CHAPTER XI.

OF THE EXPANSION, GROWTH, AND DELIVERY OF THE FOETUS, &C.

In the expansion of the foetus, two different degrees of growth make different kinds of expansion. The first, which succeeds immediately after the formation of the foetus, is not proportionable in all the parts of which it is composed. The more distant it is from the formation, the more in proportion are its parts, and it is only after it has quitted the womb of its mother that the growth of the parts is made in nearly an equal manner. It must not be imagined that the figure of the foetus, at the moment of formation, is absolutely like that of an adult. It is certain that the embryo contains every part which, must compose a man, but they differ in their successive expansion.

In an organized body, as that of an animal, we may suppose some parts are more essential than others, and though some may be useless or superfluous, there are some on which the rest seem to depend for their expansion and disposition. We must consider some as fundamental parts, without which the animal cannot exist, and which are more accessory and external, and appear to derive their origin from the first, and which seem to be formed as much for the ornament, symmetry, and external perfection of the animal, as for the necessity of its existence, and the exercise of the essential functions of life. These two kinds of different parts expand successively, and are almost equally apparent when the foetus quits the womb; but there are others which Nature seems to keep in reserve, as the teeth, which do not appear for some time, and also the glandular bodies in the testicles of females, the beards of males, &c. which do not shew themselves till the age of puberty.

In order to discover the fundamental and essential parts of an animal body, we must pay attention to the number, situation, and nature of the whole; those which are simple, those whose position is invariable, and those without which the animal cannot exist, will be the essential parts; those, on the contrary, which are double, or in a greater number, those whose size and position vary, and those which may be retrenched from the animal without destroying or even doing it an injury, may be looked upon as less necessary, and more accessory, to the animal machine. Aristotle has said that the only parts essential to animals were those with which they take their nutriment, and throw out the superfluous parts of it from the body. From the mouth to the arms are simple parts, which no other can supply. The head and spine of the back are also simple parts, whose position is invariable. The spine of the back serves for a foundation to the fabric of the body; and it is from the marrow which it contains that the motion and action of most of the members and organs proceed; it is also this part which appears one of the first in the embryo. Now these simple parts which appear the first are all essential to the existence and form of the animal. There are many more double than simple parts in the body of an animal, and seem to be produced on each side of the simple parts by a kind of vegetation; for these double parts are similar in form, and different in position. The left hand exactly resembles the right, because it is composed of the same number of parts; nevertheless, if it was placed in the situation of the right, we could not make use of it for the same purposes, and should have reason to regard it as a very different member. It is the same with respect to the other double parts; they are similar as to form, and different as to the position which is connected to the body of the animal; and by supposing a line to divide the body into two equal parts, the position of all the similar parts would refer to this line as a centre.

The spinal marrow, and the vertebræ which contains it, appear to be the real axis, to which we must refer all the double parts of the animal, for they seem to derive their origin, and to be only symmetrical branches issuing from this trunk or common base, for we see the ribs shoot out on each side of the vertebræ in the young chicken as the young branches shoot out from the principal branch of a tree. In all embryos the middle of the head and vertebræ appear to be the first formed; afterwards we see on the two sides of a vesicle which forms the middle of the head two other vesicles which appear to proceed from the first. These two vesicles contain the eyes and the other double parts of the head; so likewise we perceive little tubercles shoot out in equal numbers from each side of the vertebræ, which extend by degrees and form the ribs, and other double parts of the trunk. On the side of this trunk already formed, as the conclusion, the legs and arms appear. This first expansion is very different from that which is made afterwards; it is the production of parts which appear for the first time; that which succeeds is only a growth of all the parts already created.

This symmetrical order of all the double parts found in every animal, the regularity of their position, the equality of their extension and growth, and the perfect resemblance between them, seem to indicate that they derive their origin from the simple parts; that there must reside in these simple parts a power which acts equally on each side, or, which answers the same meaning, they are the fixed points against which the power that produces the expansion of the double parts is exercised. That the power which acts on the right is equalled by that of the left side, and consequently they are counterbalanced by this re-action.

From hence we may infer, that if there is any defect or excess in the matter which is to serve for the formation of the double parts, as the powers which impel them on each side are equal, the defect or excess must be formed the same both on the right and left; for example, if, from a defect of matter, a man has but two fingers instead of five on the right hand, he will have but two on the left hand; or if, by an excess of matter, he has six fingers on one hand, he will have six on the other; or if the matter be vitiated, and causes an alteration in the right part, it will be the same on the left. This fact is very often seen. Most monsters are made with symmetry; the disarrangement of the parts of monsters appears to be made with order: Nature, therefore, even in her errors, mistakes as little as possible.

This harmony of position in the double parts of animals is found also in vegetables; branches shoot out from buds on every side; the veins in the leaves are equally disposed as to the principal vein; and although symmetrical order appears to be less exact in vegetables than in animals, it is only because it is more varied, and its limits are more extended, and less precise; but we may nevertheless easily discover this order, and distinguish the simple and essential parts from those which are double, and the latter we must regard as having taken their origin from the former. We shall more fully discuss this point, as far as relates to vegetables, when we come to treat of them.

It is not possible to determine under What form the double parts exist before expansion, nor in what manner they are folded, nor what figure results from their position by connection with the simple parts. The body of the animal, in the instant of formation, certainly contains every part which is to compose it; but the relative position of these parts must be very different then from what it becomes afterwards. It is the same with vegetables, for if we observe the expansion of a young leaf, we shall perceive that it is folded on both sides the principal vein, and that its figure does not resemble at that time what it afterwards assumes.

When we amuse ourselves by folding paper to form crowns, boats, &c. the different folds of the paper seem to have no resemblance to the form which must result by the unfolding; we only see that these folds are always made in an uniform order, and exactly the same on one side as that we have made on t he other; but it would be a problem beyond known geometry, to determine the figures which may result from all the unfoldings of a certain given number of folds. All what immediately relates to the position, is beyond our mathematical sciences. This art, which Leibnitz calls _Analysis Situs_, is not yet found out; though the art, which would shew us the connections that result from the position of things, would perhaps be more useful than that which has only bulk for its object, for we have often more need to know the form than the matter.

