Of the Expansion, Growth, and Delivery of the Foetus, &c.
IN the expansion of the foetus, two different species of growth are distinguishable: The first, which immediately succeeds the formation of the foetus, is not uniform in all the parts of the animal. The nearer the foetus approaches to maturity, the growth of the parts is more proportional; and it is not till after the birth, that all the parts grow nearly in an equable manner. We must not imagine, that the foetus, at the time of its formation, has the exact figure of an adult. The small embryo, it is true, contains all the parts essential to a man; but they differ in their successive expansion.
In an organized body, like that of an animal, some parts may be supposed to be more essential than others; and though none of them are useless or superfluous, yet there are some to which others seem to owe their growth and disposition. Some parts may be considered as fundamental, without which the animal could not exist, and others as only superficial and accessory. The [303] latter seem to derive their origin from the former, and to be intended more for conferring symmetry and external ornament on the animal, than for enabling it to exist, or to perform the functions essential to life. These two different species of parts are successively expanded, and are almost equally apparent at the time of birth. But there are other parts, as the teeth, which arrive not at full maturity till several years after; and others, as the glandular bodies in the female testicles, the beard of males, &c. which appear not till the age of puberty.
To discover the fundamental and essential parts of an animal body, attention must be had 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, must necessarily be the most essential. Those, on the contrary, which are double, or more numerous, those which vary in size and position, and those which may be taken away without injuring or killing the creature, may be regarded as less essential, or more accessory to the animal machine. Aristotle mentions, that the only parts essential to all animals are those with which they take and digest their nourishment, and throw out the superfluous part of it from the body. The whole intestinal canal is indeed extremely simple, and no other part can supply its place. The head and back-bone are likewise simple parts, the po- [304] sition of which is invariable. The back-bone is the foundation of the animal frame; and the action and movements of most members of the body depend upon the spinal marrow which that bone contains. It is this part, also, together with the head, which appear first in the embryo. Now, these simple parts, which are first formed, are all essential to the existence and the form of the animal.
The double parts in an animal body are more numerous than the single parts; and they seem to be produced on each side of the single parts by a species of vegetation; for the double parts are similar in form, and different only in position. The left hand is perfectly similar to the right; but, if the left had was placed in the situation of the right, we could not perform the same actions with it. The same thing may be observed of all the double parts: They are similar in form, but differ in position, which is relative to the body of the particular animal; and, if a line were drawn, dividing the body into two equal parts, the position of all the similar parts would tend to this line as to a centre.
The spinal marrow, and the vertebrae in which it is inclosed, appear to be the real axis of all the double parts of the animal body, from which they seem to derive their origin, and to be only proportional branches issuing from this trunk or common base; for, in the young chick, we see the ribs shooting from each side of the [305] vertebrae as the small branches shoot out from the principal branch of a tree. In all embryos, the middle of the head and the vertebrae first appear; we then see, on each side of the vesicle which composes the middle of the head, to other vesicles which seem to proceed from the first: These two vesicles contain the eyes, and the other double parts of the head. In the same manner, we perceive an equal number of small tubercles issuing from each side of the vertebrae, which gradually extend, and form the ribs, and other double parts of the trunk. Lastly, the arms and legs appear like small tubercles on each side of the trunk. This first growth is very different from what afterwards takes place: It is the production of parts which appear for the first time; the growth which succeeds is only an expansion of parts already formed.
The order and symmetry of the double parts in all animals, their regular position, the equality of their extension and growth, and the perfect similarity of their structure, seem to indicate, that they derive their origin from the single parts; that a certain force resides in the single parts that acts equally on each side; or, which amounts to the same, they are the bases or fulcra against which the action of those powers that produce the expansion of the double parts is exerted; and that the action of these forces, both on the right and left sides, are precisely equal, and counterbalance each other. [306]
Hence we may conclude, that, if there is any defect, or redundance, in the matter destined for the formation of the double parts, as the forces are equal on each side, this defect or excess must take place both in the right and left sides. If, for example, for a defect of matter, a man has but two fingers in the right hand, in place of five, the same defect will appear in the left; if, from an excess of matter, there is six fingers in the right hand, he will have the same number in the left; or, if the matter be vitiated, and produces a change in the parts of one side, the same change will appear in the other. Of this fact we have daily proofs: The parts of monsters are always deranged in a certain order and proportion. Hence Nature, even in her errors, uniformly commits the least of possible mistakes.
