OF THE GENERATION OF ANIMALS.
As human and animal organization is the most perfect and compounded,
their propagation is also the most difficult and least abundant; I here
except those animals which, like the fresh-water polypus or worms, are
reproduced from their divided parts, as trees are by slips, or plants
by their divided roots or suckers; also those which may be found to
multiply without copulation; it appears to me that the nature of those
have been sufficiently explained in the preceding chapter; and from
which, in every kind where an individual produces its resemblance, it
is easy to deduce the explanation of the reproduction from expansion
and nutrition.
But how shall we apply this mode of reasoning to the generation of man
and animals distinguished by sexes, and where the concurrence of two
individuals is required? We understand, by what has just been advanced,
how each individual can produce its like; but we do not conceive how a
male and a female produces a third.
Before I answer this question, I cannot avoid observing, that all those
who have written upon this subject have confined their systems to the
generation of man and animals, without paying any attention to other
kinds of generation which Nature presents us with, and reproduction
in general; and as the generation of man and animals is the most
complicated of all kinds, their researches have been attended with
great disadvantages, not only by attacking the most difficult point,
but also by having no subject of comparison, from which they could draw
a solution of the question. To this it is that I principally attribute
the little success of their labours; but by the road I have taken
we may arrive at the explanation of the phenomena of every kind of
generation in a satisfactory manner.
The generation of man will serve us for an example. I take him in his
infancy, and I conceive that the expansion and growth of the different
parts of his body being made by the intimate penetration of organic
molecules analogous to each of its parts, all these organic molecules
are absorbed in his earliest years, and serve only for the expansion
and augmentation of his various members, consequently there is little
or no superfluity until the expansion is entirely completed; and this
is the reason why children are incapable of propagation; but when
the body has attained the greatest part of its growth, it begins to
have no longer need of so great a quantity of organic particles, and
the superfluity, therefore, is sent back from each part of the body
into the destined reservoirs for its reception. These reservoirs are
the testicles and seminal vessels, and it is at this period that the
expansion of the body is nearly completed, when the commencement of
puberty is dated, and every circumstance indicates the superabundance
of nutriment; the voice alters and takes a deeper tone; the beard
begins to appear, and other parts of the body are covered with hair;
those parts which are appointed for generation take a quick growth; the
seminal liquor fills the prepared reservoirs, and when the plentitude
is too great, even without any provocation, and during the time of
sleep, it emits from the body. In the female this superabundance is
more strongly marked, it discovers itself by periodical evacuation,
which begin and end with the faculty of propagating, by the quick
growth of the breasts, and by an attraction in the sexual parts, as
shall be explained.
I think, therefore, that the organical molecules, sent from every part
of the body into the testicles and seminal vessels of the male, and
into the ovarium of the female, forms there the seminal liquor, which
is, as has been observed, in both sexes, a kind of extract of every
part of the body. These organical molecules, instead of uniting and
forming an individual, like the one in which they are contained, can
only unite when the seminal liquors of the two sexes are mixed; and
when there is more organical molecules of the male than of the female,
in such mixture the produce will be a male; and, on the contrary, when
there is more of the female then a female will be the result.
I do not mean to say that the organic molecules of either could unite
to form small organized bodies of themselves, but that it is necessary
a mixture of the seminal fluid of both sexes should take place, and
that it is only those formed in that mixture which can expand and
become individuals. These small moving bodies, called _spermatic
animals_, are seen, by a microscope, in the seminal liquor of every
male, and are, probably, small organized bodies, proceeding from the
individual which contains them, but which cannot expand or produce any
thing of themselves. We shall evince that there are the same in the
seminal liquor of the female, and shall indicate the place where this
liquor is to be found.
It is very possible that organical molecules are, at first, only a
kind of foetus of a small organized body, in which there are only
essential parts. We shall not enter into a detail of proofs, in this
respect, but content ourselves with remarking, that the pretended
spermatic animals, which we have been speaking of, might possibly be
but imperfectly organized, or that these pretended animals are only
living organic particles, common both to animals and vegetables, or, at
most, only the first union of those particles.