In the unfolding of Nature's productions, not only the folded parts take new positions, but they acquire, at the same time, extent and solidity. Since we cannot therefore determine the result of the simple unfolding of a folded form, in which, as in a piece of folded paper, there is but one change of position between the parts, without any augmentation or diminution of the bulk or mass of the matter, how is it possible for us to judge of the complex unfolding of the body of an animal, in which not only the relative position of the parts, but also their mass of matter, undergoes considerable changes? We cannot, therefore, reason upon this subject, but by drawing some inductions from the examination of the things at the different periods of their unfolding, and by assisting ourselves with the observations that we have had the opportunity to make.

It is true we see the chick in the egg before incubation; it floats in a transparent liquor, contained in a small purse, formed by a very fine membrane in the centre of the cicatrice; but this chick is then only a particle of inanimate matter, in which we cannot discern any organization, nor any determined figure. We judge by the external form that one of the extremities is the head, and the rest to be the spine of the back. It appears that this is the first product of fecundation resulting from the mixture of the seed of the male and female; nevertheless, before asserting this as a fact, there are many things should be considered. When the hen has cohabited with the cock for a few days, and afterwards separated from him, the eggs she produces for a month after separation are as fertile as those she produced during the time of cohabitation with the male, and unfold at the same time; they only require twenty-one days sitting, and the embryo of the one will be as forward and as completely formed as that of the other. From hence we might think, that this form, under which the chick at first appears to us in the egg, does not immediately proceed from a mixture of the two liquors, but that it existed in other forms during the time the egg remained in the body of the mother; for the embryo in the form we see it before incubation, requires only heat to unfold and bring it forth. Now, if it had this form twenty days, or a month before, when the egg was first fecundated, why was it not hatched by the internal heat of the hen? and why is not the chicken perfectly formed in those eggs which are fecundated twenty-one days before the hen lays them?

This difficulty is not so great as it appears; for we must conceive, that in the time of the cock's cohabitation with the hen, each egg receives in its cicatrice, wherein the female liquor is contained, a small portion of the semen of the male. The egg attached to the ovary is in oviparous females, what the glandular substance is in the testicles of viviparous females. The cicatrice of the egg corresponds with the glandular bodies in which the seminal liquor of the female resides; that of the male penetrates and mixes there with it; from this mixture, the formation of the embryo instantly results. The first egg which the hen lays after coition is fecundated, and capable of producing a chicken; those which she lays afterwards were fecundated at the same instant; but as there is still wanting essential parts to this egg, the production of which is independent of the seed of the male, as the white, membranes, and shell, the young embryo contained in the cicatrice cannot unfold in this imperfect egg, although assisted by the internal heat of the mother. It remains, therefore, in the cicatrice in the state in which it was formed, until the egg has acquired all the parts necessary to the growth and nourishment of the chicken: and it is not till the egg has attained its perfection that the embryo begins to unfold: this unfolding is performed by the external heat of incubation; but it is certain, if the egg could be confined within the body of the hen for 21 days after it was completely formed, the chicken would be produced, unless the internal heat of the hen should prove too powerful, for the degrees of heat necessary to hatch chickens are not very extended, and the least defect or excess is equally prejudicial to their unfolding. The last eggs the hen lays, containing the same as the first, proves nothing more than that the egg must acquire entire perfection before the embryo can unfold itself; and for want of the heat necessary to this unfolding, eggs may be kept a considerable time before incubation, without preventing the produce of the chickens they contain.

It appears, therefore, that the state of the embryo, when the egg is laid by the hen, is the first state which succeeds fecundation; that the form under which we see it is the first form resulting from the intimate mixture, and form the penetration of the two seminal liquors; and consequently by following, as Malpighius has done, this unfolding from hour to hour, we discover all that is possible to be known, unless we could see the two liquors mix before our eyes, and how the first arrangement of the particles are made, which produces the first form of the embryo.

If we reflect on this fecundation (which is made at the same time) of these eggs, which are laid successively, and along time after each other, we shall find new arguments against the existence of eggs in viviparous animals; for if the females of viviparous animals, or if women contained eggs, like hens, why are there not many fecund at the same time? why are not some of them produced in nine months, and others at distant periods? and when women have two or three children, why do they all come into the world at one time? If these foetuses were produced by the means of eggs, would not they come successively, according as the eggs come to perfection, after the time of impregnation? And would not super-foetation be as frequent as they now are scarce, or as natural as they appear to be accidental?

We cannot follow the unfolding of the foetus in the matrix as we pursue that of the chick in the egg; the opportunities of observing it are few, and we can only know what anatomists, surgeons, and midwives have written thereon. It is by collecting all their particular observations, and by comparing their remarks and their descriptions, that we have made the following abridged history of the human foetus.

There is a great appearance that, immediately after the mixture of the two seminal liquors, the whole materials of generation exist in the matrix under the form of a globe; since we know, by anatomists, that three or four days after conception there is a small oval ball in the matrix, this ball is formed by an extremely fine membrane, which incloses a limpid liquor like the white of an egg. We can then perceive some small united fibres in this liquor, which are the first outlines of the foetus. A net-work of fine fibres collects on the surface of the ball, which extends from one of the extremities to the middle. These are the first vestiges of the placenta.

Seven days after conception we may distinguish, by the naked eye, the first lineaments of the foetus, as yet unformed; being only a mass of transparent jelly, which has acquired some small degree of solidity; the head and trunk are easily discernible, because this mass is of an oblong form, and the trunk is more delicate and somewhat longer. Some small fibres, in form of a plume of feathers, spring from the body of the foetus, and which turn towards the membrane in which it is included; these fibres are to form the umbilical cord.

Fifteen days after conception, the head, and the most apparent features of the face, are distinguishable; the nose resembles a small prominent and perpendicular thread affixed to a line, which indicates the division of the lips. Two small black points are in the places of the eyes, and two little holes in those of the ears; the body of the foetus has also received some growth. On each side of the upper and inferior parts of the trunk, little protuberances appear, which are the first outlines of the arms and legs.

Eight days after, that is in three weeks, the body of the foetus has only increased about a line; but the arms and legs, the hands and feet, are apparent; the growth of the arms is more quick than that of the legs, and the fingers separate sooner than the toes. At this time internal organization begins to be discernible; the bones appear like small threads as fine as hairs; the ribs are disposed regularly from the two sides of the back bone; and as well as the arms, legs, fingers, and toes, are represented by very small threads.

