OR [BH]REPRODUCTION IN GENERAL.
[BH] This word is used by the author in an enlarged sense of
propagation, for as generation applies to animated beings, so by this
he includes the vegetable as well as animal system.
We shall now make a more minute inspection into this common property of
animal and vegetable nature; this power of producing its resemblance;
this chain of successive individuals, which constitutes the real
existence of the species; and without attaching ourselves to the
generation of man, or to that of any particular kind of animal, let
us inspect the phenomenas of reproduction in general, let us collect
facts, and enumerate the different methods nature makes use of to renew
organized beings. The first, and as we think the most simple method,
is, to collect in one body an infinite number of resembling organic
bodies, and so to compose its substance, that there is not a part
of it which does not contain a germ of the same species, and which
consequently of itself might become a whole, resembling that of which
it constitutes a part. This preparation seems to suppose a prodigious
waste, and to carry with it profusion; yet it is a very common
munificence of nature, and which manifests itself even in the most
common and inferior kinds, such as worms, polypuses, elms, willows,
gooseberry-trees, and many other plants and insects, each part of which
contains a whole, and by the single effect of expansion alone may
become a plant, or an insect. By considering organized beings in this
point of view, an individual is a whole, uniformly organized in all
its parts; a compound of an infinity of resembling figures and similar
parts, an assemblage of germs, or small individuals of the same kind,
which can expand in the same mode according to circumstances, and form
new bodies, composed like those from whence they proceed.
By examining this idea thoroughly, we shall discover a connection
between animals, vegetables, and minerals, which we could not expect.
Salts, and some other minerals, are composed of parts resembling each
other, and to all that composes them; a grain of salt is a cube,
composed of an infinity of smaller cubes, which we may easily perceive
by a microscope; these are also composed of other cubes still smaller,
as may be perceived with a better microscope; and we cannot doubt,
but that the primitive and constituting particles of this salt are
likewise cubes so exceedingly minute as to escape our sight, and our
imagination. Animals and plants which can multiply by all their parts,
are organized bodies, of which the primitive and constituting parts are
also organic and similar, of which we discern the aggregate quantity,
but cannot perceive the primitive parts only by reason and analogy.
This leads us to believe that there is an infinity of organic particles
actually existing and living in nature, the substance of which is the
same with that of organized bodies. As we have just observed, in a
structure of a similar kind, though of inanimate matter, that it was
composed of an infinity of particles which have a perfect semblance to
the whole body, and as there must perhaps be millions of small cubes of
accumulated salts to form a sensible individual grain of sea-salt, so
likewise millions of organic particles, like the whole, are required
to form one out of that multiplicity of germs contained in an elm, or
a polypus; and as we must separate, bruise, and dissolve a cube of
sea-salt to perceive, by means of crystallization, the small cubes of
which it is composed; we must likewise separate the parts of an elm or
polypus to discover, by means of vegetation and expansion, the small
elms or polypuses contained in those parts.
The difficulty of giving way to this idea arises from a prejudice
strongly established, that there is no method of judging of the
complex, except by the simple, and that, to conceive the organic
constitution of a body we must reduce it to its simple and unorganized
parts, and that it is more easy to conceive how a cube is composed
of other cubes than how one polypus is composed of others; but if we
attentively examine what is meant by simple and complex, we shall then
find that in this, as in every thing else, the plan of nature is quite
different from the very rough draught of it formed by our ideas.
