CHAPTER XIII.

REFLECTIONS ON THE PRECEDING EXPERIMENTS.

By the experiments we have just described, I was assured that females,

as well as males, have a seminal liquor which contains moving

substances; that these substances were not real animals, but only

living organic particles; and that those particles exist, not only in

the seminal liquors of the two sexes, but even in the flesh of animals,

and in the germs of vegetables. To discover whether all the parts of

animals, and all the germs of vegetables, contained living organic

particles, I caused infusions of the flesh of different animals to

be made, and of more than twenty kinds of seeds of different plants;

and after they had infused four or five days, in phials closely stopt

up, I had the satisfaction to see moving organic parts in them all;

some appeared sooner, and others later; some preserved their motion

for months together, while others were soon deprived of it; some

directly produced large moving globules, that had the appearance of

real animals, which changed their figures, separated, and became

successively smaller: others produced only small globules, whose

motions were very brisk; others produced filaments which lengthened

and seemed to vegetate, swelled, and afterwards thousands of moving

globules issued therefrom; but it is useless to detail my observations

on the infusion of plants, since Mr. Needham has published so excellent

a treatise on the subject. I read the preceding treatise to that able

naturalist, and often reasoned with him on the subject, particularly

on the probability that the germs of vegetables contained similar

moving bodies to those in the seed of male and female animals. He

thought those views sufficiently founded to deserve to be pursued; and

therefore began to make experiments on all parts of vegetables; and I

must own that the ideas I gave him on this subject have reaped greater

profit under his hands than they would have done from me. I could quote

many examples, but shall confine myself to one, because I indicated the

circumstance I am going to relate.

To determine whether the moving substances seen in the infusions

of flesh were true animals, or only, as I supposed, moving organic

particles, Mr. Needham imagined that he had only to examine some

roasted meat, because if they were animals the fire must destroy

them; and if not animals, they might still be found there as well as

when the meat was raw; having therefore taken the jelly of veal, and

other roasted meat, he infused them for several days in water, closely

corked up in phials, and upon examination he found in every one of

them a great quantity of moving substances. He shewed me some of these

infusions, and among the rest that of the jelly of veal, in which there

were moving substances, perfectly like those in the seminal liquor of

a man, a dog, and a bitch, when they have no threads, or tails; and

although we perceived them to change their figures, their motions so

perfectly resembled those of an animal which swims, that whoever saw

them, without being acquainted with what has been already mentioned,

might certainly have taken them for real animals. I shall only add,

that Mr. Needham assured himself, by a multiplicity of experiments,

that all parts of vegetables contain moving organic particles, which

confirms what I have said, and extends my theory on the composition of

organized beings, and their reproduction.

All animals, both male and female, and all vegetables whatsoever, it is

therefore evident are composed of living organic parts. These organic

parts are in the greatest abundance in the seminal liquor of animals,

and in seeds of vegetables. It is from the union of these organic

parts returned from all parts of the animal or vegetable body, that

reproduction is performed, and is always like the animal or vegetable

in which it operates; because the union of these organic parts cannot

be made but by the means of an internal mould, in which the form of

an animal or vegetable is produced. It is in this also the essence of

the unity and continuity of the species consists, and will so continue

while the great Creator permits their existence.

But before I draw general conclusions from the system I am

establishing, I must endeavour to remove some objections which might be

made, and mention some other circumstances which will serve to place

this matter in a better light.

It will be asked, why I deny those moving substances in the seminal

liquors to be animals, since they have constantly been regarded as

such by Leeuwenhoek, and every other naturalist, who has examined

them? I may also be told, that living organic particles are not

perfectly intelligible, if they are to be looked upon as animalculæ;

and to suppose an animal is composed of a number of small animals,

is nearly the same as saying that an organized being is composed of

living organic particles. I shall therefore endeavour to answer these

objections in a satisfactory manner.

It is certain that almost all naturalists agree in looking on the

moving substances in seminal liquors as real animals; but it is no less

certain, from my own observations, and those of Mr. Needham, on the

seed of the calmar, that these moving substances are more simple and

less organized beings than animals.

The word _animal_, in the acceptation we commonly receive it,

represents a general idea formed of particular ideas drawn from

particular animals. All general ideas include many different ones,

which approach, or are more or less distant from each other, and

consequently no general idea can either be exact or precise. The

general idea which we form of an animal may be taken principally from

the particular idea of a dog, a horse, and other beasts, which appear

to us to act and move according to the impulse of their will, and which

are besides composed of flesh and blood, seek after their food, have

sexes, and the faculty of reproduction. The general idea, therefore,

expressed by the word _animal_, must comprehend a number of particular

ideas, not one of which constitutes the essence of the general idea,

for there are animals which appear to have no reason, will, progressive

motion, flesh nor blood, and which only appear to be a congealed

substance: there are some which cannot seek their food, but only

receive it from the element they live in: there are some which have no

sensation, not even that of feeling, at least in any sensible degree:

there are some have no sexes, or are both in one; there only belongs,

therefore, to the animal a general idea of what is common also to the

vegetable, that is, the faculty of reproduction.

The general idea then is formed from the whole taken together, which

whole being composed of different parts, there is consequently between

these parts degrees and links. An insect, in this sense, is something

less of an animal than a dog; an oyster still less than an insect; a

sea-nettle, or a fresh-water polypus, still less than an oyster; and

as nature acts by insensible links, we may find beings which are still

less animated than a sea-nettle, or a polypus. Our general ideas are

only artificial methods to collect a quantity of objects in the same

point of view; and they have, like the artificial methods we shall

speak of, the defect of never being able to comprehend the whole.

They are likewise opposite to the walk of nature, which is uniform,

insensible, and always particular, insomuch that by our endeavouring to

comprehend too great a number of particular ideas in one single word,

we have no longer a clear idea of what that word conveys; because, the

word being received, we imagine that it is a line drawn between the

productions of nature; that all above this line is _animal_, and all

below it _vegetable_; another word, as general as the first, and which

is used as a line of separation between organized bodies and inanimate

matter. But as we have already said, these lines of separation do

not exist in nature; there are beings which are neither animals,

vegetables, nor minerals, and which we in vain might attempt to arrange

with either. For example, when Mr. Trembly first observed the polypus,

he employed a considerable time before he could determine whether it

was an animal or a plant; and possibly from this reason that it is

perhaps neither one nor the other, and all that can be said is, that it

approaches nearest to an animal; and as we suppose every living thing

must be either an animal or a plant, we do not credit the existence of

an organized being, that cannot be referred to one of those general

names; whereas there must, and in fact are, a great number of organized

beings which are neither the one nor the other. The moving substances

perceived in seminal liquors, in infusions of the flesh of animals, in

seed, and other parts of plants, are all of this kind. We cannot call

these animals, nor can we say they are vegetables, and certainly we can

still less assert they are minerals.

We can therefore affirm, without fear of advancing too much, that the

grand division of nature's productions into _Animals_, _Vegetables_,

and _Minerals_, do not contain every material being; since there are

some that exist which cannot be classed in this division. We have

already observed, that nature passes by insensible links from the

animal to the vegetable, but from the vegetable to the mineral the

passage is quick, and the distance considerable; from whence the law of

nature's passing by imperceptible degrees appears untrue. This made me

suppose that by examining nature closely we shall discover intermediate

organized beings, which without having the power of reproduction, like

animals and vegetables, would nevertheless have a kind of life and

motion; other beings which, without being either vegetables or animals,

might possibly enter into the composition of both, and likewise other

beings which would be only the assemblage of the organic molecules I

have spoken of in the preceding chapters.

In the first class of these kind of beings eggs must be placed; those

of hens, and other birds, are fastened to a common pedicle, and draw

their nourishment and growth from the body of the animal, but when

fastened to the ovary, they are not then real eggs, but only yellow

globules which separate from the ovary as soon as they have attained a

certain growth. Their internal organization is such that they derive

nourishment from the lymph, the matrix of the hen, and by which they

form the white membranes, and at last the shell. The egg therefore has

a kind of life and organization, a growth, expansion, and a form which

it assumes by its own powers. It does not live like an animal, nor

vegetate like a plant, nor is possessed of the power of reproduction;

nevertheless it grows, acts externally, and is organized. Must we not

then look upon it as a being of a separate class, and which ought not

to be ranked either with animal or mineral? for if it is pretended that

the egg is only an animal production, destined for the nutriment of

the chicken, and should be looked upon as a part of the hen; I answer,

that the eggs, whether impregnated or not, will be always organized

after the same mode: that impregnation only changes an almost invisible

part; and that it attains its perfection and growth, as well externally

as internally, whether it contains the chicken or not, and that

consequently it ought to be considered as a separate being.

What I have said will appear more clear, if we consider the formation

and growth of the eggs of fish; when the female deposits them in the

water they are only the outlines of eggs, which being separated from

the body of the animal, attract and appropriate to themselves the

particles which agree the best for their nourishment, and grow thus

by intussusception. In the same manner as the hen's egg acquires the

white and membranes in the matrix, wherein it floats, so the eggs of

fish acquire their membranes and white in the water; and whether the

male impregnates them, by emitting on these the liquor of its roe, or

whether they remain unimpregnated, they do not the less attain their

entire perfection. It appears to me, therefore, that the eggs should

be considered as organized bodies, which being neither animals nor

vegetables, are a genus apart.

A second class of beings, of the same kind, are the organized bodies

found in the semen of all animals, and which, like those in the milt of

a calmar, are rather natural machines than animals. These are properly

the first assemblages which result from the organic molecules we have

so much spoken of, and they are, perhaps, the parts which constitute

the organized bodies of animals. They are found in the semen of all

animals, because the semen is only the residue of the organic molecules

that the animal takes in with its aliment, and which, as we have

already observed, are those parts most analogous to the animal itself,

and most organic; it is those particles which compose the matter of the

semen, and consequently we must not be astonished to find organized

bodies therein.

To be perfectly convinced that these organized bodies are not real

animals, we need only reflect on the preceding experiments. The moving

bodies in the seminal liquor have been taken for animals, because they

have a progressive motion, and are thought to have a tail; but if we

consider, on one hand, the nature of this progressive motion, which

finishes in a very short time without ever renewing its motion; and

on the other, the nature of these tails, which are only threads which

the moving bodies draw after them, we shall begin to hesitate; for an

animal goes sometimes slow, sometimes fast, and sometimes remains in

a state of rest; these moving bodies, on the contrary, always continue

the same motion, and I have never seen them stop and renew their

movement again. I ask, whether this kind of continued motion, without

any rest, is common to animals, and if that ought not to make us doubt

these moving bodies being real animals? An animal of any kind must also

have a constant form and distinct limbs; but these moving bodies vary,

and change their forms every moment, have no distinct limbs, and their

tails appear as a part which does not belong to the individual. Can

we then imagine these bodies to be real animals? In seminal liquors

filaments are seen which lengthen and appear to vegetate; after which

they swell and produce moving bodies. These filaments may be kinds

of vegetables, but the moving bodies which spring from them cannot

be animals, for a vegetable has never yet been seen to produce an

animal. These moving bodies are found in all vegetable and animal

substances; they are not produced by the modes of generation, they

have no uniformity of species, and therefore can neither be animals

nor vegetables. They are to be met with in the flesh of animals, and

in the substance of vegetables, but are most numerous in their seeds;

is it not therefore natural to regard them as living organic particles

which compose the animal or vegetable; as particles which having motion

and a kind of life, ought, by their union, to produce moving and living

beings, and so form animals and vegetables?

