PRELIMINARY LECTURE TO THE COURSE OF ANATOMY AND PHYSIOLOGY; EXHIBITING THE OUTLINE OF A NATURAL SYSTEM OF THESE SCIENCES.
Gentlemen,
The functions of man are the most
interesting objects of Science. Physics and Morals are
equally involved by them. It is in them that the physical
sciences terminate, and that the moral sciences have their
origin.
Of what avail are the former, but to develope the influence
of external bodies upon the functions of man?
What are the latter, but the results of the reaction of that
influence upon men in society?
To explain them is the business of physiology; and
if it have hitherto failed in doing so—if it have even neglected
the noblest of all the functions—I should say the
noblest branch of philosophy—the intellectual functions of
man, and have abandoned them to persons totally incapable
of developing them, because totally ignorant of the structure
on which they depend, and who have left them in a
state of greater obscurity than that in which they found
them, that is the fault of physiologists, and not of their
science.
In these lectures, I shall at least be influenced by the
deepest sense of such errors.
But it is not merely the philosophy of the human
mind, or rather of the intellectual functions of man, that
have thus been abandoned to barbarism. The science itself
has never been systematized; and all its individual
parts have been so neglected, that the other sciences and the
arts dependent upon it, have been left in similar obscurity.
I shall endeavour to shew that it is by the aid of
physiology alone that, in explaining the functions of the
eye, for instance, we can render perfect the theories of
colour and of vision; that, in explaining the functions of
the ear, we can construct rational ones of phonics and of
hearing; that in explaining the functions of the organ of
voice, we can illustrate the formation of letters, and the
origin of languages; that, in explaining the functions of
the muscles, we can establish those first principles of taste
in the fine arts, the very existence of which have so often
been questioned, and so deliver a theory of movement and
of attitude, applicable to sculpture, the higher species of
painting, gesture in oratory, &c. In fine, it is by physiological
means only, that we can construct a natural theory
of medicine, and render precise and easy, the most delicate
and the most difficult of the operations of surgery.
To effect these purposes, nothing is more necessary
than arrangement, because it at once involves facts and
their theory, or the reasonings founded upon them.
In considering a natural arrangement of Anatomy and
Physiology, it appears to me an unquestionable point, that
it ought to indicate, at a single glance, the relation of all
the functions to and their dependence upon each other.
It is upon this principle that I have constructed the
natural arrangement which I am about to detail; and a
single remark upon the arrangements adopted by the most
celebrated modern physiologists, will, at once, shew the
originality of the plan which I propose, and point out the
errors of arrangement which I deprecate.
Blumenbach, Chausier, Dumas and Bichat, treat of
circulation before absorption, on which it depends, and
even before mastication, deglutition and digestion, on
which, in general, even absorption itself chiefly depends.
If the arrangement of Chausier in particular, who,
in this respect, is as accurate as any of them, were to be
considered as indicating the relation and dependence of the
functions, so absurd is it, that absorption instead of the
cause, would be the result of nutrition, generation the result
of absorption, and digestion the result of generation.
Thus, by arranging effects in the place of causes, they confound
the relations of the functions, and reverse the very
order of their dependence.
The division of the functions into external and internal,
as anciently proposed by Aristotle, and afterwards successively
adopted and improved by Buffon, Grimaud and
Bichat (the last of whom substituted for them the terms
organic and animal) is still more faulty.
Anatomy, I divide into three parts, namely that
which considers the mechanical or loco-motive organs, that
which considers the vital organs, and that which considers
the intellectual organs.
Under the mechanical or loco-motive organs, I class,
first, the bones which support the rest of the animal structure;
second, the ligaments which unite them; and third,
the muscles which move them.
Under the vital organs, I class, first, the organs of
digestion, the absorbent surfaces, and the vessels which absorb
from these surfaces; second, the heart, lungs and
blood-vessels, which derive their contents (the blood) from
the absorbed lymph; and third, the organs of secretion,
which separate various matters from the blood. Then follow
the generative organs, which, though generally formed
into a distinct class from the vital, ought not by any means
to be so reckoned. For it is evident, that they form, as it
were, the sequel of the vital organs, being dependent on
secretion—the last of the vital functions, and destined
merely to propagate vitality, and to communicate it to a
new series of beings.