But let us return to our principal object. How can we conceive, it may
be asked, that the superfluous particles can be sent back from every
part of the body, and afterwards unite when the seminal liquor of the
two sexes are mixed? Besides, is it certain that this mixture is made?
Has it not been pretended that the female did not furnish any fluid of
this kind? Is it certain that the liquor of the male enters the matrix,
&c.
To the first question I answer, if what I have said on the subject
of the penetration of the internal mould by organic molecules, in
nutrition or expansion, be well understood, it will easily be conceived
that these molecules, not being able any longer to penetrate those
parts they did before, they will be necessitated to take a different
road, and consequently arrive at some part, as the testicles or seminal
vessels; for to explain the animal economy, and the different movements
of the human body, solely by mechanical principles, is the same as if
a man would give an account of a picture by shutting his eyes and
feeling on it; for it is evident that neither the circulation of the
blood, nor the motion of the muscles, nor the animal functions, can
be explained by impulsion, nor other common laws of mechanics: it is
as evident that nutrition, expansion, and reproduction, is made by
other laws, why therefore not admit of acting and penetrating powers
on the masses of bodies, since we have examples of it in gravity, in
magnetical attractions, and in chemical affinities? And as we are
now convinced by facts, and the multitude of constant and uniform
observations, that there exists in nature powers which do not act by
the mode of impulsion, why should we not make use of those powers as
mechanical principles? Why should we exclude them from the explanations
of effects, which we are convinced they produce? Why should we be
confined to employ only the power of impulsion? Is not this like
judging of a picture by the touch, and explaining the phenomena of the
mass by those of the surface, and the penetrating power by superficial
action? Is not this making use of one sense instead of another; and,
on the whole, is it not confining the faculty of reasoning on a small
number of mechanical principles, totally inadequate to follow the
various productions of nature.
But those penetrating powers being once admitted, is it not natural
to suppose that the most analogous particles will unite and bind
themselves intimately together; that each part of the body will
appropriate the most agreeable to itself, and that from the superfluity
of all these particles there will be formed a seminal fluid, which
will contain all the organic molecules necessary to form a small
organized body, perfectly like that from which this fluid is extracted?
A power like that which was necessary to make them penetrate into each
part, and produce expansion, may be sufficient to collect them in an
organized form, like that of the body in which they originated.
I conceive, that in the aliments we take there is a great quantity
of organical molecules, which needs no serious proof, since we live
on animals and vegetables, which are organized substances. In the
stomach and intestines a separation is made of the gross parts,
which are thrown off by the excretories. The chyle, which is the
purest part of the aliment, enters into the lacteal vessels, and from
thence is transported into every part of the body. By the motion of
the circulation it purifies itself from all inorganical molecules,
which are thrown off by secretion and transpiration; but the organic
particles remain, because they are analogous to the blood, and that
from thence there is a power of affinity which retains them afterwards;
for as the whole mass of blood passes many times through the body, I
apprehend, that in this continual circulation every particular part
of the body attracts the particles most analogous to it, without
interrupting the course of the others. In this manner every part is
expanded and nourished, not, as it is commonly said, by a simple
addition of the parts, and a superficial increase, but by an intimate
penetration of substance, produced by a power which acts on every point
of the mass; and when the parts of the body are at a certain growth,
and almost filled with these analogous particles, as their substance is
become more solid, I conceive they then lose the faculty of attracting
or receiving those particles, but as the circulation will continue
to carry them to every part of the body, which not being any longer
able to admit them as before, must necessarily be deposited in some
particular part, as in the testicles or seminal vessels. This fluid
extract of the male, when mixed with that of the female, the similar
particles, possessing a penetrating force, unite and form a small
organized body like one of the two sexes, and no more than expansion
is wanting to render it a similar individual, and which it afterwards
receives in the womb of the female.