At a month the foetus is more than an inch long; it naturally takes a curved posture, in the middle of the liquor which surrounds it, and the membranes which contain the whole are increased in extent and thickness; the mass is oval, and it is then about an inch and an half in its greatest, and an inch and a quarter the smallest diameter. The human figure is no longer equivocal, every part of the face is already discernible; the body is fashioned, the thighs and belly are seen, the limbs formed, the toes and fingers divided, the skin thin and transparent, the viscera marked by fibres, the vessels as fine as threads, and the membranes extremely delicate, the bones are as yet soft, and have only taken solidity in some few parts; the vessels which compose the umbilical cord, are as yet in a straight line by the side of each other; now the placenta only occupies a third of the whole mass; whereas in the beginning it occupied the half. It appears, therefore, that its growth, in superficial extent, has not been so great as that of the foetus, and the rest of the mass; but it has increased much more in solidity; its thickness has become greater in proportion than the membranes of the foetus, both of which are now easily distinguished.

According to Hippocrates, the male foetus is developed sooner than the female. He says all parts of the body in the first are apparent in thirty, whereas the latter are not so till the expiration of forty-two days.

In six weeks the foetus is nearly two inches long; the human figure begins to be more perfect; the head is only larger in proportion than the other parts of the body; the motion of the heart is perceived about this time. It has been seen to beat in a foetus of sixty days, a long while after it had been taken out of the womb of its mother.

In two months the foetus is more than two inches long; the ossification is discernible as far as the middle of the arm, thigh, and leg, and in the point of the lower jaw, which is then very forward before the upper. These, however, are only ossified points; but by the effect of a more ready expansion, the clavicles are wholly ossified. The umbilical cord is formed, and the vessels which compose it, begin to twist nearly like threads which compose a rope: but this cord is still very short in comparison of what it becomes hereafter.

In three months the foetus is nearly three inches long, and weighs about three ounces. Hippocrates says, that it is at this time the motion of the male foetus begins to be felt by its mother; but that those of the female are not felt till after the fourth; there are women who affirm they have felt the motions of the child at the beginning of the second month. It is very difficult to be certain on this subject, the sensations excited by the first motions of the foetus depending, perhaps more on the sensibility of the mother than the strength of the child.

Four months after conception the length of the foetus is six or seven inches; every part of its body is so greatly augmented as to be perfectly distinguished from each other; even the nails appear on the fingers and toes. The testicles of the males are shut up in the belly above the kidneys; the stomach is filled with somewhat of a thick humour, like that which incloses the amnios. We find a milky fluid in the little vessels, and in the large ones a black liquid matter. There is a little bile in the gall, and some urine in the bladder. As the foetus floats freely in the liquid which surrounds it, there is always a space between the body and membranes in which it is contained. These coverings grow at first more than the foetus; but after a certain time it is quite the contrary. Before the end of the third month the head is bent forward, the chin rests on the breast, the knees are lifted up, the legs bent backwards upon the thighs (sometimes the knees are so high as almost to touch the jaws), the arms are generally folded across the breast, and one of the hands, and often both touch the face. The foetus afterwards takes different situations, as it acquires strength. Experienced midwives have pretended to be certain that it changes much oftener than is commonly thought, and which they prove by several observations; first, the umbilical cord is often found twisted round the body and limbs of the child, in a manner which necessarily supposes, that the foetus has moved in many directions, and taken different positions; secondly, a mother feels the motions of the foetus sometimes on one side of the womb and sometimes on another; and it often strikes against many different places, which must be occasioned by different positions, and supposes that it takes different situations; thirdly, as it floats in a liquid which surrounds it on all sides, it can very easily turn and extend itself by its own strength; and it must also take different situations according to the various attitudes of the mother; for example, when she lies down, the foetus must be in another situation to what it was when she stood upright.

Most anatomists have said, that the foetus is constrained to bend its body, because it is too confined in its covering; but this opinion does not appear well founded, for in the first five or six months there is more space than is required for the foetus to extend, and yet during that time it is bent and folded. We also see the chicken is in a curved posture in the liquor of the amnios, although this membrane and its liquor are sufficient to contain a body five or six times as large as the foetus. Thus we may conclude that this curved form of the foetus is natural, and not the effect of force. I am somewhat of Harvey's opinion, who says, it takes this attitude because it is the most favourable to rest and sleep; and as the foetus sleeps almost continually, it naturally takes the most advantageous situation. "Certe (says this famous anatomist) animalia omnia, dum quiescunt & dormiunt, membra sua ut plurimum adducunt & complicant, figuramque ovalem ac conglobatam quærunt: ita pariter embryones qui ætatem suam maxime somno transigunt, membra sua positione ea qua plasmantur (tanquam naturalissima ac maxime indolenti quietique aptissima) componunt[AE]."

[AE] Harvey on Generation, page 257.

The matrix, as we have already said, takes a very ready growth after conception, and it continues also to increase in proportion with the foetus; but the foetus at length outgrows the matrix, and then, especially when it approaches maturity, it may be too much confined, and agitate the matrix by reiterated motions and violent efforts. The mother sensibly feels the impression of these painful sensations, and which are called periodic pains after the labour commences. The more power the foetus exerts to dilate the matrix the greater it finds the resistance, from the natural compression of the parts. From thence all the effect falls on the orifice, which has been increasing by degrees during the latter months of pregnancy. The head of the foetus, forcibly inclining against the sides of the orifice, dilates it, by a continual pressure, till the moment of delivery, when it opens sufficiently for the child to escape from the womb.