But in order to leave this matter as little in doubt as possible,

let us examine other substances. Can it be said, the active machines

which Mr. Needham perceived in the milt of the calmar were animals?

Can it be thought that eggs, which are active machines of another

kind, are also animals? If we turn our eyes to the representation of

almost all the moving bodies Leeuwenhoek saw in different matters,

shall we not be convinced, even at the first inspection, that those

bodies are not animals, since not one of them has any limbs, but

are all either globular or oval? If we afterwards examine what this

celebrated naturalist says, when he describes the motion of these

pretended animals, we can no longer doubt of his being in an error

when he considered them as such; and we shall be still more and more

confirmed that they are only moving organic particles by the following

examples: Leeuwenhoek gives[W] the figure of the moving bodies which he

observed in the liquor of a male frog. This figure only represents a

slender body, long, and pointed at one of its extremities; and of this

he says, "Uno tempore caput (thus he calls the thickest extremity of

this moving body) crassius mihi apparebat alio; plerumque agnoscebam

animalculum haud ulterius quam a capite ad medium corpus, ob caudæ

tenuitatem, & cum idem animalculum paulo vehementius moveretur (quod

tamen tarde fiebat) quasi volumine quodam circa caput ferebatur. Corpus

fere carebat motu; cauda tamen in tres quatuorve flexus volvebatur."

This then is the change of form which I mentioned to have seen, the

mucilage from which the moving bodies use all their efforts to be

disengaged, the slowness of their motion before they are disengaged;

and the animal, according to Leeuwenhoek, one part of which is

in motion, and the other dead: for he afterwards says, "Movebant

posteriorem solum partem, quæ ultima, morti vicinia esse judicabam."

All this does not agree with an animal, but with what I have spoken

of; excepting that I never saw the tail move but by the agitation

of the body. He afterwards says, speaking of the seminal liquor of a

cod, "Non est putandum omnia animalcula in semine aselli contenta uno

eodemque tempore vivere, sed illa potius tantum vivere quæ exitui seu

partui viciniora sunt, quæ & copiosiori humido innatant præ reliquis

vita carentibus, adhuc in crassa materia, quam humor eorum efficit,

jacentibus."

[W] Vol. I. p. 51.

If these are animals, why have they not all life? why are they in the

most fluid part of the liquor alive, while those in the thickest are

not so? Leeawenhoek did not perceive that the thick matter, the origin

of which he attributes to the humour of the animalculæ, is nothing but

a mucilaginous matter which produces them. By diluting this mucilage

with water, he would have given life to the whole of them. Even this

mucilage is oftentimes only a mass of those bodies which are set

in motion on being separated; and consequently this thick matter,

instead of being a humour, produced by the animalcules, is only the

substance of the animals themselves, or rather, as we have already

observed, the matter from which they originate. Speaking of the seed

of a cock, Leeuwenhoek says, in his letter to Grew, "Contemplando

materiam (seminalem) animadverti ibidem tantam abundantiam viventium

animalium, ut ea stuperem; forma seu externa figura sua nostrates

anguillas fluviatiles referebant, vehementissima agitatione movebantur;

quibus tamen substrati videbantur multi & admodum exiles globuli, item

multæ plan-ovales figuræ, quibus etiam vita posset attribui, & quidem

propter earundem commotiones; sed existimabam omnes hasce commotiones

& agitationes pro venire ab animalcules, sicque etiam res se habebat;

attamen ego non opinione solum, sed etiam ad veritatem mihi persuadeo

has particulas planam & ovalem figuram habentes, esse quædam animalcula

inter se ordine suo disposita & mixta vitaque adhuc carentia." Here

we see in the same seminal liquor animalcules of different forms;

and I am convinced, by my own experiments, that if Leeuwenhoek had

closely observed these oval substances, he would have discovered that

they moved by their own powers, and that consequently they were as

much alive as the rest. This change perfectly coincides with what

I have said, that they are organic particles which take different

forms, and not constant species of animals; for in the present case,

if the bodies, which have the figure of an eel, are true spermatic

animalcules, each, destined to become a cock, which supposes a very

perfect organization, and a very constant form, what will those be

which have an oval figure, and what end do they answer? He says indeed

afterwards, that these ovals maybe conceived to be the same animals,

by supposing their bodies to be twisted in a spiral form; but then

how shall we conceive that an animal, whose body is constrained, can

move without being extended? I maintain, therefore, that these oval

substances are no other than the organic particles separated from their

threads, and that the eels were the separated parts which dragged those

threads after them, as I have many times perceived in other seminal

liquors.

Leeuwenhoek, who imagined all these moving bodies were animals, and

established a system thereon; who also pretended, that spermatic

animals must become men and animals, now suspected they were only

natural machines, or organic particles in motion; for he does not doubt

these spermatic animals contained the great animal in miniature, he

says, "Progeneratio animalis ex animalculo in seminibus masculinis

omni exceptione major est; nam etiamsi in animalculo ex semine masculo

unde ortum est, figuram animalis conspicere nequeamus, attamen satis

superque certi esse possumus figuram animalis ex qua animal ortum est,

in animalculo quod in semine masculo reperitur, conclusam jacere sive

esse; & quanquam mihi sæpius conspectis animalculis in semine masculo

animalis, imaginatus fuerim me posse dicere, en ibi caput, en ibi

humeros, en ibi femora; attamen eum ne minima quidem certitudine de iis

judicium ferre potuerim, hujusque certi quid statuere supersedeo, donec

tale animal, cujus semina mascula tam magna erunt, ut in iis figuram

creaturæ ex qua provenit, agnoscere queam, invenire secunda nobis

concedat fortuna." This fortunate chance, which Leeuwenhoek desires,

presented itself to Mr. Needham. Every part of the spermatic animals of

the calmar are easy to be seen without a microscope; but they are not

young calmars, as Leeuwenhoek thinks, nor even animated, although they

are in motion, but only machines which must be regarded as the first

produce of the union of organic particles.

Although Leeuwenhoek had not such an opportunity of undeceiving

himself, he nevertheless had another phenomena which ought to have had

that effect; for example, he had remarked that the spermatic animals of

a dog often change their figures, especially when the liquor was on the

point of evaporating; that these pretended animals had a hole in the

head when they were dead, and that this hole did not appear when they

were alive; he had seen that the part which he looked upon as the head

was full and plump when it was alive, and flaccid and flat when dead.

All this ought to have led him to doubt whether these moving bodies

were real animals; and consider it as agreeing better with a machine,

which empties itself like that of the calmar, than with a moving animal.

I have said that these moving bodies, these organic particles, do

not move like animals, nor have an interval of rest. Leeuwenhoek has

observed the same: "Quotiescunque, says he, animalcula in semine

masculo animalium fucrim contemplatus, attamen illa se unquam ad

quietem contulisse, me nunquam vidisse, mihi dicendum est, si modo

sat fluidæ superesset materiæ in qua sese commode movere poterant;

et eadem in continuo manent motu, & tempore quo ipsis moriendum

appropinquante, motus magis magisque deficit, usquedum nullus prorsus

motus in illis agnoscendus sit." It appears difficult to conceive that

animals can exist, from the moment of their birth till that of their

death, in a continual rapid motion without the least interval of rest;

and I cannot possibly imagine how these animals in the semen of a dog,

which Leeuwenhoek saw the seventh day in as rapid motion as they were

when they were first taken from the body of the animal, preserved

a motion during that time so exceedingly swift, that no animal has

sufficient power to move in for an hour; especially if we consider the

resistance which proceeds from the density and the tenacity of the

liquor. This kind of continued motion, on the contrary, agrees with

the organic particles, which, like artificial machines, produce their

effects in a continual operation, and which stop when that effect is

over.

Among the great number of Leeuwenhoek's experiments, he, without

doubt, often perceived spermatic animals without tails; and he

endeavours to explain this phenomena by a supposition; for example,

he says, speaking of the semen of a cod, "Ubi vero ad lactum accederem

observationem, in iis partibus quas animalcula esse censebam neque

vitam neque caudam dignoscere potui; cujus rei rationem esse

existimabam, quod quamdiu animalcula natando loca sua perfecte mutare

non possunt tam diu etiam cauda concinne circa corpus maneat ordinata,

quodque ideo singula animalcula rotundum repræsentent corpusculorum."

It would have been better to have said, as it in fact is, that the

spermatic animals of these fish have tails at certain times and none

at others, than to suppose their tails twisted so exactly round their

bodies as to give them the shape of a globule. But this must not lead

us to think that Leeuwenhoek only attended to the moving bodies which

he saw with tails, but rather that he did not describe the others,

because, although they were in motion, he did not regard them as

animals; and this is the cause that all the spermatic animals he has

depicted resemble each other, and drawn with tails, since he only

took them for real animals in that state; and that when he saw them

under other forms, he thought them imperfect, or rather that they

were dead. On the whole it appears, by my experiments, that far from

displaying their tails the more as they are in a more perfect condition

of swimming, as Leeuwenhoek says, they, on the contrary, lose their

tails in a gradual manner, till at last these tails, which are no more

than foreign bodies of the animalcules, and which they drag after them,

entirely disappear.