The second question, Whether the female has really a seminal liquor
similar to the male? demands some discussion. I shall first observe,
as a certain matter, that if such a fluid exists, the manner in which
the emission of the female is made is not so apparent as by the male,
being in general retained within the body.[BJ] The ancients so little
doubted of the female having a seminal liquor, that it was by the
different mode of its emission that they distinguished the male from
the female. But physicians, who have endeavoured to explain generation
by the egg, or by spermatic animalcules, insinuate that females have no
particular fluid, that we have been deceived by taking the mucus for
the seminal, and that the supposition of the ancients upon this subject
was destitute of all foundation. Nevertheless this fluid does exist,
and it has only been doubted by those who chose to give way to systems,
and from the difficulty of discovering the parts which serve for its
reservoirs. The fluid which issues from the glands at the neck of the
womb, and at the orifice of the urethra, has no apparent reservoir,
and as it flows outwardly it cannot be thought to be the prolific
liquor, since it cannot concur in the formation of the foetus which
is performed within the matrix. The prolific fluid of the female must
have a reservoir in another part. It flows even in great plenty,
although such a quantity is not necessary, no more than in the male,
for the production of the embryo. It is sufficient for propagation if
ever so little of the male fluid enters the matrix, so it meets with
the smallest drop of that of the female; therefore the observations
of some anatomists, who have pretended that the seminal liquor of
the male does not enter the womb, makes nothing against what we have
advanced, especially as other anatomists, who rely on observations,
have pretended the contrary. But the subject will be better discussed
in the subsequent pages.
[BJ] Quod intra se semen jacit fæmina vocatur; quod in hac jacit, mas,
Aristotle, art. 18 de Animalibus.
Having thus given answers to possible objections, let us now look into
the reasons which may serve as proofs to our explanation. The first is
derived from the analogy there is between expansion and reproduction;
expansion cannot be explained in a satisfactory manner, without
employing those penetrating powers, and those affinities or attractions
we have already made use of to explain the formation of small organized
beings, resembling the great ones which contain them. A second analogy
is, that nutrition and reproduction are both not only produced by
the same efficient, but also by the same material cause, the organic
particles of the nutriment. And a proof that it is the superfluity of
those particles which serves for reproduction, is the body not being
in a condition to propagate before they have done growing; and we
daily see in dogs, and other animals, who more exactly follow the laws
of nature than we, that they nearly attain their full growth before
they attempt to copulate, and by which we may know whether a dog will
increase any more or not; for we may be assured he will not after being
in a condition to engender.
It is another proof that the superfluous nutriment forms the seminal
liquor, that eunuchs, and all mutilated animals, grow larger or
thicker than those who have not that deficiency. The superabundance of
nutriment not being able to evacuate, for the defect of proper organs,
alters the habit of the body; the thighs and haunches of eunuchs grow
very large: the reason is evident; after their body has attained the
common size, if the superfluous organic molecules found an issue, as
in other men, this growth would no longer increase; but as there are
no longer organs for the emission of the seminal fluid, which is no
more than the superfluous matter which served for growth remains, it
endeavours to expand the parts beyond their usual dimensions. Now it
is known, that the growth of the bones is made by the extremities,
which are soft and spongy, and when they have once acquired solidity,
they are no longer capable of extension; and for this reason, the
superfluous organic particles can only expand the spongy extremities
of bones, which causes the thighs, knees, &c. of eunuchs to thicken so
considerably.
But what more strongly proves the truth of our explanation, is the
resemblance of children to their parents. A son, in general, more
resembles his father than his mother, and the daughter more her mother
than her father; because a man has a greater resemblance to a man than
to a woman, and a woman resembles more a woman than a man, in respect
to the whole habitude of the body; but for the features and particular
habits, children sometimes resemble the father, sometimes the mother,
and sometimes both. They will have, for example, the father's eyes,
and the mouth of the mother, or the complexion of the latter, and the
size of the former; which is impossible to be conceived, unless it is
admitted that both parents have contributed to the formation of the
child, and that consequently there was a mixture of the two seminal
fluids.
I acknowledge that resemblances raised many difficulties in my own
mind; before I had maturely examined the question of generation, I
was prepossessed with ideas of a mixed system, by which it appeared
that I could explain in a probable manner every phenomena, excepting
resemblances, and these I thought I had found very specious reasons
to doubt, and which deceived me a long time, until having minutely
observed, with all the exactness I was capable of, a great number
of families, and especially the most numerous, I have not been able
to resist the multiplicity of proofs; it is only after being fully
convinced in this respect, that I have began to think differently, and
to credit what I now believe to be the fact.
