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Translator’s Preface.


THE general curiosity, which
has at times manifested itself
among Physiologists, to discover the
nature of that process, by which the
animal part of the creation is formed,
and the difficulties which oppose them-
selves to such researches, might be
considered as sufficient motives for
[Seite vi] translating any new work, whose prin-
cipal view consists in endeavouring to
correct some prevailing errors, or to
enlarge our ideas in regard to the sub-
ject in question.

The following Essay claims our
attention in both these respects. It
may be considered not only as an
attempt at a refutation of one of the
most favourite hypotheses on the sub-
ject of Generation; I mean that of the
Evolution of pre-existing organic
germs; but also, as an attempt to
establish, upon the basis of experi-
ment, a better, and more consistent

[Seite vii]

The great knowledge and exten-
sive information, which my valuable
and learned Friend the Author pos-
sesses, not only in physiology, and com-
parative anatomy, but in every branch
of natural history, and, which he has
sufficiently evinced in his numerous
writings; at the same time, that they
prepossess us with the idea, that he
is well fitted for such an enquiry,
serve also, as a further justification,
if a justification be necessary, of the
part which I have taken in it. Whe-
ther I have executed my task faith-
fully, I must leave to others to de-

[Seite viii]

That the conclusions of Spallan-
zani, whose works may be considered
as the chief support of the theory of
pre-existing organic germs, require
both some degree of restriction, and
a more accurate examination, than
they have hitherto met with, will
appear evident from the Second
Section of the following Essay, where
the doctrine of Evolution is particu-
larly noticed.

If the admirers of Haller, Bonnet,
and Spallanzani, be surprised at the
manner in which their doctrines are
attacked, they are to consider, that
[Seite ix] controversy never yet injured the cause
of truth, and that by open and candid
examination alone, we are often able
to remove the deceptions of prejudice
and error. Never did a well-founded
theory suffer by the most severe, and
critical investigation; on the contrary,
nothing is better calculated to dis-
cover its value, and establish its re-

I have only to add, that in tran-
slating the compound word (Bildung-
), I have been obliged to make
use of a Latin expression. The word
Nisus, which conveys the full sense of
[Seite x] the word Trieb, does not appear to
have any synonyme in the English


N°. 10, Spring Garden,

Nov. 23d, 1792.







Of the various Hypotheses, by which the
Phenomena of Generation have been
attempted to be explained.

[Seite 1]

WHAT is the nature of that change,
which takes place within a female,
when after having experienced the
most delightful of all sensual pleasures, and
being duly impregnated, form, and existence
are about to be given to her offspring?

[Seite 2]

Few questions have ever awakened more
general, and more ardent curiosity than this;
for however romantic it may appear to attempt
to ascertain the observations, and thoughts of
our first parents, yet the supposition is natural,
that the wonderful effects, and as it were
repeated creations produced by the indulgence
of this instinct, must first have excited their
surprise, and then led them to a train of re-

Considering the innumerable times the
phenomena of generation have occurred since
the days of Adam, it becomes a humiliating
reproach to the understanding of his descen-
dants, that during all that long succession of
time, they have not been able to give any
satisfactory explanation of the matter; espe-
cially as it appears to have soon become a
very early subject of study with speculative
men: at least most of the physiological frag-
ments of the ancient philosophers and physi-
[Seite 3] cians(a), which have been handed down to
us, consist in general of inquiries into the
mysteries of generation; and indeed since that,
there is hardly a period in which the same kind
of researches have not been more or less pro-

Even in the darkest times of the middle
ages, when the spirit of inquiry seemed almost
entirely lost in the lethargy of monastic bar-
barism, this subject appears every now and
then to have awakened a spark of curiosity,
and to have stimulated some of the holy fathers
of those times to the composition of very
sensual and obscene works, some of which
have reached our days(b), and serve to prove
[Seite 4] that their authors were at least interested in
the theoretical, if not in the practical part of

We are not therefore to be surprised,
that the attempt to solve this great problem
of nature encreased rapidly, beyond the power
of numbering, leaving no passage untrod which
afforded any hopes of leading to a solution of
the mystery; hence there hardly exists an-
other spot in the whole region of natural
knowledge, surrounded by more intricate la-
byrinths, or false guides than this.

Drelingcourt, a teacher of Boerhaave’s,
collected no less than two hundred and sixty-
two vague hypotheses on generation, from the
writings of earlier writers.

In spite of the astonishing variety, and
number of paths, which seemed to lead to the
solution of this physiological problem, yet they
are all of them but so many branches of two
principal roads; the one conducting to the
[Seite 5] doctrine of Evolution, the other to that of

It is either supposed that the prepared,
but at the same time unorganized rudiments
of the foetus, first begin to be gradually or-
ganized when it arrives at its place of desti-
nation at a due time, and under the necessary
circumstances. This is the doctrine of Epi-

Or, we deny every sort of generation,
and believe that the germ of every animal, and
every plant that ever has lived and ever will
live, were all created at one and the same
time, namely, at the beginning of the world;
and that all that is necessary is, that one
generation should be developed after the
other. Such is the celebrated theory of

But the manner in which this evolu-
tion happens, has been differently accounted

[Seite 6]

Heraclitus, surnamed the gloomy, and
Hippocrates, or whoever the author of those
books on regimen was, which appeared un-
der his name, together with many of their
followers, were of opinion, that those germs
were scattered up and down the whole globe,
where they wandered about, each in search of
the genitals of a ready made relation of their
own kind, which having once found, they
took lodgement there, threw off their enve-
lopement, and now became fit for being
themselves evolved.

If we except the imposing name of the
authors to whom this theory is ascribed, it
has little else to recommend it to our atten-
tion. It is so completely built on fanciful
suppositions, that it would be difficult to say,
what hypothesis might not be credited were
we to yield the smallest faith to such a doc-
trine. The late professor Gesner, who wrote
a commentary on this romance of Hippo-
crates, apologizes for himself by adopting the
bon mot of Queen Christina, ‘“that the chi-
[Seite 7] meras of the ancients were just as good as
those of the moderns.”’

More approbation has been given to
two other theories of evolution, according to
each of which, the germs did not wander
about, but those of the same kind were all
neatly wrapt up, and encased one within an-
other, so that the first parent of each animal,
and plant was supposed to contain all the
germs of every succeeding generation; co-
pulation only serving to awaken them to their
state of evolution. The only difference be-
tween the two theories was, that the one
supposed the germs to inhabit the testicles of
their father, whilst the other would have it,
that they resided in the ovaria of their mo-

No sooner was the art of making magni-
fying glasses discovered, and by that means
an opening procured to a new world in
the creation, than the novelty of the dis-
covery, and facility of its application, by af-
[Seite 8] fording an opportunity to a number of micro-
scopical experiments, naturally led to the most
unexpected fights.

Among the great amateurs of this kind
of amusement, was one Ludwig von Ham-
mon, a young man born at Dantzig, who
during the time of his studying medicine at
Leyden, and in the course of his microscopical
pursuits, discovered in the month of August
1677, in a drop of the semen of a cock re-
cently dissected, a kind of ocean, in which
swam thousands of little lively active animals.

The same unexpected phenomenon was
also observed in the ripe semen of other male
animals, and in these animalculae were im-
mediately thought to be seen, the germs of
subsequent perfect animals. By this discovery,
a key was supposed to be found, which would
unlock the whole mystery of generation.

Now I cannot conceive how some pro-
fessed philosophers, and natural historians have
[Seite 9] been led to deny life and voluntary motion to
those animalculae; but I am still more at a loss
to imagine, how another set of philosophers
have been induced to dignify these animalculae
of a stagnant animal fluid, to the high rank
of the organized germs of successive gene-

Without entering into a long and tedious
detail of all the doubts and difficulties, which
rise up in opposition to so singular a theory, I
shall content myself with adding a few reflec-
tions, which to the most uninformed readers,
will appear sufficient for calling in question
this imaginary dignity of the animalculae of
the semen of animals.

How comes it that the animalculae of
the semen of animals the most nearly related,
differ so much from each other, whilst scarce
any two things resemble one another so much
as the animalculae of animals, the most op-
posite to each other, both in nature and form?
[Seite 10] For instance, the animalculae in the semen of
frogs, as represented by Mr. von Gleichen,
bear no kind of resemblance to those of the
common newt, as represented by Spallan-
zani; whereas on the other hand, two drops
of water cannot resemble each other more
strongly, than the animalculae of the semen
of a man, and those of an ass, as represented
by the first of these accurate observers.