Our senses, as is well known, do not furnish us with exact
representations of external objects, insomuch that if we are desirous
of estimating, judging, comparing, measuring, &c. we are obliged to
have recourse to foreign assistance, to rules, principles, instruments,
&c. All these helps are the works of human knowledge, and partake more
or less of the abstraction of our ideas; this abstraction, therefore,
is what is called the simple, and the difficulty of reducing them to
this abstraction, the complex. Extent, for example, being a general and
abstracted property from nature, is not very complex; nevertheless,
to form a judgment of it, we have supposed extents without depth,
without breadth, and even points without any extent at all. All these
abstractions have been invented for the support of our judgment, and
the few definitions made use of in geometry have occasioned a variety
of prejudices and false conclusions. All that can be reduced by these
definitions are termed _simple_, and all that cannot be readily reduced
are called _complex_; from hence a triangle, a square, a circle, a
cube, &c. are simple subjects, as well as all curves, whose geometrical
laws we are acquainted with; but all that we cannot reduce by these
abstracted figures and laws are complex. We do not consider that these
geometrical figures exist only in our imagination; that they are not
to be found in nature, or, at least, if they are discoverable there,
it is because she exhibits every possible form, and that it is more
difficult and rare to find simple figures of an equilateral pyramid,
or an exact cube in nature, than compounded forms of a plant or an
animal. In everything, therefore, we take the abstract for the simple,
and the real for the complex. In Nature, on the contrary, the abstract
has no existence, every thing is compounded; we shall never, of course,
penetrate into the intimate structure of bodies: we cannot, therefore,
pronounce on what is complex in a greater or lesser degree, excepting
by the greater or lesser each subject has to ourselves and to the rest
of the universe; from which reason it is we judge that the animal is
more compounded than the vegetable, and the vegetable more than the
mineral. This notion is just with relation to us, but we know not, in
reality, whether the animal, vegetable, or mineral, is the most simple
or complex; and we are ignorant whether a globule, or a cube, is more
indebted for an exertion of nature, than a seed or an organic particle.
If we would form conjectures on this subject, we might suppose that the
most common and numerous things are the most simple but then animals
would be the most simple, since the number of their kind far exceeds
that of plants or minerals.
But without taking up more time on this discussion, it is sufficient
to have shewn that the opinions we commonly have of the simple and
complex are ideas of abstraction, that they cannot be applied to the
compound productions of nature, and that when we attempt to reduce
every being to elements of a regular figure, or to prismatic, cubical,
or globular particles, we substitute our own imaginations in the place
of realities; that the forms of the constituting particles of different
bodies are absolutely unknown to us, and that, consequently, we can
suppose, that an organized body is composed of organic particles, as
well as that a cube is composed of other cubes.
We have no other rule to judge by than experience. We perceive that a
cube of sea-salt is composed of other cubes, and that an elm consists
of other smaller elms, because, by taking an end of a branch, or root,
or a piece of the wood separated from the trunk, or a seed, they will
alike produce a new tree. It is the same with respect to polypuses,
and some other kinds of animals, which we can multiply by cutting off,
and separating any of the different parts;[BI] and since our rule for
judging in both is the same, why should we judge differently of them?
[BI] See Supplement to this Work, containing History of Birds, Fish,
Insects, &c. vol. V. p. 377.
It therefore appears very probable, by the above reasons, that there
really exists in nature a number of small organized beings, alike, in
every respect, to the large organized bodies seen in the world; that
these small organized beings are composed of living organic particles,
which are common to animals and vegetables, and are their primitive and
incompatible particles, that the assemblage of these particles form an
animal or plant, and consequently that reproduction, or generation, is
only a change of form made by the addition of these resembling parts
alone, and that death or dissolution is nothing more than a separation
of the same particles. Of the truth of this we apprehend there will not
remain a doubt, after reading the proofs we shall give in the following
chapters. Besides, if we reflect on the manner in which trees grow,
and consider how so considerable a volume can arise from so small an
origin, we shall be convinced that it proceeds from the simple addition
of small resembling organized particles. A grain produces a young tree,
which it contained in miniature. At the summit of this small tree a bud
is formed, which contains the young tree for the succeeding year, and
this bud is an organic part, resembling the young tree of the first
year's growth. A similar bud appears the second year, containing a tree
for the third; and thus, successively, as long as the tree continues
growing, at the extremity of each branch new buds will form, containing
young trees like that of the first year. Thus it is evident, that trees
are composed of small organized bodies, similar to themselves, and
that the whole individual is formed by the union of small resembling
individuals.