In another part Leeuwenhoek, speaking of the spermatic animals of man,

says, "Aliquando etiam animadverti inter animalcula particulas quasdam

minores & subrotundas; cum vero se ea aliquoties eo modo oculis meis

exhibuerint, ut mihi imaginarer eas exiguis instructas esse caudis,

cogitare coepi annon hæ forte particulæ forent animalcula recens

nata; certum enim mihi est ea etiam animalcula per generationem

provenire, vel ex mole minuscula ad adultam procedere quantitatem: &

quis sit annoa ea animalcula, ubi moriuntur, aliorum animalculorum

nutritioni atque augmini inserviant?" By this passage it appears that

Leeuwenhoek had seen animals without tails in the seminal liquor of

a man, and that he is obliged to suppose them to be just born, and

not adult; but I have observed quite the contrary; for the moving

bodies are never larger than when they separate from the filaments,

and begin to move. When they are entirely disengaged from the mucilage

they become smaller, and continue decreasing as long as they remain

in motion. With respect to the generation of these animals, which

Leeuwenhoek speaks of as certain, I am persuaded no sign of generation

has ever been discovered; all he says is advanced on mere suppositions,

which it is easy to prove by his own observations; for example, he

says that the milt of certain fish, as the cod, fills by degrees with

seminal liquor, which after the fish has emitted, the milt dries up,

leaving only a membrane destitute of any liquor. "Eo tempore, says

he, quo ascellus major lactes suos emisit, rugæ illæ, seu tortiles

lactium partes, usque adeo contrahuntur, ut nihil præter pelliculas

seu membranæ esse videantur." How then does he understand that this

dry membrane, in which there is no longer either seminal liquor or

animalcules, can reproduce animals of the same kind the succeeding

year? if there was a regular generation in these animals, there could

not be this interruption, which in most fishes lasts for a whole year.

To draw himself out of this difficulty, he says, "Necessario statuendum

erit, ut ascellus major semen suum emiserit, in lactibus etiamnum

multum materiæ seminalis gignendis animalculis aptæ remansisse, ex qua

materia plura oportet provenire animalcula seminalia quam anno proxime

elapso emissa fuerant." This supposition, that there remains something

in the seminal liquor in the milts to produce spermatic animals for

the succeeding year, is absolutely contrary to observations, for the

milt is in this interval only a thin and absolutely dry membrane. But

what reply can be made to a still further opposition to this point,

there being fish like the calmar, the seminal liquor of which is not

only renewed every year, but even the reservoir which contains it? Can

it be said, that there remains a seminal matter in the milt for the

production of the animals for the succeeding year, when even the milt

does not remain? it is therefore very certain that these pretended

spermatic animals are not multiplied, like other animals, by the mode

of generation; which alone is sufficient to make us presume, that those

particles which move in the seminal liquors are not real animals. Thus

Leeuwenhoek, who in the passage above quoted says, it is certain that

spermatic animals multiply and propagate by generation, nevertheless

owns, in another part, that the manner in which these animals are

produced is very obscure, and that he leaves to others the task of

clearing up this matter. "Persuadebam mihi," says he, speaking of the

spermatic animals of the dormouse, "hæcce animalcula ovibus prognasci,

quia diversa in orbem jacentia & in semet convoluta videbam; sed unde,

quæso, primam illorum originem derivabimus? in animo nostro concipiemus

horum animalculorum semen jam procreatum esse in ipsa generatione,

hocque semen tam diu in testiculis hominum hærere, usquedum ad annum

ætatis decimum-quartum vel decimum-quintum aut sextum pervenerint,

eademque animalcula tum demum vita donari vel in justam staturam

excrevisse, illoque temporis articulo generandi maturitatem adesse!

sed hæc lampada aliis trado." I do not think it necessary to make any

remarks on what Leeuwenhoek says on this subject: he saw spermatic

animals without tails, and round, in the seed of a dormouse; "in semet

convoluta," says he, because he supposes that they should have tails,

and instead of being certain, as he before had been, that the animals

propagate by generation, he here seems convinced of the contrary. But

when he had observed the generation of pucerons, and was assured[X]

that they engendered without copulation, he caught the idea to explain

the generation of spermatic animals. "Quemadmodum, says he, animalcula

hæc quæ pediculorum antea nomine designavimus (the pucerons) dum adhuc

in utero materno latent, jam prædita sunt materia seminali ex qua

ejusdem generis proditura sunt animalcula, pari ratione cogitare licet

animalculæ in seminibus masculinis ex animalium testiculis non migrate

seu ejici quin post se relinquant minuta animalcula aut saltem materiam

seminalem ex qua iterum alia ejusdem generis animalcula proventura

sunt idque absque coitu; eadem ratione qua supradicta animalcula

generari observavimus." This supposition gives no more satisfaction

than the preceding: for we do not understand by this comparison of

the generation of these animalcules with that of a puceron, why they

are not found in the seminal liquor of a man, before he has attained

the age of fourteen or fifteen years; nor do we know from whence

they proceed, nor how they are renewed every year in fish, &c. and

it appears, that whatever efforts Leeuwenhoek made to establish the

generation of spermatic animals on some probability, it still remained

an entire obscurity, and would, perhaps, perpetually have remained so,

if the preceding experiments had not evinced that they are not animals,

but moving organic particles contained in the nutriment the animal

receives, and which are found in great numbers in the seminal liquor,

which is the most pure, and in the most organic extracts drawn from

this nutriment.

[X] See vol. II. page 499, and vol. III. page 271.

Leeuwenhoek acknowledges that he had not always found animalcules

in the seminal liquor of males; in that of the cock, for example,

which he had often examined, he saw spermatic animals in the form

of eels but once, and some years after he could not discover any

under that form, but observed some with large heads and tails, which

his designer could not perceive. He says also, that one season he

could not find living animals in the seminal liquor of the cod. All

these disappointments proceeded from his desire of finding tails to

these animals; and although he perceived little bodies in motion, he

did not consider them as animals, because they were without tails,

notwithstanding it is under that form they are generally seen, either

in seminal liquors, or infusions of animal or vegetable substances. He

says, in the same place, that he was never able to make his designer

perceive the spermatic animalcules of a cod, which he had so often

seen himself.--"Non solum, says he, ob eximiam eorum exilitatem, sed

etiam quod eorum corpora adeo essent fragilia, ut corpuscula passim

dirumperentur; unde factum fuit ut nonnisi rare, nec sine attentissima

observatione, animadverterem particulas planas atque ovorum in morem

longas, in quibus ex parte caudas dignoscere licebat; particulas

has oviformes existimavi animalcula esse dirupta, quod particulæ hæ

diruptæ quadruplo fere viderentur majores corporibus animalculorum

vivorum." When an animal of any kind ceases to live, it does not then

suddenly alter its form, and from being long, like a thread, becomes

round like a ball; neither does it become four times larger after

its death than it was before. Nothing that Leeuwenhoek says here

agrees with the nature of animals; but, on the contrary, the whole

corresponds with a kind of machine, which, like those of a calmar,

empty themselves after having performed their functions. But let us

pursue this observation; he says, he has seen the spermatic animals

of the cod in different forms, "multa apparebant animalcula sphæram

pellucidam representantia;" he has also seen them of different sizes,

"hæc animalcula minori videbantur mole, quam ubi eadem antehac in tubo

vitreo rotundo examinaveram."

There needs nothing more to shew that there are no constant and

uniform species of these animalcules; and that consequently they are

not animals, but only organic particles in motion, which, by their

different combinations, take different forms and sizes. These organic

moving particles are found in great quantities in the extract and

residue of our nutriment. The matter which adheres to the teeth, and

which in healthy people has the same smell as the seminal liquor, is

only a residue of the food, and a great number of these pretended

animals are also found there, some of which have tails, and resemble

those in the seminal liquor. Mr. Baker had four different kinds of

them engraved, and which were all of a cylindrical or oval make, or

globules with and without tails. I am persuaded, after having strictly

examined them, that not any of them are real animals, but are like

those in the seed, only living organical parts of the nutriment which

present themselves under different forms, Leeuwenhoek, who did not

know how to account for these pretended animals in the matter which

adhered to the teeth, supposed them to proceed from certain food they

were previously in, as cheese, &c. but we find them among the teeth of

those who do not eat cheese, as well as in those that do; besides, they

have not the least resemblance to mites, nor the other animalcules seen

in rotten cheese. In another place he says, these animals of the teeth

may proceed from the cistern water that is drank, because he observed

animals like them in dew and rain water, especially in that which

stagnates upon lead and tiles; but with which we can prove there is not

the least resemblance.

Most seminal liquors dilute of themselves, and liquefy when exposed to

the air or a certain degree of cold; but they thicken when a moderate

degree of heat is communicated to them. I have exposed some of these

liquors to a very intense cold, as water on the point of freezing, but

it did no injury to these supposed animals; they continued to move with

the same swiftness, and as long as those which had not been so exposed,

but those which had suffered but a little warmth soon ceased to move,

because the liquor thickened. If the moving bodies were animals,

they were of a complexion and temperament quite different from all

others, to whom a gentle and moderate heat strengthens their powers and

motions, which the cold stops and destroys.

Notwithstanding it may be thought I have dwelt too long upon this

subject, I cannot conclude it without making one remark, from which

some useful conclusions may be drawn. These pretended spermatic

animals, which are only living organic particles of the nutriment, not

only exist in the seminal liquors of the two sexes, and in the residue

of the nutriment which adheres to the teeth, but also in the chyle

and excrements. Leeuwenhoek having met with them in the excrements

of frogs, and other animals, which he dissected, was at first very

much surprised, and notable to conceive from whence these animals

proceeded, so entirely like those he had observed in the seminal

liquors, accuses himself of having, in dissecting the animal, opened

the seminal vessels, and that the seed had by that means been mixed

with the excrements. But having afterwards found them in the excrements

of other animals, and even in his own, he no longer knew to what to

attribute them. Leeuwenhoek, it is worthy remark, never met with

them in his own excrements, but when they were liquid. Every time he

was disordered and the stomach did not perform its functions, and was

relaxed, he discovered these animalcules; but when the concoction of

the food was well performed, and the excrement was hard, there was not

a single one, although it was diluted with water. This seems perfectly

to agree with all we have before advanced: for when the stomach and

intestines perform their functions, the excrements are only the grosser

parts of the nutriment; and all that is really nutritive and organic

passes into the vessels which serve to nourish the animal; whereas if

the stomach and intestines are not in a condition to comminute the

food, then it passes with the inanimate parts, and we find the living

organic molecules in the excrements; from whence it may be concluded,

that those which are often lax must have less seminal liquor, and be

less proper for generation, than those of a different habit of body.

In all I have said, I constantly supposed the female furnished a

seminal liquor, which was as necessary to generation as that of the

male. I have endeavoured to establish in Chap. I. that every organized

body must contain living organic particles, and I have endeavoured to

prove Chap. II. and III. that nutrition and reproduction operates by

the same cause; that nutrition is made by the intimate penetration

of these organic particles through each part of the body, and that

reproduction operates by the superfluity of these same organic

particles collected together from all parts of the body and deposited

in proper reservoirs. I have explained in Chap. IV. how this theory

must be understood in the generation of man and animals which have

sexes. Females then being organized bodies like males, they must also

have some reservoirs for the superfluity of organic particles returned

from every part of their bodies. This superfluity cannot come there

through any other form than that of a liquor, since it is an extract of

all parts of the body; and this liquor is that to which I have given

the name of the female semen.

