articu-
late 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,  he adds, though no opportunity  has hitherto occurred of 
WHISTLING, WHISPERING, ETC.
405
   proving the fact by dissection, that those who learn this art with fa-
   cility, and carry it to perfection, possess some peculiarity in the struc-
   ture of the glottis, and particularly in respect to its muscles or carti-
   lages.  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
   face an impassive expression; or one very foreign to the verbal ex-
K. pression to which he is giving utterance.
b   On the whole, the explanation of Dr. Good appears most satisfac-
   tory :—the larynx or glottis  affording to some individuals a facility
   in acquiring the art, which others do not possess, in the same manner
   vas it makes some capable of singing, whilst others are ever incapa-
 ^citated.  It is probable, however, that  there may be a greater de-
   gree 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.   Sir David Brewster observes that
   when the ventriloquist utters sounds from the larynx without moving
   the muscles of his face, he gives them strength by a powerful action
   of the abdominal muscles: and Bennati affirms that the ventriloquist
   uses chiefly the  pharyngeal voice, of which mention will  be made
   under the head of Singing.

     Such is the  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 physi-
   ology of these functions  of expression  will fall  more appropriately
   under the head of respiration. 
406
EXPRESSION--VOICE.
  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.  It this respect it admits
o.f division into the natural or inarticulate voice, and into the artifi-
cial or articulate.

               Of Natural or Inarticulate Language.

   This, which is sometimes termed the cry  or native voice, is an in-
appreciable sound, entirely produced in the  larynx, requiring few or
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 indi-
vidual.
   The natural voice differs as much as the sentiments it is employed
to express.  Each moral affection has its appropriate cry;—the cry
of joy is  very distinct  from that of grief;—of surprise from that
of fear, &c.;  and the  pathologist finds, in  the diseases of  children
more especially, that he  can  occasionally judge of  the seat of a
disease by the character of the cry, to which the little sufferer gives
utterance; in other words, that there is,  in the  language of Brous-
sais, 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 charac-
ter, there is frequently something, which annoys the ear and pro-
duces more or less effect on those within its  sphere.  It is, indeed, by
its agency, that sympathetic relations are established 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 attend-
ed to, by a foster mother, endowed  with very different vocal pow-
ers.   In the case of  a goldfinch and chaffinch, this has been put di-
rectly 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 
ARTICULATE LANGUAGE.
407
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 ac-
quainted 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 emo-
tion 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  particular
sound by the  parent, to express a particular  emotion, as an affair
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  connexion 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 experience.
The cry of terror  or of pain  appears to  occasion, 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 succes-
sion of articulate sounds, duly regulated  by volition, and having de-
terminate 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 that
impinges  upon the organ of hearing;  the sound, thus, becomes the
sign of such idea,  and is reproduced in the larynx, at the will of the
individual.
  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 
408
EXPRESSION--VOICE.
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 pf'human
speech, and to  repeat them to  music.   The  case of the far-famed
parrot of Colonel O'Kelly  has already been  referred to; and Gall,
amongst other cases, cites that of the dog mentioned by Leib-
nitz, which could articulate some German and French words.   This
dog, of  which Leibnitz  was " an  eye-witness,"  was at  Zeitz,  in
Misnia.  A young child  had heard it utter some sounds, which he
thought  resembled German,  and this led  him to teach it to speak.
At the  end of about eight years, it  had learned thirty words,
some of which were, tea, coffee, chocolate,  assembly. It spoke  only
after its  master had pronounced the word, and appeared to do  so
only on compulsion, although it was not ill used.   In the " Dumfries
Journal," Scotland,  for January, 1829,  mention is made of a  dog,
then living  in  that  city, which  could  utter,  distinctly, the word
" William," the name  of the  young man to whom it was much
attached.  There is no doubt, however,  that,  in numerous animals,
speech would be impracticable, owing to defective  vocal organiza-
tion, 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 which
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 have 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 pau-
city of ideas, and of the means of communicating them,  which they
must have possessed; and that even  allowing  they could have in- 
ARTICULATE LANGUAGE.                  409
vented 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 natures,"
or " echo of nature," as Wachter 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 " whistles,"
the  hogs "grunt," the hen " cackles," the man  "snores," &o, words
used, originally, not perhaps in  these very shapes, but varying, ac-
cording 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-
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 iv,  (oo,)
imitates that of the passage of the air, and is found in the word cor-
responding 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.            4
  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.
Creek, xoxxuf;  Latin, cucullus; Irish, cuach;  Bask, cucua;  Scla-
vonic, kukulka, kukuscka,  &c.;  Hungarian,  kukuk; Hebrew, ca-
catha;   Syriac,  coco;  Arabic,  cuchem;  Persiac, kuku;  Koriak,
kaikuk;   Kamtschadale,  koakutschith;   Kurile,  kakkok;  Tartar,
kauk; German,  kuckucks,  or guckguck;  Dutch,  koekoek;  whence
our words .cuckoo and cuckold, and the  Scottish, gouckoo, gowk, or
golk; French,  cocu, &c.
  vol. i.                        52 
410
EXPRESSION--VOICE.
  In the greater part of languages, words, expressive of the cries of
animals, are accurate imitations.  Of this, the following arc a  few
examples.
  Bleating of  sheep.—Greek,  /3\r)xao|xai; Latin,  balare;  Italian,
belare;  Spanish, belar;  French,  beler; German,  Woken;  Dutch,
bleeten; Saxon, blcetan, &c.
  Howling of wolves.—Greek,  6XeAu£w; Latin, ululare;  German,
heulen;  Dutch,  huilen;   Spanish,  aullar;   French, hurler,  &c.
Hence the word owl.
  Neighing of the horse.—Latin, hinnire; French, hennir; German,
wiehern;  Saxon, hnagan, &c.
  Clocking, or  clucking of  hens.—Latin, glocire; French^ glous-
ser; Greek, xaxxa£siv: German, glucken;  Dutch,  klokken;  Saxon,
cloccan, &c.
  To crow, like  a cock.—Greek, xpagw; German, kr'dhen; 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 charac-
ter ; 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
them back to the mind.  On our continent, the fact has often been
noticed of a tribe of Indians, separating themselves  into two parties,
and remaining distinct for years.   In such  cases, the language has
become 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 imitative or alphabetic,—and the symbolical, allegorical, or em-
blematic, which latter consists of hieroglyphics, or designs represent-
ing 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 re-
duced 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
elementary sounds, admitted in each  language, constitutes its alpha-
bet, which differs more or less in certain  languages; but as it is en-
tirely a matter of human invention,  and as the elementary sounds,
of which the human voice is capable, are alike in the different races
of mankind, we see  readily, that the alphabets of the  different lan-
guages  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 
ARTICULATE LANGUAGE.
411
[    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 com-
     municated to Moses by the Almighty himself, and that the decalogue
     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, O, 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 ima-
     gine ; hence,  he  has to  unlearn all that he has acquired, or to ima-
     gine, that the different letters have very different  sounds, according
     to the situation in which they may be placed. To obviate this incon-
     venience, many individuals are in the habit of teaching their children
     syllabically from the very first, by which they acquire the true sound,
     attached to each letter  of the alphabet.
       In the preceding enumeration of the simple sounds, which consti-
     tute the alphabet, C, Q, W, X, and Y, have been excluded, for the
     following reasons.  Chas 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, unin-
     terupted 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 arc, 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 
412
EXPRESSION--VOICE.
Fate.		(No.
Fat.	0, as in	{ Move.
Fall.		(Not.
Me.		( Tune.
Met.	U, as in	{ Tub.
Pine.		( Bull.
Pin.		
tongue nearly into contact with the bony palate.   O, by the con-
traction of the mouth being greatest immediately under the  uvula,
the lips  being also  somewhat contracted.   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

   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,
but the  passage of the air continues  free, and the voice,  conse-
quently,  issues in  an unrestrained  manner.   Hence, perhaps, the
physiological  origin of the Danish word Aa, " a river"—a generic
term, which became afterwards applied to three rivers in the Low
Countries, 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
asi which signifies  " always, perpetually;"  and  the  German j e,
which has the same signification.
   The consonants are more difficult of enunciation than the vowels;
as they require different, and sometimes  complex, and delicate move-
ments  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 and y 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,-r-" how so accurate a gram- 
ARTICULATE LANGUAGE.
413
marian as Dr. Lowth could pronounce so definitely on the nature
of y, and insist on its being always a vowel, can only be accounted
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 subject, than the con-
clusion to which Mr. Walker  himself, has  arrived;  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  consonant;  why, when they
begin a  word, do they not admit of the euphonick 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, as/, v, s, z, x, g soft or j.
  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
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
uper  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. T and
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 absence
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 sepa-
rating 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 t 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 
414
EXPRESSION--VOICE.
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.
   In forming the letter K, the middle  and point of the  tongue
strikes 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 con-
dition.
   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,  (ganz  stum me,)  as
K, P, T.  2.  Explosives,  (w i n d m i 11 a u t e r,) as the F, H, Ch, S,
and Sh.   3.  Vocal consonants, (s t im m i 11 a u t e r,) as B, D, G, L,
M, and N; 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.  Explo-
sive  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 J LN RSTZ Ch Sh Ng-	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  Romanic
languages to another.
  " The changes of vowels," says Mr. Lhuyd, " 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 regard-
ed ; the consonants being the sinews of words, and their alterations
therefore the most perceptible.  The changes of consonants also into 
ARTICULATE LANGUAGE.
415
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 occurs
between letters of the same  class in different  languages.   In  this
view, we may regard the labials and dento-labials as belonging to the
same class.
  P into B.—Greek, pXe^; Latin, plilebs.  Latin, (and Greek,) epis-
copus;  English, bishop; Anglo-saxon, biscop; German, b i s c h o f.
  P into F and V.—Latin, pater; German, v a t e r;  Dutch, vader;
English, father.
  T into S.—German, b e s s e r; English, better.  German, w a s s e r;
English, water.
  D into Th.—German, das; Dutch, dot; English, that.
  T into Z.—-German,  zung; Dutch tang; English tongue. Ger-
man, z w eig; English twig.
   L into R.—Spanish, Gil Bias; Portuguese, Gil Bras.  Latin, ar-
bor; Spanish, albero.
  C  or K  into G.—Latin, hemicranium; French, migraine.   Latin,
eibarium; French, gibier.  Latin, acer; Italian, agro.  Latin, alacer;
Italian, allegro.  Greek, xuxvos; Latin, cygnus.
   The most harmonious languages are such as have but few conso-
 nants, in their words, compared with the vowels;  hence the musical
 superiority of the Greek and  Italian, over the English, German,  &c.
   " Among certain northern nations," says Richerand, " all articu-
 lated 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  adds,—" would it  not seem
 that the inhabitants of cold  countries have been led to  use con-
 sonants rather than vowels, because as the pronunciation does not re-
 quire the  same opening of the mouth, it does not afford  the same
 space for the continual admission of cold air into  the lungs 1"   The
 whole of Richerand's remarks on this topic are singularly fantastic
 and feeble, and unworthy of serious discussion.
   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 Wallis, in his  Grammatica Lingua Anglican^, published
 in the seventeenth  century, turned  his  attention to this matter,
 chiefly as regards the English language, and he has collected a  mul-
 titude  of examples to show, that a certain collocation of consonants,
 at the  commencement of a  word, generally  designates  the class
 of ideas, intended to be conveyed by it.  For instance, he remarks
 that:— 
416
EXPRESSION--VOICE.
  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 in  less degree—the vis inertia; 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, wreal/w, wrest,
ivring, 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
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,  (es-
pecially with the addition of the letter r,)—as spread, spring, sprig,
sprinkle, split, splinter, spill, &c.
   SI, the idea of a gently 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.   M. De  Brosses  has 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  lan-
guages.  Why, for instance, the st should enter into most words signi-
fying firmness and  stability:—as  in the  Sanskrit, stabatu, to stand,
stania, a town, &c; in the Greek, tfr*)X»i, a column, <rrsp=o?, solid, im-
movable, tfrjipa, sterile, remaining constantly without  fruit, tfT*ipi|w, I
fix firmly, &c; in the  Latin, stare, to stand, stirps, a stem, stupere, 
ARTICULATE LANGUAGE.
417
>   to be  astonished, stagnum, stagnant water, &c. and he might have
    added  in" the  German, still-stehend, stagnant,  stadt, a town,
(.    stand, condition, sterben, to die, still-stand, cessation, &c, be-
    sides the English words, commencing with st, already quoted from
    Wall is.
      He  farther  inquires; why words, commencing  with sc,  denote
    hollowness, as tfxavru, I dig; tfxaprj, a skiff or boat, in  the  Greek;
\    scutum, a shield;  scyphus,  a large jug;  scufpere, to engrave;  scrobs,
    a ditch, in the Latin; ecuelle, formerly 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, for-
    merly 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,

      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 hollowness, the  K
 •   or C has been adopted,—which are produced in the throat, the most
J^-+ hollow of the vocal organs.  The letter S serves, he conceives, mere-
    ly as an augmentative; as the sound can, by its addition, be made
    continuous.  It is  itself, however, a letter expressive of softness, when
*•-•   combined, as we have seen, with certain other consonants; 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, cpXog, flame; cpks-^,  a vein;
fcv;  <pksyeduv, a burning river in the infernal regions:—in the Latin, flam-
    ma, flame; fluo,  I flow; flatus, wind; fluctus, wave, &c:—in the
    German, fids sen, to float; fid ten, to  play on the flute; fluss, a
    river;  flug, flight, &c; and the  French and English words of the
    same meaning.
      Lastly, the idea of roughness and asperity is conveyed by  the let-
    ter r, as in the words, rude, rough, rock, romp, &c.   How different,
    for example, in smoothness are the two following lines, in which the
    S predominates;  from  those that succeed them, where  the R fre-
    quently, 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  Wallis
    and of M. de Brosses, must not be received too absolutely.   In the
    condition in  which we  find languages at the  present day, it would
     vol. i.                     53 
418
EXPRESSION--VOICE.
be impossible that they should hold good universally; but they will
tend to show, that the physiology of the voice is intimately connect-
ed 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 tp the  precise  idea it
may have  been desired  to convey;—gutturals, for example, for
sounds conveying the notion of hollowness:—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, pronounces and unites earlier  than
any other.   Hence they have become  the infantile appellations for
mother and father with  many nations;  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, frequent-
ly considered  under the head of alliteration, but by no means de-
riving  its chief beauties from that source.   It happens when a repe-
tition of the  same letter concurs with the sonorous imitations already
described; as in the following line in one of the books of the iEneid
of Virgil:—

                 " Lucfanfes venfos tempesfaiesque sonoras,"

in which the frequent occurrence of the letter of firmness and stabi-
lity, 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 sifnent sur vos t6tes,"*

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 quo sur le Zimon une riviere Zente,
           DerouZe en paix les pZis de son onde indoZente ;
           Soit qu'a travers les rocs un torrent en courroux
           Se brise avec fracas."t

   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 asperity,
R, resembles the rushing of the  stream like a torrent.  The remarks
already made will have exhibited the radical difference in the ideas

         * " For whom are those serpents that hiss o'er your heads."
         t Which may be translated as follows:—
                 " If o'er a deep slime a river laves,
                  In peace the folds of its sluggish waves;
                  Or o'er the rocks a torrent breaks
                  In wrath obslrep'rous." 
SINGING.
119
communicated by the sound of those letters, by the common consent
of languages.                                       t
  In the German language, this variety of expression is oiten  naa
recourse to;  and  by  none  more  frequently than  by  their poet
Burger.
  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.                       .  .,   ,  ,     c
  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 themselves
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 phonetic words especi-
ally, adds considerable force to the idea intended 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.

                           Of Singing.

   The  sinking voice differs from the other sounds produced by the
 glottis,  in confisting 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 intel-
 lect   In this  respect, therefore, there is a striking resemblance be-
 tween the faculty of music and that of spoken language.
   Like the spoken  language, singing admits of considerable differ-
 ence, as regards intensity, timbre, &c.
   Voices are sometimes divided into the grave  and the acute, the
 difference between them amounting to about an  octave.   Ihe for-
 mer  is the voice of the adult male; but it is capable of producing
 acute sounds, by assuming the falsetto, which Savart ^ceivesto be
 produced in the"ventricles of Ae larynx,-Bennati in t  e Pharynx
   The acute voice is that of the grown female, of  childien, and  ot

 'Tvtddinrr all the tones of an acute to those  of a  grave voice
 the/are found to  embrace nearly three octaves;  ^J™**^
 Magendie, it does  not appear, that such a compass of voice, in pure 
420
EXPRESSION--VOICE.
and agreeable tones, has ever existed in the same individual.  Some
singers can descend sixteen tones below the medium: others can rise
sixteen above it. The former are called tenor bass ; the latter soprano,
but hitherto no example has occurred  of a person, who could run
through the thirty-two notes.
   The musician establishes certain distinctions in the voice; such
as counter, tenor, treble, bass, &c.   We find it, also, differing consi-
derably in strength, sweetness, flexibility, &c.
   The singing voice, according  to Bennati, is not limited to the
larynx;  the pharynx is  likewise concerned.  The voice, elicited in
these  two different parts, has long been termed  voce di petto and
voce di testa.  Bennati calls the former laryngeal notes,  or notes of
the first register; the latter supra-laryngeal or notes of  the second
register: and  Lepelletier designates them laryngeal and pharyngeal
respectively,—comprising in the dependencies  of the  pharynx, the
tongue, the tonsils and the velum palati, by means of which tnc latter
class of sounds is  elicited.  The  laryngeal voice, which is always
more  elevated by an octave in the female than in the male, is  most
commonly met with.  It furnishes  the types called I.Alt or soprano;
2. Counteralt,  3. Tenor; 4. Tenor Bass.   The pharyngeal  voice
presents but modifications of these types.   It  is met with  in but
few persons  in its   finest developement.   It  has usually  been
supposed to  be formed  by the superior ligaments  of the larynx or
in the ventricles;  but  these  gentlemen  esteem  it demonstrated,
that  it  is  formed  at  the  guttural  aperture, circumscribed by
the base  of  the tongue, the velum palati, its pillars,  and  the tonsils.
By it is produced the baritenor, the contraltino tenor, and the soprano
sfogato.   Bennati concludes his memoir on the human voice by re-
marking,—that not only are the muscles  of the  larynx inservient to
the modulation of the notes of song; those of the os hyoides, tongue,
and of the superior, anterior and posterior part of the vocal tube are
invoked, without the simultaneous  and  properly associated operation
of which, the degree of modulation requisite for song could not take
place.
   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, singing
may be said to have originated in social life.  It  can be employed,
as it is in many of our operas, to depict the different  intellectual 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. 
                             GESTURES.                          t'^1

     Declamation  is a kind of singing, except that the intervals  be-
   tween  the  tones  are not  entirely harmonic, and the tones them-
   selves not wholly  appreciable.   With the ancients, it  has  been ima-
   gined, 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 com-

   Ht isTinthe gestures of the face chiefly, that man far exceeds other
    animals.  This is, indeed, in him, the great group of organs of ex-
K.Uression.   In animals, the function is distributed over different parts
^^f the body, the face assuming but little expression whilst the animal
    is labouring under  anv  emotion, if we  make exception 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
t   expression of internal feeling is confined to the eye and  the mouth,
h  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.
      Jn 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 panni-
    culus carnosus, would  enable it  to minister but little to  expression.
    The skin  of the  face is very fine, and on certain parts, as the lips
    and cheeks, it is habitually more or less florid,  and admits of con-
    siderable and expressive  variations in its degree  of colour.   Ihe
     union of  the  different parts, composing the face, gives occasion to-
     numerous reliefs, which are called traits or features ; and, beneath
     the skin, arc many muscles, capable, by their contraction, of modi-
     fying the features  in a thousand ways.     ,.  ,   .   . .        .    ,
       To comprehend fully the physiology  of the facial expression of
     the passions, a few observations on the muscles of  the  human face
     will be necessary.