This harmony in the position of the double parts of animals, is likewise apparent in vegetables. The branches push out smaller ramifications of each side; the small nerves in the leaves are equally disposed with regard to the principal nerve; and, if the symmetry appears to be less exact ion vegetables than in animals, this proceeds only from its being more various, and because its limits are more extensive, and less precise. But the same order is easily recognizable; and the single and essential parts are perfectly distinct from those which are double; [307] and it is evident, that the latter derive their origin from the former.
It is impossible to determine the form of these double parts before their expansion, or in what manner they are complicated, or what figure results from their position in relation to the single parts. The body of an animal, at the instant of its formation, unquestionably contains all the parts of which it ought to be composed: But the relative disposition of these parts is then very different from what afterwards appears. If we examine the expansion of a young leaf of a tree, we will find that it is plaited on each side of the principal nerve; and that its figure, at this time, has no resemblance to that which it afterwards assumes. When we amuse ourselves with plaiting paper, in order to give it the form of a crown, of a boat, &c. the different plaits of the paper seem to have no resemblance to the figure which results from their expansion: WE only perceive that the plaits are uniformly made in a certain order and proportion, and that, whatever is done on one side, is also done on the other. But, to determine the figures which may result from the expansion of any given number of folds, is a problem beyond the powers of geometry. The science of mathematics reaches not what immediately depends upon position. Leibnitz’s art of Analysis situs does not yet exist; though the art of knowing the relations that result from the posi- [308] tion of things would be, perhaps, more useful than that which has only magnitude for its object; for we have more occasion to be acquainted with form than with matter.
In the expansion of natural productions, the folded or plaited parts not only assume different positions, but they acquire, at the same time, extension and solidity. Since, therefore, we are unable to ascertain the exact result of a simple expansion of a folded figure, in which, as in folded paper, nothing takes place but a change of position among the parts, without any augmentation or diminution of the quantity of matter, how is it possible for us to judge concerning the expansion of the compound body of an animal, in which not only the relative position, but likewise the quantity of matter in these parts, suffer considerable changes? We can only reason, therefore, on this subject, by drawing conclusions from the examination of objects at different periods of their expansion.
We, indeed, perceive the chick in the egg before incubation: It swims in a transparent fluid, contained in a small purse formed by a very fine membrane in the centre of the cicatrice. But the chick is then only a particle of inanimated matter, in which no organization or determined figure can be distinguished. We can perceive, however, that one of its extremities is the head, and the other the back-bone. The embryo, in this state, seems to be the first pro- [309] duct of fecundation, resulting from the mixture of the male and female semen. To ascertain this fact, several things require attention: When the hen has, for some days, been along with the cock, and afterwards separated from him, the eggs produced 20 days or a month after this separation, are equally fertile as those laid during her cohabitation with the male. The eggs produced at the end of this period require only the usual time of 21 days in hatching; and their embryos are equally advanced both in form and consistence. From this circumstance we might be led to imagine, that the form in which the embryo appears before incubation, is not the immediate effect of the mixture of the two seminal fluids, ut that it existed in different forms during the abode of the egg in the body of the mother; for the embryo, in the form in which we see it before incubation, requires only the aid of heat in order to bring it to maturity. Now, if this form of the embryo had existed 21 days or a month before, when the egg was first impregnated, why was it not hatched by the internal heat of the mother? Why do we not find the chick compleatly [sic] formed in those eggs which have been impregnated 21 days before they are laid?