This liquor is not, as Aristotle pretends, an infecund matter of

itself, which enters neither as matter nor form into the business

of generation, but as essentially prolific as that of the male,

containing characteristic parts of the feminine sex, which the female

alone can produce, the same as the male contains particles necessary

to form the masculine organs; and each of them contains every other

organic particle that can be looked on as common to both sexes; which

causes that, by their mixture, the daughter may resemble her father,

and the son his mother. This semen Hippocrates says, is composed of

two liquors; the one strong, for the production of males; and the

other weak, for the production of females. But this supposition is

too extended; I do not see how it is to be conceived that a liquor,

which is the extract of every part of the female body, should contain

particles for the formation of the male organs.

This liquor must enter by some way into the matrix of animals which

bear and nourish their foetus within the body, and in others, as

oviparous animals, it must be absorbed by the eggs, which may be looked

upon as portable matrixes. Each of these matrixes contains a small

drop of this prolific liquor of the female, in the part that is called

the _cicatrice_. When there has been no communication with the male,

this prolific drop collects under the form of a small mole, or mass,

as Malpighius observes; but when impregnated by that of the male; it

produces a foetus which receives its nutriment from the juices of the

egg.

Eggs, instead of being parts generally found in every female, are

therefore only instruments made use of by Nature to serve as the matrix

in females which are deprived of that organ. Instead also of being

active and essential to the first fecundation, they only serve as

passive and accidental parts for the nutrition of the foetus already

formed by the mixture of the liquor of the two sexes in a particular

part of this matrix. Instead also of being existing bodies, inclosed,

_ad infinitum_, one within the other, eggs, on the contrary, are bodies

formed from the superfluity of a more gross and less organic part of

the food, than that which produces the seminal and prolific liquor; and

are in oviparous females something equivalent, not only to the matrix,

but even to the menstrua in the viviparous.

We should be perfectly convinced, that eggs are only destined by Nature

to serve as a matrix in animals who have not that viscera, by those

females producing eggs independant of the male. In the same manner as

the matrix exists in viviparous animals, as a part appertaining to the

female sex, hens, which have no matrix, have eggs in their room, which

are successively produced of themselves, and necessarily exist in the

female independently of any communication with the male. To pretend

that the foetus is pre-existing in the eggs, and that these eggs are

contained, _ad infinitum_, within each other, is nearly the same as

to pretend that the foetus, is pre-existing in the matrix, and that

the matrix of the first female inclosed all that ever were or will be

produced.

Anatomists have taken the word _egg_ in several acceptations and

meanings. When Harvey took for his motto, _Omnia ex ovo_, he understood

by the word egg, as applied to viviparous animals, the membrane which

includes the foetus and all its appendages: he thought, he perceived

this egg, or membrane, form immediately after the copulation of the

male and the female. But this egg does not proceed from the ovium

of the female; and he has even maintained, that he did not remark

the least alteration in this testicle, &c. We perceive there is here

nothing like what is commonly understood by the word egg unless the

figure of the bag may be supposed to have some resemblance thereto.

Harvey, who dissected so many viviparous females, did not, he says,

ever perceive any alteration in the ovaria; he looked on them even

as small glands, perfectly useless to general ion,[Y] although they

undergo very remarkable changes and alterations in them, since we

may perceive in cows the glandular bodies grow from the size of a

millet seed to that of a cherry. This great anatomist was led into

this error by the smallness of the glandular bodies in the species

of deer, to which he principally paid his attention. C. Peyerus, who

also made many experiments on them, says, "Exigui quidem sunt damarum

testiculi, sed post coitum foecundum, in alterutro eorum, papilla,

sive tuberculum fibrosum, semper succrescit; scrofis autem prægnantibus

tanta accidit testiculorum mutatio, ut mediocrem quoque attentionem

fugere nequeat."[Z] This author imagines, with some reason, that the

minuteness of the testicles of does, is the cause of Harvey's not

having remarked the alterations; but he is wrong in advancing that the

alterations he had remarked, and which had escaped Harvey's notice, did

not happen till after impregnation.

[Y] See Harvey Exercit. 64 and 65.

[Z] Vide Conradi Peyeri Merycologia.

It appears that Harvey was deceived in many other essential points;

he asserts, that the seed of the male does not enter into the matrix

of the female, and even that it cannot; yet Verheyen found a great

quantity of the male seed in the matrix of a cow, which he dissected

six hours after copulation.[AA] The celebrated Ruysch asserts, that

having dissected a woman who had been caught in the act of adultery,

and was assassinated, he found, not only in the cavity of the matrix,

but also in the trunks, a quantity of the seminal liquor of the

male,[AB] Valisnieri affirms, that Fallopius and other anatomists

had also discovered male seed in the matrix of many women. After the

positive testimony of these great anatomists, there can remain no doubt

but Harvey was deceived in this important point; especially when to

these are added that of Leeuwenhoek, who found the male seed in the

matrix of a great number of females of different species.

[AA] See Verheyen Sup. Anat. Tra. v. cap. iii.

[AB] See Ruysch, Thes. Anat. p. 90, tab. VI, fig. I.

Harvey makes another error in speaking of an abortion in the second

month, where the mass was as large as a pigeon's egg, but without any

foetus regularly formed; whereas, it is maintained by Ruysch, and

many other anatomists, that the foetus is perceptible, even to the

naked eye, in the first month. The History of the Academy mentions

a foetus, that was completely formed in twenty-one days after

impregnation. If to these authorities we add that of Malpighius,

who perceived the chicken in the cicatrice, immediately after the

egg was laid by the hen, we cannot doubt, but that the foetus is

formed immediately after copulation; consequently, we must not pay any

credit to what Harvey says on the parts increasing one after the other

by juxta-position, since they are all existent from the first, and

gradually expand until the whole is complete.

De Graaf took the acceptation of the word egg in a quite different

light to Harvey: he insists that the testicles of women were true

ovaries, and contain eggs like those of oviparous, animals, only that

they are much smaller, do not quit the body, and are never detached

till after impregnation, when they descend from the ovary into the

horns of the matrix. The experiments of De Graaf have contributed most

to establish the existence of these pretended eggs, which yet is not at

all founded; for this famous anatomist is deceived, first, by mistaking

the vesicles of the ovarium for eggs, whereas they are inseparable from

it, form parts of its substance, and are filled with a kind of lymph.

Secondly, he is also deceived when he considers the glandular bodies

to be the covering of those eggs, or vesicles; for it is certain,

by Malpighius's, Valisnieri's, and my own observations, that the

glandular bodies neither surround nor contain one of those vesicles.

Thirdly, he is deceived still more when he supposes the glandular body

is never formed till after fecundation; as they are invariably found in

every female who has attained the age of puberty. Fourthly, he is no

less deceived when he believes that the globules which he saw in the

matrix, and which contained the foetuses, ware the same vesicles,

or eggs, which had fallen from the ovariam, and which, he remarks,

were become ten times smaller than they were in the ovary. This remark

alone, one would imagine, Should have made him perceive his error.

Fifthly, he is wrong in saying that the glandular bodies are only the

coverings of the fecundated eggs, and that the number of coverings,

or empty follicles, always answer to the number of foetuses. This

assertion is entirely contrary to truth: for on the testicles of all

females we find a greater number of glandular bodies, or cicatrices,

than there are productions of foetuses, and they are also found in

those which have never brought forth. To this we may add, that neither

he, Verheyen, nor any other person, have ever seen these eggs, much

less these pretended coverings, on which they have, notwithstanding,

established their system.

Malpighius, who perceived the growth of the glandular bodies in the

female testicles, was deceived when he thought he had seen the egg in

their cavities, since they contain only liquor; nor indeed has anything

like an egg ever been discovered.

Valisnieri, who was not deceived in facts, has yet drawn false

conclusions in asserting that, although neither himself, nor any

anatomist in whom he could confide, ever found the egg in the cavity of

the glandular body, yet it must there exist.

Let us, therefore, examine what may be fairly called the real

discoveries of these naturalists. Graaf was the first who perceived

there were alterations in the female testicles; and he had reason

to affirm, they were parts essential and necessary to generation.

Malpighius demonstrated that these alterations were occasioned by the

glandular bodies which grew to perfect maturity, afterwards they become

flaccid, obliterated, and left only a slight cicatrice remaining.

Valisnieri has placed this discovery in a very clear light; he has

shewn that these glandular bodies are found in the testicles of every

female; that they are augmented considerably in the season of love,

that they increase at the expence of the lymphatic vesicles of the

testicles, and that at the time of their maturity they were hollow and

filled with liquor. This, then, is all that can be reduced to truth on

the subject of the pretended ovaries and eggs of viviparous animals.

What must we conclude therefrom? Two things appear very evident: the

one, that there does not exist any eggs in the female testicles; the

other, that there exists a liquor in the vesicles of the testicle, and

in the cavity of the glandular bodies. We have demonstrated by the

preceding experiments, that this last liquor is the true seed of the

female, since it contains, like that of the male, spermatic animals, or

rather organic moving particles.

We must, therefore, now be assured, that females have, as well as

males, a seminal liquor. After all that has been advanced, we cannot

doubt but the seminal liquor is the superfluity of the organic

nutriment, which is sent back from all parts of the body into the

testicles and seminal vesicles of the males, and into the testicles

and glandular bodies of females. This liquor, which issues by the

nipple of the glandular bodies, continually sprinkles the horns of the

matrix, and may easily procure admission either by the suction of the

membrane of these horns, or by the little opening which is at the upper

extremity, and thus enter into the matrix; but in the supposition of

these pretended eggs, which were ten or twenty times larger than the

opening of the horns of the matrix, we cannot comprehend how they could

enter therein.

The liquor emitted by females, when they are excited, and which,

according to de Graaf, issues from the neck of the matrix, and the

orifice of the urethra, may be a superabundant portion of the seminal

liquor which continually distills from the glandular bodies on the

trunks of the matrix. But, possibly, this liquor may be a secretion

of another kind, and perfectly useless in generation. To decide this

question observations with a microscope are requisite; but _all_

experiments are not permitted even to philosophers. I can only say,

that I am inclined to believe that the same spermatic animals would

be met with in this liquor as in that of the glandular bodies. I can

quote an Italian doctor on this subject, who made this observation with

attention, and which is thus related by Valisnieri: "Aggiugne il lodato

fig. Bono d'avergli anco veduti (animali spermatici) in questa linfa o

siero, diro cosi voluttuoso, che nel tempore dell'amorosa zuffa scappa

dalle femine libidinose, senza che si potesse sospettare che fossero

di que' del maschio, &c." If this circumstance is true, as I do not

doubt, it is certain, that this liquor is the same as that found in

the glandular bodies, and that, consequently, it is the true seminal

liquor: and although anatomists have not discovered the communication

between the vacuities of de Graaf and the testicles, that does not

prevent it being once in the matrix, from issuing out by the vacuities

about the exterior orifice of the urethra.