       * 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. 
422
EXPRESSION"—GESTURES.
  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 muscle
A, Fig. 34, and is attached to the side of the nose, has been esteem-
ed, by some, to be a distinct muscle, and to  have  a distinct opera-
tion.   It draws the inner extremity of the eyebrow  downwards.
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 furrowed, and there is an
upward inflection of the inner extremity of the eyebrow, which indi-
cates 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 Philosophy
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 displayed 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."
  Sir Charles Bell  separates the orbicularis palpebrarum  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 passion,  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 drunken-
ness, 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 superioris
alceque nasi, D, Fig.  34,  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 ala nasi, L,
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 
MUSCLES OF THE FACE.
423
   canal of the nostril; moving in consent with the muscles of respira-
f.  tion;  and thus the inflation of the nostrils indicates general excite-
   ment, and animal activity.
     .The muscles of the lips are;  1, the levator labiiproprius, F, which
   raises the upper lip;  2dly, the levator anguli oris, G, which raises
   the angle of the mouth; and 3d]y, the  zygomatic muscle, H, which
   is inserted into the angle of the mouth.  Sometimes  an additional
   muscle of the name exists;—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 labii  superioiis, M, draws
   down the septum of the nose.   The triangularis oris, or  depressor
   Isbiorum, N, indicates, by its name, its function.   The quadratus
   menti, O, is a depressor of the lower lip.  The levatores menti, P P,
   by their action, draw up the chin, and project the lower lip; and the
   buccinator, Q, 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.
jl     The union of these  various muscles at the  angle  of the mouth
Wt produces  the fleshy prominence,  noticed in those  who have thin
K;  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 or-
    bicularis, or  the  superior, or inferior muscles, inserted into it,  have
    the preponderance.
      Lastly, the temporal  is a strong  muscle, which raises the lower
   jaw.  It is assisted by the masseter,  a deep-seated muscle, 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 is a nerve of sensation, and also conveys to the muscles the
    volition, necessary for their ordinary movements of mastication, &c,
    the latter is concerned. in  the instinctive movements of expression.
    This the experiments of Sir Charles Bell have 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 
424
EXPRESSION—GESTURES.
 respiratory nerve of the face of Sir Charles  Bell's system, the*fea-
 tures are no  longer influenced by the passions.  Yet the skin con-
 tinues sensible, and the muscles of the jaws and tongue are capable
 of the actions of chewing and swallowing.  If the respiratory nerve
 of one side be cut, the expression of that side  is destroyed; whilst
 the chattering, grinning, and other  movements of expression con-
 tinue  in the other.  In a  dog,  too, if the respiratory 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 fea-
 thers around his head.   The position of his head and the raised fea-
 thers  are  the expressions  of hostile  excitement, but, on the division- >
 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.
   The views of Sir Charles Bell, regarding  the connexion, alleged
 by him to  subsist, between the seventh pair and the associated move-
 ments of respiration, have, however, been  contradicted by the ex-
 periments  of Fodere and  Mayo, and his  inferences regarding the
 fifth pair—as being jointly a nerve of sensation and voluntary mo-
 tion—have been  considered "by  Mayo to require qualification.  By
 dividing the portio dura of the seventh pair in the ass, and on both
 sides instead of one, as done by Sir Charles Bell, Mr. Mayo found, that
 the nerve presides over simple  voluntary motion only: and by a
 similar division of the second and third branches of the fifth, at their
 points of convergence, he showed, that the lips were deprived of sen-
 sation not  of motion. "No doubt, I believe," says Mr. Mayo, "is now
 entertained, that the inference, which I drew from these experiments,
 is correct;—namely, that the portio dura of the seventh pair is a sim-
 ple voluntary nerve, and that the facial branches of the fifth are exclu-
 sively sentient nerves." In the prosecution of his inquiries Mr. Mayo
 observed, that the masseler muscle, the temporal, the pterygoids, and
 the circumflexus palati receive no  branches from any nerve except
 the fifth, and yet that they receive twigs from  the ganglionic por-
 tion of  the nerve; and he thence concludes,  that almost all the
 branches of the  large  or  ganglionic portion of the fifth pair are
nerves of sensation,  whilst  those of the small fasciculus or ganglion-
less portion are nerves of motion.   This smaller portion of the  fifth
pair issues  from the peduncles of  the brain,  constitutes a gangliform
plexus with the inferior maxillary only, presents the common aspect
of most nerves of the body, and is distributed to  the chief muscles 
MENTAL EMOTIONS.
425
concerned in the process of mastication.  Hence it was termed by
Bellingeri, nervus masticator ins, and by Sir Charles Bell, long  after-
wards, the motor or manducatory portion of the fifth nerve.   To this
smaller fasciculus of the fifth, twigs from the ganglionic portion  of
the nerve, are distributed.  The ganglionless portion, and the portio
dura of the seventh, Mayo conceives to be voluntary nerves to parts,
which receive sentient nerves from the larger or ganglionic portion of
the fifth.
   Pathology affords us numerous examples of injury done to the fa-
cial nerve.  In some of these cases, the nerve itself may be in a mor-
bid condition in  some portion of its course : in others, the part of the
encephalon, whence the  nerve originates, may  be  the seat  of the
lesion.  The prognosis will, of course, vary according to the seat,
but as a general rule, paralysis  of the facial nerve is not of great
moment.   Within the last two years, the author has seen  three cases
of partial paralysis of this  kind; one of which has wholly disap-
peared; but in the others it  appears to be permanent.  In  a case,
which presented itself not long ago, in the Baltimore Infirmary-, the
mischief  was  probably seated near the origin of the nerve, as it re-
sulted from serious injury to the  head.  A carriage horse, belonging
to a friend, by exerting considerable power, forced its head through
an aperture in the partition of his stall, and was unable to withdraw
it, in consequence of the under-jaw catching the sides of the aperture.
During the efforts to  extract it,  so  much  pressure was made upon
the portio dura of one side, that  the animal lost all power of expres-
sion in the corresponding side of the head: the soft parts about the
mouth dropped,  and the ear no  longer associated with  that of the
opposite side in expression:  yet  the movements of mastication and
deglutition were  scarcely affected.   This state of paralysis continued
for a few  days, and gradually disappeared.
  Independently of the various muscular actions, which modify the
expression of the human-countenance, there are certain  other indi-
cations which mark the different mental emotions.  The  skin, for
example, varies in colour, becoming pale or  suffused;  and frequent-
ly 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 capil-
laries 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 of moisture or of heat.  It may be
dry, or bathed in perspiration;  and the perspiration may be warm
or cold;—occasionally  the two  conditions  alternating  frequently.
Particular parts of the face, again, are more susceptible 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  countenance; and the expression is
sometimes evident to a second person.
  The expression of the human eye, connected with  the action of
    vol.  i.                        54 
426
EXPRESSION--GESTURES.
the oblique muscles, has been referred to under vision.   It was there
asserted, that, in insensibility, the eye is given up to the action of the
oblique muscles, and is drawn up under the upper eyelid.  The eye
itself is, however, capable of various  expressions, depending 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 sources of ex-
pression in the human countenance, we may add the action of oscu-
lation or kissing, which, wherever  practised, is employed as an ex-
pression of love and friendship; confined with us to those of the fe-
male sex, or of opposite sexes;  but, in some countries, employed as
an expression of regard between males also.
   It is impossible for us to describe all the facial expressions—the
Prosopose, as they have  been  collectively termed—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 contracted 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  expressions;
beginning with the play of the features in broad  laughter, as being,
perhaps, the most easy of explanation.  In laughing, it  is in  vain

                            Fig. 91.
Broad laughter. 
                        MENTAL EMOTION>.                     427

that wc endeavour to confine the lips; a eomplete relaxation of the
orbicularis oris gives uneontrolled power to the opponent muscles
inserted into the angles of the mouth and upper lip.  Hence the late-
ral retraction of the angles of the mouth; the elevation of the upper
lips disclosing the teeth; the peculiar elevation 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 expression, 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 muscles  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.
  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  di-
rection of the portio dura or respiratory nerve of the face.  At the

                            Fig. 92.
Faun weeping. 
428
EXPRESSION--GESTURES.
same time, the individual holds his sides to control the contractions
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. 92, sketched by Sir Charles Bell, we
have the expression of weeping from pain.
  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 some-
what impeded.   The muscles of the  cheeks are in  action.   Those
that depress the angles of the mouth are powerfully contracted, and
the orbicularis oris is not relaxed, but drawn open  by  the  predo-
minant 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;
the cheek is raised;  the nostril drawn out, and the mouth stretched
laterally.   In weeping, also, unless the convulsive action of the mus-
cles 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  despon-
dency  and languor to the  countenance, when accompanied  by ge-
neral relaxation of the muscles.   When the corrugator co-operates,
there is mingled  in  the expression something  of  mental energy,
moroseness, or pain.   If the frontal muscle unites its action, an acute
turn upwards is  given  to  the inner part  of  the eyebrow, very dif-
ferent  from the effect of the general action of the frontal muscle, and
characteristic of  anguish, debilitating pain, or of discontent,  accord-
ing to  the prevailing cast of the rest of the countenance.
  The depression, however, of the angle of the mouth, that indicates
languor and despondency, must  be slight; as the depressor anguli
oris, (Fig. 34, N.) cannot act forcibly, without the action of the su-
perbus being induced,—a muscle, which quickly produces a revolu-
tion in the expression and makes  the under lip pout contemptuously.
  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 wit-
nessed 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 mere-
ly elevating the corner of the lips  and inner extremity of the eye-
brows, made the child, which at first seemed breaking its heart with
weeping, seem  equally in danger of bursting  its sides with immode- 
MENTAL EMOTIONS.
429
rate 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 eye-
brow, that the  expression,  which is peculiarly human, is  situated.
They are the most movable parts of the face.  In them the muscles
are concentrated, and it is  upon their changes, that expression  is
acknowledged chiefly to depend.  All the parts, however, of an im-
passioned 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 emotion, these opposite
actions cannot be combined; and, when they are united by the mimic,
the expression  is farcical and ridiculous.
   Dr. Wollaston  has shown, that the same "pair of eyes  may ap-
pear to direct  themselves either to or from the spectator, by the ad-
dition of other features in which the position of the face is changed^
The nose is obviously the  principal feature, which produces the
change of direction, as it  is more  subject to change of perspective
than any  of the other features, and Dr. Wollaston has shown, that
even a small portion  of the nose will carry the eyes  along with  it.
He obtained four exact copies  of the same  pair_pf eyes looking  at
the spectator,  by transferring them upon copper from a steel plate,
and having added to each of two pairs of them a nose—in one case
directed to the right, and in the other to the left, and to each of the oth-
er two pairs a  very small portion of the upper part of the nose—all the
four pairs of eyes lost their front direction, and looked to the right  or
to the left, according to the direction of the nose, or of the portion of it
which was added.  But the effect, thus produced, is not limited  to
 the mere  change in the direction of the eyes: for a total  difference
 of character  may be given to  the  same eyes by a due representa-
 tion of the other  features.   A lost look of devout abstraction, in  an
 uplifted countenance,  may be exchanged for an appearance of inqui-
 sitive archness in the leer of a younger face, turned downwards and
 obliquely  towards the opposite side.  This, however, as  Sir David
 Brewster has  remarked, is not  perhaps an exact expression, of the
 fact.  The new character which is said  to be given to the eyes is
 given only to  them in combination with the new features; or, what
 is probably more correct, the inquisitive archness is in the other fea-
 tures, and the eye does not belie it.   Sir David adds, that Dr. Wol-
 laston has not noticed the  converse  of these illusions, in which a
 change of direction is given to  fixed features by a change in the  di-
 rection of the eyes.   This effect is seen in  some magic lantern  sli-
 ders, where a pair  of eyes is made to move in the head of a figure,
 which* invariably follows the motion of the eyeballs.
   In bodily pain, the jaws are  pressed together, and there is grind-
 ing 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 
430
EXPRESSION--GESTURES.
same time, drawn up; the eyes are largely uncovered, and the eye-
brows 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 extremities
are  elevated; the pupils of the eyes are in part concealed by the
upper eyelids, and the nostrils are agitated.   Agony of mind is hero
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 in-
flated 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 sometimes
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 opening of the
 mouth and dropping of the jaw;—the  lips nearly concealing the
 teeth, yet allowing the tongue to be  seen, and the space between the
 nostril and lip being full.-  There is a  hollowness  and convulsive
 motion of the cheeks, and a trembling of the lips and muscle on the
 sides  of the neck.  The lungs are kept distended; 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 ap-
 proaching, 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  com-
 mon 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 indicate
 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; and distracting
 thoughts, anxiety and alarm are strongly indicated by this wtpres-
 sion, which does not belong to animals.  The cheek is slightly ele-
 vated, and all the muscles, that concentrate  about the mouth, are in
 action. 
PHYSIOGNOMY.
431
     In admiration, the forehead  is expanded and unruffled; the eye-
t   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.
     \x\joy, the eyebrow is raised moderately,  but without any angu-
   larity ; 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 expres-
   sion.  It will 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.   Allusion has been
   made to the estimate of personal  character, from the shape  of the
   head, as  described by the  older  poets.   Similar indications were
   conceived  to be deducible from the form  of  the face, the expression
   of the eyes, &c.   Thus, Shakespeare:—

          Cleopat.  Bear'st thou her face in mind ? is't long or round ?
          Messeng. Round, even to faultiness.
&,,        Cleopat.  For the most part too,
*                 They are foolish that are so.  Her hair, what colour ?
          Messeng. Brown, Madam, and her forehead
                  As low as she would wish it."
                                    Antony and Cleopatra, Act III. Scene 3.

      And again:—

                  " Which is the villain ? Let me see his eyes,
                   That when I note another man like him,
                   I may avoid him."
                                               Much Ado about Nothing.

     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,  more justly deserves
    to be termed  a science  than  physiognomy.   It is a department of
   physics including theology  and belles lettrcs,  and in the same man-
   ner  with these  sciences may  be reduced to  rule.  It may acquire
   a fixcjinnd 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 
432                EXPRESSION--GESTURES.

man;  yet  he himself was by no  means highly favoured in these
respects, and it is, consequently, difficult to say, according 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 may accurately depict the existing emo-
tion.   If, therefore, any passion be  frequently experienced, or be-
come habitual, its character may remain impressed  upon the coun-
tenance, and an opinion be formed  of the  individual accordingly.
No one, who has seen the melancholy  mad, can mistake the piteous
expression  produced by brooding over the  corroding idea that en-
grosses him.

                            Fig. 93.
  In the above sketch, from Sir Charles Bell, we have  the testy,
peevish countenance, bred of melancholy; of one who is ingpab'e
of receiving  satisfaction from  whatever source it may be*mered,
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 
PHYSIOGNOMY.
133
 point, without thinking himself contemned,  insulted, or neglected."
 Such a countenance no one can misapprehend.
   In lesser degrees, particular features are found bearing, or seem-
 ing to bear, the impress  of particular emotions; and, accordingly,
 we are in the daily habit of forming opinions at first  sight, both of
 the intellectual and moral characteristics  of individuals, by  the
 expression 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.
    What  may be,  not  inappropriately, styled  medical physiognomy
 or  the changes  of feature 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 contenance will often materially aid
 us in the 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 of  one suffering from  excruciating
 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
f- countenance is an excellent medium of discrimination,  and will  fre-
& duently 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, which af-
 fect Jfe whole body, as  regards its different attitudes  and modes 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,
    vol. i.                         55 
434
EXPRESSION--GESTURES.
we observe a  similar difference;  and can frequently surmise the
character of the passion, whether exhilarating or depressing, under
which a person, at a distance, may be labouring from the particu-
larity 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."—Byron.

   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.
   Properly speaking, the subject of cranioscopy belongs to the func-
tion of expression, but it has already been considered under another
head.
   Many of the partial movements constitute an important part of
the  language of  expression,  especially with the savage, and with
those unfortunates, who ait shut out from the advantages of spoken
language.  In almost all nations, the motions  of the head on the ver-
tebral column are  used as signs of affirmation or negation; the former
being 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 recourse
to;  and the various important inventions, by which we communicate
our feelings to a distance, such as writing  and telegraphing, 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 mainly
restricted 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 %ility.
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; 
                              passions.                        435

  and the will reproduces the gesture, in the same manner as it repro-
  duces the sound heard.
    The lower extremities  are, also, slightly concerned in the function
  of expression.  They are agitated when we are impatient, and in-
  cessantly  changing their position.  The foot is  stamped upon the
  ground in anger; and, like the upper extremity, is employed to con-
  vey 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 sigh-
  ing,  yawning, laughing, and sobbing.  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 a state of
  syncope or fainting to  that of the most violent palpitation.
    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, however, may  be  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 feeces, 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  deep 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  passion 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 incom- 
436
EXPRESSION--GESTURES,
plete; 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. 34, 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
by endearments, and frowns  as proofs of displeasure, because fol-
lowed 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 presented  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
motions, accessary to the great object of opposition, resistance, and
defence.  " In carnivorous animals,"  he remarks,  " the eyeball is
terrible,  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 expression is ever witnessed in other cases of excited  attention,
or in the simple exposure of the canine teeth, when  the animal is de-
vouring  its food; unless, indeed, the repast be effected, during the
prevalence of the passion.
   On a  former occasion,  it was remarked, that the encephalon is 
POETRY AND PAINTING.
437
exclusively concerned in the production  of the  different passions.
and that the parts to which they are usually referred, attract our at-
tention to them principally, in consequence of the sensation, which
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 func-
tion of  sensibility on  the other  functions.   Gall,  in  his system,
has feebly attempted to show, that each gesture  has a reference to
the encephalic situation of the organ, concerned in the production 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 that part of the body.
Like every professed systematist, Gall is here pushing his principles
ad absurdum.   They are, indeed, controverted 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 gesture  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 ex-
pression ;  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, there-
fore, been examined in this place; but  as the nutritive and genera-
tive 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. 
438
NUTRITIVE FUNCTIONS--DIGESTION.
CLASS II.
              NUTRITIVE FUNCTIONS.


   The human body, from the moment of its formation to the cessa-
 tion 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, undergoes
 such conversion, as  fits it for the separation of its nutritious and ex-
 crementitious portions: absorption, by which this nutritious portion,
 as well as other matters, is conveyed into the mass of  blood: respi-
 ration, 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 decomposition are accom-
 plished :  calorification, by which the system is enabled to resist the
 effects of greatly elevated or  depressed atmospheric  temperature,
 and to exist in the burning  regions within the tropics, or amidst the
 arctic  snows: and secretion, by which various fluids and  solids are
 separated from the blood;  some to serve useful purposes in the ani-
 mal 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 investiga-
 tion of which  we shall commence with a brief description of the or-
 gans 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 ex-
ternally by two outlets,—the mouth and  the anus.  It is  usually di-
vided into four chief portions—the mouth, pharynx and asophagus,
stomach, and intestines.  These we shall describe  in succession. 
DIGESTIVE ORGANS.
439
  1. The mouth is the first cavity of the digestive tube, and that into
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 ;—ante-
riorly, 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 salivary 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 ex-
ist 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 developement.   We may merely remark,
at present,  that by De Blainville they are looked upon as  analogous
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 subsequently.
  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
wedge-shaped; in the canine, conical; and in  the molar, 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 ami canine teeth  have only one root;  the molares of
the lower jaw, two; and of the upper, three.   In all cases, they are 
440                       DIGESTION.

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, called
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 capable of sustaining con-
siderable pressure without inconvenience.—But we shall have to re-
turn to the subject of the teeth hereafter.
   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, on each side,—the temporal, and masseter, which arc en-
tirely concerned in the 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 ele-
vator 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, all of 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 the 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 ar-
rangement of the
elevators and de-                     F*g- 94-
pressors  is  such,
that   the  former
predominate  over
the   latter;  and
hence during sleep
the  jaws   conti-
nue    applied   to
each   other,  and
the mouth is, con-
sequently, closed.
   The human 01'-               SkullofthePolarBear.
 