This same modern advocate for the digni-
ty of these animalculae, has already discovered
two kinds of them in the same drop of semen of
a frog, and yet both of them are perfectly dis-
tinct from those which Roesel represents as
animalculae of the semen of the same animal;
besides the former were not only discovered
in the vesiculae seminales, but also in the
kidneys: mere appearances, as evinced by the
irregular and uncertain shape of the inhabi-
tants of the male semen, and which irregu-
larity and uncertainty refutes their pretended
dignity so completely, that one might as well
[Seite 11] hope with Paracelsus(c), and the Painter
Gautier(d), to be able to produce a perfect hu-
man embryo from male semen, or expect to see,
as the famous academician Hartzoeker as-
[Seite 12] sures us he did, the little embryo sitting in the
body of each animalcule, in the same crooked
and confined posture as in the female womb(e).

Long before the animalculae of the semen
were discovered, Joseph de Aromatariis found
out a third way to explain the mystery of ge-
neration, by means of the theory of evolution;
I mean that one which supposes the ovaria
of every female, even before impregnation,
to contain a whole provision of organized
molecules or germs, perfectly ready for evo-

Swammerdam also adopted this opinion,
but owing to the great figure which the
[Seite 13] animalculae of the semen soon afterwards
made in the world, it remained but little
known until two very distinguished authors,
Haller, and Bonnet, at once raised its repu-

According to this theory we, and indeed
all the children of Adam, were at one time
ipso facto, pent up in the two ovaria of our
common mother Eve. There we lay, as it
were asleep, and although astonishing little
creatures, yet completely organized bodies,
and perfect miniatures of the forms we have
since assumed; for says Haller, ‘“All our
viscera, and the bones themselves were then
already formed, although in a kind of fluid
”’ That which we call impregnation,
is nothing else than the action of awakening
the germ from its lethargic state by means of
the male semen, which stimulates the little
creature’s heart to the first pulsation; and so

[Seite 14]

The same kind of idea has lately in-
duced a very celebrated naturalist of Geneva,
and a warm advocate of this theory, to plan
out for us a history of organized bodies pre-
vious to the state of impregnation, from
which we learn, first, that we are all much
older than what we suppose ourselves to be,
secondly, that all mankind are exactly the same
age, the great grandfather not a second older
than the youngest of his great grand children,
thirdly, that this respectable age, which we
are all of, may be about six thousand years.
The same natural historian also agrees en-
tirely in opinion with Bazin; that since that
charming long series of years, when we were
all packed together along with Cain and Abel,
and the other two hundred thousand million
of men, which according to the best calcu-
lations, have since that period gone quo pius
Aeneas quo Tellus dives et Ancus;
in a word,
since the first creation, during which time
we have been in a kind of lethargic sleep,
though not entirely without motion; that
[Seite 15] during the whole fifty-seven centuries, I say,
previous to our being awakened by the above-
mentioned stimulus, we were according to
Bazin’s opinion, always growing a little and
little: for instance, we were most probably
rather a little bigger at the time we lay beside
Cain’s nieces, than when all their uncles and
aunts were of the party, as it is very natural
to suppose, that we must then have been consi-
derably more pinched for room. In this
manner our apartment became gradually
more easy, and commodious in proportion as
our forefathers were evolved, and we agreed
with it, for we kept continually, stretching
ourselves more and more, until the succession
of evolution came at last to our turn!!

However extravagant and romantic such
conclusions must appear, yet they follow as
natural deductions from the premises of the
theory, which gave rise to them. In support
of this theory, its most celebrated abettors,
Haller, and Spallanzani, adduced many ex-
periments, and observations, which we shall
[Seite 16] examine more particularly in the next Sec-
tion. When we consider how conclusive
and striking these observations appear to be
at first sight, we shall not wonder at the
general assent, which during these thirty
years past, has been given to the doctrine of
the pre-existence of complete organized mo-
lecules in the ovaria of females before impreg-
nation. I myself not only believed in the
truth of it, but defended it in many of my
writings; so that in fact the present little
volume contains a confession of my former
errors, in regard to which, I wish that may
be true, which Mr. de Luc says some where
or other, that, ‘“An error once detected,
becomes a more material truth, than many
positive ones, which we immediately ac-
knowledge to be such.”’

The unexpected success of a small ex-
periment, which I made, however, with a
view of ascertaining the truth of the doctrine
of evolution, first brought me back to the
point from which I ought to have set out, and
[Seite 17] opened a new road to a very opposite doc-
trine. He who thus fights with nature, may
from an unexpected sight, often discover her
most concealed treasures.

What gave occasion to the instituting
the experiment was as follows: In one of my
walks during some holidays which I spent in
the country, I discovered in a stream, a sort
of green armed polypus, which differed from
the common green kind by its long spiral
body, and by having short and rather im-
moveable tentaculae. With the wonders of
this little animal, I intended to amuse my
country friends. The delightful warm sum-
mer weather which then prevailed, and the
hardy constitution of the polypus itself, fa-
voured the experiments which we made, to
discover its power of reproduction so much,
that the act of renewal of the parts became
almost perceptible. By the second and third
day, the maimed and divided animal was so
many new ones, each with arms, body, tail,
[Seite 18] &c. But we plainly remarked that the re-
generated animals, although supplied with
plenty of proper food, were always much
smaller than before, and a mutilated rump,
always diminished very evidently, both in
length and diameter, in proportion as the lost
parts were renewed(f).

Soon after my return to town, I was
called to a patient who had a caries. The
disease occupied the lower end of the femur
immediately above the knee, and had caused
[Seite 19] a pretty extensive and deep ulcer. It healed
gradually, but in proportion as the wound
filled up, and the cicactrix formed, all the
surrounding parts sunk so, that the edge of
the cicatrix being almost on an equality with
the neighbouring parts, the whole formed a
broad, though rather superficial excavation(g).
This was exactly the same thing mutatis
with what happened to the po-

I have since that period, spent a great
deal of my leisure moments in the further in-
vestigation of this subject, both in experiment
and reflection; the consequence of which has
been to convince me fully.

[Seite 20]

That there is no such thing in nature, as
pre-existing organized germs: but that the
unorganized matter of generation, after being
duly prepared, and having arrived at its place
of destination takes on a particular action, or
nisus, which nisus continues to act through the
whole life of the animal, and that by it the first
form of the animal, or plant is not only deter-
mined, but afterwards preserved, and when
deranged, is again restored. A nisus, which
seems therefore to depend on the powers of life,
but which is as distinct from the other qualities
of living bodies, (sensibility, irritability, and
contractility) as from the common properties of
dead matter: that it is the chief principle of
generation, growth, nutrition, and reproduc-
tion, and that to distinguish it from all others,
it may be denominated the
Formative Nisus
(Bildungstrieb, or Nisus formativus).

It is to be hoped, that there is no
necessity for reminding the reader, that the
expression Formative Nisus, like that of At-
[Seite 21] traction(h), serves only to denote a power,
whose constant operation is known from ex-
perience, but whose cause, like the causes
of most of the qualities of matter, is a qualitas
to us(i). We may say of this, as of
[Seite 22] all similar powers, what Ovid says: – Causa
latet, vis est notissima.
But the great merit
in the study of these powers, is to ascertain
more accurately their effects, and to reduce
them under general laws(k).

D’Alembert’s successor, Mr. de Con-
dorcet, in his Eulogy on Haller, and when
speaking of Irritability, says, ‘“The truth of
this doctrine was, as usually is the case, at
first denied; but when it was discovered,
[Seite 23] and that could not be done any longer with
honour, they concluded with observing,
that it had been discovered long before!”’

When it is considered that some people
have been lately possessed of sufficient pene-
tration to discover the doctrine of irritability
in the writings of Homer, and the circulation
of the blood described in the books of So-
lomon the Preacher; it would be really asto-
nishing if this doctrine of the Formative
Principle were allowed the merits of novelty,
and that nothing of the kind were to be dis-
covered in all the works which have been
written on the subject within these two thou-
sand years past(l); especially as the Vis
[Seite 24] Plastica
of the ancients, and more particularly
of the peripatetic schools, would seem as far
as the concordance of name goes to attempt
one to such a qui pro quo.

[Seite 25]

I should be extremely happy, however, if
any person would name one of the old writers,
who, in describing the Vis Plastica, has given
such a distinct idea of it, or such a one as
corresponds so well with the phenomena of ge-
neration(m), as that which I have attempted
to give (especially in the Third Section) of
this Essay.

[Seite 26]

Professor Wolff of Petersburg, a phy-
siologist of great penetration, hath explained
the growth of Animals, and Vegetables by
another power, which he calls Vis Essentialis,
and which one on first hearing, might be apt
to confound with the Nisus Formativus.