Under the intellectual organs, I class, first, the organs
of sense, where impressions take place; second, the brain
or organ of judgment, where these excite ideas; and third,
the nerves, where volition results from the last.
This is a natural arrangement of the anatomy of animals,
and its peculiar simplicity is illustrated by its involving,
in application, that of minerals and vegetables, and
by its being capable of instant adaption to physiological
science.
In order to arrange Animal Physiology, it is only necessary
to substitute the term “functions” for “organs;”
and that science will likewise involve, in application, the
physiology of mineral and vegetable bodies, and be, in its
turn, capable of instant adaption to medical science.
Thus, the functions also are divided into Mechanical,
Vital and Intellectual.
The mechanical functions are subdivided into that of
support, that of connection, and that of loco-motion.
The vital functions are divided into that of absorption,
that of circulation, and that of secretion.
The intellectual functions are divided into that of sensation,
that of mental operation, and that of volition.
A circle of functions, I may observe, thus exists in
animals, which exists not in minerals or vegetables, because
volition, the last of the intellectual functions, connects itself
to the mechanical ones, by rendering them subservient
to it in loco-motion. Thus the first and the last of these
functions are as intimately connected as any of the intermediate
ones, and a beautiful circle of organic function and
organic influence is formed.
The plan of the course will, therefore, be precisely
the same with that which I have proposed for Anatomy
and Physiology in general.
I. In that part of the course which relates to the mechanical
organs and functions, will be explained the structure
and uses, 1st, of the bones which support the rest of
the animal machine; 2dly, of the ligaments which unite
it; and 3dly, of the muscles which move it.
II. In the first part of the course which relates to the
vital organs and functions, will be explained the structure
and uses, 1st, of the organs of mastication, deglutition and
digestion, of the absorbent surfaces, and of the vessels which
absorb from these surfaces; 2dly, of the heart, lungs and
blood-vessels, which derive their contents, (the blood),
from the absorbed lymph; and, 3dly, of the organs of secretion,
which separate various matters from the blood.
Throughout this division in particular, the analogies from
vegetables will be explained.
III. In that part of the course which relates to the intellectual
organs and functions, will be explained the structure
and uses, 1st, of the organs of sense which receive impressions
from external objects; 2dly, of the brain, where
these impressions excite ideas; and, 3dly, of the spinal
marrow and nerves, where volition results from the last.
In this division, will be also explained, as founded upon
original observations, certain criteria of the various degrees
of the sensitive, perceptive and voluntary powers possessed
by different animals, as well as the nature of sensation, perception
and volition themselves.
As in physiological enquiries, comparative anatomy
and comparative views alone can destroy an hypothesis or
transmute it into a theory, I shall throughout the course introduce
all its principal facts.
The machines, says Cuvier, which are the object of
our researches, cannot be demonstrated without being destroyed.
We have no means of discovering what would
result from the absence of one or several of their parts, and
consequently we remain ignorant of the operation of each
of these parts in producing the total effect.
Fortunately, nature herself seems to have prepared for
us the means of supplying that want which arises from the
impossibility of making certain experiments on living bodies.
The different classes of animals exhibit almost all
the possible combinations of organs. We find them united,
two and two, three and three, and in all proportions; while
at the same time it may be said that there is no organ of
which some class or some genus is not deprived. A careful
examination of the effects which result from these unions
and privations is therefore sufficient to enable us to form
probable conclusions respecting the nature and the use of
each organ, or form of organ.
In the same manner, we may proceed to ascertain the
use of the different parts of the same organ, and to discover
those which are essential, and separate them from those
which are only accessary. It is sufficient to trace the organ
through all the classes which possess it, and to examine
what parts constantly exist, and what change is produced
in the respective functions of that organ, by the absence of
those parts which are wanting in certain classes.