What makes it probable that the labour-pains proceed only from the dilatation of the orifice of the matrix is, that this dilatation is the only means to discover whether the pains felt are in fact the pains of labour, for women often feel very sensible pains, which are not those that immediately precede delivery. To distinguish the false from true pains, it has been recommended for the midwife to touch the orifice of the matrix, as if the pains be true the dilatation will always increase, and if they are false pains, that is to say, pains which proceed from some other cause than that of the approaching delivery, the orifice will contract rather than dilate, or at least will not continue to dilate. From hence we have sufficient foundation to imagine, that these pains proceed from a forced dilatation of the orifice. The only thing which embarrasses on this occasion is that alternative of rest and sufferings the mother endures. This circumstance of the effect does not perfectly agree with the cause which we have just indicated; for the dilatation of an orifice, which is made by degrees, should produce a constant and continued pain, without any intervals of ease. But possibly the whole may be attributed to the separation of the placenta, which we know is fastened to the matrix by a number of papillæ, which penetrate into the vacuities or cavities of this viscera; therefore may it not be supposed that they do not separate from their cavities all at the same time; that each separation causes those acute pains, and the intervals between are those of ease and rest? The effect in this case perfectly answers the cause, and we can support this conjecture by another observation.--Immediately before delivery there issues a whitish and viscous liquor, like that which flows from the nipples of the placenta when drawn out of their places, which makes it probable that this liquor, which then issues from the matrix, is produced by the separation of some of the papillæ of the placenta.

It often happens that the foetus quits the matrix without bursting the membranes, and consequently without the contained liquor flowing out. This kind of delivery appears to be most natural, and resembles that of most animals; nevertheless, the human foetus commonly pierces its membranes by the resistance it meets with at the orifice of the matrix. It also sometimes brings away part of the amnios, and even the chorion, upon its head like a cap. When these membranes are pierced or torn, the liquors, called the _waters_, which they contain flow out, and the sides of the orifice of the matrix, and the vagina, being thus moistened, give way more easily to the passage of the child. After the flowing of this liquor there remains sufficient room in the matrix for the midwife to return the child, if the position is unfavourable. When the foetus is come out the delivery is not entirely completed, the placenta and membranes remain in the matrix, and the new-born infant adheres to them by the umbilical cord; the hand of the midwife, or the weight of the body of the infant alone, draws them out by means of this cord. Those organs which were necessary to the life of the foetus become useless, and even noxious to the new-born infant. They are instantly separated from the body of the child, by tying the umbilical cord about an inch distance from the navel, and by cutting it about an inch from the ligature. The remainder of this cord dries away, and separates of itself from the navel, about the sixth or seventh day.

On examining the foetus previous to its birth we may form some idea of its natural functions. It has organs, which are necessary to it while in the womb of its mother, but which become useless. For the better understanding the mechanism of these functions, we must explain a little more particularly the nature of those necessary parts, the umbilical cord, the membranes, the liquor which they contain and the placenta. The umbilical cord, which is attached to the body of the foetus at the navel, is composed of two arteries and one vein; these prolong the circulation of the blood, but the vein is larger than the arteries. At the extremity of the cord each of these vessels divide into an infinity of ramifications, which extend between two membranes. They separate at equal distances from the common trunk; so that these ramifications are round and flat, and are called, when thus collected, the _placenta_. The external surface, which is applied against the matrix, is convex; the internal concave. The blood of the foetus circulates in the cord, and in the placenta. The arteries of the cord spring from two large arteries of the foetus, and carry the blood through the arterial ramifications of the placenta; from thence it passes into the venous branches which carry it into the umbilical vessels; these communicate with a vein of the foetus, in which vessels it is received.

The concave surface of the placenta is clothed by the chorion; the convex is also covered by a kind of soft membrane, easily torn, which seems to be a continuation of the chorion, and the foetus is included under the double coat of the chorion and the amnios. The form is globular, because the intervals between the membranes and the foetus are filled with a transparent liquor. This liquor is contained by the amnios, which is the internal membrane, it is thin and transparent; it folds round the umbilical cord at its insertion into the placenta, and covers it the whole length to the navel of the foetus. The chorion is the external membrane; it is thick and spongy, sprinkled with sanguinary vessels, and composed of many coats, the exterior of which covers the convex surface of the placenta. It follows the inequalities, and covers the papillæ, which spring from the placenta, and are received in the cavities found at the bottom of the matrix, called _lacunæ_. The foetus adheres to the matrix by these insertions.

Some anatomists have thought that the human form had, like those of certain quadrupeds; a membrane called _allantois_, destined to receive the urine; and they have pretended to have found it between the chorion and the amnios, or in the middle of the placenta at the root of the umbilical cord, under the form of a very large bladder, in which the urine entered by a long pipe that composed part of the chord, and which opened on one side into the bladder, and on the other in this allantois membrane, being similar to the urachus in other animals. They owned, however, that it was not near so large in the human foetus as in quadrupeds, but that it was divided into many tubes, so minute, that they could scarcely be perceived, and that the urine passed into their cavities.

The experience and observations of most anatomists are contrary to this supposed discovery. They admit there is a kind of ligament which adheres by one end to the external surface of the bottom of the bladder, and extends to the navel; but it becomes so delicate, on entering into the cord, as to be nearly reduced to nothing: in common this ligament is not hollow, and we can see no orifice at the bottom of the bladder.

The foetus has no communication with the open air, and the experiments made upon the lungs prove they have never respired; for they sink to the bottom when put in water: whereas those of infants who have breathed always float on the top; the foetus then does not respire in the womb, consequently it cannot form any sound by its voice; and therefore what has been related of the groaning and crying of children before their birth may be considered as fables. After the flowing of the waters it may happen, that the air has found an entrance into the cavity of the matrix, and then the infant may begin to respire before it is brought forth. In this case it may be able to cry, as the chicken cries before the shell of the egg is broken, which it can do from there being air in the cavity which is between the external membrane and the shell. This air is found in all eggs, and is produced by the internal fermentation of matters contained in them[AF].

[AF] See La Statique des Vegetaux, Chap. vi.

The lungs of the foetus being without any motion, have no more blood enter into them than is requisite to nourish and make them grow; and there is another road opened for the course of its circulation. The blood in the right auricle of the heart, instead of passing into the pulmonary artery, and returning, after having ran through the lungs into the left auricle by the pulmonary vein, passes immediately into the left by an opening, called the _foramen ovale_, which is in the partition of the heart between the two auricles. It enters afterwards into the aorta, which distributes it by its ramifications, at going out of which the venous branches receive it, and bring it back to the heart by uniting all in the _vena cava_, which terminates at the right auricle of the heart. The blood which this auricle contains, instead of passing entirely by the foramen ovale, may escape in part into the pulmonary and the aorta by an arterial canal, which goes immediately from the one to the other. It is by these roads that the blood of the foetus circulates without entering into the lungs, as it enters into those of children, adults, and every animal which breathes.