Whoever takes the trouble, however,
of perusing the sentiments which Professor
Wolff entertains of the Vis Essentialis, as
given in his Theoria Generationis, will soon
discern the great difference there is between
the two(n).

[Seite 27]

According to him the Vis Essentialis is
only that power, by which the nourishment
is distributed to the different parts of an ani-
mal, or vegetable. This is, indeed, necessary
to the Formative Principle; but it is quite
distinct from the principle itself. For this
[Seite 28] Vis Essentialis exerts itself with equal force in
the growth of even the most deformed, and
unnatural excrescences of plants, and trees,
&c. where the Formative Principle does not
seem to act at all, or at least with no re-

On the other hand, the Vis Essentialis
may be very weak, or deficient, as in such
organized bodies, which are badly nourished,
whilst the Formative Principle remains in
full force, and so on.

However unpleasant it may be to me,
yet I feel myself forced, before entering more
particularly on the nature of the Formative
Principle, to premise a refutation of the ar-
guments which have been brought, and espe-
cially by Baron von Haller, in favour of
evolution of the female egg(o). What con-
[Seite 29] soles me, however, in being thus obliged to
dissent from the opinions of a man, to whose
works and writings I owe so much, is, partly
the reflection, that whatever useful may be
contained in the present sheets, was occa-
sioned by examining into, and prosecuting
his enquiries, and partly my doubts whether
he himself might not have altered his ideas,
and have relinquished, in a great degree, his
old opinions on the subject, had he lived to
have finished that part of the last edition of
his Physiology(p), which treats of this matter.

[Seite 30]

Indeed, had Haller still persisted to sup-
port the doctrine of evolution, and oppose
that of gradual formation, his fame would
have suffered as little from it, as Harvey’s
from his denying the existence of the lacteal
vessels, or Newton’s from his disbelief of the
possibility of colourless tubes in the fern.

Examination of the principal Arguments in
favour of the supposed Pre-existence of
Organized Germs in the Ovaria of Fe-
males, and Refutation of the Doctrine.

[Seite 31]

ON the 13th of May 1758 was read
before the Royal Society of Sciences
at Göttingen, the celebrated paper of Baron
von Haller, (then president of the society)
on the formation of the heart in the embryo,
in which it was believed an argumentum cru-
was offered in support of the doctrine of
pre-existing germs. The author says, That
he found that not only the membrane of the
yolk of an incubated egg, but also its blood-
vessels, constituting what was called the
figura venosa, were a continuation of the
membrane and blood-vessels of the chick.
[Seite 32] But the yolk of the egg existed in the hen
previous to impregnation, and therefore most
probably the embryo also, although too small
to be discovered by our eyes. The prudent
author however expressed himself at first very
cautiously and in an undecided manner on
this syllogism(q).

Mons. Bonnet, however, who soon after
published his work on organized bodies, and,
who was previously prepossessed in favour of
the doctrine of the evolution of pre-existing
organic germs, took hold of this observation
of Haller’s, and pronounced it to be absolute-
ly unanswerable, and considered the truth of
the hypothesis as fully established by it(r).

[Seite 33]

Haller also allowed himself to be daily
more and more convinced of the force of his
own observations, insomuch that in his later
writings he made little scruple of declaring
them equally decisive, as his friend Bonnet
had done.

[Seite 34]

In acknowledging that I myself, as well
as some hundred other physiologists, and natu-
ralists, looked on this celebrated observation
as the foundation stone of the theory of evo-
lution; I think I need make the less ceremony
in expressing my astonishment how we could
have allowed ourselves, as in the present case,
to attribute so much force to an assertion
which absolutely proves nothing!

For, granting it to be fully proved that
there existed a continuation between the
membrane and vessels of the chick and yolk,
(granting it, I say; for, the fact as the most
accurate, and scrupulous investigation teaches,
still remains uncertain, as every one will rea-
dily acknowledge who has taken the pains
of examining fecundated eggs,) yet it does
not follow that the membrane and vessels,
even if they really were a continuation of
each other, co-existed from the beginning.
Do we not see many instances in organized
bodies where this last mentioned circumstance
exists, and yet where it is impossible to grant
[Seite 35] the supposition which has been drawn as a
conclusion from it. For instance, all those
singular vegetable productions, which are
caused by the puncture of certain insects in
many plants. Thus the Spongiae cynosbatae
are produced entirely in consequence of the
puncture of the Cynips in the rose-bush. The
bark of this shrub is continued over this
spongy and quite accidental production; nay,
if we take, and cut any fresh branch which
has some of these spongy bodies on it, we
shall find that the wood of the branch appears
to be an evident continuation of the woody
part of these substances. But shall we from
hence conclude, that this accidental produc-
tion originally co-existed with the shrub
itself, and that in every trunk, and every
branch of every rose-bush in the world, the
enveloped germs of innumerable spongiae
cynosbatae should have always lain there like
so much hidden wealth, and would have
always remained so until the thousand thou-
sandth part of them were by chance excited
[Seite 36] to evolution by the benevolent puncture of
a little cynips.

Again, in the animal kingdom, do we
not often see after an accidental inflammation
of any of the viscera, a new membrane
formed as it were by the effusion of the
lymphatic part of the blood; and in the course
of a few days, do we not observe many blood-
vessels produced in this membrane, which
anastomose with the blood-vessels of the
neighbouring viscera; and yet it would be
ridiculous to suppose that these vessels co-
existed from the first with the old ones.
And for fear that it be objected to us, that
these are mere preternatural appearances in
the diseased state of animals, we beg them
to recall the late celebrated membrana deci-
dua of Dr. Hunter, which after a fruitful
impregnation, lines the whole cavity of the
uterus, and whose blood-vessels, especially
where the umbilical chord is inserted in
the placenta, are most evidently connected
[Seite 37] and anastomose with the blood-vessels of the

In all these cases, the new formed mem-
branes, and their blood-vessels are the mere
productions of the neighbouring viscera,
which renders it probable, that the mem-
brane and vessels of the embryo in a fecun-
dated egg, are produced in like manner from
the membrane and vessels of the yolk.

Mr. Paul(s), a natural historian of great
penetration, hath objected to Haller’s de-
monstration, that allowing the membranes
of the yolk with its invisible vessels to have
pre-existed in the hen, yet it is possible that
the embryo is only formed during incubation,
and that its blood-vessels afterward unite with
the blood-vessels of the membrane of the
yolk, and thus form an anastomosis.

[Seite 38]

Baron von Haller immediately declared
loudly against this objection, and denied it
altogether as a thing impossible, that the ten-
der vessels of the microscopic embryo should
be capable of anastomosing with the large
blood-vessels of the giant yolk(t).

But what is rather singular, is, that
this same most ingenious and meritorious
author, who denies the possibility of such an
anastomosis, supposes without any hesitation,
and in the same work(u), when explaining
human conception, that the very minute
germ as soon as it has arrived at the cavity
of the uterus, forms an adhesion with it by
[Seite 39] means of its placenta; – And how? Just in
the same way that he denies it to the embryo
of the hen; that is to say, by an anastomosis
taking place between the microscopic and
tender branches of the umbilical vessels, and
the giant ones of the maternal uterus.

The modern advocates for the theory of
evolution, have taken this observation of the
yolk of the egg, as the prop of their hypothesis.

Long before this however, the spawn of
the frog had been employed for the same service.

Near a century indeed before that period,
Swammerdam announced the wonderful dis-
covery, that the black points in the spawn of
a frog were so many perfectly formed little
frogs, and that they pre-existed in the ovariae,
although not to be discovered by the eye(w).

[Seite 40]

The good man seemed to have had a
pre-sentiment of the uncertainty and insta-
bility of all vain worldly honours, and he
therefore, as is well known, soon after be-
took himself to a more solid mysterious en-
joyment, in which Mlle. Bourignon bore a
part. And, indeed, it happened as he appears
[Seite 41] to have foreseen; for the ungrateful world
now ascribe the merits of that discovery to
the celebrated Abbé Spallanzani, who has
maintained it in several of his writings, but
more particularly in the second volume of his

He calls the little black points of the
fecundated spawn of frogs, Tadpoles, or young
frogs(y); and as this little black point exact-
ly resembles the same in the unfecundated
spawn(z), he reasons agreeably to his logic,
[Seite 42] that the tadpoles must have existed in the

I do not know what would be thought of
that chemist who asserted that the Arbor
Dianae pre-existed in a mass of Amalgam of
silver, because when a weak solution of silver
was poured on it, a little tree seemed to spring
out of it.