Thus, says Richerand, the cellular structure of the
lungs which cannot be clearly demonstrated in man, on account
of the excessive tenuity of their smallest lobuli, evidently
displays itself in the vesicular lungs of salamanders
and frogs; in the same manner, the scales covering the bodies
of fish and reptiles, or the claws of birds, give us a
just idea of the structure of the epidermis, and of the disposition
of its small laminæ that are laid over each other
on a part of their surface, &c.
Vegetable life, justly, says the same author, compared
in its resources and effects with animal life, would throw
very great light on several phenomena, which, at present,
it is difficult for us to conceive and to explain.
The medical treatment of vegetables, which is almost
entirely surgical, would be equally benefited by these researches.
Thus the wounds of vegetables, like those of the human
body, are much less dangerous when their surface is
smooth, than when their edges are rough, lacerated, or contused.
Trees cut down with a saw bud with difficulty,
whilst those felled with an axe vegetate more briskly.—The
saw tears the vegetable structure and produces a greater
or less alteration in organization. The unequal surface of
a tree thus cut down retains humidity, as destructive to the
trunk, of which it induces a rottenness, as too great a
quantity of pus, that so habitually moistens the surface of
an animal wound, destroys granulation and prevents cicatrization.
In considering the application, or rather the relation
of physiology to philosophy in general, the philosophy of
mind will be particularly dwelt upon.
In considering the application of physiology to the
fine arts, the error in the construction of the antique statues,
and of those of Michael Angelo, both with regard to the individual
muscles supposed to be brought into action, and
with regard to a hitherto unobserved principle of attitude,
will be carefully pointed out.
In considering the application of physiology to the medical
and surgical arts, a view of a new, simple and impressive
natural system of medical science in general, and
of its first principles as an art, will be exhibited; and rules
will also be given for performing surgical operations with
the utmost precision and ease, upon the principle of an invariable
relation between the arrangement of internal, and
the situation of certain external parts, which consequently
form accurate signs of that arrangement.
I may now observe, that the series of beings which the
arrangement I have just delivered involves, all more or less
evidence the phenomena of life and intellect, as well as exhibit
structure, and I may conclude with a few observations
concerning these phenomena.
Minerals have properly been said to exist, plants to
exist and live, animals to exist, live and think.
These are all modifications of each other, as I shall
afterwards shew; but, at present, I shall limit my observations
to the two last of these classes, and to the additional
phenomena, namely those of life and intellect, which they
more strikingly exhibit.
I shall not, however, like some of the most celebrated
modern physiologists, occupy my preliminary lectures with
long details concerning their nature; but, as I reckon life
to be the mere result of organization, I shall, throughout
the course, illustrate it in connexion with those organs on
which it depends, and shall, at present, only take a general
view of its nature.
Life is a term which some philosophers have hitherto
inaccurately employed as expressing an imaginary principle,
though it merely designates a series of dependent actions.
This they were doubtless induced to do by that artifice
which has ever induced weak men to assume an air of
knowledge by giving a particular name to what they did
not understand; and the same artifice still induces such persons
to blame those who endeavour to explain the phenomena
of life according to obvious physical laws, precisely
because a successful explanation would at once exhibit their
ignorance and their desire to conceal it.
Life has, with equal absurdity, been termed a forced
state, though it merely evinces a series of phenomena in
justest unison with those of the universe. I dissent, therefore,
from those who assert, that we employ the terms
life and vital force to express what are apparent exceptions
to general laws. This is only a repetition of the error of
Brown. It was, however, an erroneous conclusion from
accurate observations.
For example, says Cuvier, let us contemplate a female
in the prime of youth and health,—that elegant voluptuous
form—that graceful flexibility of motion—that
gentle warmth—those cheeks crimsoned with the roses of
delight—those brilliant eyes, darting rays of love, or sparkling
with the fire of genius—that countenance enlivened by
sallies of wit, or animated by the glow of passion, seem all
united to form a most fascinating being. A moment is
sufficient to destroy this illusion. Motion and sense often
cease without any apparent cause; the body loses its heat;
the muscles become flat; and the angular prominences of
the bones appear; the lustre of the eye is gone; the cheeks
and lips are livid.... These, however, are but preludes of
change still more horrible. The flesh becomes successively
blue, green and black. It attracts humidity; and while
one portion evaporates in infectious emanations, another
dissolves into a putrid sanies, which is also speedily dissipated.