DIGESTIVE ORGANS.
441
Fig. 95.
   gans  of mastication  hold an intermediate place between those of
   the  carnivorous  and herbivorous animal.   In the carnivorous ani-
   mal, which has  to  seize hold of, and retain its prey  between  its
   teeth, the jaws have considerable strength;  and the movement  of
   elevation is all that is practicable ; or, at least, that can be effected to
   any extent. This is dependent upon
   organization.     The  condyle   is
   broader from  side to side, which
   prevents motion in that  direction;
   the  glenoid 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 before and 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
fr  muscles, indicate the large size  of
jpitnese muscles in  the purely carni-
"., vorous animal; whilst the pterygoid
   muscles are extremely small.  The
   teeth,  too, are  characteristic; the
   molares being 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.
    r.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 carnivorous
   animal, is here quite loose.   The  elevator muscles are much 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-
    VOL. I.
Skull of the Cow.
50 
142
DIGESTION.
tent;  and  the muscles  of both kinds have  a medium degree of
developement.  The teeth, likewise, partake of the characteristics   i
of those of the carnivorous and herbivorous animals; twelve—the   "1
canine teeth and lesser molares—corresponding to those of the car-   ' j
nivorous, and twenty—the incisors  and larger molares—to those of   r
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 arid 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 parti-
cipates in its movements.  Of the tongue, as the organ of taste and
articulation, we have already spoken.  We have only, therefore, to v^
describe the os hyoides and its attachment to that bone.   The hyoid
bone has, as  its name imports, the shape of the Greek letter u,"(up-
silon,)  the convex  part being before. Fig. 86.)   It is  situated be-    ■<
tween the tongue and the larynx; and is divided into body or cen-   ;a
tralpart; and into branches, one extremity of which is united to the    :r.
body by an intermediate cartilage, that admits of slight motion;
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  apo-
physis or process, called the lesser cornu.                        .js»
   The os hyoides  is united to  the neighbouring parts  by  fibrous'-^^
organs, and by muscles.  The  former are;—above, the stylo-hyoid$9[
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
cornu  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-ihyroideus.
   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.      ,   ...
   Among the collateral organs of mastication are those that secrete '^
the saliva, and the various fluids, which 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, ex-
hales a serous or albuminous fluid, besides a mucous fluid secreted
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 situated 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 
I
                          DIGESTIVE ORGANS.                    443

 •' upon this part of the cheek, the saliva can be made to issue in percep-
   tibly 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 lingiiEe.
     The sublingual gland is situated under the tongue, and  its excre-
   tory 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 sublingual, the texture of which
   more nearly resembles  that of  the compound follicles  than of the
   glands; but the circumstance has not been proved by any direct ex-
r  periment.   The saliva, as met with, is a compound of every secre-
   tion  poured into the mouth;  and it is  such fluid which has alone
   been subjected  to analysis.  The secretion of the saliva, and its va-
   rious 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 an-
   tagonist to the others, which are  eight in number, on each  side—
   the  levator labii superioris alceque nasi, the levator labii superioris
   prpprius, the levator anguli oris, the zygomaticus major, the zygoma-
   tics minor, the buccinator, the triangularis, and the quadratus menti.
   ■{Fig. 34.)  To the two last muscles are added  some fibres of the
   platysma myoides.
     The pharyngeal opening is smaller than the labial, and of a quad-
P^« rilateral shape.  It is  bounded, above, by the velum palati or pendu-
I"; hus  veil of the palate; below,  by the base of the tongue; and,  late-
   rally, by two muscles, which  form the pillars of the fauces.   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, hori-
   zontal.
     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 prolongation of the membrane lining the
   mouth, and contains  numerous  follicles; the other, forming its  pos-
   terior surface, is an extension of the mucous membrane lining the
   nose, and is redder, and less  provided with  follicles than the other. 
444
DIGESTION.
The muscles, that constitute the body of the velum palati, are—the
circumflexus palati or spheno-salpingo-staphylinus of Chaussier; the
levator palati or petro-salpingo-staphylinus;  and the a~ygos uvula; 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 constric-
tores isthmi fauciuni or glosso-staphylini carry it downwards.
   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 amygdala, which are not
really glandular, but composed of a congeries of mucous follicles.
   2.  The pharynx and cesophagus are two muscular canals, forming
the media of  communication between the mouth and  stomach, and
conveying the food from the former of these cavities to the hitter.
   The pharynx has 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, the nasal fossae, Eustachian tubes, mouth, larynx, and oesopha-
gus open.   It is inservient  to useful purposes  in the  production of
voice, in respiration, and audition, as well as in diges-
tion ;  and  extends from  the basilary  process of the  Fig. 96.
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 a
which  lines the mouth,  but more so  than that of the
oesophagus, and of the rest of the digestive tubes; and it
is remarkable for the developement of its veins, which
form a  very distinct net-work.  Around this is the mus-
cular layer, the circular fibres of which are often divided
into three muscles,—the superior, middle  and inferior
constrictors.   The  longitudinal  fibres  form part of the
stylo-pharyngei and palato-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
latter 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
extends to the stomach, where it terminates.   Its. shape ectl0^hagulw
is cylindrical, and it is connected  with the surrounding ^x^txmn.
parts by  loose and extensible  cellular tissue, which,  c. The external
". , *  J  !••     •                r\       «iii  longitudinal
yields readily  to its movements.  On  entering  the abdo- fibres.
men, it passes  between the pillars of the diaphragm, with  which 
DIGESTIVE ORGANS.
445
 it is intimately united.   The  mucous membrane, lining it, is pale,
 thin,  and  smooth;  forming  longitudinal folds,  well adapted for
^favouring the dilatation of the canal.  Above, it is confounded with
 that of the pharynx;  but below, it forms several digitations,  termi-
 nated  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 mus-
  cles, but consists of circular  and longitudinal fibres; the former  of
  which  are more internal, and  very numerous;  the latter external,
  and less numerous.
    The marginal figure exhibits  the situation and arrangement of the
  two sets of fibres.
                               Fig. 97.
               The stomach seen externally.
rior.urftce.-B, Enlargement atthe lowe^part.-D. Cardiac orifice.-E. Commence-
lent of duodenum.-F and C. Coronary vessels.
-11. Omentum.
  3. The stomach is situated  in the cavity  of the abdomen  and is
the  most dilated portion of the digestive tube   It  occupies the epi-
gastric reffion  and a part of  the  left  hypochondre.  Its  shape lias
E comla'ed, not inappropriately, to that  of the bag of a bag-pipe. 
446                        DIGESTION.

It is capable of holding, in the adult male, when moderately distend-
ed, 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 pylo-
ric portion, because  it corresponds to the pylorus.  The inferior
border  of  the stomach, which is convex, is termed the great curva-
ture or  arch; the superior  border, the  lesser curvature or arch.
The  two  orifices are the esophageal,  cardiac or upper orifice,
formed by the termination of the oesophagus;  and the intestinal,
pyloric,  or  inferior orifice, which communicates with  the small
intestine.
   The three coats, which constitute the parietes of the stomach, are
arranged in a manner the most favourable for permitting variation
in the size of the organ.  The outermost or peritoneal coat consists
of two laminas, 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 distention  of the sto-
mach.   The omentum majus or gastro-colic  epiploon is the part that
hangs down from the stomach in Fig. 97.
   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 their splenic extremity; and  are more numerous
and marked, the more the stomach is  contracted.  They  are radi-
ated towards the cardiac, 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 as  perceptible
in  the  stomach   as  in  any  part  of the digestive tube.  It con-
tains,  also, many follicles, which  are especially abundant in  the
pyloric partion.  Several, also, exist in the vicinity of 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 narrowness, as
at C, Fig. 98.  Internally, the mucous membrane forms a circular
fold, which has been called the valve of the pylorus, between the two
laminae of which, a dense, fibrous tissue exists. This has been called,
by some authors, the pyloric muscle. 
DIGESTIVE ORGANS.
447
Fig. 98.
                          Section of the stomach, fyc.
         A. The crsophagus.—B. The stomach.—C. The pylorus.—D. The duodenum.
    The muscular coat  of the stomach, which is situated without the
  toucous coat,—as in  the  parts  of the digestive tube already de-
  scribed,—consists of several lamincc of fibres, less distinct than those
  of the oesophagus; or  rather more irregularly distributed.  The most
  common opinion is, that there are three laminas; some forming an
  external, longitudinal  series;  a middle, transverse stratum; and an
  inner stratum with the fibres running longitudinally.   Both circular
if and longitudinal fibres are separated from each other, especially in
^'the splenic portion;  the separation augmenting or  diminishing with
  the varying size of the stomach.
     The blood-vessels and nerves of the stomach are more numerous*
   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 gastroepiploic,
   which is a branch of the hepatic; and the left gastroepiploic,—
I  a branch of the splenic.  The splenic artery, too,  furnishes numerous
pr "branches  to  the left  cul-de-sac, behind.  These  are  called  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 accompany the
   arteries through all their ramifications.   Others are furnished 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
   svmpathizes,  indeed, with every protracted morbid  change m the
   individual  organs;  and hence it  was termed, by Hunter, the  centre
   of sympathies. 
448
DIGESTION.
   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 latter, or that it should
 remain  so  long in  the stomach.   On  this account,  the organ is ge-
 nerally  of much  smaller size.   On the other  hand, the 'herbivora,
 subsisting solely upon grass, which contains but  a small quaStity of
 nutritious matter, and that not easy of  assimilation, it is important,
 that the quantity taken in should be ample, that it should remain for
 some  time in the organ, subjected to the action of its secretions; and,
 in the ruminant class, be returned into the  mouth, to undergo fresh
 mastication.
   In this class, the stomach, taken altogether, is of prodigious extent.
                                  In the  ox, which we may take as
             Fig.  99.              an example of the general structure
                                  of the organ, it consists of four se-
                                  parate  compartments.  The first
                                  stomach, A A, Fig. 99, is the ven-
                                  triculus or paunch, which  is much
                                  the largest of the four.  Externally,
                                  it has two sacs or appendices; and,
                                  internally, it is slightly divided into
                                 four compartments.
                                   The second  stomach is  the re-
                                 ticulum, bonnet, or honeycomb bag,
                                 B, which appears to be a globular
                                 appendix to the  paunch.   It is si-
                                 tuated  to the right of the oesopha-
                                 gus, G, and has usually a thicker
                                 muscular coat than the paunch. Its
                                 inner surface is arranged in irre-
                                 gular pentagonal cells, and is  co-
                                 vered 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-
ternately varying  in breadth, and  covered with small granular pa-
pillae.
   The fourth stomach, D, is the  abomasum,  ventriculus  intestinalis,
or caillette.   It has a pyriform  shape, and is  next in  size to the
paunch.   It has a  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 the young
of the  ruminant animal, with the milk  curdled in it, forms the run-
net.  The property of curdling milk is,  however, possessed  by all
digestive stomachs.    t
           Stomach of the ox.
 A A. The paunch.—B. The reticulum —C. Ti
omasum.—D, The abomasum.—E. The pylorus.
P. Duodenum.—G. Oesophagus. 
DIGESTIVE ORGANS.
119
   The  inner surface of the three first stomachs  is covered with
 cuticle ; whilst that of the fourth is lined by a true  mucous or secre-
 ting membrane.
   There  is in the anterior arrangement of the stomachs of the ru-
 minant animal, a  sin-
 gular   pro vision,   by                   '&'
 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.  100,  a
 gutter  passes into the
 second and  third sto-
 machs.     The  third
 leads  into  the  fourth
 by a  narrow Opening,     Interior view ofthc stomach of the ruminant an.mal.
'•and the fourth terminates in the duodenum, which has a pylorus at
 its origin.  When the animal eats solid food, this is, after slight mas-
 tication, 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 temperature, 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 arrange-
 ment 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.
 Animals  of this class  may be  divided  into the granivorous and the
 carnivorous.  It is in the former, 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  herbiforous 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
   VOL. 1.                      °' 
450   r,                    DIGESTION.

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. 101.
Gaitric apparatus of the Turkey. 
DIGESTIVE ORGANS.
451
Fig. 102.
Interior of the Gastric apparatus of the Turkey.
e   The oesophagus  terminates  at the bottom of the neck in a large
Bg;sac—the ingluvies, or crop or craw—which is of the same structrue
jr_. with the oesophagus, but thinner.   On the inner side side of the crop
j,  are numerous glands, with very distinct  orifices in large birds,
B,' which secrete a fluid to assist in the solution  of the food.   To the
g- crop succeeds another cavity, in the shape of a funnel,  called the
J/gventriculus succenturiatus, infundibulum or second stomach.   This is
ft  seated in the  abdomen, and is generally smaller  than the  former.
   It is usually thicker than  the oesophagus, partly owing to its nume-
   rous glands,  which are  very large and distinct in many birds.  In
   the ostrich they are as  large  as the garden-pea, and  have very
I  manifest orifices.   The infundibulum  terminates  in the ventriculus
f' callosus, gizzard or third stomach,—the most curious of all the parts
   of the apparatus.                                            .
     In figures 101 and  l(r2, we  have an external and internal view ot 
452
DIGESTION.
  the gastric apparatus of the turkey; a, representing the oesophagus
  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
  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 remarkably small, when compared with its  outward magnitude,
  and its two orifices,  represented in Fig. 101, 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 which the digastric muscle, as it has
 been termed, acts, and the callous nature of the cuticle, are striking-
 ly manifested by certain experiments, instituted by the Academia 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 oesophagus is of great size for receiving the large substances
 swallowed by these animals, and for enabling the feathers and other
 matters,  that cannot be easily 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 animal to dis-
 pense with mastication, and yet  to admit of the stomach and intes-
tines 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, 
DIGESTIVE ORGANS.
453
i
k"
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-
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 examina-
tion 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 recognized 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 apparatus;
constituting a musculo-membranous
canal, which extends from the pylo-            Fig. 103.
riciorifice of the stomach to the
   anus.
---  The  human  intestines are  six
L  or eight  times  longer  than  the
   body; and  hence  the number of
   convolutions in the abdominal ca-
   vity.  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 intes-
   tine is bound down, or floats~in the
   abdominal cavity.  Their structure
   is nearly  alike throughout:  a mu-
   cous membrane lines them:  imme-
   diately  without this is a muscular
   coat; and, externally, a serous coat,
   formed  by  a prolongation  of  the
     ritoneum.   The  mucous   mem-
      e is soft and velvety,  and is the
   seat of a similar secretion to  that of
   other membranes of the same class
                                           Abdominal viscera.
                                 ,  A, A. The liver.—B. The pall bladder.—C, C
The mUSCular COat is Composed Of The stomach.—n, D, D, D. The small intestines.
     ,       „ _,           •,  j +L.„* —E. Commencement of the large intestines.—
IWO planCS Of fibres,  SO United, inaiFFF. Thecolon.—G, H. Sigmoid flexure of the
♦U«. „„    i  \ ^ c-.^o,.atorl ___thp  in- colon.—I, I. Rectum.—K. Anus with sphincter
they cannot  be sepai ated,—tne  in ani_L  L Levatorea ani.
nermost consisting of circular, and 
454
DIGESTION.
the outermost of longitudinal fibres; the arrangement of which differs
in the small and large intestines.  The serous  or peritoneal coat re-
ceives the intestine between two of its lamina*, which, in their pas-
sage to it, form the mesentery. The serous coat only comes in direct
contact with the intestine at 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 in-
testine, (see Fig. 103.)   Its calibre differs in  different parts;  but it
may be regarded on the average as about one inch.  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 ventriculis 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 valvula?  conniventes.  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 ab-
sorbent vessels are situated, forming, in part, 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.
The  most obvious use of these villi, as Dr. Roget and  Dr. Horner 
DIGESTIVE ORGANS.
455
 have suggested, is to increase the surface from which the secretion
 is prepared.  Within the membrane are numerous follicles, which,
 with the exhalants,  secrete a mucous fluid, called by Haller  succus
£ intestinahs.  Their entire number  in  the whole alimentary canal is
 estimated by Dr.  Horner to be 46.896.000.
    At about four  or five  fingers' breadth from the pylorus, the duo-
 denum is perforated by the termination of the biliary and pancreatic
 ducts, which pour the bile and pancreatic fluids into it.   Generally,
 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 de-
'i scribed 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
Jjbileum  terminating,  in the right iliac fossa, in the first of the  great
 (festines—the  caecum.   They occupy the middle and almost the
  whole of the abdomen, being surrounded by the great intestine E F
  FFGHI, Fig. 103.  The jejunum is so called, from  being gene-
'  rally found  empty; and the ileum,  from  its  numerous  windings.
c 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 great-
  est number of valvulae conniventes  and villi.  The ileum is the low-
It' est portion.   It is of a paler colour, and has fewer valvulae conni-
  ventes.  The jejunum is  situated at the upper part of the umbilical
(^region; the ileum at  the lower  part of it, extending  as far  as the
' hypogastric and iliac regions.   The mucous  membrane of the jeju-
  num and ileum resembles, in essential  respects, that of the duodenum;
P the valvulae  conniventes  are, however, more numerous in the jeju-
  num 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 Peyer, Brunner, and Lieberkiihn,  which secrete the
  succus intestinalis,—a mucous fluid, to which Haller attached unne-
  cessary  importance in digestion.    Lelut estimates the number of
IT these glands, in the small intestine, at 40.000.  The muscular coat is
  composed of circular and longitudinal fibres;  and the outer coat is
fc; formed by the prolongation of the  peritoneum, which, after  having
  surrounded the  intestines,  completes the mesentery, by which the
  gut floats, as it were, in  the abdominal cavity.
I    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 
456                        DIGESTION.
abdominal cavity than the portion of the  tube which we have de-
scribed. It commences at the right iliac fossa, (Fig. 103, E,) ascends
along the right flank, as far as the under surface of the fiver; crosses
over the abdomen to gain the left flank, along which it descends 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.
   The ccecum 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 caseum,
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 cozcal valve, &c.

                              Fig. 104.
      Commencement of the large Intestines.—Valve of Tulpius.
A. C Small intestine.—B B. Large intestine.—D. Appendix vermiformis caeci.
  Fi<*. 104 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-cacal.                                                 .
  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 extremities  of 
DIGESTIVE ORGANS.
457
  this valve are small tendons, which give it  strength, and have been
  termed the frama 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, stercoraceous  vo-
  miting is a frequent concomitant,  and there have been instances of
  substances,  thrown into  the rectum,  having been evacuated by
   vomiting.
     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 ccuci.
   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  fiscal 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,
   which  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, (F F F
   G H, Fi«*.  103.)  It  is a continuation  of the caecum, from  which
   it cannot be distinguished; but is considered to commence at the
1  termination  of the ileum.   From the right iliac fossa, it ascends
1  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
f   of the  colon, or colon transversum.  The right portion of the great
   arch is situated under  the liver and gall-bladder;  and hence is
l-  found  after death tinged yellow, owing to the transudation  ol  bile.
   The left portion of the  arch is  situated under the stomach;  and,
i  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 closelv  connected.   This portion  is  termed the colon
I  sinistrum, descending or left lumbar colon.  In  the left  ihac  region
f  it forms two convolutions, which have been compared to the L-neek s,
*  *- toThe Roman s;  and hence this part  of the  intestine has been
or ...
                                ON
  VOL.  I. 
158
DICTATION.
designated the sigmoid flexure, or Rinnan 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 exeunt.  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, but  they  are thinner, and not as
easily  separated  by dissection.   The  mucous  membrane  is less
villous and velvety.   The  most characteristic diflerence, however,
in the general appearance  of the great and small intestines, is the
pouched or cellular  aspect of the former.   These pouches are reser-
voirs for the excrement, and in them it becomes more indurated, 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
ligamentous 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 appendicular epiploiece, or appendicular pinguedinosa?.  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, following
the concavities of the sacrum and coccyx; and, consequently, is not
straight, as its name would import.   At its upper part, there are a
few appendicular epiploicae;  and a small duplicature of the mesen-
tery, called meso-rectum, attaches it to the sacrum.  It differs 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.  Immediately within
the anus is the widest portion of the rectum ; and, in this part, accu- 
DIGESTIVE ORGANS.
159
   mulations of indurated faeces  sometimes take place in old people to
   a surprising  extent, owing to torpor  of the muscular powers, con-
   cerned in the expulsion of the fieces.
     Lastly, there are a few muscles, which are concerned in the act
   of  expelling the faeces.  These require a short reference.   1. The
   sphincter am or  coccygeo-anal, which keeps the anus constantly
   closed, except during defecation.  2. The levator ani or  subpubio-
   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 rais-
  , ing the  lower extremity of  the  rectum; and 4.  The transversus
   perinei or ischio-perineal, some fibres  of which unite both with
   the bulbo-cavernosi and with  the sphincter ani muscles; and, con-
   sequently, 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 ani-
   mal—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 colon.   Cuvier has given tables  of the length of the canal,
   compared with that of the body; but, where the comparison 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 omnivorous animal;  but, as a
   general  rule, it may be affirmed, that the capacity of the canal is
   much more considerable.
      5. The abdomen, in which the principal digestive  organs are situ-
   ated, and whose parietes exert considerable influence on the diges-
   tive function, will require a brief description.  It is that division of
   the body, which is betwixt the thorax and pelvis ;  and is bounded,
   above, by the arch of the diaphragm ; behind, by the vertebral co-
   lumn ; laterally, and  anteriorly, by the abdominal muscles; and, be-
   low, 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 divisions
   on the surface, which have been called regions.
      The epigastric region, A,  Fig. 105, 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 hypoelmndre—constitute the 
DIGESTH>.\
upper
liv«
Ion.   The space, „.
region and a line  drawn from  the crest ot  one os iln
                       C.   Here the  small  intestines are  chiefly
                                            situated.  This region
is the umbilical  region,
Fig. 105.
                                           is bounded by lines,
                                           raised perpdndicular-
                                           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, in which the
                                           bladder  is  situated;
                                           and  an inguinal  (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
           Regions of the abdomen.                 considerably  concave
towards  the  abdominal cavity.  Below,  if we add  the  pelvic
cavity,—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 lum-
bar 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. 105, by a solid, aponeurotic band, extending
from the cartilage ensiformis of the sternum  to the pubis, called the
 