One ought to be ashamed of wasting
much time in the refutation of an assertion, the
falsity of which any unprejudiced person who
is not altogether unaccustomed to observations
of the kind may convince himself of every

[Seite 43]

Whoever has taken the trouble, accu-
rately, to examine the spawn of the frog must
confess, that the idea of demonstrating the little
black points contained in it to be so many
complete formed tadpoles, partakes greatly of
Brother Peters's method of reasoning in the
Tale of the Tub, where he demonstrates to his
brothers that the brown loaf is a piece of ex-
cellent roast mutton.

But the abettors of the theory of orga-
nized germs have gone a step further in support
of their opinions. They refer to cases where
even young girls, in all their maiden innocence,
have become pregnant from the untimely, and
premature evolution of one of these organized

The concurrence of facts is sometimes
most wonderful. It happened that in the very
same year that Swammerdam announced his
discovery in the spawn of the frog, that a case
was published in the Ephem. rerum. nat. curios.
[Seite 44] delivered to the society by a celebrated court-
physician of those times Dr. Claudius, which
exactly suited as a confirmation of Swam-
merdam's opinion. – A miller's wife was

delivered of a little girl whose belly seemed of
an unusual size. Eight days afterwards this
little big-bellied child was seized with such
violent pains and restlessness, that every one
who was present thought it could not outlive
the next instant. The sick infant however in
the mean time actually bore a well-formed, ele-
gant, lively, little daughter about the size of
one's middle finger, which was regularly
baptized. During the time, and after the
birth, the waters, placenta, and all other
impurities were rightly discharged. But both
the little mother and daughter died early the
following day(b).

[Seite 45]

Baron von Haller very judiciously classes
this case with another from the Transactions
of the Academy of Sciences of Stockholm,
where on dissecting a young girl, bones, teeth,
and hairs were found in a tumor of the my-
sentery. These two cases he looks on as
principal evidences for the truth of the doc-
trine of germs pre-existing in the mother.

In Schmucker's Miscellaneous Surgical
Essays an anonymus correspondent sends the
history of the dissection of a girl, in whom,
instead of an uterus, there was found a hard
hairy body of the size of a large walnut, and
[Seite 46] which resembled an ill-shaped head. It had
two perfect teeth, and contained in its cavity
something like brain.

Now since the abettors of the theory of
evolution so loudly remonstrate against, and
complain of the unfair method of proceeding
by opposing mere argument to the facts which
they bring forward in support of their opini-
ons, I shall for the present totally abstain from
all reasoning, and endeavour to satisfy these
gentlemen by adducing fact for fact, observa-
tion for observation, and those of no less won-
derful, and entertaining a nature than theirs;
for they will prove, that not only men but
male animals have been equally in a thriving
way with young virgins; and I trust the tes-
timonies of the truth of these stories will be
found equally respectable with those of the
opposite party.

To the case extracted from the Memoirs
of the Academy of Stockholm I oppose one
from the History of the Royal Academy of
[Seite 47] Sciences of Paris, where an Abbé was inter-
rupted very mal apropos whilst instituting some
experiments on generation. He was alarmed
by an extraordinary encreased of bulk in a cer-
tain part, which another Abbé (the unfortunate
Abelard) was deprived of in consequence of a
similar experiment.

The tumor encreased so much that he
was obliged to submit to an operation, and his
surgeon assured the academy that he cut an
ossified child(c) from the part.

To the story of the miller's wife I beg
leave to subjoin one from the Philosophical
Transactions of London, where an account is
given of a male greyhound that bore a living
puppy per anum; and in the place of Drs.
Otto and Claudius, who witnessed the truth of
the first fact, I shall mention two names of
[Seite 48] which England ought to boast: Dr. Wallis,
and Edmund Halley.

Lastly to the anonymous in Schmucker
I oppose an anonymous in the works of the
respectable Fr. Ruysh, who was presented with
a similar production. It was a bony case,
half as big as a common walnut, together with
four perfect mollares, and a knot of hair,
which, he assured the doctor, he had cut from
the stomach of a male subject.

Thus I have adduced authority for au-
thority; nor do I believe it possible for any
one to go more conscienteously to work than
I have done; and so far therefore I [...]ust we
are quits.

Were I allowed however to speak my
mind freely on this matter, I should advise
all such auxiliary troops to be withdrawn.
My only reason for bringing them on the field
was merely to oppose those of my antago-

[Seite 49]

These therefore are the principal argu-
ments, which, I have to oppose to what the
advocates for the theory of evolution consider
as the strongest, and most decisive proofs of
their theory.

But experience supplies me with another
source of facts, which may be used as argu-
ments against this theory, and which, to
unprejudiced, and judicious readers, ought to
be sufficient whereby to ascertain its true degree
of probability.

For instance, the well established, and
universal truth; that the first appearance of a
newly conceived animal, or plant, is never to
be discovered immediately on impregnation,
even by the most powerful armed eye; no
such thing is to be seen until a considerable
time has elapsed.

It is not worth while to enter into a refu-
tation of the fabulous assertion of Hippocrates,
and of so many others of his old and worthy
followers, that perfectly distinct, and well
[Seite 50] formed human embryos were to be seen in the
very first days of conception. Considering
the few aids, and little opportunity they had
in those days of making such observations,
great allowance is to be made; and the more
so, when we consider that even modern phy-
sicians of much more extensive experience in
these matters, have been guilty of similar
assertions. Mauriceau has amused us with re-
presentations of foetusses of one day, and of
three days and a half, &c. and Malpighi and
Croune have assured us that they had seen the
embryo of the chick and its appendices in
the egg of a trod hen before the egg had been
sate upon. The last author indeed observed
it, he says, in the addle egg of hens that never
had been cocked.

It is impossible however to discover
any thing before the third week after concep-
tion, which any cautious and creditable obser-
ver would presume to pronounce a human em-
bryo, and in the fecundated egg nothing can
be observed, which has even the most distant
[Seite 51] resemblance to a chick in the first twelve
hours, nor indeed until the end of the second
day. Previous to this period of time peculiar
to each animal, and vegetable,(d) it is quite
impossible to distinguish the newly conceived
offspring; which circumstance, considering
the perfection, and powers of our microscopes,
is by no means favourable to the theory of

Nor, is it at all easy to comprehend how the
advocates for that theory make the phenomena
of the accidental origin and growth of certain
preternatural parts agree with their doctrine
of pre-existing organic germs.

A few instances of this kind will serve
instead of many.

[Seite 52]

A woman conceives, but the foetus in-
stead of being in the uterus, is situated in one of
the Fallopean tubes. The tube at last bursts
from the increase of bulk of this strayed animal,
and it falls into the cavity of the abdomen.
What does nature do? She pours out a quan-
tity of plastic lymph, which forms itself evidently
into organized membranes, incrusting and
inveloping the foetus like a mummy, by which
it is prevented from putrefaction; for were
this allowed to take place, it would occasion
certain death to the mother, but who, preserved
by this contrivance, is enabled to carry the
troublesome, though not dangerous load, for
a considerable number of years. On opening
the body after death, we evidently perceive
this new, and, accidentally formed membrane,
to be richly supplied with blood vessels,(e)
[Seite 53] which it would be rather difficult to prove, had
pre-existed in the organic germ.

A person breaks both bones of the fore-
arm, but is so restless as to disturb nature in
her usual process of healing them, that is, by
means of a new ossification. In this case what
does she do? She forms a new joint of the
broken ends of both bones; making as it were
a second elbow which can be moved at
pleasure without any assistance from the other

Another person dislocates his thigh bone
from its natural situation in the Ilium, and
nature endeavours to remedy the evil, by for-
ming a new socket for it(f).