It has been thought that the blood of the mother passes into the body of the foetus, by means of the placenta and umbilical cord. It was supposed that the sanguinary vessels of the matrix opened into the vacuities, and those of the placenta into the nipples, and that they joined one to the other; but experience is quite contrary to this opinion; for if the arteries of the umbilical cord is injected the liquor returns by the veins, and not any part of it escapes externally. Besides, the nipples may be drawn from the vacuities where they are lodged, without any blood issuing either from the matrix or placenta: a milky liquor only issues from both, and which, we have already observed, serves the foetus for nutriment. This liquor possibly enters into the veins of the placenta, as the chyle enters into the subclavian vein; and perhaps the placenta in a great measure performs the office of the lungs in bringing the blood to maturity. It is certain that the blood appears much sooner in the placenta than in the foetus, and I have often observed in eggs that have been under the hen for a day or two, that the blood appeared at first in the membranes, and that their sanguinary vessels are very large and numerous, while the whole body of the chicken, excepting the point where these blood-vessels terminate, is only a white and almost transparent matter, in which there is not the smallest sign of a sanguinary vessel.

It has been imagined, that the liquor of the amnios is a nutriment the foetus receives by its mouth. Some naturalists pretend to have observed this liquor in the stomach, and to have seen some foetuses to which the umbilical cord was entirely wanting, and others who had but a very small portion, which did not at, all adhere to the placenta; but in this case might not the liquor have entered into the body of the foetus by the small portion of the umbilical cord, or by the umbilical vessel itself? Besides, to these observations we may oppose others. Some foetuses have been found whose lips were not separated, and others without any opening in the oesophagus. To conciliate these circumstances, some anatomists have thought that the aliments passed into the foetus partly by the umbilical cord, and partly by the mouth: none of these opinions appear to have any foundation. It is not the question to examine the growth of the foetus alone, and to seek from whence and by what it draws its nutriment, but how the growth of the whole is made; for the placenta, liquor, and membrane increase in size as well as in the foetus; and consequently the instruments and canals employed to receive or carry this nutriment to the foetus, have a kind of life themselves. The expansion of the placenta and membranes is as difficult to conceive as that of the foetus; and we might say, with equal propriety, that the foetus nourishes the placenta, as that the placenta nourishes the foetus. The whole mass is floating in the matrix, and without any adherence at the commencement of this growth: therefore the nourishment can be only made by an absorption of the milky matter contained in the matrix. The placenta appears first to draw this nutriment, to convert this milk into blood, and to carry it to the foetus by veins. The liquor of the amnios appears to be only this milky liquor depurated, the quantity of which increases by a like absorption, proportionate to the increase of the membranes, and the foetus probably absorbs the liquor, which appears to be the necessary nutriment for its expansion. For we must observe, that for the first two or three months the foetus contains very little blood; it is as white as ivory, and appears to be composed of lymph which has taken some solidity; and as the skin is transparent, and all the parts very soft, we may easily conceive that the liquor in which the foetus swims may penetrate them, and thus furnish the necessary matter for its nutrition and expansion. It may be supposed that the foetus in the latter stages takes its nutriment by the mouth, since in the stomach we find a liquor similar to that in the amnios, urine in the bladder, and excrements in the intestines; and as we find neither urine nor _meconium_ in the amnios, there is reason to conclude that the foetus does not void its excrements, especially as some are born without having the anus pierced, although they had a great quantity of _meconium_ in the intestines.

Although the foetus does not immediately adhere to the matrix, but is only attached to it by small external nipples, though it has no communication with the blood of its mother, but is as independant of her who bears it, in many respects, as the egg is of the hen that hatches it, yet it has been pretended, that all which affects the mother affects the foetus; that the impressions of the one act on the brain of the other; and to this imaginary influence resemblances, monsters, and especially marks on the skin of some children, have been attributed. I have examined many of these marks, and they all appear to me to have been caused by a derangement in the texture of the skin. Every mark must have a figure which will resemble something or other; but I am certain the resemblances so formed depend rather on the imagination of those who see them than on that of the mother. On this subject the marvellous has been carried as far as it could go. It has not been only said that the foetus carried real representations of the longings of its mother, but that, by a singular sympathy, the marks, which represent strawberries, cherries, &c. change their colour, and become deeper in the season of those fruits. With a little more consideration, and less prejudice, this colour may be seen to change much oftener, and that it must happen every time the motion of the blood is accelerated, whether by the heat of summer or from any other cause. These marks are either yellow, red, or black, because the blood gives these tints to the skin when it enters in too great quantities into the vessels. If these marks have the longings of the mother for their cause, why have they not the forms and colours as varied as the objects of her desires? What a curious assemblage of figures would be seen if all the whimsical desires of the mother were written on the skin of the child?

As our sensations have no resemblance to the objects which cause them, it is impossible that desire, fear, horror, or any passion, or internal emotion, can produce real representations of those objects; and the child being in this respect as independant of the mother as the egg is of the hen, I should as soon believe that a hen, which saw the neck of a cock twisted, would hatch chickens with wry necks, as that, by the power of imagination, a woman, who happened to see a man broke upon the wheel, would bring forth a child with its limbs broken in the same manner.

But even supposing this circumstance attested, I should still support the opinion, that the imagination of the mother had not been the cause, for what is the effect of horror? an internal motion, a convulsion in the body of the mother, which might shake, compress, and agitate the womb. What can result from this commotion? nothing similar to the cause, for if this commotion was very violent the foetus might be killed, wounded, or deformed in some of its parts; but how is it to be conceived that this commotion can produce any thing resembling the fancy of the mother in the foetus, unless we believe, with Harvey, that the matrix has the faculty of conceiving ideas, and realizing them on the foetus?