DIGESTIVE ORGANS.
461
linea alba.  The abdominal muscles, properly so called, are,—reckon-
ing 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 pyramadalis, which
occupy the anterior part.  The greater oblique, obliquus externus or
costo-abdominalis ;—the lesser oblique, obliquus  internus or ilio-abdo-
minalis, and the transversalis, transversus abdominis  or lumbo-abdo-
minalis, support and compress the abdominal viscera;  assist in the
evacuation of the fasces and  urine, and in the expulsion of the foetus;
besides other uses, connected with respiration and the attitudes. The
rectus, pubio-sternalis or  sterno pubialis;  and the pyramidalis  or
pubio-sub-umbilica/is, are more limited in their action, and compress
the forepart of the abdomen  ; besides having other functions.
   Lastly, a serous membrane—the peritoneum—lines the abdomen,
and gives  a coat to most  of
the  viscera.  The  mode,  in
which  its  various reflections
are made, is singular, but easi-
ly intelligible from the accom-
panying figure.   It has neither
beginning nor end, constituting
a shut sac,  and, in reality,
having no  viscus within it.  If
we  assume the  diaphragm as
the  part  at  which it com-
mences, we find  it  continued
from the surface of that mus-
cle  over the  abdominal mus-
cles, D; then reflected,  as ex-
hibited by  the dotted line, over
the  bladder,  E;  and, in  the
female, over the uterus, G;
from thence over the rectum,
P;  the kidney, H; enveloping
the  intestine, B, and  consti-
tuting, by  its  two laminae, the
mesentery, C;  giving  a coat
to the liver, A ;  and receiving
the  stomach between its dupli-
catures.
  The use of this membrane is
to fix and  support the different
viscera; to constitute, for each,
a pedicle, along which the ves-
sels and nerves  may reach the
intestine; and to secrete a fluid,
which enables them to move
Fig. 106.
Reflections of the peritoneum.
readily upon each other.   When we speak of the cavity of the peri- 
462
digem'io.y.
toneum, 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.
  The omenta or epiploa arc fatty membranes, which hang over the
face of the bowels, and are  reflections, formed by the peritoneum
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 appendicular epiphicce,  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 ante-
riorly in the course of the linea alba,  but which is closed  after birth,
—the umbilicus; and two anteriorly and interiorly; 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 ex-
tremity.   Lastly, two others exist in  the inferior paries, for  the pas-
sage of the obturator vessels and nerves, and of the  sciatic  arteries
and nerves, respectively.
   Su<h is a brief view of the various organs concerned in digestion.
To this might have been added the general anatomy of the liver and
pancreas,—each of which organs furnishes  a fluid, which is a ma-
terial 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 function of these  organs will be
considered in another place, wre 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, the term
food or aliment, is applied to  substance.s, which, when received into
the digestive organs, are capable of being converted  into chyle; but,
from this class again, the  products of the  mineral kingdom cannot,
with entire propriety, be excluded.
   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; the phytivorous on vegetables;  thegra-
nivorous on seeds;  the frugivorous on the  fruits;  the graminivorous
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 
FOOD OF MAN.
463
aliment they chiefly used.   Thus, there were the  ^Ethiopian and
Asiatic Icthyophagi or fish-eaters;  the hyhphagi, who fed on  the
young shoots of certain trees; the elephantophagi, and strulhiophagi,
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 pro-
ducts 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 more  favourable for vegetable, than  for animal, life-
  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 arc 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 on  their own
resources.   This is the great cause, why  the Esquimaux,  the  Sa-
moiedes, &c. live  wholly on animal  food; and why the  cocoanut,
 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,  arc 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 sup-
 ply 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 political pur-
 poses, and not  in consequence of the unwholesome character of the
 interdicted articles.
  The same remark applies to many of the dietetic rules of Moses,
 for the 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. &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 Helvctius,  that he was  exclusively  carnivorous.  Brous-
 sonet affirms,  that he  is more herbivorous than carnivorous; since, 
464
DIGESTION.
of his thirty-two teeth, twenty resemble those of the herbivorous,
whilst twelve only resemble those of the carnivorous, animal.   Ac-
cordingly, he infers, that, in the origin of society, his diet must have
been  exclusively vegetable.   Mr. Lawrence, too, concludes,  that,
whether we consider  the teeth and jaws, or the immediate instru-
ments of digestion, the human structure closely resembles that of the
simiae,—the great archetypes,  according,  to  Lord  Monboddo  and
Rousseau of the human race—all of which are, in their natural state,
completely herbivorous.
  Again, we observe  a wide dcscrepancy 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.   Independently, h< >wcvor, of all argu-
ments deduced from  organization, experience sufficiently shows the
inaccuracy of these assertions.  If  we trace back  nations to their
state of infancy, we find, that  then,  as in their more  advanced con-
dition, the  diet was animal, or vegetable, or both, according to cir-
cumstances.  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 prevailed 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 Ichthyophagi.  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 sup.  Close to them were the Hyhphagi,  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
elephantophagi and struthiophagi.  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.   Al-
though 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  wTest, dwells  a tribe, who sub- 
FOOD OF MAN.
465
sist, 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 subsist-
ence would be too scattered for him, whilst the crowding together
of a number of nutritious vegetables into a small space, and the cul-
tivation 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 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.
  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 inunda-
tions of the  rivers, or thrown  on  the sea-coast,  ministered to their
necessities, without the  slightest effort  on their  part;  and,  hence,
they had but little  incentive to mental or corporeal exertion.  This
is the cause of the abject  condition of the ichthyophagous tribes of
old;  and of their comparatively' low state of civilization at the pre-
sent day.
  Again, the savages, in various parts of the globe, live by the  chace
or the fishery; and must, consequently, be  regarded as  essentially
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 prerogatives, one of which is
the capability of rendering the organized kingdom subservient to his
wishes and necessities;  and, by the invention 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 restric-
tion 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, entirely
on vegetables:—
              " His food the fruits; his drink the crystal well;"

unsolicitous for  the future, in consequence  of the abundant subsist-
  vol. i.                       59 
406
DIGESTION.
ence spread  before  him; independent, and always  at  peace with
his fellows, and with the other animals; but he gradually sacrificed
his  liberty to  the bonds of  society, and  cruelty, with an insatiable
appetite for flesh and blood, were the first  fruits of a depraved na-
ture.  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  which
mankind are  accustomed to be omnivorous, or to unite animal with
vegetable food, are those, that  are most distinguished for both mental
and corporeal endowments.   The tribes, which feed altogether on
animal  food,—as the Laplanders, the Samoiedes, the Esquimaux,
&c.—are far inferior, in both these respects, to the European or Eu-
ropeo-American; and the same may be  said, although not  to the
like 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 few Europeans.
  Attempts have frequently been  made to refer the nutrient proper-
ties of all articles of diet to a particular principle of a constant cha-
racter, 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 combination  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;  and Halle, that it  is
a  hydro-carbonous  oxide,  very  analogous  to gummi-saccharine
matter!
  It is probable, that there is no such particular principle as the one
contended for;  and that, 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  impelled, when we
reflect that the chyle can  be formed from both animal and vegetable
substances; in other words,  that, when  vegetable  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  vegetation.   In an
early part of  this work, we had occasion to mention,  that animals
and  vegetables are reducible into  nearly the same ultimate elements,
—in some cases into precisely the same,—oxygen, hydrogen, car-
bon  and  azote; the. latter being  wanting, however, in most vege-
tables and in  several animal  substances; and all organized bodies
probably possess the power of reducing substances, received as food,
into their elements;  and of recomposing them, by virtue of affinities
which are controlled by the vital agency. 
FOOD OF MAN.
467
     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 case  of the herbivorous animal, which sub-
   sists  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  containing  azote,
   the origin of the azote  of the  body must  be looked for  elsewhere
   than m the food.  Magendie, however, has properly remarked, that
   they do not lead legitimately to this  conclusion.  Almost all the
   vegetables, eaten by man and animals, contain, 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 ot
   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
  PV days the animal appeared to thrive well, was  lively, and  ate and
r ' drank with avidity.  In the second  week,  he began  to  tall off,
   although his appetite continued good, and he ate six or eight ounces
   ofsucrar in the twenty-four hours.  In  the third  week, he became
    emaciated, his strength  diminished, his gaiety was gone, and  his
    appetite impaired.   An ulcer formed on each eye, at the centre  ot
    the cornea, which subsequently perforated the  cornea, and allowed
    the humours of the eye to escape.  The  emaciation  went on pro-
    gressively 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
    commencement 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 i  e,
    tines were  much diminished in size,  and  powerfully contracted;
    and the gall and urinary bladders were filled with fluids not proper
    to them   These were  examined by M. Chevreul, who found them
    to possess almost all the characters of the bile and urine o  the he.
    bivorous animal.  The urine, in place of being  acid, as it is in the
     3™!!  sensibly alkaline, and presented no trace  of uric
    carmvora, was  senslDl^h  bUe contained a considerable proportion
    ^S£i^    onhe ox and the herbivora in general.  The 
468
DIGESTION.
excrements  contained  very little azote,  which they usually exhibit
in abundance.
   A second dog was subjected to the like regimen, and with similar
results.   He died on the thirty-fourth day of the experiment.
   A third experiment, having  afforded  analogous results, Magendie
concluded, that sugar alone is  incapable of nourishing the dog.
   In all these cases, ulceration of the cornea  occurred, but not ex-
actly at the  same period of the experiment.
   He next endeavoured to discover,  whether these effects might not
be peculiar to sugar;  or whether the non-azoted substances, gene-
rally  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,
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, Magendie
was desirous  of establishing  this  in a positive manner.   Accord-
ingly, after  having  fed  animals for several days on oil, gum, o r
sugar, he opened them, and found that each of these substances 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 trans-
parent, 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 likely, that the  azote,
found in different parts of the  animal economy, is originally obtain-
ed from  the food taken in.  This is, however, extremely 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  ad-
ministered.  It must be recollected,  moreover, that the  subjects of
these experiments were dogs ;—animals which, in their natural state,
are carnivorous, 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 Precis  Eltmentaire de Physiologie, Magendie founH 
FOOD OF MAN.
469
that his deductions were not, perhaps, as absolute or demonstrative
as he had at first imagined; and additional experiments induced him
to conclude,—as Dr. Bostock  and Sir Charles Bell have since done,
without being aware, apparently, of Magendie's observation,—" that
variety and  multiplicity of articles of food constitute  an important
hygienic  rule."   " This," Magendie adds, "is indicated to us by our
instinct, as well as by the changes that wait upon the seasons, as re-
gards the nature and kind of alimentary substances."
  The additional facts, detailed by Magendie, are the following:—
A dog, fed at discretion  on pure  wheaten bread, and drinking
common  water, does  not live  beyond  fifty days;  whilst another,
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, that 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
completely  modifying the function of assimilation, as it has been or-
dinarily  practised.   It has been  long  known,  that if man,  pre-
viously habituated to 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,

  * The rodentia are gnawing animals, having large incisors in each jaw, with which
they divide  hard substances.   They arc the rongeurs of the French naturalists.   The
Bquirrel, mouse, rat, Guinea-pig, hare, rabbit, beaver, kangaroo, porcupine, &c. belong
to this division. 
470                       DIGESTION.
 has been sufficiently shown by the reference already made to carni-
 vorous and herbivorous tribes  existing in  different regions of  our
 globe.  The importance of variety  of diet  is illustrated by  the ex-
 periments, which Dr. Stark, of  Vienna, made upon his own diges-
 tive  powers,  and to which he ultimately  became a martyr.   His
 object was to discover the relative effect of various simple  sub-
 stances, 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 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,  Indian
 corn, potato, sago, salep, peas, haricots, lentils, &c.
   2.  Mucilaginous aliments; carrot,  salsify, beet, turnip, asparagus,
 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, rasp-
 berry, strawberry, mulberry, grapes, prunes, pears, apples,  tomatos,
 &c.
   5.  Oily and fatty; cocoa, olives, sweet almonds, hazelnuts, wal-
 nuts,  animal fats, oils, butter, &c.
   6.  Caseous  aliments; the different species of milk, cheese, &c.
   7.  Gelatinous aliments; the tendons, aponeuroses, skin, cellular
 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.
   To these proximate  principles, may be added gluten, which is
 the only vegetable compound of organization that contains a notable
 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.   According to Prout, 
                         FOOD OF MAN.                       471

it is separable into two portions,  analogous to gelatine and albumen.
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 fecula of vegetables in general; but it is especially abun-
dant 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.
  The different drinks may, like the solid  food, be classed according
to their chemical  character:—1. Water of different kinds.  2.  Vege-
table 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, kirsch-
wasser, rum, gin, whisky, 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 to
this variety of  aliments; and it has been  contended, that  water is
the most natural  drink; and  that all others, which are the  products
of art, ought to be avoided.  The remarks, we have already made
on this subject, will  be sufficient.   Water was, doubtless, at one
period, the only beverage of  man; as nakedness and the use of raw
ttliment, and the most profound  ignorance of the  universe  was his
"original condition; but no one will be presumptuous enough  to de-
clare,  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 moderate
 use of fermented liquors, even if habitual, except in particular con-
 stitutions, 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. Kit-
 chener has, for this reason, termed beer, not inaptly, " liquid bread."
 With regard to distilled spirits, no evil would  result from their total
 rejection3from  the table.   Although they may, by  their action on
 the digestive organs, be the indirect  means of nutrition, they  them-
 selves contain  no alimentary property.  They are received into the
 vessels of the stomach by  imbibition;  and  always produce, when
 taken even to  a  small amount, undue stimulation.   This may be
 productive of little or no  mischief, provided they are only  used oc-
 casionally ; but,  if taken habitually, serious visceral and mental dis-
 order may sooner or later ensue.
   Lastly.  There are certain substances, called condiments, employed
 ■in  diet, not simply because they are nutritive,—for  many of them
 possess  no such properties,—but because, when taken with tood
 capable of nourishing the frame, they promote its digestion, correct 
472
DIGESTION.
some injurious  property it possesses,  or add to its sapidity.   Dr.
Paris has  divided  these  into  the  saline, the spicy or aromatic, and
the oily.  It may be remarked, however,  that  certain  articles  are
called, at times, aliments,  at  others, condiments, according  as they
may constitute the basis  or  the accessory to any dish;—such  are
cream,  butter,  mushrooms, olives, occ.  The advantage of condi-
ments to animal digestion is strongly exemplified by  many cases.
The bitter  principle, which exists in grasses  and other plants,  ap-
pears 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 rurai
economy for fattening poultry, in many parts of England,—striking-
ly exhibits  the  advantage  of  administering a condiment: it is a sub-
stance 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 asserted, 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 augmented action; and a  more bountiful separation of nutritious
matter  or  of chyle is the consequence.  The aromatic condiments
act in  a similar manner.
   These few remarks on  the  food of man  will introduce us to the
mode in which the various  digestive processes  are accomplished.
The more intimate consideration of  alimentary substances,  with
their comparative digestibility, &c, will be found in another  work,
to which the reader is referred.*

                     Physiology of Digestion.

   The detail  entered into 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 im-
mediate contact  with the being to be  nourished;  consequently an
act of  volition is  necessary to procure it,  and to convey it to the
upper  orifice of the digestive tube.   This act  of volition is excited

  * On the influence of atmosphere and locality; change of air and climate; seasons;
food; clothing; bathing; exercise;  sleep; corporeal and intellectual pursuits, &c.&c.
on human health; constituting Elements  of Hygiene.  By Roblev Dunslison, M. D.
p. 205.  Philadelphia, 1835. 
                              HUNGER.                        473

 by an internal  sensation—that  of hunger—which  indicates to the
 animal  the necessity for taking fresh nourishment  into the  system.
 Ine appetite, arid  hunger, with the prehension or reception of food,
 must therefore  be  regarded parts of the digestive operations.   These
 may be enumerated and investigated  in the following order:—1st.
 Hunger, or the  sensation, which excites us  to  take  food.  2d. Pre-
 hension  of food, the voluntary muscular 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.  Chymi-
 jication, or the action of the  stomach on the food.  6th. The action
 of the small intestine.  7th. The action of the large  intestine.  And
 8th.  Defecation or the  expulsion of the fceces.   AH  these processes
 are not  equally  concerned in the formation of chyle.   It is separated
 in the small intestine: the first six consequently belong to it;—the
 remainder relate only to the excrementitious part of the food.  The
 digestion of solid food  requires all  the eight processes.   That of
 liquids is more simple ;  comprising only thirst, prehension, degluti-
 tion, 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
'■\ lhall 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  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 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, by the  sight  of  a disgusting
 object, or anything 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 sensation
   vol. i.                      G0 
474
DIGESTION—OF SOLID FOOD.
soon appears, and cannot be long postponed by any of these means.
Hence, it has been proposed to make a distinction between the ap-
petite and hunger; applying the former term to the artificial, the
latter to the natural, desire.  In these  respects, there is certainly a
wide distinction  between them, as well as in the  capriciousncss,
which occasionally characterizes the former, and gives rise to the
most singular and fantastic preferences.
   The sensation  of hunger varies in intensity according to different
circumstances.   It is more powerful in the child and the youth, than
it is in the adult,  who has attained his full height.  In the period of
seeond childhood, it is urgent, probably owing to the diminished
power of assimilation requiring, that  more aliment should  be re-
ceived  into the stomach.  In the state of disease, the sensation is
generally suppressed, and its place is often supplied by loathing or
disgust for  food: at times, again, its intensity makes it a  true
disease, as in bulimia, and in pica; in the latter of which, the ap-
petite is, at times, irresistibly directed to substances, which the per-
son 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 has quoted, 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 ap-
petite.  " 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 despatched 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 oppor-
tunities 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; but many of their assertions on these points appear to be
imaginative.  We are told by Adelon and others, that the stomach
becomes contracted, and that this change is effected by the sole ac-
tion of its muscular coat;—the mucous or lining membrane becom-
ing 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  observations.   Magendie,
however, affirms, that after twenty-four, forty-eight, and even sixty 
HUNGER.
475
hours of complete  abstinence, he  has never  witnessed  this con-
traction of the  stomach.  The organ  had always  considerable di-
mensions,  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, the duodenum is said to be drawn slightly towards it; its pa-
rietes to appear thicker,—and the mucous follicles and nervous pa-
pillae  to 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 circulation
of the blood in the stomach experiences any mutation.   ■D«mas 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 omen-
tum ; and he regards^these organs as diverticula for the blood ot the
 stomach, especially as the liver and spleen are then less  compressed,
 and the omentum  more extensive,  owing to the retraction of the

   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 great
 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  viscera
 to escape through the  opening   During the state of vanity of the
 onran  die remarked, that the diflercut reservoirs  in the cavity ot
 Lgabdomen!-as the bladder and gall-bladder,-were more easily 
476
DIGESTION—OF SOLID FOOD.
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 organ 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 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 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 decom-
position  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  quantity, 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 nas  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, which probably modified the symptoms but little, inasmuch
as we  shall find hereafter, that but little nutritive  absorption can be
effected through the cuticle.  At one period he had a parched 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 unim- 
HUNGER.
477
paired, until the last four 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 eve was un-
usually  sensible, and the  sense  of touch remarkably acute.   The
surface and extremities were at times of a burning heat; at others,
clammy  and cold.  On the fourth, the pulse became feeble and ir-
regular, and  the respiration laborious; and, in ninety-six hours after
all means of nutrition as well as all 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 tran-
quilly to  death.  In- others, the distressing accompaniments,  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 rule 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 survi-
vorship,  that may arise when several individuals have perished to-
gether from  this cause.    The  picture, drawn  by  Dante,  of the
sufferings  and  death of Count  Ugolino  della Gherardescha who
fsaw his  sons successively expire before  him  from hunger, in this
respect true to nature:—