But, it may be asked, were not all these organized bodies contained
in the seed, and may not the order of their expansion be traced from
that source, for the bud which first appeared was evidently surmounted
by another similar bud, which was not expanded till the second year,
and soon to the third; and consequently the seed may be said really
to contain all the buds, or young trees that would be produced for a
hundred years, or till the dissolution of the tree itself? This seed it
is also plain not only contained all the small organized bodies which
one day must constitute the individual tree, but also every seed, every
individual, and every succession of seeds and individuals, to the total
destruction of the species.
This is the principal difficulty, and we shall examine it with the
strictest attention. It is certain that the seed produces by the single
expansion of the bud, or germ, it contains, a young tree the first
year, and that this tree existed in miniature in that bud, but it is
not equally certain that the bud of the second year, and those of the
succeeding, were all contained in the first seed, no more than that
every organized body and seed, which must succeed to the end of the
world, or to the destruction of the species, were so. This opinion
supposes a progress to infinity, and forms, of each individual, a
source of eternal generations. The first seed, in that case, must have
contained every plant of its kind which have existed or ever will
exist; and the first man must actually and individually have contained
in his loins every man which has or will appear on the face of the
earth. Each seed, and each animal, agreeable to this opinion, must
have possessed within an infinite posterity. But the more we suffer
ourselves to wander into these kind of reasonings, the more we lose the
sight of truth in the labyrinth of infinity; and instead of clearing up
and solving the question, we confuse and involve it in more obscurity;
it is placing the object out of sight, and afterwards saying it is
impossible to see it.
Let us investigate a little these ideas of infinite progression and
expansion. From whence do they arise? What do they represent? The ideas
of infinity can only spring from an idea of that which is limited, for
it is in that manner we have an idea of an infinity of succession, a
geometrical infinity: each individual is an unit, many individuals
compose a finite number, and the whole species is the infinite
multitude. Thus in the same manner as a geometrical infinity may be
demonstrated not to exist, so we may be assured that an infinite
progression or expansion does not exist; that it is only an abstract
idea, a retrenchment of the idea of finity, of which we take away the
limits that necessarily terminate all size; and that, of course, we
must reject from philosophy every opinion which leads to an idea of the
actual existence of geometrical or arithmetical infinity.
The partizans, therefore, of this opinion must acknowledge, that
their infinity of succession and multiplication is, in fact, only an
indeterminate or indefinite number; a number greater than any we can
have an idea of, but which is not infinite. This being granted, they
will tell us, that the first seed of an elm, for example, which does
not weigh a grain, really contains all the organic particles necessary
for the formation of this, and every other tree of the same kind which
ever shall appear. But what do they explain to us by this answer? Is it
not cutting the knot instead of untying it, and eluding the question
when it should be resolved.
When we ask how beings are multiplied? and it is answered that this
multiplication was compleatly made in the first body, is it not
acknowledging that they are ignorant how it is made, and renouncing
the will of conceiving it? The question is asked, how one body produces
its like? and it is answered, that the whole was created at once.
Can we receive this as a solution? for whether one or a million of
generations have passed the like difficulty remains, and so far from
explaining the supposition of an indefinite number of germs, increases
the obscurity, and renders it incomprehensible.
I own, that in this circumstance, it is easier to start objections
than to establish probabilities, and that the question of reproduction
is of such subtle nature, as possibly never to be fully resolved; but
then we should search whether it is totally inscrutable, and by that
examination, we shall discover all that is possible to be known of the
subject; or at least, why we must remain ignorant of it.