[Seite 54]

A child is born with a hydrocephalus,
occasioned by mere accidental circumstances;
such for instance as the frequent, and too
violent connection of the father with the
mother, during the time of her gestation.
Owing to this disease, the cranium becomes
preternaturally distended, and immence spaces
are left between the very thin, and greatly
distended bones. In order to remedy this,
nature forms detached osseous points in these
interstices, which points, at last become true
ossa triquetra, filling up all the dangerous
voids, and uniting all the bones of the head

These ossa triquetra however do not belong
to the natural structure of the foetus, and are
very seldom to be met with in the sculls of
savages, or of brute animals. It is hardly
possible therefore that they should have pre-
existed in the organic germ: and yet they are
as perfect bones as any others of the head,
having true, and well formed sutures. The
sutures of these bones are not always locked
[Seite 55] in with the sutures of the other bones of the
head; but it often happens, that they are so
numerous, and so thick together, that those
in the middle, evidently construct their own
ones. What is there however which exhi-
bits more art than the structure of a true
suture; its double, nay treble row of teeth,
the corresponding depressions, and the asto-
nishing manner in which they are clasped

The conclusion which naturally follows,
is, that is perfect bones, new and preter-
natural joints, new organized and vascular
membranes can be formed, where there was
no ground for supposing a pre-existing germ,
what necessity is there for this doctrine of

But the phenomena which occur in the
generation of mules, so completely refute all
our ideas of pre-existing organic germs, that
one is at a loss to imagine, how, after a due
attention to this subject, such a theory should
[Seite 56] have found any serious abettors. I should
suppose that a single experiment, such as that
of Mr. Koelreuter, who by repeatedly produ-
cing prolific bastard plants, transformed one
species of tobacco (nicotiana rustica) into
another (nicotiana paniculata) so completely,
that it had not the smallest resemblance to its
maternal parent; that such an experiment, I say
must cure the most partial advocate for the
theory of evolution, of his error. This
excellent observer, by artificially impregna-
ting the first species of tobacco with the farina
of the last mentioned, obtained prolific bastard
seeds from it, and with the plants which sprung
from these, he repeated the same experiment,
impregnating them with the farina of
the Nicotiana paniculata. As the plants
which he procured from the seeds of this last
combination, differed more from the original
maternal plant, he repeated the same process
with it, and proceeded to do so with every new
offspring, untill he obtained six plants, which
in every respect appeared perfectly similar to
the paniculata; so that in the classical work,
[Seite 57] in which he gives a narrative of this, he
appears perfectly justifiable in entitling it, A
complete metamorphosis of one natural species of
plants into another.

I know perfectly well, that the favour-
ers of the theory of evolution endeavour to
explain the production of bastards, or mules,
by saying, that the male semen, besides its
stimulating power of awakening the female
germs from their state of stupor, and inactivi-
ty; also ascribe to it certain formative powers,
by which the germ maybe altered in a certain
degree, so as so resemble the father a little.
But what in the name of Heaven is such a
subterfuge than the silent acknowledgement of
the insufficiency of the germ theory, and of
the necessity of having recourse to formative
powers, in order to extricate it? If these
formative powers, however, are so strong as
totally to change the structure and appear-
ance of the maternal germ, and that in the
course of a few generations, it is rather diffi-
cult to conceive the utility of such a theory.

[Seite 58]

Proofs of the Formative Nisus, and an Attempt
to ascertain some of its Laws.

[Seite 59]

IT is easier to overturn, than to establish a
theory; and the reproach has been often
applied to old reformers, that they have suc-
ceeded better in attempts of the first, than of
the last kind. Yet what Mons. Bonnet ex-
cellently remarks on this subject may be very
true(g), that the detection of an error is often
of greater consequence than the discovery of
[Seite 60] a new fact. In this respect therefore, I trust
the present sheets will at least be allowed
some merits, since they point out the defects
of a late beloved, and almost universally
adopted theory. I hope, however, at the
same time, that the one which I give in
its place will be found more agreeable to what
we observe in nature.

No one can be more fully persuaded of
the immense gap which exists between the
organised, and unorganised, between the ani-
mated, and the inanimate world, than I am;
and although I have the greatest respect for
the penetration of those who discover a
gradual scale of ascent and descent in the
works of nature, yet I confess I am at a loss
to guess how they make it pass from organic
to inorganic bodies. Such a reflection, how-
ever, ought by no means, to deter us from em-
ploying the phenomena of either of these
classes of bodies for explaining the phenomena
of the other: and so far do I consider it as
an argument, not of the least importance, for
[Seite 61] proving the existence of the Formative Nisus
in organic bodies, that even in the inorganic
ones there exists traces of a Formative Power;
not of a Formative Nisus however, at least,
in the sense this word is used in this work;
for here it is considered as one of the pro-
perties of the living principle, and conse-
quently not to be imagined as belonging to
dead matter: but that this last Formative
Power is demonstrated by the regularity and
invariable shape of certain bodies which we
find to be formed of it.

For only to adduce one or two instances,
we find nothing more elegant, than certain
metallic crystallizations, which as to their
external aspect, bear so striking a resemblance
to certain organized bodies, that they become
a very good example for explaining to us the
manner in which bodies are formed from rude
and unorganized matter. Such for instance,
is that species of native dendritical silver,
imbeded in a matrix of quartz from Mexico,
Farnkrautsilber, and which resembles the fo-
[Seite 62] liage of the fern, or to name something more
common, that undescribable beautiful moss-
looking texture of brass, which is observed
in breaking a piece of it, after the first

These as I have already said, are ad-
duced as mere examples of the existence of
a Formative Principle in unorganized bodies.

And now for the true formative effort in
the animated world.

I know no means so well calculated for
rendering the existence, and activity of this
nisus evident to an impartial eye, as to ob-
serve the origin and progress of such orga-
nized bodies, which increase so rapidly in
bulk, that the action of the growth becomes
almost evident; and which are of so delicate
and semitransparent a texture, as to be capable
of being evidently seen through with the as-
sistance of a microscope, and a due degree of

[Seite 63]

The vegetable kingdom supplies us with
a very good example of this kind, in the
simple production of a most simple water
plant, (conferva fontinalis) which is com-
monly to be met with every spring, in wells,
ponds, and springs, or in the wooden pipes
through which water flows.

The whole plant consists of a single
uniform straight fine thread, of a bright
green colour, and about half an inch in
length, and whose under extremity is generally
inserted in a bed of slime. As these threads,
however, are extremely numerous, and grow
very close together, they look like a very fine
fur of the most beautiful green colour, with
which considerable spaces of the places above
mentioned are sometimes covered.

I have attentively observed the propaga-
tion of this water plant in the beginning of
the spring, and to me it appeared to take place
in the following manner. The upper end
[Seite 64] of the fibrile began gradually to swell, and
divide into a number of small round points,
which at last disengaged themselves from the
parental thread, and in the number of some
thousands, attached themselves to the sides
of the glass in which I made the experiment.
Soon afterwards, these round bodies began
to shoot out a small point, which almost
visibly lengthened till they had acquired their
due size. All this took place in the space of
twice twenty-four hours, counting from the
first moment that the end of the old thread
began to swell.

Both the rapid growth of this plant,
and its transparent texture, afforded me means
of discovering not only its structure, but also
the slightest changes that took place in it.
This kind of moss is equally simple inter-
nally, as externally; and under the strongest
magnifying powers, and by the best light,
we can discover nothing else than a fine ve-
sicular appearance, like a green froth, sur-
rounded by a very thin delicate membrane.
[Seite 65] But in spite of the distinctness of texture
of the little green points which adhered to
the sides of the vessel, there was nothing to
be seen like the germ of an enveloped filament
in them, such as was soon to be produced from
it: but only when the little round body had
attained a certain degree of perfection, a small
shoot seemed to spring out of it, in such a
manner, that its act of evolution seemed to be
promoted merely by that part of the vesicular
texture of the round point, which was most
contiguous to the filament, passing gradually
over to it. As the filament encreased in
length, the little round body gradually de-
creased in magnitude, and became of a paler
colour, so that at last, when the filament had
arrived at its full growth, there remained just
a perceptible swelling at the inferior end, and
which served as a root to the new filament.

With an equal degree of distinctness
with which the progress of the Formative
Nisus of this plant becomes conspicuous, we
can also clearly discover it in many animals;
[Seite 66] especially in such, as like this kind of moss,
possess the advantages of a rapid growth, and
great transparency of texture. This is the
case with the armed polypi, which on account
of the miracles they are capable of performing,
have within these last forty years been an object
of general surprise, and admiration. All the
known species of this animal have a kind of
gelatinous body, which, whether it be of a
green, yellow or brown colour, &c. is still
sufficiently transparent to be capable of being
distinctly seen through, if a proper lens and
light be employed. Its texture is uniform,
and simple, and so homogenous, consisting en-
tirely of gelatinous points, which seem to be kept
together by a still thinner jelly, that nothing
seems concealed from or obscured to the eye of
the observer. Now, when this animal is about
to produce its young, a swelling or tumefaction
takes place on a single spot of its body; and
from this swelling there shoots out first the
cylindrical body, and then the tentaculae of
the young polypus. These are all of so con-
siderable a size as to be observed with the
[Seite 67] naked eye: and when we consider this cir-
cumstance, and all the others already mention-
ed, there does not appear the smallest probable
ground for supposing, that an organized germ
had pre-existed there, and was now evolving.