       " Now when our fourth sad morning was renew'd,
         Gaddo fell at my feet, outstretch'd and cold
         Crying :—' Wilt thou 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 achieved 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 impression,
 conduction, and perception.  That the  brain is the organ  of the
 last part of the process is proved by all  the arguments used in the
 case of the internal sensations in general.  Without its intervention,
 in this,  as in every other case, no sensation can be  accomplished.
 The stomach is the organ in which  the  impression is  effected;
 and, by  means  of the  nerves, this impression  is conveyed  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 Ba<divi, Valsalva,  Haller, Dumas, Legallois, Chaussier, and
 others that  if these  nerves be  divided  in  the neck, although the
stomach  may be, in  other respects, favourably circumstanced for
the developement of the impression of hunger, and the brain ready 
478
DIGESTION--OF SOLID POOD.
 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 cat
 after the stomach  was filled.   To  these experiments we shall have
 occasion  to refer hereafter.  They by no means exhibit, that this
 internal sensation differs from others; and that the three actions arc
 not equally necessary for its accomplishment.
   The difficulty, which the physiologist  has always felt, regards
 the precise nature of the action" of impression.   Its  scat is clearly
 in the  stomach.   This was incontestably shown, in  a case of fistu-
 lous opening into  the stomach, which fell  under the  care of Dr.
 Beaumont, and to  which we shall have frequent occasion to  refer:
 when the  subject  of the case  was made to fast until the  appetite
 was urgent, it was immediately assuaged by feeding him  through
 the aperture.  To the stomach, all our feelings  refer the sensation.
 It is dependent 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 1   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 papilla? 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  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  referred to an action after
death, and are, consequently, totally unconnected with the sensation 
HUNOER.
479
  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 Sommering 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, produc-
  tive of the sensation; his remarks, however, tend simply to show,—
  what we have so many opportunities of observing,—that the  sensa-
   tion can be postponed by exciting vomiting, or by inducing-, for the
   time, a morbid condition of the  stomach.  The unanswerable ob-
  jection, however, to all these views is the fact—repeatedly proved by
  Dr. Beaumont and  which the author had an opportunity of observing
   —that, in the fasting state, there  is no gastric juice in the cavity of
   the stomach.   Dr.  Beaumont, himself, thinks, that the sensation of
   hunger is  produced by  distention of the vessels, which secrete the
f,  gastric solvent; but such distention, if it exist—which is by no means
K  proved—must itself be  consecutive on the nervous  condition, that
Wk engenders the sensation; the efficient cause of such conduction has
   still to be explained.
*     Bichat, again, attributed it to the lassitude or fatigue of the sto-
   mach, occasioned by the contraction of its muscular coat, when pro-
J   longed beyond a certain  time.  In answer to this, it may be re-
j  marked, that, if anything impedes the  nutrition of the body,  hunger
   still continues, although  the stomach may be distended.  This nap-
s'  pens in cases of scirrhous pylorus, where the nutritive mass  cannot
   pass into  the small intestine, to be subjected to the action of the
f.  chyliferous vessels, and the losses  of the body cannot, therefore, be
   repaired;—facts which  would  seem to  show, that hunger is a sen-
   sation, 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 inappreciable to
   us.  It appears, from the experiments of  Magendie, that when the
   cerebrum and  great part of the cerebellum were removed in ducks,
   the  instinct  of  seeking food was lost in every instance, and  the
   instinct of deglutition in many : food, however, introduced  into the
   stomach was found to be digested.
      2. Prehension of food.  The arms and the mouth have been de-
    scribed 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 m which this is
    effected has  given rise  to much controversy; and strange to say is
   not  yet considered determined. 
480
DIGESTION—OF SOLID FOOD.
   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 correct 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  im-
 movably to the head;  the whole head must, of necessity, participate
 in this movement; and the question arises, what are the agents that
 produce  it 1   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 ex-
 tensors 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 mo-
 tion be " forced"  or extensive, the  upper jaw participates  slightly.
 The  experiment,  however, with the knife, which is adduced by
 Adelon nimself,  completely overthrows this notion, and shows, that
 both jaws act, whenever the mouth is  slightly  opened.
   Magendie agrees with Boerhaave, Monro, and Pringle, that, when-
 ever 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 occasioned
 by the action of the stylo-hyoideus  muscle,  and of the  posterior
 belly of  the  digastricus; and he affirms, that whilst the anterior
 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 of the head with the atlas; whilst
 the styloid process, to which the stylo-hyoideus is attached, is an-
 terior to  the  articulation, and its effect ought, therefore, to be  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.   The temporo-maxillary
 articulation  is not formed  by a single condyle, but by two, which
 are so disposed, that the lower cannot roll downwards during the
 depression of the lower jaw, without  causing the upper condyle to
roll upwards, and, consequently, to slightly elevate the upper jaw.
  Under ordinary circumstances, then, the jaws cannot be at all 
rilEMlvV-hi\ OK Kl.'Dl;.
is I
   separated without both participating; but if we determine to fix the
   upper jnw wc 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.   Frequentlv, 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 muscles;
   and the resistance in the substance between the teeth.   The arm of
f   the resistance is, consequently, the whole length of the lever;  and we
   can readily understand,  why we arc capable of developing so much
   more force, when the resistance is placed  between the molares;
   and why old  people,—who have become toothless, and  are, conse-
   quently, constrained to bite with the anterior part of the  jaws,—the
   only portion, that admits of contact,—cannot bite  with any degree
1$  of strength.
^.  The size of the body, put between the incisor teeth, influences the
^tlegree of force that  can be brought to bear upon  it.   When small,
   the force can  be  much  greater, as the levator muscles are  inserted
   perpendicularly 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 insertion of the levator
"'   muscles into the jaw being rendered very oblique ; and the  greater
   part of the  force they develope being consequently lost.  This will
   be readily  seen  by the illustration,  Fig. 107.  When  the mouth
   is closed, or nearly so,  the masseter and temporal muscles, repre-
   sented respectively by the lines B E and J j, are inserted nearer the
   perpendicular; but when the lower jaw is depressed, so that the si-
   tuation 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.
VOL. I.
61 
482
DIGESTION--OF SOLID FOOD.
Fig. 107.
  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.—II. 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.—g-. 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
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 
M^TICATln.Y.
183
   transmitted along the oesophagus; 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, especi-
Lj  ally, if of any size or density, it is divided into  separate portions, 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
   their coronee come to  an edge; the canine teeth  penetrate and la
   cerate, and their coronas  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 fulcrum.
   To preclude displacement, by the efforts  they have occasionally
   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. 
 184                  DIGESTION--OF  -OLID FOOD.

  The  gums  add materially to the  solidity of the  junction of the
teeth with the jaw.   They are themselves  formed of highly resist-
ing materials, so as to withstand the pressure of hard and irregular
substances.   Whenever they become spongy, and  fall  away "from
the teeth, the latter become loose ; and are frequently obliged to be
extracted, 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  is 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
operated.
  During the whole time that mastication  is going on, the mouth 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
various  fluids poured into the  mouth,  and particularly with the
saliva,  the  secretion of which is  augmented,  not only by the pre-
sence of food, but even by the sight of it, especially if the food be
desirable;—giving rise to what  is called '-mouth-watering."  It is
probable, 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 demon-
strated, both anatomically and by experiment, that  such is not the
case.
  It has been supposed, by some, that the admixture with the saliva
communicates to the food its first  degree of animalization;  or in
other words, its first approximation  to the  substance of the animal
it has to nourish.   Such are the opinions of Drs. Jackson and Voi-
sin.  The former  asserts, that  he  has ascertained positively, that
the saliva exerts a very energetic operation on the food, separating,
by its solvent properties, some of its constituent principles, and per-
forming a species  of digestion.  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, consequently, 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,
weighing a  drachm, for three hours.  At  the expiration  of this
time, the ham was  white on its  surface, and had  increased in
weight  twelve grains.  Krimer, it may be remarked, believes, that 
DEGLUTITION'.
485
the tears assist in digestion,  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,
wc 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.   Ade-
lon, whose views are generally worthy of  great  favour  and atten-
tion,  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 favourably  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 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 oesophagus.   It has been  well  analyzed by Magendie,—
first of all in a thesis,  maintained at the Ecole de Mi.decine of  Paris,
in 1808, and subsequently, in his Precis  climentaire de  Physiologic.
To facilitate its study, he divides it  into  three stages.  In the first,
the food passes from the mouth into the pharynx; in  the s-eond. it
clears the apertures of the glottis and nasal fossae,  and  attains  the
oesophagus; and, in the third, it clears  the oesophagus  and enters
the stomach.
  I.  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 the last organ;—the mass being more or
less rounded, and hence, usually termed the alimentary bolus.   Mas-
tication now stops, the tongue is raised and applied against the bony 
480
DIGESTION—OF SOLID FOOD.
palate, in succession from the  tip to  the  root, and the alimentary
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 had been applied to the base of the  tongue.   The
bolus now  raises it to  the horizontal position:  the circuinflcxus
palati muscles render the velum tense, so that the  food cannot pass
into the nasal fossa); and  the muscles that  constitute the pillars of
the fauces—the palato-pharyngei and  the  glosso-staphylini—contri-
bute to this  effect.  By this combination of results, the food is im-
pelled 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, 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 con-
vulsion.
  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
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 
DEGLUTITION.
187
 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 oesophagus.                                  r   J
   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 de-
 struction  of the  epiglottis, deglutition is laboriously and  imperfectly
 accomplished, it  is owing to the carious condition of the arytenoid
 cartilages, and to the lips  of  the  glottis being so much ulcerated 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 the  cough is  excited,  which  is not appeased, until the
 cause is removed.   This is  what is  called, in common language,
 " the food going 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  descent
 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 preventing
 it from passing into the larynx.
   The whole of this second  stage  consists of rapid movements, of
 an entirely involuntary  character,  which,  according to Bellingeri,
 are  under  the presidency of  the  palatine filaments of  the fifth
 pair.
   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  ease  in the 
488
DIGESTION—OF SOLID FOOD.
lowest third, the circular fibres remaining contracted, lor some time
after the entrance of the bolus into the stomach,—probably to pre-
vent its return into the oesophagus.
  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  oesophagus  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,
indeed, must have felt the slowness  of the, progression of  the food
through the oesophagus when a rather larger morsel than usual  has
been swallowed.   If  it  stops, we  are  in the habit of aiding its pro-
gress by drinking some fluid, or by taking a piece of bread to drive
it onwards.  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 per-
mitted the interior of the stomach to be seen, Halle noticed, that
whenever 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
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 
CHYMIFICATION.
489
In the stomach, the air acquires  the  temperature of the  viscus, be-
comes rarefied, and distends the organ; exciting, in some, a feeling
of burning heat; in others, an 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 oesophagus, 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 cavity, and simulating tympanites.  Ma-
gendie refers to the case of a young conscript, who feigned the dis-
ease 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 diffi-
cult, 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.   Dr. Beaumont observed, that
when a  portion of food  was  received into  the  stomach, the rugrc
of the latter gently close upon it, and, if it be sufficiently  fluid, they
gradually diffuse it through the cavity of the organ, entirely exclud-
ing  more during this action.   The  contraction ceasing, another
quantity of food is received in the same manner.   It was found, in the
subject  of his experiments, that when  the valvular portion of the
stomach, situated at the  fistulous aperture was  depressed, and solid
food introduced, either in larger pieces or finely divided, the same
gentle contraction or grasping  motion took place, and  continued
for fifty or eighty seconds, and would not allow of another quantity,
until that period had  elapsed, when the valve could be  depressed,
and more food put in.  When he was so  placed, that  the cardia
could be seen, and was  then permitted to  swallow a mouthful of
food, the same contraction of the stomach and grasping of the bolus
were invariably observed to  commence  at the oesophageal ring. 
490
DIGESTION--OF SOLID FOOD.
Hence,  when food  is swallowed too rapidly,  irregular contrac-
tions of the muscular  fibres of the oesophagus and stomach are pro-
duced, the vermicular  motions of the ruga) are disturbed, and the
 regular process of digestion is interrupted.
  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 effect  its  three coats  equally.  The two
lamina, 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
particular shape  of the  organ; whilst the mucous  coat yields, in
those parts especially where the ruga 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 pene-
trate the stomach in a very different part, according as it  may  be,
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
augmented: the belly becomes prominent;  and  the abdominal vis-
cera  are compressed, sometimes so  much so, as to excite a desire
to evacuate 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-disten-
tion, 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- 
CHYMIFICATION.
491
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 prolong 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 pas-
sage of the food back along the oesophagus, as well as through the
pylorus.
  Magendie  found, in his vivisections, that the lower portion of
the oesophagus experiences,  continuously,  an alternate motion of
contraction and relaxation.  This contraction begins at the junction
of the  two upper  thirds with the lowest third;  and is propagated,
with some rapidity, to the termination of the oesophagus  in  the  sto-
mach.  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  suc-
ceeds 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 that 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 relaxed.  Its fibres, thus deprived of ner-
 vous influence, were shortened with a certain degree  of force; and
 the canal remained in a state intermediate between  contraction and
 relaxation.                            ,.,,/•            r
   The lower part of the  oesophagus  of the horse, for an extent ot
 eight or ten  inches, is  not  contractile in  the manner  of  muscles.
 Magendie found, that when  the eighth pair of nerves  was irritated;
 or when the parts were exposed to the galvanic stimulus, no  con-
 traction 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 introduce the finger
 into it;  and considerable pressure is required to force air into it.   1 his
 arrangement Magendie considers to be the true reason,  why horses
 vomit° with  such difficulty  as occasionally to rupture the stomach

  yThe alternate motion of the oesophagus, 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, com-
 monly coincides with inspiration; the time at which the stomach is, 
492
DIGESTION--OF SOLID FOOD.
of course, most  strongly compressed.   The  relaxation is synchro-
nous 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
oesophagus, 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
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," say  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 passing
from the former 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 unfit 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,
(irvXwpos, "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 
CHYMIFICATION.
193
  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 chyle; and would be so,
  if it could be retained in the  stomach; yet there is  no agent, which
  arrests its onward progress.  Still, from these, and  other  circum-
  stances, Broussais has inferred, that there is an internal gastric sense,
  which exerts an elective agency; detaining as a general rule, sub-
  stances that are nutritive, but suffering others to pass.
     The presence  of food  in  the stomach, after a meal, soon excites
  the organ to action, although no  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 secre-
  tions 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
  E fasting for some time,  and then be made  to swallow dry  food,  or
  '"even stones, and be deprived of liquid aliment, the substances, swal-
   lowed, will  be found—on  killing  it some  time  afterwards—sur-
   rounded by a considerable quantity of fluid.  Such is not the case
   with animals,  killed  after fasting.  The stomach then contains no-
   fluid matter.   The augmented secretion, in the former case, must
  fi therefore, be owing to the presence of the dry food in the stomach.
   That it is not  simply the fluid, passed down by deglutition—the sa-
   livary and mucous secretions, for example,—is proved by  the fact,
   that the  same thing  occurs when  the oesophagus  has  been tied.
K, 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
   bewithdrawn,-th? 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.   In Dr. Beau-
   mont's case, the collection  of gastric secretion was  obtained by in-
    serting an elastic gum tube through the opening; in a short time fluid
    enough was secreted to flow through the tube.
      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  onlyapparen.changj ™ "^
    for some time after the reception of solid ^f^™™™*™.
    cording to circumstances, the pyloric portion of he orga« contiarts,


    SnStt-   After this time, chyme only is found 
494
DIGESTION--OF SOLID FOOD.
, in  the  pyloric portion,  mixed with  a very small quantity of unal-
 tered 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 fulness of the  stomach.  He made dogs  swallow  forced-meat
 balls, in the centre of which he placed cartilage, and he found, that
 when the stomach  was greatly charged, the cartilages were pressed
 out of  the balls.  This did not happen, when the organ contained a
 smaller quantity of food.
    The ordinary course and direction of the revolutions of the food,
 according to Dr. Beaumont, are as follows:—The bolus, as it enters
 the cardia, turns to the left, passes  the aperture, descends into the
 splenic extremity, and follows  the great curvature towards the
 pyloric end.  It then returns in the course of the lesser curvature,
 and makes its appearance again at the aperture, in  its descent into
 the great curvature to perform similar revolutions.   That these are
 the revolutions  of the contents  of the stomach, he  ascertained by
 identifying  particular portions of food, and by the fact,  that the
 bulb of the thermometer, introduced during chymification, invari-
 ably indicated the  same movements.  Each revolution is completed
 in  from one to three minutes, and the motions are  slower at first,
 than when  chymification has made considerable progress.
   In addition to  these movements, the stomach is subjected to more
 or  less succussion from the neighbouring organs.   At  each inspi-
 ration,  it is pressed upon by the diaphragm; whilst the large  arte-
 rial 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 system;
 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  persisting after  the
 alimentary canal has been removed  from the  body.  MM. Ticde-
 mann and Gmelin, however, affirm, that by irritating the plexus of
 the eighth pair of nerves, which is situated around the oesophagus,
 with the point of a  scalpel, or by touching it with alcohol, the peris-
 taltic action of both stomach and intestines can be constantly ex-
 cited.
  This  involuntary function, as well as that exerted by the heart
% 
*                            CHYMIFICATION.                    495
1
\  and other involuntary organs, affords us a striking instance of the
  little nervous influence, that seems  to  be requisite for carrying on
  those functions, which 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.
     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 oesophagus; or by what
  have been termed the gastric glands.   The analogy of many ani-
(-v mals, especially of birds,  would render the  last opinion the most
  probable.   In them we find, in the second stomach, the cardiac  or
hgastric glands  largely developed ;  and it is probable, that  they are
  tie great agents of the secretion of the digestive fluid. (See Fig. 101.)
     RM. Tiedcmann and Gmelin affirm, that the  more liquid portion of
     e gastric fluid is exhaled, and the thicker, more  ropy and 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.   Dr. Beaumont, who had an excellent opportunity for  experi-
  menting in  this matter, remarks, that on applying aliment, or any
  irritant, to the internal c6at of the stomach, and  observing the effect
  through a magnifying glass, innumerable, minute, lucid points, and
  very fine papillae, could  be  seen protruding, from which a pure,
  limpid, colourless, slightly viscid fluid, distilled, which was invariably
\.  distinctly acid.   On  applying the tongue to the mucous coat in  its
  empty, unirritated state, no acid taste could be perceived.  Although
  no apertures were perceptible in the papillae, even with the assistance
  of the best microscope that, could be obtained, the points, whence the
  fluid issued, were clearly indicated by the gradual appearance  of
  innumerable, very fine, lucid specks,  rising through the transparent
  mucous coat, and seeming to burst, and discharge themselves upon
  the very points  of the papilla;, diffusing a limpid, thin fluid  over the
  whole interior gastric surface.
     A like difference of opinion has prevailed regarding the chymical
  character of the fluids; and this has partly arisen from the difficulty of
  obtaining 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
* 
49G
DIGESTION--OF SOLID FOOD.
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 it 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 Sir Benjamin Brodie and  others,
 would seem to  showr, 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 unaffected, 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
 acid taste.   Such, are its most common characters; it varies, how-
 ever, according to the food  that has been taken,  as may be easily
 observed, by feeding animals on  different simple  alimentary sub-
 stances, and killing them during the process of digestion.   This dif-
 ference, in its properties, accounts for the discrepancy, observable in
 the  accounts of writers on the 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
hospital La  Charite, of Paris, who had been gored by a bull, and
had a  fistulous opening in the stomach, the food, during its conver-
sion  into  chyme,  appeared  to  have acquired an increase of its
gelatine; a  greater proportion of the muriate and phosphate of
soda and phosphate of lime, and a substance, in appearance, fibri-
nous.   Marcet however affirms,  that  he could  never discover
gelatine in it.
   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 
CHYMIFICATION.
497

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
Murcet found it to be neither acid nor  alkaline.  In the chyme, ex-
amined by the latter gentleman, he detected albumen, an animal
matter, and some salts, differing, however, slightly,  according as it
proceeded 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 stomach 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 animal 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 diges-
tion.   He detected it in the stomachs of the rabbit, hare, horse, calf,
and dog, and in  the sour matter, ejected from the stomachs of per-
sons, labouring under indigestion:—a fact which has since been con-
firmed by Mr. Children.
   MM. Tiedemann and Gmelin, and Dr. Beaumont, 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 gentlemen  were not con-
 fined to the  chymous mass, obtained  from  digestible food.  They
 examined the fluids, secreted by the mucous membrane,  when indi-
 gestible substances were sent into the stomach, and the acid character
 was equally manifested.   These experiments, consequently, remove
 an objection, made by Bostock, regarding the detection of the muri-
 atic acid by Prout;—that, as  there  did not  appear to be any evi-
 dence of the existence of this acid, before the introduction of food
 into the stomach, it might rather be inferred, that it is, in some way
 or other, developed during the  process  of digestion.  In all Dr.
 Beaumont's experiments,  the chyme, as before observed, was inva-
 riably distinctly acid.
   The principal theories  on  chymification  have been  the follow-
ing:—                                                        ,
  1.  Coction, or elixation.—This originated with Hippocrates, and
was vaguely used by him to signify the maceration and maturation
from the raw state, experienced by the  food  in the stomach.   The
doctrine was embraced by Galen, and  others,  who ascribed to the
  vol. i.                         63 
498
DIGESTION--OF SOLID FOOD.
organ, an  attracting, retaining, concocting,  and expelling quality
effected by heat.
  In proof of this, they affirmed, that the heat of the stomach is in-
creased 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 experiments on artificial digestion,
made by Spallanzani, heat was always necessary, and the greater
the decree of heat the more easy and complete the  digestion.  It
is  hardly  necessary, however, to  say, that the heat of the sto-
mach is totally insufficient to excite any coction or ebullition, in the
physical sense of the term, and 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 putrefac-
tion, which, we are informed by Celsus, was embraced by Plistoni-
cus, 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 fector of the excrements.    The objections are,  1.
That when the contents of the  stomach are rejected, during chymi-
fication, they exhibit no evidence of putridity.  2.  That in all the
experiments, 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 situa-
tion 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,
lastly, in Spallanzani's and  other experiments, to be  detailed pre-
sently, it was found, that,  when food, in  a state of putridity, was
taken into the stomach, or mixed with the  gastric juice  out of 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.
   Trituration.—The mathematical physiologists,—Borelli,  Hecquet,
Megallotti, Pitcairne, Redi,  and  others—after  the example  of
Erisistratus,  attempted to  refer the whole  process of  digestion
to  trituration, imagining,  that  the  food  is  subjected, in the sto- 
THEORIES OF CHYMIFICATION.
499
mach, 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.                                   J
  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 possessed of the
surprising powers which we have elsewhere described; whilst mas-
tication, in  man, is accomplished  by distinct organs.  No compa-
rison can, indeed, be instituted between the gentle oscillatory mo-
tion 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 Reaumur
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 compressive force at five
ounces.
  4. Fermentation.—The system  of fermentation  had many parti-
sans ;  amongst  whom  may be mentioned Van  Helmont, Sylvius,
Willis, Boyle, Grew, Charleton, Lower, Raspail, &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 under-
gone digestion,  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.
  The objections  to the doctrine of fermentation are;—that diges-
tion ought to be totally independent of the stomach, except as regards
temperature;  and that  the  food ought to be converted into chyme,
exactly in the same manner,—if it were  reduced to the same con-
sistence, 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 
500
DIGESTION--OF SOLID FOOD.
 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 truth is;  in healthy  digestion, fermentation does not occur;
 and, whenever the aliments 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 maceration
 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 diges-
 tion ; and, moreover, the product is not chyme.   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.   Independent-
 ly, however, of the  fact, that no parallel can be drawn between the
 stomach of the herbivorous animal, and  that of man,  it  must be
 borne in mind, that the  important, and truly digestive changes, ef-
 fected upon the food, take  place in the fourth stomach, and not  in
 those concerned in rumination.
   6. Chymical solution.—The theory of chymical solution, as proposed
 by Spallanzani, has met with more favour from physiologists than any
 of the others that have been mentioned.  It may now, we think, be
 regarded as  completely established.   According to him, chymifica-
 tion is owing to the solvent action of a fluid, secreted by the stomach,
 accumulating in that viscus between  meals  and during hunger,* and
 acting as a true menstruum on the substances exposed to its action.
 This fluid,—to which he gave the name gastric juice,—he affirmed  to
 be peculiar in each animal, according to its kind of alimentation,—
 a fact  confirmed  by the experiments of Voisin—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 volatile,
 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  tnem  swallow tubes,