But, it may be urged, if it was not affected by the imagination of the mother, why did the child come into the world with broken limbs? However rash it may appear to explain a matter which is extraordinary and uncertain, and of which we have no right to exact a solution, yet this question appears to me answerable in a satisfactory manner. Circumstances of the most rare and extraordinary kind happen as necessarily as those which are frequent and common. In the infinite combinations which matter can take, the most extraordinary arrangements must sometimes happen; hence we might venture to wager, that in a million, or a thousand millions of children, there will be one born with two heads, four legs, or with broken limbs; it may, therefore, naturally happen, without the concurrence of the mother's imagination, that a child should be born with broken limbs. This may have happened more than once, and the mother, while pregnant, might have been present at the breaking on the wheel, and therefore the defect of the child's formation has been attributed to what she had seen, and to her impressed imagination. But, independant of this general answer, we may give a more direct explanation. The foetus, as we have said, has nothing in common with the mother; its functions, organs, blood, &c. are all particular, and belong to itself; the only thing which it derives from its mother is the liquor, or nutritive lymph, which filtrates from the matrix. If this lymph is bad, or envenomed with the venereal virus, the child will be alike disordered; and it may be imagined, that all the diseases which proceed from vitiated humours may be communicated from the mother to the child. We know that the small-pox is communicative, and we have but too many examples of children who are, directly after their birth, the victims of the debauches of their parents. The venereal virus attacks the most solid parts of the bones, and it appears to act with more force towards the middle of the bone, where ossification commences; I conceive, therefore, that the child here spoken of has been attacked by the venereal disorder while in its mother's womb, and from that cause it came into the world with its bones broken through the middle.

Rickets may also produce the same effect. There is a skeleton of a rickety child in the French king's cabinet, whose arms and legs have callosities in the middle of their bones. By the inspection of this skeleton, it appeared evident that the bones had been broken during the time it was in the womb, and that afterwards the bones re-united, and formed these callosities.

But enough of a subject which credulity alone has rendered marvellous. Prejudice, especially that sort which is founded on the marvellous, will always triumph over reason, and we should have but little philosophy if we were astonished at it. We must not therefore ever expect to be able to persuade women, that the marks on their children have no connection with their unsatisfied longings. Yet might it not be asked them, before the birth of the child, of what particular longings they had been disappointed, and consequently what will be the marks their children will bear? I have often asked this question, and have only made persons angry without having ever convinced them.

The time that a woman goes with child is generally about nine months; but it is however sometimes longer and sometimes shorter. Many children are born at seven or eight months, and some not till after the ninth; but in general the deliveries which precede the term of nine months are more frequent than the others. The common time of a natural delivery extends to twenty days, that is, from eight months fourteen days to nine months and four hours.

Many children are born before the 260th day, and although these deliveries precede the general term, they are not abortions, because these children mostly live. It is commonly thought that children born at eight months cannot live, or at least that many more of them die than those born at seven months. This opinion appears to be a paradox; and by consulting experience I think we shall find it an error. The child brought forth at eight months is more formed, and consequently more vigorous, and likely to live than that which is born at the seventh. Nevertheless this opinion is pretty generally received, and founded on the authority of Aristotle.

The beginning of the seventh month is the earliest term for delivery; if the foetus is brought forth sooner it dies, and is termed an abortion. There are, however, great limits for the time of human delivery, since they extend from the seventh to the tenth, and perhaps to the eleventh month.

Women who have had many children assert, that girls remain longer in the womb than boys. If this is really the case, we must not be surprized at female children being born at ten months. When children come before nine months they are not so well proportioned as those who are not brought into the world till ten months, the bodies of the latter are sensibly larger and better formed; their hair is longer, the growth of the teeth, although still hid under the gums, is more advanced; the voice is clearer, and the tone more deep.

There is much uncertainty on the occasional causes of delivery, and we do not perfectly know what obliges the infant to quit the womb. Some imagine, that the foetus having acquired a certain size, the matrix is too confined for its longer stay, and that the constraint felt by the foetus, obliges it to use every effort to quit its prison; others say, and it is nearly to the same purport, that the weight of the foetus becomes so great, that the matrix is forced to open to free itself from the burthen. These reasons do not appear satisfactory; for the matrix must always have capacity and strength to contain and sustain the weight of a foetus of nine months, since it often contains two, and it is certain that the weight and size of the twins of eight months are more considerable than the weight and size of a single child of nine. Besides, it often happens that a child born at nine months is smaller than the foetus of eight months, although it continues in the womb.

Galen pretends, that the child remains in the matrix till it is able to receive its food by the mouth, and that it only forces its escape from the need of nutriment. Others have said, that the foetus always receives its nourishment by the mouth from the liquor of the amnios; but which becomes at length so contaminated, by the transpiration and urine of the foetus, that it becomes disgustful, and obliges the foetus to use every exertion to quit its confinement. These reasons do not appear better than the first; for it would from thence follow, that the weakest and smallest foetuses would remain longer in the womb than the strongest and largest, which never happens; besides, it is not food that the foetus seeks immediately after it is born, for it can stay some time without it; on the contrary, it seems most desirous to disembarrass itself from the nutriment it took when in the womb of its mother, and to return the meconium. Other anatomists have supposed that the excrement accumulated in the bowels of the foetus, gives it great pain, and causes it to make such efforts, that the matrix is at length obliged to give way, and to open a passage for its escape. I acknowledge I am not better satisfied with this explanation than the rest; because, why cannot the foetus void its excrements in the amnios, if it was pressed so to do? Now this never happens; it appears, on the contrary, that this necessity of voiding the meconium is not felt till after the birth, when the motion of the diaphragm, occasioned by that of the lungs, compresses the intestines and causes this evacuation; for the meconium has never been found in the amnios of a foetus of ten months who had not respired, whereas a foetus of six or seven months voids this meconium a short time after respiration.

Other anatomists, and among them Fabricius de Aquapendente, have supposed the foetus quitted the matrix through the need of procuring refreshment by means of respiration. This cause appears to me still more remote than all the rest, because the foetus can have no idea of respiration without having respired.

After having weighed all these explanations, I suppose the foetus's quitting the matrix depends on a quite different cause. The flowing of the menstrua is periodical, and at determined intervals; and although conception suppresses its appearance, it does not destroy the cause; for notwithstanding the blood does not appear at the accustomed times, yet a kind of revolution takes place, like that which is made before conception. Thus it is, there are many women whose menstrua are not suppressed in the first two or three months. I imagine, therefore, that when a woman has conceived, the periodical revolution is made as regular as before; but as the matrix is swelled, the excretory canals cannot give issue to the blood, at least unless it arrives there with such force, and in such quantities, as to open a passage in spite of the resistance, that is opposed to it. In this case blood will appear, and if it flows in a great quantity abortion will ensue, and the matrix take the form it had before. But if the blood only forces one part of these canals, the business of generation will not be destroyed, although the blood appears, because the greatest part of the matrix still remains in the state which is necessary for that purpose.