I refer it to the internal feelings of
every one who has attentively observed this
kind of production in animals, and plants of
so simple a texture as those alluded to, and
who at the same time have well attended to
all the arguments brought forward in the fore-
going section against the doctrine of the
pre-existence of the embryo of the chick in
the yolk of the egg, whether in passing in
his own mind to the generation of the more
perfect or warm-blooded animals (as for
instance by the most accurate investigation of
the phenomena of the beginning, progress, and
form of the embryo in the fecundated egg, and
also of the many other parts(h) which are
[Seite 68] to be found in the unfecunded one) whether,
I say, his conviction leads him to believe in
the pre-existence of enveloped organic germs;
or, in the existence of a nisus, by which a new
being is formed from the unorganized mate-
rials of generation.

All the arguments which have hitherto
been deduced from the phenomena of genera-
tion in support of the existence of a Nisus
gains new, and additional weight
from the consideration of the phenomena of
reproduction; this so wonderful power of
organised bodies by which lost, and mutilated
parts are again renewed.

Generation, and reproduction are both
modifications of one, and the same power;
the last being nothing else than a partial
repetition of the first. Whatever tends to
elucidate the one, must therefore throw light
on the other.

[Seite 69]

I have frequently repeated the experi-
ments alluded to in the First Section, by
which I endeavoured to discover the power
of reproduction in the green armed polypus,
and have constantly met with the same suc-
cess. The little mutilated animal was always
diminished in bulk, in proportion as its new
arms or new body were pushed out. It be-
came evident with what efforts nature hastened
to renew the determinate form of the maimed
animal, and also, that from the short period
of time, and the improbability of the polypus
having taken a sufficient quantity of nourish-
ment to supply materials for the new mem-
bers (since all wounded polypi eat less than
usual); From these circumstances I say, it
became evident, that owing to the force of
the Formative Nisus with which the parts
were endowed, the remaining portion of
the mutilated animal, was in some degree,
converted into the new members, and thus
the disturbed structure renewed.

[Seite 70]

I am well aware, that the advocates for
the theory of Evolution, will, in order to
help themselves out of this difficulty, have
recourse to an hypothesis, which of all im-
probable ones, may be stiled the most ro-
mantic, and improbable; and according to
which it is supposed, ‘“That in every part of
the polypus, there exists innumerable germs
enveloped, and torpid as it were, which
lie like a hidden store, untill it shall please
the fancy of a naturalist to rouse them
into action, and free them from their state
of imprisonment, by the enlivening cut of
a pair of scissars.”’

Now, let any one compare this expla-
nation with the naked appearances which take
place in the above, and many other experi-
ments on the armed polypus, the process of
which are so easy to be discovered. – I shall
at present content myself with relating two of
these experiments. When we take the half
of two polypi of different kinds, for instance,
[Seite 71] the anterior half of a green one, and the pos-
terior half of a brown one, and bring them
together at the bottom of a proper glass, they
join together, and form in this manner, one
of these monsters of mythology, representing
a group composed of different parts of different

According to the theory of Evolution,
however, very different phenomena must have
occurred. Instead of this junction between
the two halves, each one ought to have
evolved from an organic germ that part of
which it had been deprived of; but this is not
what we observe; it was more natural that
the two parts should join by the means of
their formative powers, than that each of
the halves should of itself have been metamor-
phosed to a complete animal by the manner
described above.

There is a well known experiment how-
ever, which is admirably calculated to de-
monstrate both the improbability of the sup-
[Seite 72] posed pre-existing germs, and at the same
time, the activity of the Formative Nisus.
When we take the polypus, and do not divide
it in pieces, but merely slit open its belly
longitudinally, so as to destroy that cavity;
and as it were, metamorphose the shape of
the animal from a cylindrical to a flat form;
instead of a number of organic germs being
set free from the cut edges, and of their being
each evolved, one of the two following oc-
currences takes place; either the animal rolls
itself together in the usual form, so that the
edges of the wound meet and coalesce, or
if it remains like a piece of flat tape, it begins
soon after to swell in the middle, as if it were
blown up, and there is gradually formed within
it a new belly.

In both these cases there is no occasion
for new materials, all that is done is a mere
reparation of the disturbed structure.

In man and other warm-blooded animals
the power of reproduction is much more li-
[Seite 73] mited not only on account of the great diversity
of materials of which they are composed, but also
the different quantity of living principle peculiar
to each of these materials, and by the mutual de-
pendance and action which they exercise on
each other. And yet we often observe in them
evident marks of this power of reproduction,
tending to confirm all that has been said on this
head, concerning the polypus; nails have been
observed to grow on the stump of a finger, even
although the first joint was completely lost(i).
It would be rather a bold conjecture to suppose
that nature had foreseen such accidents, and had
therefore sown all the fingers and toes with
the organic germs of nails, &c. And on the
contrary, how agreeable to nature is it to
deduce the whole phenomenon from the
activity of the formative powers, whose efforts
are sufficiently strong to reproduce nails on the
extremities of the fingers, nay even in un-
usual parts.

[Seite 74]

Another equally well known, and inter-
esting fact of this kind, is, where nature en-
deavours to supply the loss of an extremity, whose
complicated structure it would have been
difficult for her to restore, by the production
of a more simple and uniform substance.
Thus, that celebrated surgeon, Morand, gives
the description of a hare, which, a considerable
time before its death, had had one of its fore
legs shot off, the place of which nature
had endeavoured to supply with a kind of bony
stump, which, although not like the original,
quoad materiem, yet resembled taliter qualiter
quoad forman

If, as I flatter myself, the few phenome-
na of generation, and reproduction already
taken notice of, are sufficient to prove the un-
[Seite 75] deniable existence of the Formative Nisus
there remain many others tending to explain
its modus operandi; and to ascertain some of
the laws by which that mode seems to be
regulated. I look upon the following to be
of this kind, that is, as the mere result of
undoubted observation.

I. The activity of the Nisus, is, in an
inverse ratio, to the age of the organized body.

For however certain it may be, as has been
formerly remarked, that some time is neces-
sary before the first marks of the new conceived
fruit becomes visible, yet it is equally well
ascertained, that after this interval, the forma-
tion proceeds with astonishing celerity.

In general, the embryos of the earlier
months are represented in a very unshapely
form, but this may be owing either to the
person who gives the representation; or to
this, that such abortions generally suffer much
by external violence, are squeezed, compressed,
[Seite 76] or from putrefaction having already begun,
lose much of their uncommon elegance, which
otherwise render them objects of admiration.
I possess some of these beautiful human foetusses
of the first months of pregnancy, especially
those which I received from my dear friend
Mr. Bückner of Gotha, where in one of five
weeks old, and of the size of a common bee,
all the features of the face, every finger com-
plete, every toe, and the organs of generation
were to be distinctly seen.

Now this early activity of the Formative
Nisus, is by no means confined to the external
form of the embryo, but is still more remark-
able in the internal structure. I have often
been astonished at the early perfection of the
vicera, which I have discovered in dissecting
recent human embryos of the first months.
Thus, merely to mention one circumstance
in its head, which was hardly larger than a
pea, the whole cartilaginous basis cranii, with
all its depressions, apertures, and processes,
were marked in the most sharp and distinct
[Seite 77] manner, although, indeed, there was not the
smallest point of ossification, either in the
sphenoid bone, or the petrous part of the
temporal one.

However difficult it may be on the sup-
position of pre-existing germs, to explain
what becomes of them for so long a time after
they arrive at the place of their destination,
and are fecundated and stimulated to evolu-
tion; it is equally difficult to imagine, why
immediately after this interval, they should
so suddenly acquire so respectable a size. On
the contrary, after it has been fully understood,
what was said concerning the time necessary
for the preparation of the fluids of generation,
before the Formative Nisus takes place;
there remains nothing puzzling in this,
that then the new awakened action should so
soon form the ground work of the new

That the inverse ratio between the For-
mative Nisus, and the increase of age,
[Seite 78] continues even after birth, is proved by the
remarkable ease with which reproduction takes
place in very young animals, especially those
of the lizard kind, as in the common newt.

II. The Formative Nisus is much more
active in the embryos of mamelia, than in
those of oviparous animals.

In the chick for instance, the first ap-
pearance of the ribs is observed one hundred
and twenty-nine hours after impregnation.
This period is equal to the nineteenth week
of gestation in the human species. But I
have in my possession, human foetusses, which
are not more than six weeks old, and yet in
which, the cartilaginous rudiments of the
ribs are to be distinctly discovered. It would
appear as if nature made greater haste with
the formation of viviparous animals, to secure
them against deformity, from accidental
causes, such as pressure, external violence,
&c. from which causes all oviparous animals
are defended by their shell.