  * It has been already shown, that the experiments of Dr. Bea .mont have satisfacto-
rily proved that no such accumulation takes place during hunger 
THEORIES OF CHYMIFICATION.               501
 pierced with holes, and filled with small sponges.  By withdrawing
 these tubes, by means of a thread attached to them, and suffered
 to nang 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  destined 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 mus-
 cular or membranous, 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,—originally 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.  Hav-
 ing 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
 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 w7ere entirely empty.
   Lastly.—Spallanzani was  desirous of seeing whether this  solvent
 juice could  effect digestion out of the body.   He put some well
 masticated food in small glass tubes, and mixed gastric juice with
 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
 less,—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 dif-
ferent substances.                 .
  Similar  experiments  were instituted  by  Dr. Beaumont.   In all
cases, solution occurred as perfectly in the artificial as in  the real 
502
DIGESTION--OF SOLID FOOD.
digestions, but they were longer in being accomplished, for reasons,
which appear sufficient to explain the difference.   In the former,
the gastric secretion is not continuous;  the  temperature cannot be
as accurately maintained, and there is an  absence of those  gentle
motions  of the stomach, which are manifestly so useful in accom-
plishing the real digestion.
   With  regard to the precise nature of this gastric juice of Spal-
lanzani, we have already observed that great contrariety of senti-
ment has prevailed; and that in ordinary cases, it is  impracticable
to procure it unmixed with the other fluids  of the digestive mucous
membrane.  Spallanzani affirmed, that the only properties he detect-
ed 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 al-
ways acid in the former.  Dumas held the same  sentiments,  and
proved, by experiments on dogs, that it was  acid  or alkaline, ac-
cording as the animal had fed on vegetable or on animal diet.  lie
declared it, moreover, to be mawkish, thick,  and viscid.  Viridct,
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 ammonia,  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 pro-
cure,  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 vomit-
ing 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 occa-
sion, 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.
  Tiedemann and Gmelin procured the gastric fluid by making ani-
mals, that had fasted, swallow indigestible substances, such as flints.
It always appeared to  them to be produced in greater quantity, and to
have a more acid character, in proportion as the alimentary matter
was less digestible and less  soluble;  and they assign it, as constituent 
CHYMIFICATION.
503
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.  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.  In the winter of 1832-3,  the author was favoured, by
Dr. Beaumont,  with a  quantity of the  gastric secretion,  obtained
from the individual with the fistulous opening into the stomach, which
was examined by Professor Emmett, of the University of Virginia,
and himself,  and found to contain free muriatic and acetic acids,
phosphates, and muriates, with bases of potassa, soda, magnesia and
lime, with an animal matter soluble in cold water, but insoluble in
hot  The quantity of  free muriatic acid was surprising:  on dis-
tilling the  gastric fluid,  the acids passed over,  the salts and animal
matter remaining in the retort.  The  quantity of chloride of silver,
4hrown down on the addition of the nitrate of silver to the distilled
fluid was astonishing.
  The author had  many opportunities of examining  the gastric se-
cretion obtained from the case in question.   At all times,  when
pure or unmixed, except with a portion of the mucus of the lining
membrane of the digestive tube, it was a transparent fluid, having a
marked smell of muriatic  acid; of a slightly salt, and very percep-
tibly acid, taste.   The  source of the  chlorine or muriatic acid,  as
Dr. Prout suggests, must be the common salt, existing in the blood,
which he conceives to be decomposed  by galvanic  action.   The
soda, which  is set free, remains, he thinks, in the blood, a portion of
it being "requisite  to preserve the weak alkaline  condition  essential
to the fluidity of the blood;" but the larger part being directed to the
liver to unite with  the  bile. This is plausible, but it need scarcely  be
added, not the less hypothetical.
  Still, the diversity of the results obtained by chymical analysts;
the difficulty of comprehending how the same fluid can digest sub-
stances of such opposite character;  and the uncertainty we are in,
regarding the organs concerned in its production, have led  some
physiologists to doubt the existence of any such gastric juice or sol-
vent, as that described  by Spallanzani.  Montegre, for example, in
the year 1812,  presented to the French Institute a series of experi-
ments, from  which he  concluded, that the gastric juice of Spallan-
zani was nothing more than saliva, either in a pure state or changed
by the chymifying action of the stomach and become acid.  As Mon-
tegre was able to vomit at pleasure, he obtained the gastric juice,
as it had been done by previous 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 irritate the throat, and to render the teeth rough.  He
was desirous of proving, whether this fluid was in any manner in- 
504
DIGESTION--OF SOLID FOOD.
servient to  chymification.  For this purpose, he began by rejecting
as much as possible by vomiting;  and, afterwards, swallowed mag-
nesia to neutralize  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 chymifica-
tion, it was, itself, nothing more than the saliva and the mucous se-
cretions of the stomach, changed by the chymifying  action  of that
viscus.  To confirm himself in  this view,  he repeated,  with this
juice, Spallanzani'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  experi-
ments,—in twelve hours it was in  a complete state of putrefaction.
The same occurred to saliva, 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 same thing happened to
the saliva, when rendered acid by the addition 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, and Dr. Beaumont, for example, performed those
relating to artificial digestion  after the manner of Spallanzani, and
succeeded perfectly; whilst they failed altogether in producing chy-
mification with the  saliva, either in its pure state, or acidulated with
vinegar.
   But even were the evidence adduced less positive, the following
would be overwhelming, in favour of the existence of some secre-
tion 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  stomach,  we find the secretions 
                         CHYMIFICATION.                      505

 from its lining membrane possessing  the power of coagulating al-
 buminous fluids.  It is upon the coagulating property of these secre-
 tions,  hat  he method of making cheese is dependent.  Rennet, em-
 ployed tor 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 produce this striking effect.  Fordyce
 and \ oung  found,  that six or seven grains of  the inner coat of a
 calf's stomach, infused fn water, afforded a liquid, which coagulated
 more than one hundred ounces  of  milk,—that  is, more trfan six
 thousand eight hundred  and fifty-seven times its own weight;  and
 yet its weight was  probably but  little  diminished.  What the sub-
 stance is, that possesses  this  property,  is not known to the chymist.
 It appears not to be very soluble 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  coagu-
 lates milk.
  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
 Eart of the membrane possesses the same property.  Hunter found,
 y experiment, that  the mucus of the fourth cavity 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 contents,
 likewise coagulated  milk; but  the process  was  so slow, as to give
 rise to the suggestion, that it  might have occurred independently 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 animal 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 9(5°, the coagulation took place in half  an hour; when it
was cold in an hour and a quarter.   The stomachs of the salmon
  VOL.  1.                        °^ 
506
DIGESTION--OF SOLID FOOD.
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 whether 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  care-
fully 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; and
similar experiments were made 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 stomach.   Coagulation,  and the
separation into curds and whey, were  first effected by the rennet.
Next to  this, and simultaneously,  came  the  gastric glands, and
the fresh stomach of the calf; and lastly the cardiac  membrane of
the turkey."
                                             From these  expe-
                 Fig.  108.                  riments,  Sir  Everard
Gastric glands of the a-snphagus magnified fifteen times.    the   appearance   of
                                        infundibular    cells, 
CHYMIFICATION.
507
whose depth does not exceed the thickness of the membrane.  This
structure, although different from that of the gastric glands of birds,
is a nearer approach to it, than is  to be met .with in any part oi
the inner  surface  of the  stomach  or duodenum.    It  also re-
sembles them, in the secretion it produces coagulating 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 respecting the cavity of the
stomach as in birds.  Yet M. Montegre denies 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 Thackran deny it this
property also, but there can be no doubt of its  existence.  Spallan-
zani, Fordyce, and others, have ascertained,  that, in those animals,
that frequently take their food in a half putrid state, the first opera-
tion of the  stomach is to  disinfect, or remove the fcetor frorn, the
aliment received into it.   We have already  alluded to  many  fac s,
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; and  the same power of re-
 sisting and obviating putrefaction has been exhibited in experiments,
 made  out  of the body.   Nothing could be more unequivocal  as re-
 gards the possession of this property by  the gastric fluid, than the
 experiments of Dr. Beaumont and the author,  with the secretion
 obtained from the subject of  his varied investigations.   In he pre-
 sence  of the author's friend, N. P. Trist,  Esq -the consul of the
 United States at the  Havanna,-the odour of putrid food was as
 speedily removed by it, as by the chloride of soda, employed at the
 same time on other portions.                          oft„m..t;.n
    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 chynncd
  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
  ^havetyIHtle, in the way of analogy, which can ass,  - m
  referring it to any more  general principle, or to any  of the estabhsh-

  ^Tirclf ^ttfreSr'med digestion of the stomach after death
  afford us,  likewTse, remarkable examples of  the  F-^so^
  powerful agent in  the —^11 l^^Ttctnlf


  t,K; gaSt?C'tJUnnon the coaS  of the stomach during  life.  Being en-
  not exert  it upon tl«£oat               ^   But when that viscus 
508                DIGESTION--OF SOLID FOOD.

contained juices;  and become softened,  and,  in  part, destroyed.
Hunter found the  lining membrane  of the stomach destroyed,  in
several parts, in the body of a criminal, who, for some time before
his execution, had  been prevailed upon, in consideration 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, Haviland, Grimaud, Pascalis,  Cheeseman, J. B. Beck, Chaus-
sier, Yelloly, Gardner, Treviranus, Gbdecke, Jager 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 anything noxious has been swallowed.
  The experiments of Drs. Wilson Philip and Carswell, are signally
corroborative of this physiological action of the gastric juice.  On
opening the  abdomen of rabbits, which had been killed immediately
after having eaten, and were  allowed to  lie undisturbed for some
time  before  examination, the  former found  the great end  of
the stomach soft,  eaten through,  and sometimes altogether con-
sumed ; the chyme being covered only by the  peritoneal coat, or
lying quite bare for the  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 alte-
ration that had taken  place, in the external parts of the mass it had
formed, in consequence of imbibing  gastric fluid from the half-di-
gested 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 con-
stantly  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 remark-
; ble, 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, 
CFtVMIFICATIOJf.
509
F
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
nature of the action is unlike what takes place in any other  chymi-
cal process, and that it is,  therefore, necessarily organic and vital,
and appertaining to vital chymistry.   Such are the sentiments of
Fordyce, of Broussais, of Chaussier and Adelon, and others.  Prout
suggests, that the stomach must have within certain limits, the power
of organizing and vitalizing  the different alimentary substances ; so
as to render them fit for being brought into  more  intimate union
with a living body, than the crude aliments can be supposed to be.
 It  is  impossible,  he conceives,  to  imagine, that  this  organizing
 agency of the  stomach can be chymical.  It is vital, and its  na-
 ture completely unknown.  The physiologist should not however,
 have  recourse to this explanation, until every other has  failed him.
 It is, in truth, another method of expressing our ignorance, when we
 affirm that any function is  executed in an organic or vital manner ;
 nor is this mode of explaining the conversion  of the aliment into
 chyme necessary.   The  secretion of the fluid, which is the great
 agent of chymication,  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 regarded 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 func-
  ion is often evinced, and has already been alluded to;  but the im-
 portance 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
  mat 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,
   S  unchanged, and chymification totally prevented.  Legallois,
  SePhdip,Dupuy, Clarke  Abel, Hastings, and others, on care-
  fcft2 the experiments,  also  announced   that,  after this
  nn/ration the festive process was entirely suspended.
  0peCre'siH offhese experiments ^^Ttha^^te^^
  ral ohvsiolomsts of eminence, who affirmed, that, a  ter the div sion
  ti^S^r of nerves, digestion continued nearly m the. natura


  'TlialhTK^
  serted, that he haf™^stion was not destroyed.  Magendie ex-
  two ho^es;  and that d  c*           of  ch    ffication was owing
  pressed his belief, that the a               g   ^  ^.^ of  the
  to the disturbance o^jespir    ,           J     when  care was

  ZZ^^t^^ the°thorax, lower down than the part, 
510
DIGESTION--OF SOLID FOOD.
which furnishes  the pulmonary branches.  MM.  Leuret arid I.as-
saigne assert, that they found chymification continue, notwithstanding
the division of these nerves; and Dr. Holland thinks he has proved,
that the suspension of the digestive function is not produced by the
influence of these nerves being withdrawn from the stomach, but
by the disturbance of the circulating system;  for when the natural
conditions of this system were maintained,  after the division of the
nerves in question, the function of digestion  still continued to be pro-
perly performed; showing that the  nervous connexion between the
brain and stomach is not essential to the process of digestion, to the
secretion of the gastric solvent, or to the possession of contractility
by the muscular fibres of the stomach.
  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  ap-
paratuses, and always found, that, when the section  was made  be-
low the pulmonary plexus, chymification was suspended.  But how
are we to explain the discrepancy between these  results, and those
of MM. Broughton and Magendie ?  Adelon has  supposed,  that as
the eighth pair is not  the only nerve  distributed to the  stomach,—
the great sympathetic  sending numerous  filaments to it,—these fila-
ments, in the experiments of MM. Broughton and Magendie, may
have been sufficient to keep dp for some time the chymifying action
of the stomach;  and, again, he suggests, whether the  nervous influ-
ence of the stomach may not have still persisted for a time after the
section  of the nerve, like other nervous influences, which, he con-
ceives, continue  for some time,  even after death;  and, lastly, he
thinks it probable, that, in the cases, in  which chymification con-
tinued, the experiment was badly performed. Most of these reasons,
however, would apply with as much force to the experiments on the
other side of the question.  Why were not the agency of the great
sympathetic, and the continuance of the nervous influence for some
time after the section  of the nerve,  evidenced in the experiments of
Dupuytren, and of Wilson Philip, Hastings, and others ?
  More recent experiments by Wilson Philip, Breschet, Milne Ed-
wards, 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, chymifi-
cation is wholly, or in part, suspended.
  Most of the experimenters agree with Sir Benjamin Brodie in the
opinion, that chymification is suspended, owing to the secretion of
the gastric 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 
CHYMIFICATION.
511
   section of the nerves ;  in consequence of which the different portions
   ot the alimentary mass are not brought properly into contact with
   the coats ot  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 me-
_  chanical 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 conclude, that the  use of the  par  vagum, as connected
   with the functions  of the  stomach,  is to bring the alimentary mass
   into the necessary contact with  the  gastric juice.   These  experi-
   ments were  repeated in  London by Mr. Cutler, under the inspection
   of Dr. Philip and Sir B. Brodie; but the effects of mechanical irrita-
   tion of the lower part of the divided nerve did not correspond with
   that observed 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;  although it  must,  we think
   be admitted  with Mr. Mayo, that the matter remains involved  in
1   great  uncertainty.  Analogy,  in the  absence of direct  evidence,
   would suggest, that the  secretion  of the gastric juice should be
   under  the presidency  of the  organic  nervous  system, and that it
*f »might persist after the section of the eighth pair, except for the gene-
   ral deranging influences induced by such section.
     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 re-
   moval 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-
   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
   detection, and which is capable  of rapidly reducing to chyme  all
   substances—both  animal and  vegetable—when placed  under the
   favourable circumstances in which the gastric  juice is  situated in
   the stomach.  In the existing state  of our knowledge, however, re-
   garding this wonderful and mysterious process, we might perhaps
   be justified  in adopting the well-known pithy and laconic observa- 
512
DIGESTION—OF SOLID FOOD.
 tion of Dr. William 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 stomach."
   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 peri-
 staltic motion  of the stomach itself.   Thirdly. It is  exposed  to a
 temperature  of 100° of  Fahrenheit;  the temperature during the
 ingestion of food does not  rise higher:  exercise  elevates, whilst
 sleep, or rest, or a recumbent posture, depresses it.  (Beaumont.)
   After the food has been,  for some time, subjected to these influ-
 ences, the conversion into chyme commences.  This  always takes
 plaee 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.
   Dr.  Wilson Philip  asserts, that the new food, is never  mixed with
 the old;  the former  being always found in  the centre, surrounded
 on all  sides by  the latter.  If the old and new be of different kinds,
 the line of separation between them  is so  evident, that the old may
 be completely removed without disturbing the new; and, if they be
 of different colours, the line of demarcation  can frequently be dis-
 tinctly traced through the parietes  of  the organ, before  they are
 laid  open.  Dr. Beaumont, however, affirms,  that this statement is
 not  correct; that, in a very short  time, the food, already in the
 stomach,  and that subsequently  eaten, become combined.   In the
 subject of his experiments, he invariably found, that old and  new
 food, if  in  the same  state  of  comminution, were readily   and
 speedily united  in the stomach.
  The conversion of the  food into  chyme, it has been  conceived,
 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 accom-
plished in the splenic  portion 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 alimentary 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 
CHYMIFICATION.
513
 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 with perhaps one exception,
 these opportunities have  not been improved.  Burrows, in the 4th
 volume of the Transactions of the Royal Irish Academy,  relates a
 case of fistulous opening into the stomach.  The subject of the  case
 was not seen by him, until twenty-seven  years  after the injury, at
 which time he was,  to  all  appearance, healthy.   But  he  was
 drunken, and dissipated,  and the following year he died.   Such a
 case is related by Schenckius; and Louis, in the 4th volume of the
 Memoires de VAcaUtmie Royale de  Chirurgie, refers to similar cases
 that occurred to Foubert and Covillard.  Helm, of Vienna,  published
 a case of the kind^to v hich reference has already been made; and
 an interesting castT occurred  at  the  Hospital La Charite  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
i escape of the food which the stomach could no longer contain, when
' the contents came out quickly, accompanied by more or less air.
 They possessed a faint smell but had neither  acid nor  alkaline pro-
 perties; the grayish  paste, of which they consisted, when diluted
 with distilled water, not affecting the  vegetable blues.  The digestion
 was far from complete; yet, frequently, the odour of wine was de-
 stroyed ;  and  bread  was reduced to a soft, viscid, thick  substance,
 resembling fibrine recently precipitated by the acetous  acid, and
 swimming in a stringy fluid of the colour of common soup.  Experi-
 ments, made on this  half-digested food, at the  Ecole de  Medecine,
  showed, that tne changes, which it  had undergone  were an in-
  crease of gelatine ; the formation of a  substance like fibrine; and
  a considerable portion of muriate and  phosphate of  soda and phos-
  phate of lime.  This patient could never sleep until she had  emptied
  her stomach, and washed it out by  drinking infusion of chamomile.
  In the morning, it contained a small quantity of thick, frothy liquid,
  analogous to °saliva,-which did  not  affect vegetable blues  wi h
  matters of greater consistence, and some ™m^%°V^2b"'f
  minous  flocculi, mingled  with  the  liquid  portion.  The  lesults o
  chymica experiments3, on this liquid, were similar to those obtained
  on the analysis of saliva.  But the  most interesting case, in its ob-
  served  phenomena   is one that occurred to Dr. Beaumont of the
  United States Army, which the author had an opportunity of exami-
  ning  To tinTcTJe, reference  has already been repeatedly  made
  A Canadianlad, Alexis  San Martin, eighteen years of age, received
     u   It nf hnck shot in his left side,  which carried away the inte-
  a charge oTbuck^shot in n          ^ ^^       fractur ng,  and

  rTo^tTnSr'half of the  sixth rib,  fracturing the fifth;