But this difficulty, though seemingly great, is not insurmountable. When the hen cohabits with the cock, the cicatrice of each egg, which contains the semen of the female, receives a small [310] quantity of the male fluid. The eggs in the ovarium of oviparous females are analogous to the glandular bodies in the testicles of the viviparous: The cicatrice of the egg corresponds to the cavity of those glandular bodies which contain the female semen; and that of the male penetrates and mixes with it. The formation of the embryo instantly results from this mixture or union of the two fluids. The first egg laid by the hen after her communication with the cock, is fecundated and capable of being hatched. Those which she is afterwards to lay were all impregnated at the same instant: But, as they want some essential parts, the production of which has no dependence on the male fluid; as they have neither the white, the membranes, nor the shell, the small embryos contained in the cicatrices of these imperfect eggs, are incapable of being hatched, though aided by the internal heat of the mother. The embryo, therefore, remains in the cicatrice, in the same state in which it was first formed, till the egg acquires all the parts necessary to the growth and nourishment of the foetus; and it is not till after the egg has arrived at full perfection, that the expansion of the embryo commences. This expansion is effected by the external heat of incubation: But it is unquestionable, that, if the egg could be retained in the body 21 days after it was completely formed, the chick would be hatched, unless the internal heat of the mother [311] was too great; for the degrees of heat necessary for hatching eggs are very limited; and the least excess or defect is equally fatal to this operation. The last eggs, therefore, laid by the hen, containing the embryos in the same state as the first, prove nothing more than the necessity of their acquiring full perfection before they can be hatched.
It is apparent, therefore, that the state of the embryo when the egg is laid by the hen, is its first state, and that which immediately succeeds impregnation; that it undergoes no intermediate changes of form; and consequently, by tracing, as Malpighius has done, its gradual expansion, hour after hour, we discover every thing that it is possible for us to know, unless we could perceive the mixture of the two fluids, and the manner in which the particles arrange themselves during the first formation of the embryo.
If we reflect on this instantaneous fecundation of a number of eggs, which are to be laid at successive intervals, we shall discover a new argument against the existence of eggs in viviparous animals: For, if women contained eggs, like hens, why are not many of them fecundated at the same time? Why does not one impregnation give birth to a successive race of children? And, when women conceive two or three children, why do they always come into the world at the same time? If these fetuses were produced [312] from eggs, would they not succeed each other according to the different states of perfection of the several eggs at the time of impregnation? And, would not superfoetations be as frequent as they are rare, and as natural as they are accidental?
It is impossible to trace the gradual expansion of the human foetus, as we can that of the chick in the egg. The opportunities for observation are few; and all we know of this subject is derived from the writings of anatomists, surgeons, and accoucheurs [sic]. It is from collecting all their particular observations, and comparing their remarks with their descriptions, that the follow abridged history of the human foetus has been compiled.
Immediately after the mixture of the two seminal fluids, it is probable that the whole materials of generation exist in the uterus under the form of a small globe; for we learn from anatomists, that, three or four days after conception, there is a small globular mass in the uterus, the greatest diameter of which is about 6 lines, and the least 4. This globe is formed by a delicate membrane, which contains a limpid liquor very like the white of an egg. We may already perceive, in this liquor, some small fibres [sic], which are the first rudiments of the foetus. Upon the surface of the globe there is a network of delicate fibres, which extends from one [313] of the extremities to the middle: These are the first vestiges of the placenta.
Seven days after conception, the lineaments of the foetus are distinguishable by the naked eye. They are, however, very imperfect, and have the appearance of a gelly [sic] almost transparent, though it has acquired some degree of solidity. The head and trunk may be easily distinguished; because this mass is of an oblong figure, and the trunk is longest and most delicate. Some small fibres, resembling a plume of feathers, issue from the middle of the foetus, and terminate in the membrane in which it is inclosed. These fibres are the rudiments of the umbilical cord.
Fifteen days after conception, the head and the most prominent features of the face are apparent. The nose resembles a small elevated thread perpendicular to a line which marks the division of the lips: Two small black points represent the eyes; and we see two holes in place of ears. The body of the foetus has also acquired some growth. On each side of the superior and inferior parts of the trunk those small protuberances appear, which are the rudiments of the arms and legs. The length of the whole body is about five French lines.
Eight days after, in all three weeks, the body of the foetus is only augmented about a line: But the arms and legs are apparent. The growth of the arms is quicker than that of the [314] legs; and the fingers separate sooner than the toes. The internal organization now begins to be visible: The bones appear like fine threads. The ribs are disposed on each side of the back-bone like minute threads: The arms, the legs, the fingers and toes, are also represented by similar threads.