III. In the formation of some particular
parts of any organized body, the Formative
Nisus is much more regular in its process, than
in that of others.
Thus the brain, says old
Conr. Vict. Schneider, a man much distin-
guished in physiology, is seldom or never found
to deviate from the usual structure(l). On
the contrary, how great and frequent are the
variations in many other parts, such as in the
kidneys, and Thoracic Duct, &c.

[Seite 79]

Amongst the many deviations of the
formative process from its usual course, these
are principally to be mentioned.

1st, Where one species of organic body
takes on the action of that of another.

To this belong some of the most unac-
countable phenomena in nature, which, as
[Seite 80] far as I am able to judge, cannot be explained
in any satisfactory manner by the theory
of pre-existing germs. It is a well-known
fact, that women have in general, and ac-
cording to the strict laws of nature, only
one uterus for the reception of the new con-
ceived foetus. But that most of the other fe-
males in the class of mamalia, have a double
one. Yet instances are not wanting, where
a real uterus bicornis has been found in women.
This singularity, if I am not mistaken, is
accounted for by the previous reflection. In
the same manner, I would reckon all those
hares, which have been so frequently ob-
served with small horns like those of deers,
and also many of those strange deviations,
which take place now and then in the struc-
ture of the vegetable kingdom, such as the
alder-tree with oak leaves, described by

[Seite 81]

2dly, Where the organs of generation of
one sex take on more or less the structure of
that of the other.

In our sceptical days, the possibility of
human hermaphrodites, and that of other
warm-blooded animals, has been much doubt-
ed. And yet Baron Haller of this university,
and Mr. John Hunter of London, have in-
stituted, and given relations of the most care-
ful dissections of such animals, especially in
the cow, and goat tribes, and which leave no
room for further doubts in this matter. It is
true, that in none of the instances, the most
essential parts of generation, for instance,
the male testicles, and female ovaria, were to
be distinctly discovered in the same individual.
But though the chief form seemed to be always
that of one of the sexes, yet there was evidently
to be discovered in one part or another, the
most unequivocal, though imperfect marks of
the organs of the other sex. In general, the
male organs lay internally, whilst the external
ones had more the resemblance of the female.

[Seite 82]

3dly, When the formative process does not,
as in the former instances, take an action which
is FOREIGN, but one that is completely
PRETERNATURAL to the individual.

And yet from an attentive consideration of
the astonishing uniformity, which reigns
amongst the different kinds of monsters, it
would appear as if the causes of the deviation
in their formation, was regulated by certain
fixed laws. Whoever has seen any consider-
able number of monsters, or only looked into
the loose and wretched compilations of re-
presentations of them, can hardly have escaped
being struck by the resemblance which unites,
even to the most inconsiderable parts, cer-
tain species of them, so that the individuals of
that species, seem as if they had all been cast
in the same mould.

To conclude, there is still one other
phenomenon, which the reader is at liberty to
explain, either on the principle of pre-existing
[Seite 83] organic germs, or that of the Formative
Nisus. Many animal monsters, such for in-
stance, as those with two bodies and a single
head, are of that kind, according to the ex-
press assertion of Baron Haller, and other
evolutionists, that they cannot have arisen
from the accidental growth of two germs, but
that the fault lies in the original monstrosity
of a single germ. Now it is singular, that
such monsters are only common in animals
which have been domesticated, and that they
are never, or at least seldom to be heard of
in their wild state. Can the Author of nature
have ordained it, that from amongst the in-
volved germs of any one species of animals,
for instance, swine, the monsters should ar-
rive at evolution, just when taken under the
care of men, and that the monsters should be
produced only by the tame, and not by the
wild also?

On the other hand, there is nothing un-
reasonable in supposing, that after the sub-
jection of these animals, their whole frame
[Seite 84] and oeconomy suffer a very great change;
that then the Formative Nisus deviates in
some degree from its original laws, and there-
fore these animals as they degenerate into
endless varieties, are also more subjected to

Such, in my opinion, are the principal
observations and experiments which serve to
prove the existence of the Formative Nisus,
and to ascertain some of its laws; observations
which have drawn my conviction more and
more from the system of involved germs, and
confirmed my belief in the very opposite doc-
trine, which I have endeavoured to establish.


Appendix A ERRATA.

Page line for read
  5   5 begins, begin.
29   4 of the Note, Sonebier, Senebier.
38   4 of the Note, oviatur, oriatur.
42   4 assertes, asserted.
45   7 of the Note, Disquisitionum, Disquisitio num.
71 13 dele of.
[interleaf] [interleaf] [interleaf] [interleaf] [binding_verso]
[Seite 3]

For instance, those of Orpheus, Pythagoras,
Anaxagoras, &c.

[Seite 3]

Such as that of Pope John XXth, or
Bishop Abert the Great, or whatever holy father of
the church it was, who wrote that vile book de Se-
cretis Mulierum. One may also add Mich. Scotus,
the scrutinizer of natural things.

[Seite 11]

On the nature of things, addressed to John
Winkelsteiner von Feyburg at Uchtland, in the
sixth volume of Huser’s edition of his works,
p. 263.

Amatus Lusitanas describes a similar pro-
duction: Vide Curation, Medicinal Cent.
curat. 55, scholi, p. 612. ‘“Certo scimus chemico
artifcio puerum conflatum esse et omnia sua mem-
bra perfecta contraxisse, ac motum habuisse, qui
cum a vase ubi continebatur esset extractus mo-
veri desiit. Novit haec accuratius Julius Ca-
millus vir singularis doctrinae et rerum occulta-
rum, et variarum hac nostra aetate magnus scru-
tator et Hetrusca sua lingua scriptor diligentissimus
et accuratissimus.

[Seite 11]

Vide Generation de l’Homme et des Ani-
maux, Paris
1750. 12. Also his Observations sur
l’Hist. Nat.
1 p. and the mishapen representation of
a foetus drawn by himself and coloured after life.
A. fig. 3.

[Seite 12]

Essai de Dioptrique, Paris 1694. 4. p.
230, where the lynx-eyed man gives an accurate
figure of a child, which he observed in the body
of one of the animalculae of the semen, and which
appeared to him as if anxiously expecting its de-

[Seite 18]

It is probable that this circumstance has
been either totally overlooked by such as were en-
gaged in observing phenomena of greater magnitude
in the history of this animal, or if it has been ob-
served by any, it does not seem to have appeared to
them, of sufficient importance to be noticed. That
attentive, and accurate observer Roesel, however,
seems to have noticed this fact. Vide Hist. der Poly-
pen, in the third vol. of the Insecten-belustigungen.

[Seite 19]

An observation which has been also made
by Messrs. Louis and Fabre, vide their treatises Des
Playes avec perte de substance in the Mem. de
l’Acad. de Chirurg.
vol. iv. p. 64 and 106.

[Seite 21]

Vid. Newton at the end of his Optics:
‘“What I call ATTRACTION, may be performed
by IMPULSE, or by some other means unknown
to me. I use that word here to signify only in
general any FORCE by which bodies tend to-
wards one another, whatever be the CAUSE.

[Seite 21]

Qualitas occulta – ‘“Se l’on entend par ce
mot un principe reel dont on ne peut rendre raison
tout l’univers est dans ce cas.
”’ &c. says Vol-
taire, vid. his Elements de la Philosphie de Newton.

And in another place he further adds, ‘“Il
falloit respecter les qualités occultes; car depuis
le brin d’herbe que l’ambre attira, jusqu’à la
route que tant d’astres suivent dans l’espace;
depuis la formation d’une mite dans un fromage
jusqu’à la Galaxie; soit que vous considerer, une
pierre qui tombe, soit que vous suiviez le cours
[Seite 22] d’une cométe traversant les cieux tout est qualité

[Seite 22]

One of the most learned, and ingenious
English physicians of the present time, Dr. G. For-
dyce, has very lately said, in treating a physiological
point something similar to this,
‘“Although the
study of causes of original powers be totally absurd
and futile, yet the laws of their action are ca-
pable of investigation by experiment, and ap-
plicable to the evolving much useful knowledge.
Philosoph. Trans. V. LXXVIII. P. 1. p. 36.