From hence we must conclude that the most abandoned women will be the

least fruitful, because they emit that liquor which ought to remain in

the matrix for the formation of the foetus. Thus we see why common

prostitutes seldom have children, and why women in hot countries, where

they have stronger desires than in the cold, are much less fertile; but

we shall have occasion to speak of this hereafter.

It is natural to think that the seminal liquor of the male or female

would not be fertile but when it contains moving bodies; nevertheless

that is still a question, and I should be led to think, as there are

different states of this liquor, that in which these organic particles

are seen in motion is not absolutely necessary for the purpose of

generation. The Italian physician, above quoted, never perceived

spermatic animals in his semen till he had attained a middle age,

although he was father of several children before, and continued to

have them afterwards.

These spermatic bodies, which move, may be looked upon as the first

assemblages of the organic molecules which proceed from every part of

the body; when a quantity of them collect they may be perceived with

the microscope; but if they collect only in small quantity the body

which they form will be too minute to be perceived, and in this case we

shall not be able to distinguish any in the seminal liquor. A very long

continuance of observations would be necessary to determine what can be

the cause of all the differences remarked in the states of this liquor.

I can assert, from having often tried it, that by infusing the seminal

liquors in water closely corked, at the end of three or four days

an infinite multitude of moving bodies will be found, although the

seminal liquors had no motion on being first taken from the body of

the animal. Flesh, blood, chyle, urine, nay all animal or vegetable

substances, contain organic particles, which move at the end of some

days in an infusion of water; they appear to act and move nearly in the

same manner, and though produced from different bodies are perfectly

similar, without any of them having a power peculiar to themselves.

If these bodies must absolutely be termed animals, it must be allowed

they are so imperfect that they ought to be looked upon as the outlines

of them, or rather as bodies simply composed of particles the most

essential to the existence of an animal; for natural machines, such as

those found in the roe of a calmar, although they put themselves in

action at certain times, are certainly not animals, although they are

organized, acting, and, as I may say, living beings.

If it is once allowed, that the productions of Nature follow in an

uniform order, and advance by imperceptible degrees and links, we shall

have no difficulty in conceiving there are organic bodies existing,

which belong neither to animals, vegetables, nor minerals.

It is certain, however, that all animals and vegetables contain an

infinity of organic living molecules. These molecules successively

take different forms, and different degrees of motion and activity,

according to different circumstances They are in a much greater number

in the seminal liquor of both sexes, and in the germs of plants, than

in other parts of the animal or vegetable. There exists, then, a

living substance in animals and vegetables, common to both, and which

substance is necessary to their nutrition. An animal procures nutriment

from an animal or vegetable substance, and the vegetable can likewise

be nourished from an animal or vegetable in a decomposed state. This

nutritive substance, common to both, is always living, always active,

and produces an animal or vegetable, as it finds an internal mould or

an analogous matrix, as we have explained in the first chapters; but

when this active substance collects in great abundance, in those parts

where it can unite, it forms in the animal body other living creatures,

such as the tape-worm, ascarides, and worms, which are sometimes found

in the veins, in the sinus of the brain, in the liver, &c. These kinds

of animals do not owe their existence to the animals of the same

species, and we may, therefore, suppose, they are produced by this

organic matter when it is extravasated, or is too abundant for the

lacteal vessels to absorb. We shall hereafter have occasion to examine

more largely the nature of those worms, and many other animals which

are formed in a similar manner.

When this organic matter, which may be looked on as an universal seed,

is collected in any great quantity, as in the seminal liquors, and in

the mucilaginous parts of the infusion of plants, its first effect is

to vegetate, or rather to produce vegetating beings. These zoophytes

swell, extend, ramify, and produce globules, ovals, and other small

bodies, of different figures, which have all a kind of animal life, a

progressive motion, which is often very swift, and sometimes very slow.

These globules themselves decompose, change their figures, and become

smaller; and in proportion as they diminish in size the rapidity of

their motion augments.

I have sometimes thought that the venom of the viper, and other active

poisons, even that of the bite of a mad dog, might possibly be this

active matter too rarefied; but I have not as yet had time to make the

experiments which I had projected on this matter, as well as on drugs

used in medicine; all that I can at present ascertain is, that all

infusions of the most active drugs swarm with moving bodies, which form

therein in much less time than in other substances.

Almost all microscopic animals are of the same nature as the organized

bodies which move in the seminal liquor, in the infusions of vegetables

and the flesh of animals; the eel-like bodies in flour, vinegar, and

water, in which lead has been soaked, are beings of the same nature as

the first, and have a like origin.

CHAPTER IX.

VARIETIES IN THE GENERATION OF ANIMALS.

The matter which serves for the nutrition and reproduction of animals

and vegetables is therefore the same; it is a productive and universal

substance, composed of organic molecules, and whose union produces

organized bodies. Nature always works on the same fund, which is

inexhaustible, but the means she employs to stamp its value are

different, and these differences, or general agreements, deserve

attention, because it is from thence we must derive our reasons to

account for exceptions and particular varieties.

In general large animals are less productive than small. The whale,

elephant, rhinoceros, camel, horse, the human species, &c. only

produce one, and very seldom two, at a birth; whereas small animals,

as rats, herrings, insects, &c. produce a great number at a time. Does

not this difference proceed from there being more food required to

support a large body than to nourish a small one, and from hence the

former has less superfluous organic particles, which would convert

into semen, than the latter? It is certain that small animals eat more

in proportion than large ones; but it is likewise probable that the

prodigious multiplication of the small animals, as bees, flies, and

other insects, may be attributed to their being endowed with very fine

and slender limbs and organs, by which they are in a condition to chuse

what is most substantial and organic in the vegetable or animal matters

from whence they derive their nutriment. A bee, who lives on the

purest parts of flowers, certainly receives more organic particles in

proportion than a horse who feeds on the grosser parts of vegetables,

hay, &c. The horse produces but one at one time, whereas the bee will

bring forth three thousand.

Oviparous animals are in general smaller than the viviparous, and

produce also more at a birth. The duration of the foetus in the

matrix of viviparous animals likewise opposes their increase, nor can

there be any new generation take place during gestation, or while they

are suckling their young; whereas oviparous animals produce at the same

time both matrix and foetuses, which they cast out of the body, and

are therefore almost always in a state of reproduction; and it is well

known that by preventing a hen from setting, and largely feeding, the

number of her eggs will be considerably increased. If hens cease to

lay when they sit, it is because they have ceased to feed; and it is

the fear lest their eggs should not produce which causes them not to

quit their nests but once a day, and that for a very short time, during

which they take a little nutriment, but not one-tenth part of what they

take at other times.

Animals which produce but a small number at a time, acquire the chief

part of their growth before they are fit for engendering, whereas those

which multiply numerously generate before they have received half their

growth. The human species, the horse, the ass, the goat, and the ram,

are not able to engender until they have obtained nearly the whole of

their growth. It is the same with pigeons and other birds, who lay but

a few eggs; but those which produce in great numbers, as poultry, fish,

&c. engender much sooner. A cock is capable of engendering at the age

of three months, when he has not attained a third part of his growth;

a fish, which at the end of twenty years will weigh thirty pounds,

engenders in the first or second year, when perhaps it does not weigh

half a pound. But exact observations on the growth and duration of

the life of fish are still wanting: their age may be nearly known by

examining the annual layers of their scales; but we are not certain how

far that may extend. I have seen carp in the Comte de Maurepas' canals,

at his castle at Pont Chartrain, which were said to be 150 years old,

and they appeared as brisk and lively as the common carp. I will not

say, with Leeuwenhoek, that fish are immortal, or at least can never

die with age; all must perish in time, that is; all which have a

beginning, a birth, must arrive to an end, or death; but fish, living

in an uniform element, and being sheltered from the vicissitudes and

all the injuries of the air, must live a longer time in the same state

than other animals, especially if these vicissitudes of the air be, as

a great philosopher asserts, the principal causes of the destruction of

living beings. But what must contribute to the long duration of their

life is, that their bones are softer than those of other animals, and

do not harden with age. The bones of fish lengthen, and grow thick

without taking any more solidity; whereas the bones of other animals

continually increase in hardness and density, until at length, being

absolutely full, the motion of their fluid ceases, and death ensues. In

their bones the repletion or obstruction, which is the cause of natural

death, is formed by such slow and insensible degrees, that fish must

require much time to arrive at what we call old age.

All quadrupeds covered with hair are viviparous; all those covered

with scales oviparous. May we not then believe than in oviparous

quadrupeds, a much less waste is made by transpiration, than the

cloathing of scales retains; whereas in animals covered with hair

this transpiration is more free and abundant? and is it not partly

by this superabundance of nutriment, which cannot be carried off by

transpiration, that those animals multiply so abundantly, and are

enabled to go so long without food? All birds and all insects that fly

are oviparous, excepting some kinds of flies which bring forth their

young alive. These flies have no wings at their birth, but they shoot

out and grow by degrees, and which they cannot use before they are of

full growth. Scaly fish are likewise oviparous; as are all reptiles

which have no legs, such as snakes and different kinds of serpents;

they change their skins, which are composed of small scales. The viper

is only a slight exception to the general rule, for it is not truly

viviparous, as it produces eggs, from which the young are hatched; it

is certain this is performed in the body of the mother, who instead

of casting those eggs, like other oviparous animals, she retains and

hatches them in her own body. The salamander, in which eggs and young

ones are found at the same time, as observed by M. de Maupertuis, is

an exception of the same kind in oviparous quadrupeds.

Most animals are perpetuated by copulation; yet many birds seem only

strongly to compress the females; indeed the ostrich, Crane, and

some few others, are so well supplied as to leave intromission no

ways equivocal. Male fish approach the female in the spawning time;

they seem even to rub their bellies against each other, for the male

often turns upon its back to meet the belly of the female; but the

necessary part for copulation does not exist in them; and the male

fish approaches the female only to emit the liquor in their milts on

the eggs, which the female then deposits; and it seems rather to be

attracted by the eggs than the female; for when she ceases throwing out

the eggs, he instantly forsakes her, and with eagerness pursues the

eggs, which the stream carries away, or that the wind disperses. Male

fish may be seen to pass and repass every spot where eggs are deposited

several times. It is certainly not for the love he bears the female

that all these motions are made, because it is not to be presumed he

always knows her; often being seen to emit his liquor on all eggs that

he comes near, and that often before he has met with the female to

which they belonged.