At one month, the foetus is more than an inch in length: It naturally assumes a curved posture in the middle of the liquor that surrounds it; and the membranes in which the whole is included, are both augmented and thickened. The whole mass is of an oval figure, the greatest diameter of which is about an inch and a half, and the least about an inch and a quarter. The human figure is no longer equivocal: all the parts of the face are already distinguishable; the body is delineated; the haunches and the belly are prominent; the hands and legs are formed, and their fingers and toes are divided; the skin is thin and transparent; the viscera resemble a knot or plexus of fibres; the vessels are like fine threads, and the membranes are extremely delicate: The bones are still soft, and it is only in a few places that they have begun to assume some degree of solidity. The vessels which form the umbilical cord lie parallel to each other in a straight line. The placenta now occupies only a third of the whole mass, instead of a half, which it did during the first days; the superficial growth of the placenta, [315] therefore, has not been so great as that of the foetus and mass; but it has received a great augmentation in solidity; it has become proportionally thicker than the membranes of the foetus, both of which are now distinguishable.
According to Hippocrates, the male foetus expands sooner than the female.
At the end of six weeks, the foetus is about two inches long, and the human form begins to be more perfect, only the head is very large in proportion to the other parts of the body. About this time the motion of the heart becomes visible: In 50 days, the heart has been perceived to beat for a considerable time after the foetus was extracted from the uterus.
In two months, the foetus is more than two inches in length; and the ossification is perceptible in the middle of the two arm-bones, in the thigh and leg, and in the point of the under jaw, which is then greatly advanced before the upper. These, however, are only osseous points. But, by means of a quicker growth, the clavicles are entirely ossified: The umbilical cord in formed, and the vessels which compose it begin to twist like the threads of a rope: But this cord is very short in comparison of the length it afterwards acquires.
In three months, the foetus is nearly three inches long, and weights about three ounces. Hippocrates asserts, that at this time the motions of the male foetus begin to be felt by the mo- [316] ther; but that those of the female are not perceptible till four months. Some women, however, affirm that they have felt the motions of the foetus at the beginning of the second month. It is difficult to acquire any certain knowledge on this subject: The sensations excited by the first movements of the foetus depend more, perhaps, on the sensibility of the mother, than the strength of the child.
Four months and a half after conception, the length of the foetus is from six to seven inches. All the parts are greatly augmented, and easily distinguishable from each other: Even the nails appear on the fingers and toes. The testicles of the male are shut up in the belly above the kidneys. The stomach is filled with a thick fluid, similar to that which is contained in the amnios. In the small guts we find a milky fluid, and a black liquid matter in the great guts. There is a small quantity of bile in the vesica felis [sic], and a little urine in the bladder. As the foetus floats freely in the fluid that surrounds it, there is always some space between its body and the membranes in which it is contained. These membranes, at first, grow more rapidly than the foetus; but, after a certain time, the reverse takes place. Before the end of the third month, the head is bent forward; the chin rests on the breast; the knees are elevated, and the legs folded back upon the thighs. One of the hands, and often both, touch the face. Afterwards, [317] when the foetus acquires more strength, it perpetually changes its position, as we learn from the following observations made by persons skilled in the art of midwifery: 1. The umbilical cord is often twisted round the body and members of the child, in a manner that necessarily supposed different motions and positions. 2. Mothers feel the motion of the child sometimes on one side of the uterus, and sometimes on the other; and it often strikes against many different places, which could not happen unless it assumed different positions. 3. As the foetus swims in a fluid which surrounds it on all sides, it may easily turn, extend, and twist itself by its own powers: It must likewise take different situations, according to the various attitudes of the mother’s body; when the mother, for example, lies down, the position of the foetus must differ from what it is when she stands.