[Seite 23]

No one has given such a clear proof of
this as Ad. Mich. Birkholz, Philos. et Med. Dr.
et Facult. Med. Assess in his Dissert. de Respira-
tione ejusque fine summo atque ultimo, Lips.
After informing us, that the animal spirits (Spiritus
[Seite 24] vitales) which the blood derives from the air, is
nothing more than the principium vitale of the an-
tients, or the irritability and sensibility of Haller, he
‘“Veteres philosophi hoc principium agnorerint
vicarium Dei ministrum et presidentiam superioris
agentis, et apud Graecos quidem sub persona Jovis
colebatur: Jovis omnia plena! a vetustissimis phi-
losophis, a Platone, et platonicis Arabibus, et le
Cat, appellatur anima, spiritus et idea mundi, vis
et naura genetrix et plastica, ideae operatrices: a
Rayo flamma vitalis; ab eodem et postea imprimis
a Newtono principium trahens: a chemicis humi-
dum radicale, et quintum elementum: a Colonne
invisibilia fermenta: a Blumenbachio nisus for-
mativus. A philosophis Hermeticis mercurius
universalis et philosophorum: a Thouvenel Gas
Aeroelectricum, ab aliis aliter appellatur.

[Seite 25]

Of all authors who have treated of
this power, F. Bonamica, the well-known disciple
of Aristotle, explains himself perhaps the most cor-
rectly, de formatione foetus,
p. 528. ‘“Spiritus
in aërea seminis substantia comprehensus, aspersus
autem a calore caelesti, et vi a patre accepta, et
ea quam a coelo participat in uterum foeminae con-
jectus, concoquet materias a foemena infusas,
et pro ratione ipsarum variis modis afficiens efficit
instrumenta. Dum vero ea fabricat appellatur.
Facultas διαπλαςικη seu δημιεργικη. Sed ubi ex-
tructa fuerint instrumenta, ut iis uti queat, quae
prius erat vis formatrix, illis utens degenerat in

[Seite 26]

For example, p. 12. ‘“Vis vegetabilium
essentialis ea est vis, quá humores ex circumjacente
terra, vel aliis corporibus collinguntur subire radicem
coguntur, per omnem plantam distribuuntur, par-
tem ad diversa loca deponuntur, partem foras

P. 13. ‘“Quae cunque vero sit haec vis, sive
attractrix, sive propulsiva, sive aeri expanso debita
sive composita ex omnibus hisce et pluribus; modo
[Seite 27] praestet enarratos effectus, et ponatur, posita planta
et humoribus nutriciis applicatis, id quod experien-
tia confirmatum est: sufficiet ea praesenti scopo et
vocabitur a me Vis vegetabilium Essentialis:

And in respect to the generation of animals,
p. 73. ‘“Embryonem hoc tempore (ovo sc. 36. horas
incubato) ex substantia ovi nutriredemonstrant il-
lius volumen auctum, perfectiones acquisitae, absen-
tia cujuscunque alius materiae consumtio alluminis et
vitelli succedens, experimenta inferius recensenda;
consequenter: transire particulas nurientes ex ovo
ad embryones: et existere vim quâ perficitur
quae non est systaltica cordis et arteriarum, neque
hinc facta pressio in venas vicinas neque harum
compressio a motu musculorum, adeoque analogam
(§. 1.) quam aeque vocabo essentialem.”’

[Seite 28]

But in doing so, I shall pass over all
those arguments against the doctrine of evolution,
[Seite 29] which have lately appeared in a most ingenious and
witty publication, written expressly for that pur-
pose. Vide Doubts concerning the Theory of Evolution,
in a letter addressed to Mons.
Senebier, from L.P.
(Patrin) translated form the original French ma-
nuscript into German by G. Forster, Goettengen,


[Seite 29]

He himself wrote me a letter, dated the
28th August 1776, in which he says ‘“I thank
Providence for having granted me so long a life
[Seite 30] as has enabled to give an improved and
corrected edition of my Physiology, without which,
I must have left many errors to be detected after
my death.

[Seite 32]

‘“L’evolution commence à me paroitre la
plus probable.

[Seite 32]

Vide his preface to the work alluded to.
Ed. 5 th. ‘“Enfin cette decouverte importante
(que le germe appartenoit à la femelle, qu’il pre-
[Seite 33] existoit ainsi a la foecondation, et que l’evolution
etoit la loi naturelle des etres organisés) que
j’attendois et que j’avois osé predire me fut an-
noncée en
1757, par Mons. le Baron de Haller
qui la tenoit de la nature elle même.
decouverte de Mr. de Haller prouvoit d’une ma-
niêre incontestable que le poulet appartenoit ori-
ginairement à la poule et qu’il pre-existoit à la

And in his letter to Mr. von Haller, dated
30th of October 1757, he says, ‘“Vos poulets
m’enchantent: je n’avois pas espéré que le secret
de la generation commonceroit sitôt a se devoiler.
C’est bien vous, Monsieur, qui avez sçu prendre
la nature sur le fait.

[Seite 37]

In the preface to the 8th vol. of the Col-
lection Academique par étrangere,
p. 22, sqq.

[Seite 38]

‘“Nunquam fieri potest ut inter tubulum
millionesies minorem, et millionesies majorem con-
oriatur.”’ Element. Physiol. T. VIII.
P.I.p. 94. compare with his first lines of Phy-
§ 883, and with the Opera Minora, T.
XI. p. 419.

[Seite 38]

Elem. Physiolog.

[Seite 39]

Miracl. Natur. p. 21. ‘“Admiratione
dignum est, nigrum illud punctum, quod in ovis
[Seite 40] ranarum videre est, ipsum ranunculum omnibus
suis partibus absolutum; albicantem verum et
circumfusum illum liquorem non nisi alimentum
ejus esse; quod ipsum sensim dilatatum ita at-
tenuatur, ut exire cum velet possit,
”’ &c.

‘“Magis mirum est hunc ipsum ranunculum in
ovaris usque adeo exiguum ortus et incrementi sui
principium habere, ut sere visum effugiat, ut
ipsum animal sub hac tantula mole delitescat.

And a little way further on, he draws the
general conclusion;
‘“Nullus mihi in rerum naturae
generationi, sed soli propagatione vel incremento
partium locus esse videtur ubi casus omnis exclu-

[Seite 41]

Dissertazioni di fisica animale e vegeta-
T. XI. in Modena, 1780, 8.

[Seite 41]

‘“A parlare filosofocamente l’uovo non è
che il gerino in se stesso concentrato, e ristretto, il
quale mediante la fecondazione si sviluppa ed ac-
quista le fatezze di animale.
”’ p. 11. § XVII.

[Seite 41]

‘“Questi globetti non fecondati non sono
per verun conto distinguibili dai fecondati.
”’ §

[Seite 42]

‘“Ma i globetti fecondati non sono che i
feti ranini,
§ XVII. Adunque i globetti non
fecondati lo saranno altresi; e consiguemente nella
nostra rana il feta esiste in lei pria che abbiasi
la fecondazione del maschio.
”’ p. 12. § XIX.

[Seite 44]

I adopt the very words of a contemporary
physician, Dr. Otto, who was consulted by the
grandmother (the miller's wife) during her preg-
[Seite 45] nancy. His nephew has vindicated and illustrated
the whole history in a most learned and subtile manner.
D.C.J. Aug. Ottonis Epistola de foetu puerpera
sive de foetu in foetu. Weissenfels,
1748. 8vo.

That this extraordinary history is also well
calculated to interest the casuist is evident, from the

Disquisitio num filiola, quam acto dierum enfans
vivam enixa est babtismi capax?

[Seite 47]

‘“On y distinguoit la téte, les pieds, et les

[Seite 51]

In the hare the first traces of the young are
not seen until the ninth day; in the sheep not before
the nineteenth; in the deer not before the seventh

[Seite 52]

In the eighth volume of the Commentaries of
the Royal Society of Göttingen I have given the
description of a foetus of this kind which had lain
[Seite 53] eight years within the mother. This specimen
was presented to the Museum of the Academy by my
very worthy friend Mr. Buchner of Gotha.

[Seite 53]

In my Osteology I have given numerous
examples of this, vid. page

[Seite 58]

Demontrer une erreur, c’est plus que de-
couvrir une verité: car l'on peut ignorer beaucoup;
mais le peut que l’on scait, il faut au moins le savoir
bien. Preface de l’Essai sur l’ame.

[Seite 67]

Nidus pulli, bulla amnion, figura venosa,

[Seite 73]

Pecklin and Talp have seen instances of
this kind.

[Seite 74]

‘“C'etoit,”’ to use his own expression ‘“une
espéce de jambe de bois, dont la nature seule avoit
faet le pais.

[Seite 79]

‘“In corpore humano,”’ he says, ‘“nulla
pars faciem suam rarius mutat quam cerebrum.

[Seite 80]

Betula alnus quercifolia vid. Gleditch
hinterlassene Abhandl. das practishe Fortwesen be-

Blumenbach, Johann Friedrich. Date:
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