There are therefore animals, distinguished by sexes, which have proper

parts for copulation, and some which are deficient in them; others, as

snails, have both, and the two sexes in the same individual; others,

as vine-fretters, have no sex, and engender in themselves separately;

although they couple together when they please, we cannot determine

whether that is a conjunction of sexes; if it is so, we must suppose

that Nature has included in this small individual more faculties for

generation than in any other kind of animal, and that it not only has

the power of reproducing distinctly, but also the means of multiplying

by the communication of another individual.

But whatever difference takes place in generation, Nature, by a new

production, prepares the body for it, and which, whether manifested

outwardly, or concealed internally, always precedes generation. The

ovaries of oviparous animals, and the testicles of female viviparous

animals, before the season of impregnation, experience a considerable

change. Oviparous animals produce eggs, which at first are attached to

the ovaries, by degrees they increase in size, until they fall into

the canal of the matrix, where they acquire their white membranes, and

shell. This production has marks of the fecundity of the female, and

without which generation cannot be performed: so in viviparous females

there are always one or more glandular bodies on the testicles, which

by degrees grow under the membrane that surrounds them; these glandular

bodies enlarge and pierce, or rather impel and lift up the membrane of

the testicle; when their maturity is complete, a small slit or several

small holes appear at their extremities, by which the seminal liquor

escapes, and falls into the matrix: these glandular bodies are new

productions that precede generation, and without which there would not

be any.

In males there is also a similar change which always precedes their

capacity for generating. In oviparous animals a great quantity of

liquor fills a considerable reservoir, and which reservoir itself is

sometimes formed every year; as in the calmar and some other fish. The

testicles of birds swell surprisingly just preceding their amorous

season. In viviparous males the testicles also swell considerably in

those who have seasons, and in general there is a swelling and an

extension of the genital members in all species, which, although it be

external, must be regarded as a new production necessarily preceding

generation.

In the body of every animal, male or female, new productions are formed

which precede generation; and when there is no real production there

is always a swelling, and considerable extension in some of the parts.

There are species in which this new production is not only manifest,

but even the whole body seems to be renewed before generation can be

performed; as is the case with insects whose various metamorphoses

seem to be only for the purpose of generating; for the growth of the

animal is completed before it is transformed. It ceases from taking

nutriment, has no organs for generation, no means of converting the

nutritive particles, of which they abound, into eggs or seminal liquor,

and therefore this superfluity unites and moulds itself at first into

a form something like that of the original. The caterpillar becomes

a butterfly, because, for these reasons, it is unable to produce

small organized beings like itself; the organic particles, always

active, take another form, by uniting, whose figure answers in part,

and even in essential constitution, to that of the caterpillar, but

in which the organs of generation are developed, and may receive

and transmit the organic particles of the nutriment which forms the

eggs, and the individuals of the species. The individuals which

proceed from the butterfly ought not to be butterflies, because the

nutriment, from whence the organic particles proceed, was taken while

in the form of caterpillars; the produce therefore must be similar,

and not butterflies, which is only an occasional production of the

superabundant nutriment; a method adapted by Nature to accomplish the

purposes of generation in these species, as by the glandular bodies and

milts in other animals.

When the superabundant quantity of organic nutriment is not great,

as in man and most large animals, generation is not made till the

growth of the animal is nearly complete, and then it is confined to

the production of a small number of individuals. When these particles

are more abundant, as in many kinds of birds, and in oviparous fishes,

generation is completed before the animal has received its full

growth, and their production of individuals is very numerous. When

the quantity of particles is still greater, as in insects, it first

forms a large organic body, which, though retaining the essential

constitution of its original, differs in many parts, as the butterfly

from the caterpillar, but shortly produces an astonishing number of

young, similar in form to the animal which selected the nutriment. When

the superabundance is greater still, and when at the same time the

animal has the necessary organs for generation, as the vine-fretter, it

immediately produces a generation in every individual, and afterwards

a transformation, like other insects. The vine-fretter becomes a fly,

but cannot produce any thing, because it is only the remainder of the

organized particles which had not been made use of in the production of

the young.

Almost every animal except man has stated times for generation. Spring

is marked out for birds. Carp, and many kinds of fish, spawn in June

and August. Barbel, and other kinds, in spring. Cats have three

seasons, in January, May, and September. Roebucks, in December. Wolves

and Foxes, in January. Horses, in summer. Stags, in September and

October; and almost all insects generate in autumn: these last seem to

be totally exhausted by generation, and die a short time after. Other

animals, though not exhausted, become extremely lean and very weak,

and require a considerable time to repair the loss which is made of

the organic substance. Others are exhausted still less, and are soon

restored to an engendering state; while man is scarcely in the least

affected; his loss is speedily repaired, and therefore may be said to

be at all times in a state for propagation; all which depends solely

on the particular construction of the animal organs. The grand limits

Nature has placed in the mode of existence are equally conspicuous

in the manner of receiving and digesting the food, in the manner of

retaining it in, or excluding it from, the body, and in the means by

which the organic molecules, necessary for reproduction, are extracted.

In a word, we shall find throughout all nature, that all what can be,

is.

The same difference exists in the time of female gestation; some, as

mares, carry their young eleven or twelve months; others, as women,

cows, &c. nine months; others, as foxes, wolves, &c. five months;

bitches, nine weeks; cats, six weeks; rabbits, thirty-one days. Most

birds come out of the egg at the end of twenty-one days; though some,

as canary birds, hatch in thirteen or fourteen days. The variety is

as great here as in every thing else relative to animals. The largest

animals which produce only few, are those which go the longest with

young; this still more confirms what we have already said, that the

quantity of organic food is in proportion less in large than in small

animals; for it is from the superfluity of the mother's food that the

foetus derives what is necessary to the growth and expansion of its

parts, and since this expansion demands much more time in large than

in small animals, it is a proof that the quantity of matter which

contributes is not so abundant in the first as in the last.

There is, therefore, an infinite variety in animals, with respect to

the time and manner of gestation, engendering, and bringing forth; and

this variety is found even in the causes of generation; for although

the general principle of production is this organic matter common to

all that lives or vegetates, the manner in which the union is made,

must have infinite combinations, which must all proceed from the source

of new productions. My experiments clearly demonstrate, that there are

no pre-existing germs, and at the same time prove that the generation

of animals and vegetables is not equivocal; there are, perhaps, as

many beings, either living or vegetating, which are produced by the

fortuitous assemblage of organic molecules, as by a constant and

successive generation. It is to those productions we should apply

the axiom of the ancients, "Corruptio unius, generatio alterius."

The corruption and composition of animals and vegetables produce an

infinite number of organized bodies; some, as those of the calmar, form

only kinds of machines, which, although very simple, are exceedingly

active; others, as the spermatic animalcules, seem by their motion, to

imitate animals; others imitate vegetables by their manner of growing

or extending; there are others, as those of blighted corn, which may

be made to live and die alternately, and as often as we please; there

are still others, even in great quantities, which are at first kinds of

vegetables, afterwards become species of animals, then return again to

vegetables, and so on alternately. There is a great appearance, that

the more we shall observe this race of organized beings, the more we

shall discover varieties, always so much the more singular as they are

the more remote from our sight, and from the varieties of other animals

that have already become known to us.

For example, spurred barley, which is produced by an alteration or

decomposition of the organic substance of the grain, is composed of

an infinity of little organized bodies, like to eels. By infusing

the grain for ten or twelve hours in water, we find them to have a

remarkable twirling, and a slight progressive motion; when almost dry,

they cease to move, but by adding fresh water their motion returns.

The same effects may be produced for months, or even years; insomuch

that we can make these little machines act as often and as long as we

please without destroying them, or their losing any of their power or

activity. Their threads will sometimes open, like the filaments of

semen, and produce moving globules; we may therefore suppose them to be

of the same nature, only more fixed and solid.

Eels, in paste made with flour, have no other origin than the union of

the organic particles of the most essential parts of the grain: the

first which appear are certainly not produced by many others; yet,

although they have not been engendered, they engender others. By

cutting them with the point of a lancet, we may perceive small eels

come from their bodies in great numbers; the body of the animal appears

to be only a sheath or bag which contains a multitude of other little

animals, which perhaps are themselves only sheaths of the same kind, in

which the organic matter assimilates, and takes the form of eels.

There requires a great number of observations to be made to establish

classes and races between such singular beings, which are at present so

little known; there are some which may be regarded as real zoophytes,

which vegetate, and at the same time appear to twirl and move like

animals. There are some that at first appear to be animals, which

afterwards join and form kinds of vegetables. A little attention to the

decomposition of a grain of wheat infused in water will elucidate all I

have asserted. I could add more examples, but I have related these only

to point out the varieties there are in generation. There are certainly

organized beings which we regard as animals, but which are not

engendered by others of the same kind; there are some which are only

a kind of machines, whose action is limited to a certain effect, and

which can act but once in such a certain time, as those in the calmar;

and there are others, as we have just remarked, which we can cause to

act as long and as often as we please. There are vegetating beings

which produce animated bodies, as the filaments of the human seed,

from whence the active globules spring, and which move by their own

powers. In the corruption, fermentation, or rather the decomposition

of animal and vegetable substances, there are organized bodies which

are real animals, and can propagate their like, although they have

not been so produced. The limits of these varieties are perhaps still

greater than we can imagine. We may extend our ideas, and exert every

effort to reduce the effects of Nature to certain points, and class her

productions to certain classes, yet an infinite number of links will

always escape us.

CHAPTER X.

OF THE FORMATION OF THE FOETUS.

It appears to be clearly ascertained by the experiments of Verheyen,

who in one of them found the seed of a bull in the matrix of a cow;

and by those of Ruysch, Fallopius, Leeuwenhoek, and many others, who

perceived the male semen in the uterus of women, and numberless other

animals, that the seminal liquor of the male enters by some means

into the matrix of the female. It is probable, that in the time of

copulation the orifice of the matrix opens to receive the seminal

liquor, but if that is not the case, the active and prolific substance

of this liquor, may penetrate the membranes of the matrix; for the

seminal liquor being, as we have proved, almost all composed of organic

molecules, which are in great motion, and extremely minute, they may

pass across the coat of the closest membranes, and penetrate those of

the matrix with the greatest facility.

What proves that the active part of this liquor may not only pass

through the pores of the matrix, but even penetrate its substance, is

the sudden change that immediately takes place after conception. The

menses are suppressed, the matrix becomes softer, swells, and appears

inflamed. All these alterations can only happen by the action of an

external cause; by the penetration of some part of the seminal liquor

into the substance even of the matrix. This penetration not only

operates on the external surface of the matrix, but on all the other

parts of which this viscera is composed, like that penetration by which

nutrition and expansion is produced.