     VOL. I. 
514
DIGESTION--OF SOLID FOOD.
lacerating the lower portion of the  left  lobe of the lungs, and the
diaphragm, and perforating the stomach.
  When Dr. Beaumont saw the lad, twenty-five  or thirty minutes
after the accident, he found a portion of  the  lining,  as  large  as a
turkey's egg, protruding through the  external wound, lacerated, and
burnt; and, immediately below this, another protrusion, which, on in-
spection, proved to be a portion of the stomach, lacerated through all
its coats, and suffering the food  he had  taken at breakfast to escape
through an aperture large enough to admit the  forefinger.   It need
scarcely be said, that numerous  untoward  symptoms occurred in the
cicatrization of so formidable a wound.  Portions  of the  ribs exfo-
liated ; abscesses formed to allow the exit of extraneous  substances,
and the patient was worn down by febrile irritation.  Ultimately,
however, the  care and  attention of Dr.  Beaumont were crowned
with success, and the instinctive actions of the system repaired the
extensive injury.
  The wound was received in 1822, and, one year  from the time
of the accident, the injured parts were all  sound, and  firmly cica-
trized, with the exception of the stomach, which continued in much
the same condition as it was six months after the wound was re-
ceived, the aperture being about the  size  of a shilling, and the food
and  drinks continually exuding, unless prevented by a plug, com-
press, or bandage.
  On the Oth of June, 1823, one year from  the date of the accident,
the injured parts were  all sound, and firmly cicatrized, with the
exception of the perforation leading into the stomach, which was
about two inches and a half in  circumference. Until the winter of
1823-4, compresses  and  bandages  were  needed to prevent the es-
cape of the food from the stomach.   At this period, a small  fold or
doubling of the inner coats of  the organ  appeared  forming  at the
superior margin  of the orifice, slightly protruding, and increasing, in
size until it filled theaperture.   This valvular  formation adapted it-
self to the  opening [into  the  stomach, so as to completely prevent
the escape of the contents, when the  organ  was full, but it could be
readily depressed by the finger.
  Since the spring of 1824, San Martin has enjoyed general good
health;  he is active, athletic, and vigorous,  eating and drinking like
a healthy individual.
  From the summer of 1825, Dr. Beaumont has been engaged in the
prosecution of numerous experiments upon him ; the results of which
he has given to the world.  In the winter  of 1833, he was in Wash-
ington, when the author—at the time, Professor of Medicine in the
University  of Virginia—was politely invited to  examine him for
physiological purposes.  Many of the results of this examination are
given by Dr. Beaumont, in the publication referred to,  and have
already been, or will  be,  referred  to in  the present  work.  Dr.
Beaumont's researches into the comparative digestibility  of different
alimentary  substances  belong to another  department of Medical 
CHYMIFICATION.
515
I
 Science, and  have accordingly received attention from  the author,
 elsewhere.'
   What then  it may be asked, are the changes wrought on the food
 in the stomach by the gastric  secretions.   Dr. Prout classes them
 under three operations ;—the reducing, the converting, and the organ-
 rung and vitalizing.
   The first of these is probably the main operation.  In order to de-
 cide, whether the action of the stomach in digestion is a simple solu-
 tion, or a total or partial conversion,  certain compounds of organiza-
 tion easy of detection—as gelatine, albumen, and fibrine—were intro-
 duced into the stomach through the fistulous opening in the subject of
 Dr. Beaumont's case; whilst other portions were digested artificially
 in gastric juice obtained from the same individual, the solutions pre-
 sented the same appearance, and were similarly affected by reagents;
 and, in all  cases—whether the digestion  were artificial or real—the
 proximate  principles could be thrown down in the state of gelatine,
fibrine, or albumen, as the case might be.  Farther experiments are
 necessary, but these, so far as they go, justify the conclusion, that the
 digestive process, accomplished in the stomach, is a simple solution
 of  alimentary substances, and  an admixture with the mucous se-
 cretions of that organ, and the various  fluids  from  the  supra-dia-
 phragmatic portion of the digestive tube.
   With regard to the existence of the other two gastric operations de-
 scribed by  Dr. Prout, well-founded doubts may be entertained.   To
 his proposition that—whatever may be the nature of the food, the
 general composition and character of the chyle remain always the
 same,—no  objection can be urged but, admitting its accuracy, it by
 no means follows, that the conversion must be effected in the stomach,
 or  that any organizing or vitalizing powers are exerted upon  the
 chyme in that organ.   On the contrary, it appears to us, that  the
 whole of the changes effected on the aliment in the stomach, are of
 a purely physical character, so  as to adapt it for the separation of
 the chylous portion in the digestive tube, by organs whose vital  en-
 dowments and influences cannot be contested.
  In proportion as the food is digested, it passes through the pylo-
 rus. As the layer, which  lies next to the mucous membrane,  first
 experiences the requisite change, and is propelled onwards by  the
 muscular action  of the organ, the portion, lying next to it, becomes
 subjected 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

  *"On the influence of atmosphere and locality," &c. &c. constituting' Elements of
Hygiene, page 223, &.c. 
51G
DIGESTION--OF SOLID FOOD.
the pylorus into the duodenum.  In the early stages of digestion, the
passage of the chyme from the stomach is more slow than  in the
latter°stages.   At first, it is more mixed with the undigested portions
of food, and, as Dr. Beaumont suggests, is probably separated with
difficulty by the powers of the stomach.   In the  more  advanced
stages, as the  whole mass becomes chymified, the  process is more
rapid, and is  accelerated by the peculiar contraction of the stomach,
already described.
   After the expulsion of the last  particle  of  chyme, the  stomach
becomes quiescent, and no more gastric secretion takes place, until
a fresh supply of food is received into the organ,  or some mechani-
cal irritation is produced on  its inner coat.
   The time,  required for the complete chymification of  a meal, is
stated by the  generality of physiologists,  to be about four or five
hours.   In Dr. Beaumont's case,  a moderate meal of meat, with
bread, &c. was  digested in from three hours  to  three hours and a
half.  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,
according to the digestive capability of the individual;  the state  of
his general  health; and  the relative digestibility  of the aliments
employed;  all which, as we have  already  seen, admit  of great
diversity.
   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 crimi-
nal, and had it analyzed by Chevreul, who  found it to  consist of
oxygen, 11  parts; carbonic  acid,  14; pure  hydrogen,  3.55; and
 azote, 71.15  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 sub-
ject for future inquiry.
    In a robust individual, chymification is effected without  conscious-
 ness  of the  process.   He finds, especially if the stomach be over-
 distended, that the feeling of  fulness  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 manifes-
 tations to  be blunted; and  for a  disposition  to sleep  to be expe- 
CHYMIFICATION.
517
rienced.  " This concentration of the whole vital activity," according
to Adelon, "is so natural to the animal economy, that there is always
danger  in opposing  or  crossing it  by any  extraneous  or organic
influence; as by bathing, the use of medicine, violent exercise, any
mental emotion, intense  intellectual  effort,  &c."  Gentle exercise
would seem, however, to favour  digestion.   Such is the conviction
of Dr.  Beaumont, from his observations.   In the subject of  his ex-
periment, he found the temperature of the  stomach generally raised
by it a degree and a half, and chymification  expedited.
  Where the digestion is imperfect, the signs, already mentioned,
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
ordinary decomposition or fermentation, and appertain to the patho-
logical 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 sup-
ply the losses, and even to add to the bulk of the body.
   It has been already observed, that the chyme, first formed, does
not  continue in the  stomach, until  the  whole meal has undergone
chymification; 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 permitted
 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
 contracts inversely, and the pyloric portion of the stomach, at the
 same time, drives its contents into  the  splenic.  This movement is,
 however, 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 chvme 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 
518
DIGESTION"
--OF SOLID FOOD.
    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
    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 proceeds  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
    agency 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 choledoch us, 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 imagined.
    As the chyme is  acid, it necessarily induces the  same  effects as
    the acid employed in the experiments of Leuret and Lassaigne.
     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 or-
    gan, proceeding  generally from above to below, so  as to propel the
    chyme downwards.  When the chyme reaches any point  of the in-
    testine, 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  in-
   testines.   The longitudinal  fibres, by their contraction, shorten the
   intestine, and in this manner  meet the chyme, so as to facilitate its 
ACTION OF THE SMALL INTESTINE.
519
progress;  but their effect cannot be considerable.  When digestion
is  not going on, the peristaltic action occurs only  at intervals;  al-
ways slowly  and irregularly;  and, perhaps, as has been suggested,
only when a quantity of mucous secretion has collected on the inner
coat of the intestine sufficient to provoke  it.  During digestion, it is
much more energetic and frequent, and is more marked in the duo-
denum  and small  intestine than in the large;  occurring  not conti-
nuously, but at intervals, as the chyme arrives and excites it.  When
the small  intestine 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 re-
 tarded 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 on
 it through the influence chiefly of the bile and pancreatic juice, and
 that its nutritive portion is here absorbed.   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  greater
 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  chyhfication  and the
  absorption of chyle; although by some the former term has been ap-

  ^Vove'tne?SSTwhich 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^t y acid taste;  having been simply mixed with the exhaled
  ™d  Seular secretions  of  he lining membrane.  But, immedi-
        nftpr i: h^sTa^cd the part, at which the hepatic and  cystic
   wtY  nf be oancSc juice1 are  poured into the intestine  it as-
   bl    n ,1 fferSn  appearance, its colour is found to be changed; and
   sumes a different^PP^1 af\ ^tcr taste. its sour smell  diminishes;
   and" ^n Tow ta  grated from  it by the lacteal,   Ac- 
520
DIGESTION—OF SOLID FOOD.
 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
 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, which con-
 tain 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.   Leuret and Lassaigne also state, that if an animal be opened,
 whilst digestion is going on,—on the  surface  of the chyme be-
 tween the pylorus and the orifice of  the  ductus communis  choledo-
 chus, a substance,  of a grayish-white appearance, homogeneous,
 dense, fluid and acid,  is perceived  applied to  the  villi of the  in-
 testine.  Neither of these, however, is chyle.  It  is merely the sub-
 stance whence chyle is obtained by the action of the chyliferous
 vessels.
   The fact, mentioned by Magendie,—regarding the appearance of
 irregular filaments, when animal or vegetable substances, containing
 fat or oil, have  been taken as a 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
 applicable 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 
IN THE SMALL INTESTINE.
521
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 intes-
tine, at the time of chylification, secretes a juice, which he estimated
at the enormous quantity of eight pounds  in the twenty-four hours.
To this he gave  the  name—succus intestinalis—and assigned 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,  whilst fasting,  swallow small
sponges, enveloped in fine linen, and killing  them 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 ol
these juices,  they discovered, that the gastric juice communicated  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 .gastnc
 and intestinal juices, and the fluids  respectively  found in the diffe-

 reWePnafeS'strong reason for  believing, that, even  if food should
 escape the action of the stomach, it is capable of being digested11111 the
 small intestine.   This may be owing to some  of the true gastric
 juice passing into the intestinal canal,  and  impregnating it,  ,or  it
 mav be produced by some similar  secretion from follicles seated
 mefe   The Sg membrane of  the small  intestine possesses the
 property  of coagulating milk; and pathological cases  occur   in
 wheh the stomach  is, to  all appearance, completely disorganized
 vet  the Mttente survive so long  as to  compel us to presume, that
 E^CsX^been effected elsewhere than in the stomach
 digestion  mus>i  w                              h  duodenum of a
    Magendie placed a  piece  ot.aw         ^ ^^ ^
 healthy dog.  Atjhe^xpirauo                    diminished; the
 turn, and  ^ ^" ™ tou             wfech was discoloured.
 only change appeared to be             ,          ^ & thread>

 l^e^Zr^olt ofje small intestine.  Three  hours
VOL. I. 
522
DIGESTION--OF SOLID FOOD.
 afterwards, 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 ex-
 tremely fetid. In some experiments by Yoisin, aliment was introduced
 into the small intestines of animals,—in the one case masticated and
 mixed with saliva, and in  the other  without any preparation.  In a
 few hours in  the first instance, and  after a longer period in the
 second, the food was as completely chyn lined as if  the process had
 taken place in the stomach.  The same experiments were repeated
 upon animals in which the pylorus  had been secured by a ligature,
 and with similar  results.   One of  the animals lived for a month
 after the pylorus was tied, being nourished for that period by food
 introduced into the duodenum.
   These facts sufficiently  show, that a solvent  property  is exerted
 in the small intestine.
   The  biliary and pancreatic juices are usually esteemed the great
 agents  in chylification.  We have already remarked, that the chy-
 liferous vessels  do not begin to appear above the part at which these
 juices are poured 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 marked 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.  Sir Benjamin Brodie tied the ductus com-
 munis choledochus in young cats, so as to prevent both the hepatic
 and cystic bile  from  reaching the intestine.   He found that chylifi-
 cation was interrupted, and that there were neither  traces of chyle
 in the intestines nor  in  the chyliferous vessels.  The former con-
 tained 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.  Mr. Mayo  likewise found, that when
 the  ductus communis choledochus  was  tied in the  cat or dog, and
 the animals killed at various intervals after eating, there was no trace
 whatever of chyle in the lacteals.
  Magendie, however, repeated these experiments on adult animals,
 and with dissimilar  results.  The greater  part died of the  conse-
 quences of opening the abdomen,  and of  the operation required for
 tying the choledoch  duct.   But in two cases, in which the animals
 survived some  days, he  discovered that digestion had  persisted;
 that white chyle had been formed,  and  stercoraceous matter pro-
duced.  This last had not  the usual colour, which,  as he  remarks,
 is not surprising, as it contained no bile.   The experiment was like-
wise repeated by MM. Leuret and Lassaigne, and with results simi-
lar to those obtained by Magendie.  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 afford-
ed, on analysis, the same constituents as chyle; although the animals, 
I\ THE SMAM. INTESTINE.
523
which were the subjects of the operations, had been kept, for some
time, without food.
  The experiments of Tiedemann and Gmelin  on  this subject, were
marked by the usual care and accuracy of those  observers.  They
remarked, that the animals were attacked with vomiting, soon after
the operation,  and  afterwards with thirst and aversion for food;
on the second or third day, the conjunctiva became yellow, the eva-
cuations chalky, and very fetid, and the urine yellow.  Some of the
animals died: others were killed; of the latter/some had previously
recovered from the jaundice, owing to a singular  recuperative phe-
nomenon, noticed by Dr.  Blundell and Sir B. Brodie in thefr experi-
ments—the re-establishment of the choledoch duct, by the effusion of
lymph around the tied part, and the subsequent dropping off of the li-
gature. Like Sir B. Brodie, Mayo, Leuret and Lassaigne, and ^ oisin,
they observed that  chymification went on as in the  sound animal.
The thoracic  duct and chyliferous vessels, in animals fed recently be-
fore death, always contained an abundant fluid, which was generally
of a yellowish colour.  It coagulated like ordinary chyle; the crassa-
mentum  acquired the usual red colour, and  the  only difference be-
 tween it and  the chvle of a sound  animal was, that  after tying the
 choledoch duct  it was never white.  The reason of the difference,
they conceived to  be,  that  the white colour  is owing  to tatty
 matter taken up from the  food by means  of the bile, whicht pos-
 sesses  the power  of dissolving  fat, and  may probably,  there-
 fore, aid in effecting its solution in the chyle at  the mouths of the
 chyliferous vessels." Sir Benjamin  Brodie, and Mr Mayo are con-
 sidered to have been  misled by the  absence of the white colour,
 whfoh the chyle usually possesses, but which it  wants  mi ordinary
 digestion, if the food does  not contain fatty matter.  The expen-
 S of Dr. Beaumont showed, that oil undergoes bu little change
 m the stomach, and  that bile is  probably necessary to give it  he
 requisite  physical constitution, in order that chyle may be separated
 from i    Professors Tiedemann and Gmelin restricted the agency of
  heble  in chylification  to accomplishing  the solution of the fatty
 matter! and  to  azotizing or animalizing food that does not contain

 ^The experiments of M.  Voisin equally show,  that  the ligature of
 the chotedo^h duct does  not prevent the formation of chyle, provided
 the nassSe of the pancreatic fluid is not at the same time prevented.
 the passage 01jne pai   ..           applied so as to completely
  In a number of dogs, a ^J"^^^^^^  Two  lived three

 preT it^^^^^^^^^five died shortly
 itoSe^tSS was applied.  In'no instance, did death appear to
 aftei the "gature w    j w             or assimilatlon.   Almost all
  beowing to the suspens^n o   f             food ^     d

  t oSi^^^y-^; and Uu eUorated chyle in the
  chyliferous vessels           hat the  bile  although important, is
  not^^^ntiTagenrin the  digestion effected in  the  duodenum. 
524
DIGESTION—OF SOLID FOOD.
  As to the mode in which the biliary and pancreatic fluids act on the
chyme, we have only conjectures to guide us.   MM. Tiedemann and
Gmelin suggest, that the soda of the bile unites with the muriatic aty}
acetic acids of the chyme; whilst, at the same time, the latter precipi-
tates 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 a part of
the animal matter, uniting with the chyle; the other, which contains
the coagulated albumen, the coloured, concrete, acrid, and bitter oil,
uniting 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, giving  to  the  excrements their
smell,  colour, and, according to some, the necessary stimulating
property for exciting the flow of the intestinal fluids, and for solicit-
ing the peristaltic action of the intestines so as  to  produce their
evacuation.  It is more  than doubtful, however, 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  natu-
rally destined to pass,  unless such part be in a morbid condition:
and, moreover, were it otherwise, the mucous  membrane of the in-
testine   would be soon accustomed to such  stimulation; and, con-
sequently, the effect be null.   MM. Tiedemann and Gmelin farther
suggest, that from the abundance of highly azoted principles, which
the bile contains, it probably  contributes to animalize  those articles
of food, that do not contain azote; and that it  may tend to prevent
the putrefaction of the food in its course through the  intestines, be-
cause, when it is prevented from flowing into them,  their contents
appear much farther advanced in decay than in the healthy state.
  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 af-
firm, that it yields  to the chyme the richly azoted  principles, which
enter into its composition; and, consequently, aids in its assimilation.
In testimony of this, they remark, that the pancreas is larger in her-
bivorous than in carnivorous  animals; and that, in proportion as the
chymous matter proceeds  along the intestinal canal, it exhibits it-
self less rich in albumen and  other azoted matters, which have pro-
bably been abstracted from it by absorption.
  Marcet discovered in the chyme of the  small intestine a notable
developement of albumen; which was first perceptible at a few inches
from the pylorus, and did not exist in the large  intestine, and Tiede-
mann  and Gmelin  found  that in animals, which had  swallowed
pebbles while fasting, there was, in the  intestinal contents, more al-
bumen than the pancreatic  juice could account for.  Albumen must 
IN THE SMALL INTESTINE.
525
    consequently be either developed from the food or secreted from the
    mucous membrane.   The latter is more probable.
     ^The  influence of the temperature  of the interior of the  intestine,
|   and of  the peristaltic motion, on chylification, can only be looked
    upon as accessory and indirect.
      Whilst the chyme is  passing through the small intestine, it is
    subjected 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 mark-
    ed ; and, in the  ileum, it has a greenish or brownish  tint; and  be-
    comes  less and less acid; until, at the lower  part of the small  in-
    testine, it seems to be the useless residue of the alimentary matter,
    and of the various  secretions from the digestive apparatus.   It is
    now merely excrementitious matter or fasces, although not yet pos-
!    sessing the odour.
      During the formation of chyle, gases are almost always present
;    in the small intestine.  These were first examined by Jurine;  but
    chymical analysis was by no means as perfect at that  day as it is
\   now ;  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.
      The second of the criminals was twenty-three years old.  In other
i,    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 gases contained:—oxygen, 0.00; carbonic  acid, 25.00 ; pure
    hydrogen, 8.40 ; and azote, 66.G0.
      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  quan-
    tity 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 
526
DIGESTION--OF SOLID FOOD.
are alone exhaled from the tissues.  We would still have to account
for the existence of the hydrogen.
  Lastly, they might arise from the reaction of the elements of -jc
chyme upon each other, and  this is the most probable origin.  Ma-
gendie has frequently seen bubbles of gas escaping from the chy-
mous mass, situated between the mouth of the ductus communis
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 published,
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 in estine.
  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, re-
curs 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  ana1  excretory  canal  for the  fasces.  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
caseum;  which being cellular or pouched, like the colon, necessarily
detains it for some time.  In proportion, however, as the caecum
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  co-
lon, as far as the annulus  or commencement of 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.
  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 
IN THE LARGE INTESTINE.
527
i
I
  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 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 secretions,
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 takes place
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,
 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 means of the  albumen it contains, and that
 the faecal matter is formed in this intestine.  The fact of the  separa-
 tion of chyle in the caecum and colon is  proved by the experiments
 of Voisin, which consisted in  introducing food into these intestines
 after the  ileo-caecal valve had been closed by ligature.
   The physical characters of the faeces have already been described.
 When extruded, they have the shape of the large intestine, or of
 the aperture, through which they  are evacuated.   If, therefore  the
 shane of either of these be modified, that of the excrement is so coi-
  espPonden  y   In stricture of the colon, especially about the sigmoid
 flexTe  and^f the  rectum, the fceces are squeezed^through the con-
 stricted portion, and often evacuated in the shape  of nbands.   lhe
 quant1tyPmust, of  course, vary,  according to  circumstances, and
 Snnot be^idly estimated.   Approximately, they have been pre-
 sumed to be" in  the adult male,  from a  quarter  to half a pound
 inThe twenty-four hours, the  evacuation being  usually made once