Most anatomists maintain, that the foetus is obliged to end its body, because it is too much confined by the membranes. But this opinion seems not to be well founded; for, during the first five or six months, at least, there is room more than sufficient to admit a full extension of the foetus; and yet, during all this period, the foetus is bended. We see likewise, that the chick is bended in the liquor of the amnios, while, at the same time, this membrane, and the fluid it contains, afford room sufficient to hold a body five or six times larger than the foetus. We [318] may, therefore, conclude that the bended posture of the foetus is natural, and not the effect of restraint. I am inclined to think, with Harvey, that the foetus takes this posture, because it is most favourable to rest and sleep; for all animals bend their bodies when they want to repose themselves, or to sleep: And, as the foetus sleeps almost continually, it naturally assumes this advantageous position. “Certe,” says this celebrated anatomist, “animalia omnia, dum quiescent et dormiunt, membra sua ut plurimum adducunt et complicant, figuramque ovalem ac conglobatam quaerunt: Ita partier embryones qui aetatem suam maxime somno transigunt, membra sua positione ea qua plasmantur (tanquam naturalissima ac maxime indolenti quietique aptissima) component.”*
The uterus, as formerly remarked, grows very quickly after pregnancy; and it continues to increase proportionally with the foetus. But the growth of the foetus at last exceeds that of the uterus; and it is natural to think, that the foetus, when near maturity, is too much confined, and agitates the uterus by repeated motions. The mother feels those successive efforts, which are called periodic pains, after the labour of child-bearing commences. The more force the foetus exerts in order to dilate the uterus, it finds an increased resistance from the natural elasticity of the parts. Hence every ef- [319] fort tends to open the os tincae [sic], or orifice of the uterus, which has already been gradually enlarged during the last months of pregnancy. The head of the foetus pushes along against the margins of this orifice, and dilates it by a constant pressure, till the moment of delivery, when it opens so wide as to allow a free passage to the child.
What renders it probable that the labour-pains are occasioned by the dilations of the os tincae is, that this dilation is the only certain mode of distinguishing the real from the false pains. Women often feel very brisk pains, which are not those that immediately precede delivery. To distinguish those false from the true pains, Deventer advises the accoucheur to feel the orifice of the uterus, and maintains, that, if the pains be true, the dilation will augment upon the occasion of every pain; and that, on the contrary, if the pains be false, the orifice will rather contract than dilate, or, at least, that it will not continue to dilate. Hence we may conclude, that these pains proceed not from a forced dilation of the orifice of the uterus. The only thing that is embarrassing, is the alternation of pain and of ease experienced by the mother. This circumstance does not perfectly correspond with the cause we have assigned; for the gradual and continued dilation of an orifice should produce a constant pain, without any intervals of ease. Perhaps the alternation [320] may be ascribed to the separation of the placenta: It adheres to the uterus by the insertions of a number of small papillae. May we not, therefore, suppose that these papillae separate not from their cavities all at once; and that the successive separation of these papillae gives rise, at different intervals, to the fresh accessions of pains? Here the effect perfectly corresponds with the cause; and this conjecture may be supported by another remark: Immediately before delivery, there issues out a viscous whitish liquor, similar to that which flows from the papillae of the placenta, when torn from the uterus. It is therefore extremely probable, that this liquor, which issues from the uterus, is produced by the separation of some of the papillae of the placenta.
It sometimes happens, that the foetus escapes from the uterus without bursting the membranes, and, consequently, without discharging the liquor they contain. This species of birth seems to be the most natural, and is similar to that of most animals. The human foetus, however, commonly pierces the membranes, by the resistance it meets with at the orifice of the uterus: And sometimes a part of the amnios, and even of the chorion, is brought away adhering to the head of the child like a cap. AS soon as the membranes are pierced or torn, the liquor, which is called the waters, runs out, and, by lubricating the vagina and orifice of the uterus, facilitates the passage of the child. After the discharge [321] of the waters, there is sufficient room left in the uterus for the midwife to return the child, when its position is unfavourable to the birth. After the child comes into the world, the delivery is not completed. The placenta and membranes still remain in the uterus; and the child is attached to them by means of the umbilical cord: They are easily brought away by the hand of the midwife; and sometimes the weight of the child is sufficient for that purpose. These organs, which were necessary to the existence of the foetus, become useless, and even noxious to the child, after its birth. They are, therefore, instantly disengaged from the child’s body, by casting a knot on the umbilical cord, about an inch from the navel, and by cutting the cord an inch above the ligature. In six or seven days, the remains of the cord dry up, and fall off close to the navel.