We shall be easily persuaded that it is so, when we consider that

the matrix, during the time of gestation, not only augments in bulk

but also in quantity of matter, and that it has a kind of life or

vegetation, which is continually increasing till the time of delivery;

for if the matrix was only a pouch, a destined receptacle to receive

the seed and contain the foetus, it would extend and grow thin in

proportion as the foetus increased in size; but in reality the matrix

not only extends in proportion as the foetus grows larger, but

receives at the same time a thickness and solidity. This augmentation

is a real growth, like the expansion of the body in young animals,

which can only be produced by the intimate penetration of the organic

molecules analogous to the substance of the parts: and as this

expansion of the matrix never happens but after impregnation, we cannot

doubt its being produced by the liquor of the male, especially as the

expansion takes place before the foetus has sufficient bulk to dilate

it.

It seems certain, by my experiments, that the female has a seminal

liquor which commences to be formed in the testicles, and is completed

in the glandular bodies: this liquor distills through the small holes,

at the extremities of these bodies; and may, like that of the male,

enter into the matrix in two different manners, either by these holes

at the extremities, or through the membraneous coat of the matrix.

These seminal liquors are both extracts from all parts of the body, and

in the mixture of them there is every thing necessary to form a certain

number of males and females; and the more the animal abounds with this

liquor, and the more that abounds with organic molecules, the greater

is their number of young; as we have already remarked is the case with

the small animals, and diminishes in the large.

But to pursue our subject with greater attention, we shall first

examine the particular formation of the human foetus, and afterwards

return to the other animals. In the human species, as well as in large

animals, the seminal liquors of the male and female do not contain a

great abundance of organic molecules, and therefore seldom produce

more than one at a time: the foetus is a male, if the number of the

organic molecules of the male predominates in the mixture, and a female

if the contrary; and it resembles the father or the mother as they

happen to abound in the mixture of the two liquors.

I conceive, therefore, that the seminal liquor of both are two matters

equally active and necessary for generation; and this I think is

sufficiently proved by my experiments, since I have seen the same

moving bodies in the one as the other. I perceived that the liquor

of the male enters into the matrix, where it meets with that of the

female: that they have a perfect analogy, and are both not only

composed of similar parts by their form, but also in their motions and

actions; as we have remarked in Chap. VI.

By the mixture of these two liquors I conceive the activity of the

organic molecules of each is stopped, and that the actions of one

counterbalance that of the other, insomuch that each particle ceasing

to move, remains in the place most analogous to itself, and that they

will naturally take the same position, and will dispose themselves in

the same order they held in the animal body; those that came from the

head will arrange themselves in the head of the foetus, those of the

back the same, and so of every other part; consequently they will form

a small organized being, in every thing like the animal from which they

are extracted.

It must be observed that this mixture of organic molecules of the two

sexes contains similar and different particles; the similar ones

are those which have been extracted from every part common to both

sexes. The different particles are those which have been extracted

from the parts whereby the sexes are distinguished; thus there is,

in this mixture, double the number of organic molecules to form the

head, or the heart, or such other parts common to both, whereas there

are only what are requisite to form the parts of the sex. Now the

similar particles may act upon each other without being disordered,

and collect together as if they had been extracted from the same body;

but the dissimilar parts cannot act on each other, nor unite together,

because they have not any relation; hence these particles will preserve

their nature without mixture, and will fix of themselves the first,

without the need of being penetrated by the others. Thus the molecules

proceeding from the sexual parts will be the first fixed, and all the

rest which are common to both, will afterwards fix indiscriminately,

whether they are those of the male or female, and form an organized

being which, in its sexual parts, will perfectly resemble its father,

if it is a male, and its mother if a female; but which may resemble

one another, or both, in all the other parts of the body.

It seems to me that if this was well understood, we shall in a great

measure be enabled to answer the objections made to the sentiments pf

Aristotle, and which might also be advanced against this system. The

question is, Why each individual, male and female, does not produce of

itself an animal of its own sex? It must be acknowledged this question

seems to carry weight with it; but having reflected a long time on this

subject I think I have found an answer, and which I shall endeavour to

explain.

It is certainly evident, from what we have said in the preceding

chapters, and the experiments we have described, that reproduction is

effected by the union of organic molecules returned from each part

of the body of the animal, or vegetable, into one or many common

reservoirs; and that they are the same molecules which serve for

nutriment and expansion of the body. This appears to me to have been

so clearly proved, that I apprehend no scruple can remain as to the

foundation of the theory; but I admit there may be some reason to ask,

Why each animal and vegetable does not produce its own likeness, since

each individual returns from every part of its body, and collects

in a common reservoir, all the organic molecules necessary for the

formation of a small organized being? Why then is not this organized

being formed? and why, in almost every animal, is a mixture of the

liquors of the two sexes required to produce an animal? If I content

myself with answering, that in almost all vegetables, and all kinds

of animals which multiply by cutting, that it appears the design of

Nature that each individual should increase its own species, and that

we must regard as an exception to this rule, the use which is made of

the sexes in other kind of animals; it may be said, that the exception

is more universal than the rule itself. This difficulty will be very

little weakened, if we were to say, that each individual perhaps would

produce its like, if it had proper organs, and contained the necessary

matter towards the nutriment of the embryo; because females have both

this matter, and organs, and yet do not produce either male or female

foetus without the intervention of the male; which intervention of

sexes in all animals is essential and absolutely necessary.

Although the testicles and seminal vesicles of a man, contain all the

necessary molecules to form a male, yet the local establishment and

arrangement of these molecules cannot be made, because the effect of

an union is prevented by the continual circulation of the seed both

by absorption, and the action of the new organic molecules which

constantly come into this reservoir from all parts of the body. The

same circumstances taking place with the organic molecules of the

female, is an evident reason why neither can produce of themselves,

because when the seminal liquors of the male and female are mixed,

they have more analogy to each other, than with the parts of the

body of the female where the mixture is performed. By admitting of

this explication, it may be asked, Why the common mode of generation

in animals does not agree with it; for, upon that supposition, each

individual would produce like snails, and impregnate each other, and

each individual receiving the organic molecules the other furnished,

the union would be made of itself, and by the sole power of the

affinity of these molecules among themselves? I own, if it was by this

cause alone the organic molecules could unite it would be natural

to conclude, that the shortest mode to perform the reproduction of

animals, would be to give to one individual both sexes. But it is

quite contrary to the general rule pursued by Nature, as this manner of

generation is confined to snails, and a small number of other animals.

This answer cannot be said to fully satisfy the question, as it merely

supposes the male does not produce, as it cannot receive any thing from

the female, and that having besides no proper viscera to contain and

nourish the foetus.

We may also suppose that the activity of the organic molecules, in

the semen of one individual, has need of being counterbalanced by the

activity or force of those of another individual, in order to fix

and bring them into a kind of equilibrium, a state of rest highly

necessary to the formation of the animal; and that this activity in

the organic molecules can only be counterbalanced by there being a

contrary action in those which come from the male, and those proceeding

from the female; so that, in this sense, all living or vegetating

beings must have two sexes, conjointly and separately, to produce

their resemblances. But this answer is too general to be entirely

clear; nevertheless, if we pay attention to all the phenomena, we

shall find some explanation resulting therefrom. The mixture of those

two liquors produces not only a male or female foetus, but also

other organized bodies, which have a kind of growth or expansion. The

placenta, membranes, &c. are produced at the same time as the foetus.

There are, therefore, in the seminal liquor of the male or female, or

in the mixture of both, not only organic molecules necessary for the

production of the foetus, but also those which form the placenta and

membranes. We know not from whence these molecules come, since there

is no part of the body, either of the male or female, from which they

could be sent back. From hence it seems it must be admitted, that the

molecules of the seminal liquors of each, being alike active, form

organized bodies every time they can fix, by acting mutually one on the

other: that the particles employed to form a male, will be those of the

masculine sex, which will fix the first, and form the sexual parts; and

that those common to both sexes will then fix indifferently to form the

rest of the body, and that the placenta and membranes are then formed

from the superabundant particles, which have not been used to form

the foetus; if, as we suppose, the foetus is a male, then there

remains to form the placenta, and membranes, all the organic particles

peculiar to the feminine sex which have not been employed; and also

all those of both which shall not have entered the composition of the

foetus, and which cannot be less than one half. So likewise, if the

foetus is a female, the same abundance will be left for the formation

of the placenta, and membranes, and the whole effects be the same,

excepting it will have the superfluity of the male, instead of that of

the female.

But, it may be said, that in that case the placenta and membranes

ought to become another foetus, which would be a female, if the

first was a male; and a male if the first was a female; for the first

having consumed the organic molecules of the sexual parts of only

one individual, and half those common to both, there remains all the

molecules of the sexual parts of the other individual, and the other

half of those common to both. To this I answer, that the first union

of the organic molecules prevents a second, at least, under a similar

form; that the foetus, being the first formed, exercises an external

power, which disorders the arrangement of the other organic molecules,

prevents the formation of a second foetus, and throws them into a

state from which the form of the placenta and membranes result.

We are assured by the experiments and observations we have made, that

every living being contains a great quantity of living and active

molecules. The life of the animal or vegetable appears to be only the

result of all the young lives (if that expression is permitted me) of

each of these active molecules, whose life is primitive, and appears

impossible to be destroyed. We have found these living molecules in

every living or vegetating being, and are assured, that they are alike

necessary for nutrition, and consequently, for the reproduction of

animals or vegetables. It is not, then, difficult to conceive, that a

certain number of those molecules united should compose a living being.

Each of these particles possessing animation, an assemblage of them

must be endowed with life, and thus these living organic molecules,

being common to all living beings, they necessarily form any particular

animal or vegetable, according as they are arranged. Now, this

arrangement absolutely depends on the form of the individuals which

furnish those molecules. If they are furnished by an animal, they will

arrange under the form of an individual like to it, exactly as they

were arranged when they served for the expansion of the animal itself;

but must we not then suppose that this arrangement cannot be made

either in animals or vegetables, but by the means of a kind of base,

round which the molecules might unite to form the foetus? Now, it is

plain, this basis is furnished by particles peculiar to the different

sexes, as I shall explain.

While the molecules of either sex remain by themselves, their action

produces no effect, because they are without any opposition from any

different kind of particles; but, when these molecules are mixed, then

there are dissimilar parts, and those serve for the base and point of

rest to the other molecules, and fix their activity.

In this supposition that the organic molecules, which, in the mixture

of the seminal liquors of the two individuals, represent the sexual

parts of the male, can alone serve for a base to the organic molecules

proceeding from every part of the female, and those peculiar to the

female sex as a base to them which are extracted from the male, we

might conclude, that the sexual part of the male infant is formed of

the organic molecules of the father, and from those of the mother, for

the rest of the body: and that, on the contrary, the female partakes

of its mother only in sex, and takes the rest of its body from its

father. Boys, therefore, ought, excepting the parts of the sex, to have

a greater resemblance to their mother than to their father, and girls

more to the father than to the mother; but this consequence is not,

perhaps, conformable to experience.