When no blood appears, as is generally the case, the first periodical revolution is remarkable and felt by the same pains and symptoms. From the first suppression of the menses, therefore, a violent action on the matrix is made, and provided the action is augmented, it destroys the product of generation. It may from thence be concluded, that every conception which is made just before the useful return of the menses seldom succeeds, and that the action of that blood easily destroys the weak roots of a germ so tender and so delicate. The conceptions, on the contrary, which are made just after the periodical evacuations succeed the best, because the produce of the conception has more time to grow, strengthen, and resist the action of the blood, by the time the next revolution happens.

The foetus having undergone this first trial, and having resisted it, receives more strength and growth, and is more in a condition to contend against the succeeding revolutions. Miscarriages may and do happen in all the periodical revolutions; but they are less frequent in the fourth and fifth months, than either at the beginning or near the end. We have assigned the reasons why they are more frequent at the beginning; it therefore only remains to explain why they are also more frequent towards the end.

The foetus generally comes into the world during the tenth revolution. When it is born at the eighth or ninth it lives, and these deliveries are not looked upon as miscarriages, because the child, although not so perfectly formed, is still sufficiently so for the purpose of life. It has been pretended, that examples have been seen of children born at the seventh and even at the sixth revolution, that is, at five or six months, which have lived. There is, therefore, no difference between a birth and a miscarriage but what is relative to the living powers of the infant. In general the number of miscarriages in the first, second, and third months are very considerable for the reasons we have given ; and the number of deliveries of the seventh and eighth months are also very great, in comparison with the miscarriages of the fourth, fifth, and sixth months, because in this middle period the product of generation has received more solidity and strength, and having resisted the action of the four first periodical revolutions, a more violent force than the preceding is required to destroy it. The same reason subsists, with additional force, for the fifth and sixth months. But the foetus, which till then is weak, and can act only by its own feeble strength, begins to get strong, and move with vigour; and at the eighth revolution the foetus, uniting its efforts with those of the matrix, facilitates its exclusion, and it may come into the world in the seventh month, and be capable of living, especially if it happens, as is sometimes the case, to have more than ordinary strength for that period. But if it comes into the world only through the weakness of the matrix, which could not resist the action of the blood in this eighth revolution, the delivery would be regarded as a miscarriage, and the child would not live. But these cases are very rare, for if the foetus has resisted the seven first revolutions, only particular accidents can prevent it from resisting the eighth. The foetus, which has acquired this same degree of strength and vigour only a little later, will come into the world at the ninth revolution; and those which require nine months to obtain this same strength, will come at the tenth revolution, which is the most common and general term; but when the foetus has not acquired in nine months this degree of perfection, it may remain in the womb till the eleventh, and even till the twelfth revolution; that is, till the tenth or eleventh month, as we have many examples.

This opinion, that it is the menstrua which is the occasional cause of delivery at different times, may be confirmed by many other reasons. The females of every animal which have no menses, bring forth at nearly the same terms, and there is but a very slight variation in the duration of their gestation. We may, therefore, suppose that this variation, which is so great in women, comes from the action of the menstrual blood, which is constantly exerted at every periodic return.

We have observed, that the placenta adheres to the papillæ, or the matrix, only by nipples; that there is no blood either in these nipples or in the vacuities they are niched into, and that when they are separated (which is easily done) a milky liquor only issues from them. Now, how happens it that delivery is always accompanied with a considerable hæmorrhage, at first of pure blood, and afterwards mixed with a watery liquor? This blood does not proceed from the separation of the placenta, as the nipples are drawn out without any effusion of blood. Delivery, which entirely consists, of this separation, should not, therefore, produce any blood. Is it not then more accordant with reason to suppose, that it is the action of the blood which causes delivery, and that it is this menstrual blood which forces the vessels as soon as the matrix is emptied, and which begins to flow immediately after delivery as it did before conception?

It is known, that in the first months of pregnancy that which contains the seed of generation is not adherent to the matrix. By the experiments of De Graaf it has been seen, that by blowing on the little ball we can make it move. The adhesion to the matrix is never very strong, and at first the placenta with difficulty adheres to the internal membrane of the viscera, and those parts are only contiguous, or joined by a mucilaginous matter, which has scarcely any adhesion. Why then does it occur, that in miscarriages of the first and second month this ball never escapes without a great effusion of blood? It is certainly not caused by the passage of the ball quitting the matrix, since it does not adhere to it; but it is, on the contrary, by the action of this blood that the ball is driven out. Must we not then conclude this blood to be menstrual, which by forcing the canals, through which it had been accustomed to pass before impregnation, destroys the product of conception by retaking its common road?

It appears, therefore, that the periodical revolution of the menstrual blood has great influence on delivery, and that it is the cause why the times of delivery in women vary so much more than in every other female who is not subject to the periodical evacuation, and which always bring forth at the same times. It also appears that this revolution, occasioned by the action of the menstrual blood, is not the sole cause of birth, but that the action of the foetus itself contributes towards it, since there are instances of a child escaping from the womb after the death of the mother, which necessarily supposes an action proper and particular in itself.

The space of time which cows, sheep, and other animals go with young is always the same, and their deliveries are not attended with an hæmorrhage. May we not then conclude, that the blood voided by women after delivery is the menstrual blood, and that the human foetus being born at such different terms, can only be by the actions of this blood on the matrix during every periodical revolution? It is natural to imagine, that if the females of viviparous animals had menses like women, their deliveries would be followed with an effusion of blood, and happen at different terms. The foetuses of animals come into the world clothed with their membranes (and it seldom happens that the membranes are broken), and the waters flow before the delivery; whereas it is very rare a child is brought forth with its membranes entire. This seems to prove that the human foetus makes more efforts than other animals to quit its prison; or that the matrix of a woman does not so naturally incline to the passage of the child, for it is the foetus which tears its membranes, by the efforts it makes against the resistance it meets with at the orifice of the viscera.

RECAPITULATION.