There are two kinds of questions, some belonging to the first causes,
the others have only particular effects; for example, if it is
asked, why matter is impenetrable? it must either remain unanswered,
or be replied to by saying, matter is impenetrable, because it is
impenetrable. It will be the same with respect to all the general
qualities of matter, whether relative to gravity, extension, motion
or rest; no other reply can be given, and we shall not be surprised
that such is the case, if we attentively consider, that in order to
give a reason for a thing, we must have a different subject from which
we may deduce a comparison, and therefore if the reason of a general
cause is asked, that is, of a quality which belongs to all in general,
and of which we have no subject to which it does not belong, we are
consequently unable to reason upon it; from thence it is demonstrable,
it would be useless to make such enquiries, since we should go against
the supposition that quality is general and universal.
If, on the contrary, the reason of a particular effect depends
immediately on one of the general causes above mentioned, and whether
it partakes of the general effect immediately, or by a chain of other
effects, the question will be equally solved, provided we distinctly
perceive the dependence these effects have on each other, and the
connections there are between them.
But if the particular effect, of which we enquire the reason, does not
appear to depend on these general effects, nor to have any analogy
with other known effects, then this effect, being the only one of its
kind, and having nothing in common with other effects, at least known
to us, the question is insolvable: because, not having, in this point,
any known subject which has any connection with that we would explain,
there is nothing from whence we can draw the reason sought after.
When the reason of a general cause is demanded, it is unanswerable,
because it exists in every object; and, on the other hand, the reason
of a singular or isolated effect is not found, because not any thing
known has the same qualities. We cannot explain the reason of a general
effect, without discovering one more general; whereas the reason of
an isolated effect may be explained by the discovery of some other
relative effect, which although we are ignorant of at present, chance
or experience may bring to light.
Besides these, there is another kind of question, which may be called,
the question of fact. For example. Why do trees, dogs, &c. exist?
All these fact questions are totally insoluble, for those who answer
them by final causes do not consider that they take the effect for
the cause; the connection particular objects have with us having no
influence on their origin. Moral affinity can never become a physical
reason.
We must carefully distinguish these questions where the _why_ is used,
from those where the _how_ is employed, and more so from those where
the _how many_ is mentioned. _Why_ is always relative to the cause of
the effect, or to the effect itself. _How_ is relative to the mode from
which the effect springs, and the _how many_ has relation only to the
proportionate quantity of the effect.
All these distinctions being explained, let us proceed to examine the
question concerning the reproduction of bodies. If it is asked, why
animals and vegetables reproduce? we shall clearly discover, that this
being a question of fact, it is insolvable, and useless to endeavour at
the solution of it. But if it is asked, _how_ animals and vegetables
reproduce; we reply by relating the history of the generation of every
species of animal, and of the reproduction of each distinct vegetable;
but, after having run over all the methods of an animal engendering
its resemblance, accompanied even with the most exact observations, we
shall find it has only taught us facts without indicating causes; and
that the apparent methods which Nature makes use of for reproduction,
do not appear to have any connection with the effects resulting
therefrom; we shall be still obliged to ask, what is the secret mode by
which she enables different bodies to propagate their own species?
This question is very different from the first and second; it gives
liberty of enquiry and admits the employment of imagination, and
therefore is not insolvable, for it does not immediately belong to a
general cause; nor is it entirely a question of fact, for provided we
can conceive a mode of reproduction dependent upon, or not repugnant
to, original causes, we shall have gained a satisfactory answer; and
the more it shall have a connection with other effects of nature, the
better foundation will it be raised upon.
By the question itself it is, therefore, permitted to form hypotheses,
and to select that which shall appear to have the greatest analogy with
the other phenomena of nature. But we must exclude from the number
all those which supposes the thing already done; for example, such
as suppose that all the germs of the same species were contained in
the first seed, or that every reproduction is a new creation, and
immediate effect of the Almighty's will; because these hypotheses are
questions of fact, and on which it is impossible to reason. We must
also reject every hypothesis which might have final causes for its
object; such as, we might say, that reproduction is made in order for
the living to supply the place of the dead, that the earth may be
always covered with vegetables, and peopled with animals; that man may
find plenty for his subsistence, &c. because these hypotheses, instead
of explaining the effects by physical causes, are founded only on
arbitrary connections and moral agreements. At the same time we must
not rely on these absolute axioms and physical problems, which so many
people have improperly made use of, as principles; for example, there
is no fecundation made apart from the body, _nulla foecondatio extra
corpus_; every living thing is produced from an egg; all generation
supposes sexes, &c. We must not take these maxims in an absolute sense,
but consider them only as signifying things generally performed in one
particular mode rather than in any other.