In a word, after a few short days, there remains
only a small number of earthy and saline principles. The
other elements are dispersed in air and in water to enter
again into new combinations.
This, Cuvier adduces as a proof that the possession
of life prevents the operation of external physical causes.
The picture is perfectly correct, but the conclusion unauthorised.
It was indeed impossible for us not to feel the frequent
necessity of deploring those we loved. We therefore
thought that we perceived this principle operating when the
evident influence of external causes, or some mysterious
agency seemed to drive the noblest results of life, intellect
and genius, from the philosopher and statesman, who had,
by the diffusion of truth and resistance to arbitrary power,
preserved the liberties, and aggrandized the happiness of
nations; we thought we perceived their influence when
imagination’s powers fled from the poet whose song had
once almost conferred new life on the heroes of ancient
times; we thought we perceived their influence when the
phenomena of vital action disappeared in the body of the
patriot hero in whom they had once developed the noblest
specimen of that generous love of social life which induced
him to devote his existence to his country’s weal; we
thought we perceived their influence when those magic
charms abandoned the lovely female whose powers had
once excited from the philosopher those splendid epithets
that ranked her with the other objects of his adoration, celestial
truth and god-like genius—which had obtained even
from the poet those wonderful strains that at once immortalized
him and the object of his song—which had commanded,
even in the hero, those glorious devotions which,
for far too short a period, illustrated the ever memorable
days of chivalry. When those eyes whose soft languor
had fascinated every beholder, those cheeks where life had
often spread the crimson veil of love—when these were
gone, those eyes were dim and sunk, those cheeks were
pale, those lips were livid, that bosom depressed, that form
rigid and icy cold, when all had thus assumed the darkest
and most frightful hues, had gradually lost cohesion and
become one mass of horrible putrescence, whose infectious
effluvia now threatened destruction almost welcome to those
who once adored the animated being—it was scarcely possible
to feel all this, and avoid the conclusion that life was
a state of force.
It was doubtless this unknown and imaginary power
connecting the various phenomena of organic structure that
gave origin to the idea of life. But that they are no state
of force is proved by this, that while the only notion we
have of them is motion—successive attraction and repulsion,
electricity, fire &c. exhibit precisely corresponding
phenomena, and the last of these was, I believe, on that
single account, considered as the symbol of life and intellect
by the great Zoroaster.
This and similar facts, I may remark, convince me,
that the earth has myriads of times been illumed by the
highest attainments of intellect, and as often plunged into
darkness. This single point of Indian philosophy was, in
my opinion, but the mere shadow of the highest excellence
in philosophy in general; and as the greatest cultivation of
the human mind, and the greatest misapplication of its faculties,
cannot well exist together, I am equally convinced,
that the beautiful specimens of art, blended with heterogeneous
absurdities, in the monuments of Upper Egypt, afford
the most striking proof that, contrary to the common
assertion, there were periods in that country when tyrants
held no despotic sway over the physical, nor the priests of
a false religion over the moral structure of man.
But to return to the subject.—True it is that the affinities
of external agents with the molecules of organic bodies
are precisely the same during life when their influence
is resisted as after death when it operates with the greatest
energy; but the power which during life organic bodies
possess of resisting the influence of external agents, and
even the extension of the sphere of their action beyond the
mere bounds of the living body, is, in my opinion, very
easily accounted for.
All the particles of matter possess attraction and repulsion,
and the largest homogeneous masses, coeteris paribus,
evidence them most. Hence, organic bodies, while
they possess homogeneity by the subsistence of intimate relations
between their parts, evidence attraction and repulsion
in the highest degree. While in infancy, these relations
are merely forming, the powers of attraction and repulsion
are weak; when, in the vigour of life, these relations
are most intimate, these powers are greatest; when,
in old age, these relations are interrupted, these powers are
also diminished; and when, in death, these relations cease
to exist between the molecules, or in other words, when the
body is no longer organized, the power of combined resistance
terminates.