All animals procure nutriment from vegetables, or other animals which feed upon vegetables; there is, therefore, one common matter to both, which serves for the nutrition and expansion bf every thing which lives or vegetates. This matter cannot perform them but by assimilating itself to each part of the animal or vegetable, and by intimately penetrating the texture and form of these parts, which I have called the _internal mould_. When this nutritive matter is more abundant than is necessary to nourish and expand the animal or vegetable, it is sent back from every part of the body, and deposited in one or more reservoirs, in the form of a liquor; this liquor contains all the molecules analogous to all parts of the body; and consequently all that is necessary for the reproduction of a young being, perfectly resembling the first. Commonly this nutritive matter does not become superabundant, in most kinds of animals, till they have acquired the greatest part of their growth; and it is for this reason that animals are not in a state of engendering before that time.

When this nutritive and productive matter, which is universally spread abroad, has passed through the internal mould of an animal or vegetable, and has found a proper matrix, it produces an animal or vegetable, of the same kind; but when it does not meet with a proper matrix, it produces organized beings different from animals and vegetables, as the moving and vegetating bodies seen in the seminal liquor of animals, in the infusion of the germ of plants, &c.

This productive matter is composed of organic particles, always active, the motion and action of which are fixed by the inanimate parts of matter in general, and particularly by oily and saline bodies, but as soon as they are disengaged from this foreign matter, they retake their action, and produce different kinds of vegetations and other animated, beings.

By the microscope, the effects of this productive matter may be perceived in the seminal liquors of animals of both sexes. The seed of the female viviparous animals is filtered through the glandular bodies which grow upon their testicles, and these glandular bodies contain a large quantity of seminal fluid in their internal cavities. Oviparous females have, as well as the viviparous, a seminal liquor, which is still more active than the viviparous. The seed of the female is in general like that of the male, when, they are both in a natural state: they decompose after the same manner, contain similar organic bodies, and they alike offer the same phenomena.

All animal or vegetable substances include a great quantity of this organic and productive matter. To perceive it, we need only separate the inanimate parts in which the active particles of this matter are engaged. And this is done by infusing animal or vegetable substances in water. The salts will dissolve, the oils separate, and the organic particles will be seen by their putting themselves in motion. They are in greater abundance in the seminal liquors than in any other parts, or rather, they are less entangled by the inanimate parts. In the beginning of this infusion, when the flesh is but slightly dissolved, the organic matter is seen under the form of moving bodies, which are almost as large as those of the seminal liquors: but, in proportion as the decomposition augments, these organnic particles diminish in size and increase in motion; and when the flesh is entirely decomposed, or corrupted, these same particles are exceedingly minute, and their motion exceedingly rapid. It is then that their matter may become a poison, like that of the tooth of a viper, wherein Mr. Mead perceived an infinite number of small pointed bodies, which he took for salts, although they are only these same organic particles in a state of great activity. The pus which issues from wounds abounds with little insects, and it may take such a degree of corruption as to become one of the most subtle poisons; for every time this active matter is exalted to a certain point, which may be known by the rapidity and minuteness of the moving bodies it contains, it will become a species of poison. It is the same with the poison of vegetables. The same matter which serves to feed us when in its natural state, will destroy us when corrupted. Spurred barley, for instance, throws the limbs of men and animals into a gangrene who feed on it. It is also evident by comparing the matter which adheres to our teeth, which is the residue of our food, with that from the teeth of a viper or mad dog, which is only the same matter too much exalted, and corrupted to the last degree.

When this organic and productive matter is found collected in a great quantity in some part of an animal, where it is obliged to remain, it forms living beings which have been ever regarded as animals; the tænia, ascarides, all the worms found in the veins, liver, in wounds, in corrupted flesh, and pus, have no other origin; the eels in paste, vinegar, and all the pretended microscopical animals are only different forms which this active matter takes of itself, according to circumstances, and which invariably tends to organization.

In all animal and vegetable substances, decomposed by infusion, this productive matter manifests itself immediately under the form of vegetation. Filaments are seen to form, which grow and extend like plants. Afterwards these extremities and knots swell and burst, to give passage to a multitude of bodies in motion, which appear to be animals; so that it seems as if all nature began by a motion of vegetation. It is seen by microscopical objects, and likewise by the expansion or unfolding of the animal embryo; for the foetus at first has only a species of vegetable motion.

Sound food does not furnish any of these moving molecules for a considerable time. Several days infusion in water is required for fresh meat, grain, kernels, &c. before they offer to our sight any moving bodies; but the more matters are corrupted, decomposed, or exalted, the more suddenly these moving bodies manifest themselves; they are all free from other matters in seminal liquors; but a few hours infusion is required to see them in pus, spurred barley, honey, drugs, &c.

There exists therefore, an organic matter, universally diffused in all animal and vegetable substances, which alike serves for their nutrition, their growth, and their reproduction. Nutrition is performed by the intimate penetration of this matter in all parts of the animal or vegetable body. Expansion or growth is only a kind of more extended nutrition, which is made and performed as long as the parts have sufficient ductility to swell and extend; and reproduction is made by the same matter when it superabounds in the body of the animal or vegetable; each part of the body sends back, to the appropriate reservoirs, the organic particles which exceed what are sufficient for their nourishment. These particles are absolutely analogous to each part from which they are sent back, because they were destined to nourish those parts from hence, when all the particles sent back from, collect together, they must form a body similar to the first, since each particle is like that part from which it was detached; thus it is that reproduction is effected in all kinds of trees, plants, polypuses, pucerons, &c. where one individual can produce its like; and it is also the first mode which Nature uses for the reproduction of animals which have need of the communication of different sexes; for the seminal liquors of both sexes contain all the necessary molecules for reproduction; but something more is required for its effectual completion, which is the mixture of these two liquors in some places suitable to the expansion of the foetus which must result therefrom, which place is the matrix of the female.

There are, therefore, no pre-existing germs, no germs contained one in the other, _ad infinitum_; but there is an organic matter perpetually active, and always ready to form, assimilate, and produce beings similar to those which receive it. Animals and vegetables, therefore, can never be extinct; so long as there subsist individuals the species will ever be new; they are the same at present as they were three thousand years ago, and will perpetually exist, by the powers they are endowed with, unless annihilated by the will of the Almighty Creator.

HISTORY OF MAN.