Let us, therefore, search after an hypothesis which has not any
of those defects, and by which we cannot fall into any of these
inconveniences; if, then, we do not succeed in the explanation of the
mechanical power Nature makes use of to effect the reproduction of
beings, we shall, at least, arrive at something more probable than what
has hitherto been advanced.
As we can make moulds, by which we can give to the external parts of
bodies whatever figure we please, let us suppose Nature can form the
same, by which she not only bestows on bodies the external figure but
also the internal. Would not this be one mode by which reproduction may
be performed?
Let us, then, consider on what foundation this supposition is raised:
let us examine if it contains any thing contradictory, and afterwards
we shall discover what consequences may be derived from it. Though our
senses are only judges of the external parts of bodies, we perfectly
comprehend external affection and different figures. We can also
imitate Nature, by representing external figures by different modes, as
by painting, sculpture, and moulds; but although our senses are only
judges of external qualities, we know there are internal qualities,
some of which are general, as gravity. This quality, or power, does
not act relatively to surfaces, but proportionably to the masses, or
quantities of matter; there is, therefore, very active qualities in
Nature, which even penetrate bodies to the most internal parts; but we
shall never gain a perfect idea of these qualities, because, not being
external, they cannot fall within the compass of our senses; but we can
compare their effects, and deduce analogies therefrom, to answer for
the effect of similar qualities.
If our eyes, instead of representing to us the surface of objects only,
were so formed as to shew us the internal parts alone, we should then
have clear ideas of the latter, without the smallest knowledge of the
former. In this supposition the internal moulds, which I have supposed
to be made use of by Nature, might be as easily seen and conceived as
the moulds for external figures. In that case we should have modes of
imitating the internal parts of bodies as we now have for the external.
These internal moulds, although we cannot acquire, Nature may be
possessed of, as she is of the qualities of gravity, which penetrate
to the internal particles of matter. The supposition of these moulds
being formed on good analogies it only remains for us to examine if it
includes any contradiction.
It may be argued that the expression of _an internal mould_ includes
two contradictory ideas; that the idea of a mould can only be related
to the surface, and that the internal, according to this, must have a
connection with the whole mass, and, therefore, it might as well be
called a massive surface as an internal mould.
I admit, that when we are about to represent ideas which have not
hitherto been expressed, we are obliged to make use of terms which seem
contradictory; for this reason philosophers have often employed foreign
terms on such occasions, instead of applying those in common use, and
which have a received signification; but this artifice is useless,
since we can shew the opposition is only in the words, and that there
is nothing contradictory in the idea. Now I affirm that a simple idea
cannot contain a contradiction, that is, when we can form an idea of
a thing; if this idea is simple it cannot be compounded; it cannot
include any other idea, and, consequently, it will contain nothing
opposite nor contrary.
Simple ideas are not only the primary apprehensions which strike
us by the senses, but also the primary comparisons which form from
those apprehensions; for the first apprehension, itself is always a
comparison. The idea of the size of an object, or of its remoteness,
necessarily includes a comparison with bulk or distance in general;
therefore, when an idea only includes comparison it must be regarded
as simple, and from that circumstance, as containing nothing
contradictory. Such is the idea of the internal mould. There is a
quality in Nature, called _gravity_, which penetrates the internal
parts of bodies. I take the idea of internal mould relatively to this
quality, and, therefore, including only comparison, it bears not any
contradiction.