Besides, although I had found the mode to avoid those arguments that
would be made on the subject of mulattos, mongrels, and mules, I could
not be prevented from observing that every explanation, where a reason
could be given for the phenomena, cannot be satisfactory; and I am
now perfectly convinced that the objections which might be used with
respect to them, as well as particular parental resemblances, instead
of opposing would confirm my explanation.
I now proceed to draw some consequences. In youth the seminal fluid
is less abundant, although more stimulating; its quantity encreases
to a certain age, because in proportion as we approach that age, the
parts of the body become more solid, admit less nutriment, send back a
greater quantity to the common reservoirs, and consequently produce a
greater abundance of seminal fluid. When the external organs have not
been used, persons of a middling age, and even old men, more easily
engender than young ones. This is evident in the vegetable system, the
older a tree is, the more fruit or seed it produces.
Young people who emit, or force irritation, draw a greater quantity of
seminal fluid towards the organs of generation than would naturally
arrive there, the consequence is, they cease from growing, become
thin, and fall at length into consumptions, and that because they lose
by premature, and too often reiterated evacuations, the necessary
substance for the growth and nutrition of every part of the body.
Those whose bodies are thin without emaciation, or fleshy without being
fat, are the most vigorous; as soon as the superabundant nutriment has
begun to form fat, it is always at the expence of the seminal fluid,
and other faculties of generation. When also, not only the growth of
every part of the body is entirely completed, but the bones are grown
solid, the cartilages begin to ossify, the membranes have received
all the solidity possible, the fibres are become hard and rough, and
at length every part of the body can no longer scarcely admit of
nutriment, the fat considerably increases, and the quantity of seminal
fluid diminishes, because the superfluous particles, stopped in every
part of the body, and the fibres, having no longer any suppleness or
elasticity, cannot return it into the reservoirs of generation.
The seminal liquor not only becomes more abundant till a certain age,
but it also becomes thicker, and contains a greater quantity of matter
under the same bulk. A person, very observant in this point, assured me
that the seminal fluid is as heavy again as the blood, and consequently
specifically heavier than any other fluid of the body.
When a man is in good health the evacuation of this fluid produces
an appetite, and he soon feels the necessity of repairing, by a new
nutriment, the loss of the old; from whence it may be concluded, that
the most efficacious check to every kind of luxury is abstinence and
fasting.
A number of other things remain to be said on this subject, but which
I have treated of in the History of Man; however, before I entirely
close, I shall make some few observations. The greatest part of animals
do not seek for copulation until they are nearly arrived at their
full growth; those which have only a particular season in the year
have only seminal liquor at that time. A very capable observer of
Nature[BK] not only saw this liquor forming in the roe of a Calmar, but
even observed the spermatic animals and the roe itself, which have no
existence till the month of October, the time when the Calmar spawns
on the coast of Portugal, where Mr. Needham made these observations.
As soon as the season is over neither seminal liquor nor spermatic
animals are longer seen in the milt, which then dries up and becomes
imperceptible till the season returns in the succeeding year, when
the superfluous nutriment renews the milt, and fills it as before. In
the history of the stag we have an opportunity of remarking on the
different effects of rutting; the most general is, the increased size
of the animal; and in those kinds of animals whose rutting or spawning
is only made at great intervals, the extenuation of the body is
proportionably great.
[BK] Mr. Needham's New Microscopical Discoveries, London, 1745.
As women are smaller and weaker than men, of a more delicate
temperament, and eat much less, it is natural to imagine that their
superfluous organic particles are not so plentiful; from hence their
seminal liquor will be weaker, and less in quantity, than that of men.
Since, likewise, the seminal liquor of females contains fewer organic
particles than that of males, must there not result a greater number
of males than females from the mixture of these two liquors? This is
really the case, for which it has hitherto been thought impossible
to find a reason. About a sixteenth more male children are born than
females; and we find that the same cause produces the same effect
in all kinds of animals on which we have been able to make this
observation.