Thus, life is no forced state, but an intrinsic power
arising merely from the intimate relation of these molecules,
and the greater effects which, in such combinations,
they are capable of producing, than when, in death, they
have become independent of each other, and their powers
disunited, are capable of much less effectual resistance.
Thus, it is, that I would endeavour to shew a connexion
between the phenomena of living bodies, and the general
laws of nature.
This general and common motion of all the parts,
says even Cuvier, forms so peculiarly the essence of life,
that the parts which are separated from a living body soon
die, because they possess no motion of their own, and only
participate in the general motion produced by their union.
Thus, according to the beautiful expression of Kant, the
mode of existence of each part of inanimate bodies belongs
to itself; but, in living bodies, it resides in the whole.
When, I say, that life consists in motion, I make no
assertion derogatory to the Deity, for every philosopher is of
opinion that motion is to us as mysterious as life; and
when I endeavour to trace in its phenomena a correspondence
with physical laws, I conceive that I pay the truest
homage to a Deity. At all events, it would be dishonest
of me to give my sanction to opinions respecting a difference
which seems to me not to subsist.
The same causes which terminate motion terminate life.
Life begins by motion, and terminates when it ceases; but
very curiously it also terminates in consequence of it. In
other words, the motion wears out the machine in which it
takes place. For, while the functions are most dependent,
life encreases; and their very independence, though, to a certain
extent, the grand aim of existence, destroys it. The very
cause of decay commencing when the different functions have
acquired their greatest vigour, arises precisely from their
having acquired that vigour, and being, at that moment,
most capable of a species of warfare, if I may so term it,
with each other, as well, as in some measure, from the
greater number of accidents to which a complexity of functions
is liable.
That, at this period, the functions may, in a certain
sense, be said to combat each other, will be evident to
every one who, for a moment, considers that great exercise
of the loco-motive functions uniformly interrupts the vital
and intellectual, or of the vital functions injures the loco-motive
and intellectual, or of the intellectual functions injures
the loco-motive and vital.
These powers are always in an inverse relation to each
other.
Grimaud seems to have had some idea of this, with
regard to the first and second classes of functions. He,
says Richerand, has given the most extensive developement
to the idea of the constant opposition between those
two series of actions, over which preside, according to the
opinion of this physician, two powers, which he calls
loco-motive and digestive. It is marked in no species of
animals more than in the carnivorous, which connect with
senses abounding in stratagem, and muscles capable of extraordinary
action, an assimilating power of so low a degree,
that their aliment, in order to be conveniently digested,
must posses a composition analogous to that of their
organs.
Thus, the independence which the functions acquire,
and the interruptions which their operations present to each
other, subjects them to the common laws of impeded motion,
and its result, a separation of parts.
When, in manhood, their unison is most complete, life
is most vigorous. When, in old age, this unison ceases,
life disappears. Hence also, I am convinced, it is, that
those animals whose functions are longest dependent on
each other, and who remain longest helpless, longest enjoy
organic existence.
As motion only can result from motion, so life can
only result from life. The vital actions of all animals originate
in those of their parents, from whom they are detached
precisely when their actions become sufficiently independent
of them. I am convinced it is upon this principle,
that the egg is detached from the ovary and the fœtus
from the uterus, as well as because, in these cases, the
ovary and the uterus themselves, after long quiescence,
recover an independent action of their own. The same
power which enables an organic body to act by itself, forces
it to separate from another.
Life then seems, in a great measure, to consist in the
successive attraction and repulsion of particles—properties
equally common to minerals, vegetables and animals,
though in different manners and degrees. Life, however,
is not here to be confounded with sensibility, which nevertheless
I shall afterwards shew is also possessed by all of
them. Life seems inseparable from generation, nutrition
and decay, or, in other words, from origin, increase, diminution—a
progression which minerals and vegetables
pass through as well as animals. Minerals also increase by
additions to their external surfaces, vegetables by absorbing
from without inward, and animals by absorbing from
their internal as well as external surfaces.