Let us now see the consequences that may be deduced from this
supposition; let us also search after facts corresponding therewith, as
it will become so much the more probable, as the number of analogies
shall be greater. Let us begin by unfolding this idea of internal
moulds, and by explaining in what manner we understand it, we shall be
brought to conceive the modes of reproduction.
Nature, in general, seems to have a greater tendency to life than
death, and to organize bodies as much as possible; the multiplication
of germs, which may be infinitely encreased, is a proof of it; and
we may assert with safety, that if all matter is not organized, it
is because organized beings destroy each other; or we can augment as
much as we please the quantity of living and vegetating beings, but we
cannot augment the quantity of stones or other inanimate matters. This
seems to indicate that the most common work of Nature is the production
of the organic part, and in which her power knows no bounds.
To render this intelligible, let us make a calculation of what a
single germ might produce. The seed of an elm, which does not weigh
the hundredth part of an ounce, at the end of 100 years will produce a
tree whose volume will be 60 cubic feet. At the tenth year this tree
will have produced 1000 seeds, which being all sown, at the end of 100
years would each have also a volume equal to 60 cubic feet. Thus in
110 years there is produced more than 60,000 cubic feet of organized
matter; 10 years more there will be 10,000,000 of fathoms, without
including the 10,000 encreased every year, which would make 100,000
more; and ten years after there will be three times that number; thus
in 130 years a single shoot will produce a volume of organized matter,
which would fill up a space of 1000 cubic leagues; 10 years after it
would comprehend a 1,000,000, and in 10 years more 1,000,000 times
1,000,000 cubic leagues; so that in 150 years the whole terrestrial
globe might be entirely converted into one single kind of organized
matter. In this production of organized body Nature would know no
bounds, if it were not for the resistance of matters which are not
susceptible of organization, and this proves that she does not incline
to form inanimate but organized beings, and that in this she never
stops but when irresistible inconveniences are opposed thereto. What
we have already said on the seed of an elm may be said of any other;
and it would be easy to demonstrate, that if we were to hatch every egg
produced by hens for the space of 30 years, there would be a sufficient
number of fowls to cover the whole surface of the earth.
These kind of calculations demonstrate that organic formation is the
most common work of Nature, and, apparently, that which costs her
the least labour. But I will go farther; the general division which
we ought to make of matter seems to me to be in _living_ and _dead
matter_, instead of organized and brute; the brute is only that matter
produced by the death of animals or vegetables; I could prove it by
that enormous quantity of shells, and other cast-off matters of living
animals, which compose the principal part of stones, marble, chalk,
marle, earth, turf, and other substances, which we call brute matter,
and which are only the ruins of dead animals or vegetables; but a
reflection, which seems to me well founded, will, perhaps, make it
better understood.
Having meditated on the activity of Nature to produce organized bodies,
and seen that her power, in this respect, is not limited; having
proved that infinity of organic living particles, which constitute
life, must exist; having shewn that the living body costs the least
trouble to Nature, I now search after the principal causes of death and
destruction, and I find that bodies in general, which have the power
of converting matter into their proper substance, and to assimilate
the parts of other bodies, are the greatest destroyers. Fire, for
example, turns into its own substance almost every species of matter,
and is the greatest means of destruction known to us. Animals seem to
participate of the qualities of flame; their internal heat is a kind of
fire; therefore, after fire, animals are the greatest destroyers, and
they assimilate and convert into their own substance every matter which
may serve them for food: but although these two causes of destruction
are very considerable, and their effects perpetually incline to
the annihilation of organized beings, the cause of reproduction is
infinitely more powerful and active; she seems to borrow, even from
destruction itself, means to multiply, since assimilation, which is one
cause of death, is at the same time a necessary means of producing life.
To destroy an organized being is, as we have observed, only to separate
the organic particles of which it is composed; these particles remain
separated till they are re-united by some active power. But what is
this active power?--It is the power which animals and vegetables have
to assimilate the matter that serves them for food; and is not this
the same, or at least has it not great connection with that which is
the cause of reproduction?