 °rf4e Miary^cretion appears to modify greatly  the appearance of 
528
DIGESTION--OF SOLID FOOD.
 the faeces.   If, as in cases of jaundice, it is prevented from flowing
 into  the  intestine, the  evacuations  are  clay-coloured.   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  remarks, "it is
 certain, that if the bile does not flow, the excrements 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, whether the  varying
 quantity of the biliary secretion has much influence on the number
 of the evacuations, unless the canal, through 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  re-
 ferred to  some  pathological condition of the biliary  secretion;
 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  fseces have been repeatedly exa-
 mined.  They must, of course, vary according to the nature  of the
 food, its quantity, the  kind of digestion, &c.  They are different in
 each animal species.  Those of  the herbivora  contain less  animal
 matter than those of the carnivora and omnivora;  and the  agricul-
 turist 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
 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 gr&cum, cynocoprus,
 spodium Grcecorum, album  canis, or stercus  caninum album of the
 older writers.   It was formerly  employed as a discutient to the  in-
 side of the  throat in quinsies, but is now justly discarded.
  Vauquelin, on 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 inte-
 rest to  the physiologist.   He found, that a hen devoured, in ten
 days 11111.843 grains troy of oats.  These contained of  phosphate
 of lime,  136.509  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
contained 98.779  grains  of  phosphate of lime and  58.494 grains
of carbonate of lime; and passed  185.266 grains  of silica.   The
fixed parts, thrown out of the system, during the ten days, amount-
ed to:— 
IN THE LARGE INTESTINE.
529
Phosphate of lime      .    .    .    274.305 grains.
L/arbonatc of lime      .    .    .    511.911
SlIlca'      -----    185.266
Given out,    ....     971.482
I aken 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 phosphate of lime, 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.  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 experiments
 appear to have shown, that certain  birds cannot produce eggs  un-
 less 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 satisfacto-
 rily 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 potassa, 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 diffi-
culty, obtained any where.   Every one of them is necessary for  the
constitution of the urine:  and many must  be  formed by a chemical
                                67
VOL.  !• 
530
DIGESTION—OF SOLID FOOD.
union of their  elements  under the vital  agency.  Some  are  met
with in the animal body exclusively.
  Berzelius found, in 100 parts of human fnoces:—water, 73.3; un-
altered 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 carbu-
retted 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, -----Pure hydrogen, -Carburetted hydrogen, ... Azote,...... Traces of sulphuretted hydrogen,	Coscum.	Rectum.
	0.00 12.50 7.50 12.50 67.50 Some.	0.00 42.86 11.18 45.96 Some.
	100.00	100.00
  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,
according to him, goes on decreasing  from the  stomach to the rec-
tum.  The analyses, given, show  that the proportion increases  in-
stead 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 large intestine, without  any
consciousness on the part of the individual.  Sooner or later, the
desire  or  want  to evacuate  them  arises.   This is usually classed  * 
IN THE LARGE INTESTINE.
531
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 intestine 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 usually  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,
Panarolus,  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
serious 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, it be-
comes 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 expe-
rienced,  when  the desire  is  urgent, is  usually  accompanied by a
manifest return of the faecal matters from  the  sigmoid  flexure into
the colon.
   In evacuating the faeces the object to be accomplished is,—that
the contents of the large intestine shall be pressed  upon with a force
superior  to the resistance, presented by the annulus or upper ex-
tremity of the contracted rectum, and  by the muscles of the anus.
The contraction  of the rectum is generally insufficient to effect this
last object, notwithstanding the considerable thickness  of its mus-
cular 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-
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
vprtohral column.  In this way, considerable force  is exerted upon
the contents of the colon and rectum: the resistance  of the sphincter, 
532
DIGESTION—OF SOLID FOOD.
__already  diminished  by the direct  exertion of  volition,—is sur-
mounted ;  it yields  and the faeces  are  extruded.   The levator ani
and ischio-coecygeus, aided by the transversus perinei muscles, sup-
port 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
contract, 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  the food is  passing from  the oesophagus  into that
organ.  If this extrusion occurs to a great extent  it constitutes the
disease, called prolapsus ani.
  Of late, Dr. O'Beirne has directed  his attention to the  subject of
defecation; and, guided by the following facts and  arguments;—that
great irritation  would be produced in the  sphincter ani,  and in the
bladder, if the  faeces descended readily  into the rectum;—that the
difficulty experienced in throwing up an injection is inconsistent with
the idea of the rectum being open, and proves that it is firmly con-
tracted and closed ;—that when the surgeon has occasion to pass his
finger up the rectum, he rarely encounters either solid or fluid faeces;
—that the two sphincter muscles of the anus are considerably weak-
ened  in certain diseases, and divided in  certain  operations, yet it
rarely happens, that the power of retaining the faeces is  destroyed ;
—that on passing a stomach tube  to the  height of half  an inch up
the rectum, in a number of healthy persons, it was found, that nothing
escaped, and that it could be moved about freely in a space, which,
on  introducing the finger, was ascertained to be the pouch of the
rectum; but that from  the highest  part  of the pouch to the upper
extremity  of the gut—generally a distance of from six or seven to
eight inches—the tube could not be passed upwards without meeting
with  considerable resistance, and using a degree of force to mecha-
nically dilate the intestine, which was plainly felt to be contracted
so as to leave no cavity for this  extent;—that when the instrument
 reached,  in this way, the uppermost point of the rectum, the  resist-
ance to its passage  upward was felt to be sensibly increased, until,
at  length, by using a  proportionate degree of pressure, it passed
rapidly forward—as if through a ring—into a  space in which its
extremity could be moved with great freedom, and as instantly a
rush  of flatus, of fluid faeces, or of both, took  place through the tube;
—that in every instance, where the tube presented the least appear-
ance of faeces  after being removed, this  appearance was confined
to  that portion, which  had  entered the  sigmoid flexure:—led by
these and other facts, Dr. O'Beirne concludes; that, in the healthy
and natural  state, all that part of the rectum above its pouch, is at
all times, with the single exception of a  few  minutes previous to the 
DEFECATION.
533
evacuation of the bowels, firmly contracted, and perfectly empty, at
the same time that  the pouch  itself as well as the sigmoid flexure
of the colon, are always  more or less open, and pervious;—and
that the sphincter ani muscles are merely subsidiary agents in re-
taining- the faeces.
   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 its undue evolution is, indeed, generally an indica-
tion.   The leguminous and the succulent vegetables, in  general, be-
long to this class.   Where digestion  is tardily accomplished, they
undergo fermentation, and the disengagement of gas is the  conse-
quence.   Too often, however, the disgusting habit of constantly dis-
charging air streperously from the bowels is encouraged, rather than
repressed ; and there are those, who are 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.

                      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 them.
   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,
 oesophagus, 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 •iccelcralfon of the  circulation, and short breathing,  the mouth 
534
DIGESTION--OF LIQUIDS.
 being frequently and largely open, so as to admit the air to come in
 contact with the irritated parts, and thus to  afford momentary re-
 lief.
   Thirst is a very common  symptom of febrile and  inflammatory
 diseases in which the fluid is  desired, in consequence of the local
 relief it affords,—especially when cold,—to the parched and heated
 membrane of the  alimentary  canal.  It is also developed by cir-
 cumstances 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;—
 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  need 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, cannot 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:—impression, conduction
 and perception.  The last, as in  every similar case, is effected by
 the brain, and  the second by the nerves passing between the part
 impressed and that organ.
   The act of impression—its seat and cause—will alone arrest our
 attention;  we shall find, that we are still less instructed  on  these
 points, than on the physiology of hunger.  Even with  regard to the
 seat of the impression, we are in  a stale of uncertainty.  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 opinion,  however, ap-
 pears  the  more  probable.  In a remarkable case, published  bv
 Dr. Gairdner of Edinburgh, it was found impracticable to allay the
thirst, by merely  supplying the mouth, tongue and fauces with fluid.
 A man had cut through the oesophagus.   An insatiable 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 quan-
tity of fluid circulating  in the vessels, is shown by the fact, men-
tioned by Dupuytren, that he  succeeded in allaying  the  thirst of
animals,  by injecting milk,  whey,  water or  other fluids into  the
veins; and Orfila states,  that in" his  toxicological  experiments, he
frequently allayed, in this way, the  excessive thirst of animals to
which he had administered  poison;  and  which  were  incapable of 
                     PREHENSION OF LIQUIDS.                  535

drinking, owing to the oesophagus having been 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 undeserving of enumeration.
rru' J^a 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 it in.
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
palate.  The fluid,—now, no  longer compressed equally by the at-
mosphere,—is deplaced, 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-
iuls;  and, as they collect, the thirst disappears with all its local and
general attendants.  If, however, the organ be over-distended, a dis-
position 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, »!ti'.   Water  experiences  the admixture already men- 
536
DIGESTION.
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  liquor 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
i§, in such cases,—to use the language of the eccentric Kitchener,—a
good "peristaltic persuader."
  Of the liquids, which are capable of being converted into chyme
or chyle, some are so altogether; others in part only.  Oil remains
longer in the stomach than any other liquid, experiences little change
there, but  is probably altogether converted into chyle.  Milk, as is
well known, coagulates in the stomach, soon  after  it is swallowed,
after which  the clot  is digested, and the whey absorbed.   Yet the
existence of coagula, in the stomach, is  constantly regarded, by the
unprofessional, as a pathological condition!  Where the  liquid,
aqueous or spirituous, holds  in  suspension the immediate principles
of animals or vegetables, as gelatine, albumen,  osmazome,  sugar,
gum, fecula, colouring matter,  &c, a separation occurs, in the sto-
mach, between the water, or alcohol and the substances combined
with them.   The  latter remain in the stomach and  undergo chymi-
fication;  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 digested.
  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. 
                   ERUCTATION, REGURGITATION, &C.           537

  The mode, in which liquids arc  expelled,  is the same as in the
case of the solid excrements.

         OF ERUCTATION, REGURGITATION, AND RUMINATION.

  Although the contraction of the oesophagus generally prevents
the  return of matters from the stomach; occasionally this occurs,
giving rise to eructation, or regurgitation, or vomiting.
  1. Eructation or  belching is the  escape of gas from the stomach.
If air exist in that organ, 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  oesophagus,
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 regurgitation.
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
orifice°and the  relaxation of the lower part of the  oesophagus;
owing to the direct pressure of the stomach on its contents, and the
abdominal muscles contracting and compressing that viscus. When
the food has once passed  into the oesophagus, the latter contracts
upon  it, but inversely, or from  below  to above.  In this way the
food ascends into the "pharynx, and ultimately into the mouth.
   Generally, regurgitation takes place in an involuntary manner;
but there arc some  who are capable of  effecting it at will; and can
thus  discharge the contents of their stomach at pleasure.  To ac-
complish 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 reoion.  When these  efforts are simultaneous  with the re-
laxation of the lower third of the oesophagus, the alimentary matters
pass into the oesophagus.  This voluntary regurgitation seems to be
what  is called vomiting at pleasure.
   3  Rumination.—Some  individuals have taken  advantage ot this
 nower 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.   Beyer
 has  civoii  numerous examples in his Merycohgia;  and Percy and
 Laurent, in the article  Merycismc of the Dictionnaire  des Sciences
 Medicates.
                              OCT
VOL. 1- 
538                        DIGESflON.
   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 editions of
the English translation of Richerand's physiology—appears to have
seen more than one instance of human rumination, and he describes
it as an affection rather to be courted than shunned, so far as regards
the feelings of the individual.  Under usual circumstances, accord-
ing 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 sensa-
tion.  The returned alimentary bolus is  attended with no unpleasant
flavour;  is in no degree  aciduIous[?] ; is equally agreeable;  and is
masticated with additional  pleasure, and with much greater  delibe-
ration than when first taken.   The whole of  the food swallowed 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.
   From regurgitation it differs  essentially,—in  the sensation that
precedes, the retching that accompanies, and  the fatigue, that gene-
rally succeeds it; in short,  whilst in regurgitation  no indisposition
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 accom-
panied with a sensation  of circumgyration, either in  the head or
epigastric, 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, which produce nausea,  show that it may be either
an external or  internal sensation.  Those, that occasion it directly
or externally, 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 duode-
num, &c.  All these are so  many immediate irritants,  which de-
velope the  sensation, as the external  sensations  in  general  are
developed.  In other cases,  however, the cause acts at a distance.
Between the stomach and various organs of the  body, such  exten-
sive sympathetic relations exist, that if  one of these  be long and 
                             VOMITING.                        539

 painfully affected, the stomach sooner or  later sympathizes,  and
 S'f,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 offensive  smell, or nauseous taste will as  cer-
 tainly produce the sensation as any of the more direct agents.
   lo this class of causes belongs the nausea, produced by riding in
 a carriage with the back to the horses, by swinging, and particularly
 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
 affection  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 different
 diseases,"—ascribes it to irritation  of the  optic  nerves,  caused by
 the impossibility of fixing the eyes on objects soon after embarking.
 The objection to these views is, that the sickness ought to be pre-
 vented by simply covering the eyes, and that the blind ought to be
 exempt from it, which is not the case.  Wollaston attempted to ex-
 plain it, by some change in  the distribution of the blood; the  de-
 scending motion of the vessel causing an accumulation of blood in
 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 interferes greatly with the action of
 causes, that are purely physical.  Were it otherwise we should be
 liable to alarming accidents, whenever 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 diffi-
 cult 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 
540
DIGESTION.
rejected matters after an emetic has been  taken, which is there-
fore 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 lon-
gitudinal fibres  take their  fixed  point below, and contract from
above downwards;  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-cae-
cal 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.   Francis
Bayle, Professor in the University  of Toulouse, in  1681, appears to
have been the first, who suggested, that the stomach is nearly pas-
sive in the act; and that  vomiting is caused, almost exclusively, by
the pressure, exerted upon that organ, by the diaphragm and abdo-
minal muscles.   His reason for this belief was founded on the fact,
that, having introduced his finger into the abdomen of a living ani-
mal, whilst it was vomiting, he could not perceive  any contraction
of  the stomach.  In  1686,  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
the muscular fibres  of the stomach is not  essential to the act of
vomiting.
   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 unaflected.   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 
VOMITING.                        541

                               case
bladder, when it has been  long and largely  distended.   This .
seemed to prove to  him, that the  stomach is most concerned in the
act ot  vomiting, as  the abdominal muscles and diaphragm appeared
healthy, and no obstacle existed to their contraction.  It is singular,
however, that the emetic  substances  should  not have  excited the
contractions of the  diaphragm and  abdominal muscles; especially
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 resistance
to the ordinary effects of nauseating substances, and cannot be look-
ed 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 sys-
tem be suspended by the inordinate  use of narcotics, or by violent
injuries of the head.
  Lieutaud farther remarks, that, according to his theory, vomiting
occurs at the time of inspiration;  but  this  cannot  be, as the lower
part of the oesophagus is, at this time  contracted,  and if the  vomit-
ed  matters could  reach the pharynx,  they would pass  into the
larynx.
  Dr.  Marshal]  Hall  has  attempted and successfully,  to  show,
that the  larynx is  closed  during vomiting;  and has concluded,
that the act is a modification of expiration, or that the muscles of
expiration, by a sudden and violent contraction, press upon the  con-
tents of the stomach, and project them through the oesophagus.
  Haller maintained the ancient doctrine, that the stomach, alone,
is competent to the  operation.   His views were chiefly founded on
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 Academie des Sciences of Paris, unsatisfied with the  results
of previous observations, appointed Duverney to examine into the
question, experimentally and otherwise; mfco, 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 ste-mach as in a  press, so that its contents are compelled
to return by the oesophagus.
  On the other hand,  in 1771, Portal, in his  lectures at the college
of France, endeavoured to  show, that the stomach  is the great
a^ent 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 
542
DIGESTION.
 upon the stomach, it occurred at the  time  of expiration; and was
 arrested during inspiration, because the  depressed  diaphragm then
 closes the inferior extremity of the oesophagus ;—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
 were confirmed by the experiments of Haighton.  He opened seve-
 ral animals during the  efforts of vomiting; and he states,  that  he
 distinctly 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, com-
 pletely 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 out of the cavity.  Although the retching continued, the vis-
 cus remained 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 diaphragm and abdominal muscles, and thus evidencing the close
 sympathetic 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 ab-
domen ; the parietes of which were closed by  suture.   A solution
of emetic tartar was now injected into the jugular vein of the ani-
mal : nausea—and, afterwards, vomiting—supervened, and the fluid
 was forced from the bladder. 
VOMITING.                       543
  On another dog,  the  phrenic  nerves  were divided; by which
 nree-tourths  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 occurred; and this ceased, when the abdomen was opened
and the  stomach forcibly pressed upon.
  In another dog, the abdominal muscles were detached from the
sides and hnea alba; the only part of  the parietes remaining being
the peritoneum.  A solution of emetic tartar was now injected into
the veins: nausea and vomiting supervened ; and, through the  peri-
toneum, 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 concluded, that, the stomach  is almost passive in the act; that
the diaphragm 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 vomit-
ing,  as  is  indicated by their evident and  powerful contractions
during the act, and by 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
overthrown by similar experiments.
  Soon  after the appearance of Magendie's memoir, M. Maingault,
laid before  the Society of the Faculte de Midecine of Paris, a series
of experiments, from which he decuced very different  results.  In
all, vomiting was produced without the aid of the diaphragm and
abdominal  muscles.  The vomiting was  excited, in  these  experi-
ments, 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-
inn- the paries of the cavity.   This was  brought together, and the
vomiting continued.
  On another dog, three-quarters of the diaphragm were paralyzed 
541
DIGESTION.
by the section of the phrenic nerves.   The abdomen was now
opened, and a ligature placed round a portion of intestine.   Vomit-
ing occurred.
  Lastly;—these two experiments were united in one.   The abdo-
minal 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 on numerous  repetitions of the  ex-
periment, Maingault conceived himself justified, in deducing infe-
rences, 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 oesophagus, 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-
gan ?  If the diaphragm does all, in the act of vomiting, why do we
not vomit whenever the diaphragm contracts forcibly T  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 con-
tradictory results.  Richerand embraced the  views of Magendie;
and  affirmed, that he had never  observed contraction of the  sto-
mach; 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  dia-
phragm.   Again, to object that, according  to the theory of JVIa<ren- 
VOMITING.
545
die, vomiting ought to be a voluntarv  phenomenon, is a  feeble ar-
gument ; for it  is admitted, that the muscles, which, at the time,
compress the stomach, act convulsively.  If the diaphragm, in pa-
ralysis 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 vomiting, although  they have no diaphragm, is also in-
sufficient ; for it is not absolutely necessary that it should be a dia-
phragm,  but any muscle, which can compress the stomach.
  When the Memoir of Maingault was presented  to the society of
the Faculte de Medecine, M. Legallois  and Professor Beclard were
named reporters.  The  experiments were repeated before them by
M. Maingault, but, instead  of  appearing contradictory  to those of
Magendie, these gentlemen declared that they  were not sufficiently
multiplied, or sufficiently various, to lead to any positive  conclusion.
MM. Legallois and  Beclard, subsequently, repeated those  experi-
ments;  varied  them, and instituted others; from which they de-
duced  corollaries, entirely conformable to those  of Magendie;  and
lastly, Begin boldly affirms,  "without fear of being contradicted by
facts, that there is no direct  or  authentic experiment, which demon-
strates the activity of the stomach during vomiting:"—and he adds,
" I have  repeated the greater part of the experiments of Magendie;
he has performed all, in presence of a great number of spectators, of
whom I was one; and I can  say, with the commissioners of the
Academie des Sciences, that I have seen, examined, touched, and my
conviction is full and entire."  Still, there are many eminent physio-
logists, who  hold on to the idea, that  the stomach is the main agent in
vomiting; and amongst these is Broussais. He manifestly, 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 pres-
sure, 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 ap-
propriate 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 oesopha-
gus, and  out of the mouth.  These efforts arc repeated several times
in succession, and then cease,—at times, to reappear.
  Whilst the rejected  matters pass through the pharynx and mouth,
     vol. i.                     6!> 
546                        DIGESTION.

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. 
 
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