By the intellectual functions, I understand the actions
of the intellectual organs, or, in other words, those actions
which constitute mind. With soul—the sacred and revered
province of theologians, I do not wish in the slightest degree
to interfere; not for the harsh reason assigned by
atheists, namely, that the whole empire of ignorance, the
direction of the basest passions, and the gun or bayonet of
the soldier are under their command (these are sentiments
which I never shall profess), but for a juster and a better
reason, namely this, that soul is, in truth, their proper
province.
Sensation, then, seems to be entirely dependent on
touch, which, in the other senses, is only modified so that
one receives one kind of it, and another receives another;
thus the tongue is touched by means of liquids, the nose
by means of odours, the ear by aeriform vibrations, and the
eye by light.
All the other intellectual functions are nevertheless mere
modifications of sensation. Upon them, therefore, we shall
not dwell, but, by taking into view some important facts
in anatomy, which have a relation to all of them, I shall
be able to explain sensation in particular.
Sommering has observed, that man has the largest brain
in proportion to the nerves given off from it; and that this
proportional magnitude, may, in every instance, be referred
to as the best criterion of the degrees of intelligence.
Now, it appears to me not at all difficult to account for this
fact (the general truth of which may be granted), by comparing
it with another not less important, viz. that, in the
inferior classes of animals, the nervous system becomes,
as you descend, more and more widely diffused.
Hence, I deduce this important principle, viz. that
the degrees of intellect are, in all animals, in exact proportion
to the concentration of the nervous system.
Now, the more equally distributed this system is, the
more independent of each other are the parts of organized
beings, or, in other words, the necessity of a connection
of these parts increases, in proportion to the magnitude of
the common trunk compared with the rami. It is only,
therefore, in the more perfect animals, that the connection
of the different parts of the nervous system, and particularly
the presence of central parts, is necessary to the existence
of the different functions.
Animals, on the contrary, having this sensitive substance
very generally diffused, when mutilated, recover
their figure, or, when cut into pieces, form several individuals,
having each a system of sensation and volition.
The larger warm-blooded animals acquire pieces of flesh
analogous to those which have been cut away; crabs acquire
new claws; the tadpoles of frogs and water newts
acquire new limbs and tails; and the lower end of the
snail, having been divided from the upper, acquires a new
head. The earth and boatworm, when divided into considerable
pieces, form several new individuals; but animals
having this system still more generally diffused, as the
polypus, when divided into the smallest fragments,
each fragment self-exists and becomes a perfect individual.
This also is more or less the case with plants. As
you descend among them, their parts become less dependent
on each other. The dicotyledons, which possess irritability,
sleep and the principle of life most diffused, and
which, among plants, are analogous to the dicordated animals,
namely quadrupeds and birds, possess concentric
fibres and the most diffused sensibility; the monocotyledons,
analogous to the monocordated animals, namely reptiles
and fishes, possess more numerous centers and less
diffused sensibility; and the acotyledons, analogous to the
acordated animals, possess most numerous centers and least
diffused sensibility.
As, in some worms and zoophytes, there is indeed no
appearance of nerves, and certainly none in plants, which
yet possess sensibility, all this gradually approaches to the
attraction and repulsion of the magnet and electrics, which,
like some of these, are divisible almost to infinity, and
yet possess their various powers, which, like the sensibility
of the superior animals, connected by nerves, are only
evidenced when led by conductors.
Hence, I conclude, that sensation, understood in this
limited sense, as distinct from perception, and differing,
toto coelo, from soul, is, like extension, an imprescriptible
property of all matter: but it may exist in as many forms
and as many relations as it; in its separate particles; in
larger combinations, as polypes; in still larger ones, as
worms and insects, where these extended and sentient
particles, connected by nerves, have more extensive relations
and more complete dependence on each other; or uniting
to constitute perception in whole bodies, as in the
more perfect animals, where a sensorium commune exists,
and where, in consequence of the most exquisite arrangement,
and the finest relations, no particle can be deranged
without affecting all the rest.