By considering, under this point of view, generation by sexes, we

should conclude it to be the most general mode of reproduction, as

it is in fact. Beings, whose organization is the most complete, as

animals, whose bodies compose a whole, which can neither be separated

nor divided, and whose powers are con-centered to one single point, can

only reproduce by this mode; because they contain only particles which

resemble each other, and whose union can only be made by different

particles, furnished by another individual. Those where organization is

less perfect, as that of vegetables, whose bodies may be divided and

separated without being destroyed, can be reproduced by other modes.

First, because they contain dissimilar particles; secondly, because

their forms not being so determinate and fixed as that of animals,

the particles may supply the functions of each other, and change

according to circumstances; as we see roots become branches, and shoot

out leaves when exposed to the air, which causes that the vegetable

particles obtain a local establishment, become fixed, and are enabled

to multiply, by various modes.

It will be the same with animals, whose organization is less perfect,

as the fresh water polypus, and others, which can reproduce by division

of their parts. These organized beings are not so much a single animal,

as a number united under one common covering, as trees are composed of

a multiplicity of young trees, (see Chap, II.) Pucerons, which engender

singly, also contain dissimilar particles, since, after producing

their young they change into flies which do not produce at all. Snails

communicate mutually these dissimilar particles, and afterwards they

both produce. Thus, in all known matters of generation, we see that the

requisite union of organic particles, can only be made by the mixture

of different particles, which serve as a basis capable of fixing their

motions.

If to the idea of the word _sex_, we give all the extent here supposed,

we shall say, that sexes are found throughout all nature; for then

sex will mean only the parts which furnish the organic particles,

different from the common particles, and which must serve as a fixed

point for their union. But, enough of reasoning on a question that

can be at once resolved, by saying, that God having created sexes, it

necessarily follows that animals should reproduce by their connection.

In fact, we are not made, as I have formerly said, to give a reason

for every _why_. We are not in a state of explaining _why_ Nature,

almost throughout her works, makes use of sexes for the reproduction of

animals, or why sexes exist; we ought, therefore, to content ourselves

with reasoning on what is, on things as they are, since we cannot go

beyond, by forming suppositions which will remove us from the sphere

we ought to contain ourselves in, and to which the small extent of our

knowledge is limited.

Quitting, therefore, all doubtful conjectures, I shall rest on facts

and observations. I find, that the reproduction of beings is formed in

many different manners; but, at the same time, I clearly perceive, that

it is by the union of the organic particles sent back from every part

of the individual, that the reproduction of vegetables and animals are

effected. I am certain of the existence of these organic and active

molecules in the seminal liquors of male and female animals and seed

of vegetables; and cannot doubt but every species of reproduction

is accomplished by the union of these organic molecules. Nor can I

doubt, that in the generation of animals, and particularly in that of

man, that the male and female particles mix in the formation of the

foetus, since we see infants which resemble both father and mother;

and what confirms this conclusion is, that those parts, common to both

sexes, mix promiscuously; whereas those never mix which represent the

sexual parts. For we every day see children with eyes like the father,

and the forehead and mouth like the mother; but we never find a like

mixture of the sexual parts; it never happens that they have the

testicles of the father, and the vagina of the mother, for even the

fact of hermaphrodites is very doubtful.

In the parts of generation of the two sexes in the human species,

there is so much resemblance, and so singular a conformity, that we

might be inclined to think those which appear so different externally,

are at bottom the same organs, only more or less developed; this was

the opinion of the ancients, and M. Daubenton's ideas on this subject

appear to me very ingenious.

The formation of the foetus is, then, made by the union of the

organic particles contained in the mixture of the seminal liquor

of both sexes; this union produces the local establishment of the

particles, which determines them to arrange themselves as they were in

the individuals which furnished them; insomuch, that the molecules,

which proceed from the head, cannot, by virtue of these laws, place

themselves in the legs, or any other part of the foetus. All these

molecules must be in motion when they unite, and in a motion which must

cause them to tend to a kind of centre, about which the union is made.

This centre, or fixed point, which is necessary to the union of the

molecules, and which, by its re-action and inertia, fixes the activity,

and destroys the motion, is, probably, the first assemblage of the

molecules which proceed from the sexual parts of the other individual;

they must arrange under the form of an organized body which will not be

another foetus, for the reasons we have before given.[AC]

[AC] In this, as in some other places, our author has gone into a

diffuse repetition which we have considered unnecessary and therefore

avoid.

On the whole, I conceive there are organic particles of the sexual

parts, which serve as a fixed point, or a centre of union, around which

all the other parts that form the embryo collect. I speak of it only

as probable; but as they are the only particles which differ, I have

thought it more natural to imagine, that it is around these different

particles the union is formed than those which are common to both sexes.

We have before observed, that those who have imagined the heart was the

first formed, are deceived: those who say it is the blood, are no less

so. All is formed at the same time. If we only consult observation, the

chicken is seen in the egg before it has been sat upon; we perceive the

spine of the back and the head, and, at the same time, the appendages

which form the placenta. I have opened a great number of eggs, before

and after incubation; and I am convinced, by my sight, that the chicken

exists entirely in the middle of the cicatrice, the moment it comes

from the body of the hen. The heat, communicated to it by incubation,

only expands the parts by setting the liquors in motion; but it is not

possible to determine which parts of the foetus are fixed in the

instant of formation.

I have always said, that the organic molecules were fixed, and that

their uniting was caused only by their loss of motion. This appears

to me certain: for, if we separately examine the seminal liquor of

the male and female, we shall see an infinity of small bodies in

great motion, but being mixed, their motion is instantly suspended,

and heat is necessary to renew their activity; for the chicken which

exists in the centre of the cicatrice is without any motion before

incubation; and even twenty-four hours after, when it begins to become

perceptible with a microscope, there is not the least appearance of

motion then, nor even the day following. During the first day it is

only a small white mucilaginous mass, which is of a consistence on

the second, and insensibly increases, but whose motion is very slow,

and does not at all resemble that of the organic particles which move

rapidly in the seminal liquor. Besides, I have reason to say, that

this motion of the organic molecules is absolutely destroyed; for if

we keep an egg without exposing it to a degree of heat necessary to

expand the chicken, the embryo, although formed entirely, will remain

without any motion; and the organic molecules of which it is composed,

will remain fixed without being able to give motion and life to the

embryo which has been formed by their union. Thus, after the motion

of the organic molecules has been destroyed, after the union of these

molecules, necessary to form an animal body, there is still an external

agent required to animate and give it life and motion; and this agent

is heat, which, by rarefying the liquors, obliges them to circulate

and put also every organ in action, which afterwards do no more than

develope and grow, provided that this external heat continues to assist

them in their functions.

Before the action of this external heat, not the least appearance of

blood is to be seen; and it is not till twenty-four hours after, that

I have perceived any change in the colour of the vessels. The blood

first appears in the placenta, which communicates with the body of

the chicken: but this blood seems to lose its colour as it approaches

the body of the animal; for the chicken is entirely white, and we

with difficulty discover in the first, second, and third days after

incubation, a few small sanguinary points which are close to the body

of the animal, but which seem not to make part of it, although it is

these sanguinary points which afterwards form the heart. Thus, the

formation of the blood is a change occasioned in the liquors by the

motion heat communicates to them, and this blood is formed even out of

the body of the animal, the whole substance of which is then only a

kind of mucilage, or thick jelly.

The foetus, as well as the placenta, derives the necessary nutriment

for expansion, by a kind of absorption, and they assimilate the organic

parts of the liquor in which they float: for the placenta cannot be

said to nourish the animal, no more than the animal nourishes the

placenta; since, if the one nourished the other, the first would soon

appear to diminish, while the other increased, whereas both increase

together, I have indeed observed in eggs, that the placenta at first

increases much more in proportion than the foetus, and therefore

it may nourish the animal, or rather convey the nutriment to it, by

intussusception.

What we have just said concerning the chicken, is easily applied

to the human foetus, which is formed by the union of the organic

molecules of the two sexes. The membranes, and placenta, are formed

from the superabundance of the particles which have entered into the

composition of the embryo: which is then inclosed in a double membrane,

where there is also a quantity of liquor, which is, perhaps, at first,

but a portion of the semen of the father and the mother; and as the

foetus does not quit the matrix, it enjoys, from the instant even

of its formation, an external heat necessary for its expansion; this

heat communicates a motion to liquors, and sets the organs in play, and

blood is formed in the placenta, and in the body of the embryo, by the

motion occasioned by this heat. It may be even said, that the formation

of the blood of the infant is as independent of the mother, as that

which passes into the egg, is of the hen which hatches it, or of the

oven which heats it.

It is certain, that the foetus, placenta, and membranes, grow by

intussusception: for, in the earliest days of conception, the pouch,

which contains the whole product of generation, is not adherent to

the matrix. De Graaf, in his experiments on doe rabbits, made these

globules, wherein the whole business of generation lies, move about

in the matrix. Thus, in the first stages, they increase and grow by

drawing nutriment from the liquors which bathe the matrix, to which

they are afterwards attached by a mucilage, in which small vessels are

formed with time, as we shall hereafter explain.

But, not to quit the subject, let us return to the immediate formation

of the foetus, on which there are many remarks to be made, both as

to its situation, and the different circumstances which may prevent or

stop its formation.

In the human species, the seed of the male enters into the matrix, the

cavity of which is considerable; and when it meets with a sufficient

quantity of female semen, a mixture of the organic particles succeed,

and the formation of the foetus ensues: the whole, perhaps, is done

instantaneously, especially if the liquors are both in an active and

flourishing state. The place where the foetus is formed, is the

cavity of the matrix, because the seed of the male can enter there

more easily than into the trunks; and as this viscera has but one

small orifice, which is always shut, excepting when the ardour of

love causes it to open, the materials of generation remain there

with safety, and scarcely ever reissue but by rare and unfrequent

circumstances: but as the liquor of the male sprinkles the vagina,

before it penetrates the matrix, by the activity of the organic

molecules which compose it, it may go farther into the trunks, and,

perhaps, into the ovarium. As the liquor of the female has already its

perfection in the glandular bodies of the testicles, from which it

flows and moistens the trunks and other parts before it descends into

the matrix, and as it may issue out of the vacuities left around the

neck of the matrix, it is not impossible, that the mixture of the two

liquors may be made in all these different places. It is, therefore,

probable that foetuses are often formed in the vagina, but which fall

out as soon as they are formed, because there is nothing to retain

them. It may also sometimes happen, that foetuses are formed in the

trunks; but this case is very rare, and cannot happen but when the

seminal liquor of the male enters the matrix in great plenty.