It is indeed, these various degrees in which it appears,
that afford a strictly analogical proof of its existence as a
primary property of matter.
As man then has not only sensation in the separate
parts, but perception arising from the whole, the descent
is gradual to beings which have merely sensation in distinct
parts, but no general perception; and thence equally
gradual to beings which have sensation limited to their individual
particles.
Now, as the perceptions of two of the superior animals
cannot unite to form one perception, so the sensations
of two parts of a polyp cannot combine in perception; nor
is it of course more wonderful, that the sensations of two
of the minute particles of matter cannot unite in one
common sensation.
As we do not expect electricity to be evidenced without
conductors, why should we expect sensation, in any
great degree, without those nerves which are its conductors?
It would be as irrational to deny the former, when
conductors are not present, as to deny the latter (understood
as I have defined it), when nerves are absent.
Neither is it more wonderful that these sensations, thus
limited, are not evidenced; because it is scarcely to be expected,
that the functions of that should be evident, the absolute
structure of which is unknown, and because it is exactly
in proportion to the concentration of sensation (and by no
means to its division) that it is, at any time, evidenced.
Upon the same principle, it is, that the particles of a
pigment, when in contact, are more evident than when extended
over an immense surface, or that a combination of
pullies and one cord produce more evident motion than
each of them, with separate cords, could separately. But
it is unnecessary to accumulate illustrations—the principle
pervades all nature, and every natural operation illustrates
it.
Nor do we merely find evident sensibility thus produced
by the various arrangements of matter: it is implicitly
dependent on all the changes of bodies, and is identified
with their motions, by being suspended whenever
these are suspended. Of this, the hybernation of animals,
the winter state of most plants, the state of the embryo in
utero or in ovo, of the chrysalids of insects, the nymphs
of worms, and the seeds of plants, afford examples.
Nor is this all: but evident sensibility may be produced
and destroyed at pleasure by a mere alteration in the
arrangement of the particles of one and the same body; as
in the wheel animal, and the anguillæ of tiles.
Nor is even this all: you may, if you choose, by the
mere arrangement of the particles of matter, as I shall afterwards
prove by experiment, at once produce myriads of
animals, and bestow upon them motion, or in other words,
the phenomena of sensibility. This, the experiments of Spallanzani,
contrary to his own inclination, decidedly prove.
If it be objected, that it may be as fairly argued, that
sensation is something combined with these forms of matter,
I answer, that we are not entitled to suppose any thing
an independent being which never appears but in combination.
Now, as we have shown that sensation is implicitly
dependent upon, or connected with motion; and as this and
all the other functions of the brain, are entirely the results
and modifications of sensation, they also must be dependent
on or connected with motion.
Far be it from me to pretend to account for mental
operation by mere physical motion. But, that motion accompanies
all these processes, I am certain; nor can the
supposition that motion is made use of in the most mysterious
operations of the mind, possibly detract from the honour
of a Deity, or from our admiration of natural operations.
We have little need to be afraid of a moderate and rational
materialism. It is the idealism of Berkeley, it is
the scepticism of Hume—those dangerous opponents of
such materialism, that have so deeply injured philosophy
and religion. It is according to these systems, that prophets,
apostles and miracles, are only ideas in the mind;
and, indeed, the unreasonable dislike to a rational materialism,
is alone chargeable with having led to the dangerous
scepticism of Hume.
That physiologists, then, should so long have permitted
others to encroach upon their proper province, is
disgraceful to them, and has been most mischievous to
science. To this is owing the barbarism of the doctrine
of mind. As physiologists abandoned it, philosophers found
it difficult to give it a name.—Some called it morals—others
metaphysics—and others, the philosophy of the mind.
But I have just endeavoured to shew, that it is neither
morals nor metaphysics, nor the philosophy of the mind—but
the philosophy of the intellectual organs of the human
body.