By examining the foetus before birth, we are enabled to form some ideas concerning the mechanism of its natural functions. There are organs necessary to it while in the womb of the mother, but which become useless immediately after birth. The better to comprehend these functions, we must explain more fully the nature of these accessory parts, the umbilical cord, the membranes, with the liquor 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 a vein: By [322] these the course of the circulation is lengthened; but the vein is larger than the arteries. At the extremity of the cord, each of these vessels divide into an infinite number of ramifications, and extend themselves between two membranes. They set off from the common trunk in such a manner, that the whole ramifications assume a round form, and are distinguished by the name of placenta, because they resemble a cake. The central part of the placenta is thicker than its edges: Its mean thickness is about an inch, and its diameter is eight or nine inches, and sometimes more. The external surface of it, which is applied to the uterus, is convex, and the internal surface is concave. The blood of the foetus circulates in the cord and in the placenta. The arteries of the cord proceed from two large arteries in the foetus, and carry the blood through all the arterial ramifications of the placenta; and the blood is collected and returned to the foetus by the venous branches of the placenta and the umbilical vein.
The concave surface of the placenta is covered with the chorion [sic]: Its convex surface is also covered with a soft membrane, which seems to be a continuation of the chorion, and is easily torn; and the foetus is inclosed in the double covering of the chorion and amnios. The figure of the whole is globular; because the intervals between the foetus and membranes are filled with a transparent fluid. This liquor is imme- [323] diately confined by the amnios, which is the internal membrane: It is thin and transparent, and folds itself into round the umbilical cord, at its insertion into the placenta, and continues to cover it the whole way to the navel of the foetus. The chorion is the external membrane; it is thick, spongy, and interspersed with blood-vessels. It consists of several coats, the outermost of which covers the convex surface of the placenta. It sends off duplicates to cover the papillae, which are inserted into the cavities at the fundus of the uterus, called lacunae. These insertions connect the foetus to the uterus.
Some anatomists have maintained, that the human foetus, like those of certain quadrupeds, was furnished with an allantois, a membrane destined for the reception of the urine; and they have pretended to have discovered it between the chorion and amnios, or in the middle of the placenta, at the root of the umbilical cord, under the form of a pretty large bladder; and that it received the urine by means of a long tube which made a part of the cord, and which opened at one end into the bladder, and, at the other, into the allantois, answering the same purposes as the urachus in other animals. They acknowledge, however, that the urachus of the human foetus is not near so large as in the quadrupeds; but they assert that it is divided into a number of small tubes, and that the urine passes into their cavities. [324]
To these facts are opposed the experience and observation of most anatomists. They seldom find any vestiges of an allantois either between the chorion and amnios, or in the placenta; nor do they perceive any urachus in the umbilical cord. A kind of ligament, indeed, runs from the external surface of the bottom of the bladder to the navel; but, when entering the cord, it become so delicate as to be almost reduced to nothing. Neither is this ligament commonly hollow; and we can perceive no corresponding aperture in the bottom of the bladder.
The foetus has no communication with the open air; and the experiments made upon the lungs demonstrate that they have never respired; for they sink in water, while those of infants, who have breathed, uniformly swim: The foetus, therefore, has no respiration in the womb of the mother; consequently, it can make no sound with its voice, and all the stories of children groaning and crying before birth must be regarded as fabulous. After the waters run off, however, the air may find admission into the cavity of the uterus, and the child may begin to respire before its birth. In this case, the child may cry, in the same manner as the chicken cries before the shell of the egg is broken, which it is enabled to do by means of the air lodged in a cavity between the external membrane and the shell: This air exists in all eggs, [325] and is produced by the fermentation of the matters they contain.*
The lungs in the foetus, having no motion, receive no more blood than is sufficient for their nourishment and growth: Another passage, therefore, is open for its circulation. The blood in the right auricle of the heart, instead of passing into the pulmonary artery, and, after circulating through the lungs, returning into the left auricle by the pulmonary vein, passes directly from the right to the left auricle, through an aperture called the foramen ovale, which is in the partition of the heart that separates the two auricles: The blood then enters the aorta, by the ramifications of which it is distributed to every part of the body; it is then taken up by the numerous branches of the veins, which gradually unite into one trunk, called the vena cava, that terminates in the right auricle of the heart. The blood contained in this auricle does not all pass through the foramen ovale; part of it escapes into the pulmonary artery, but it enters not into the body of the lungs; for there is a communication between the pulmonary artery and the aorta, by an arterial canal which leads immediately from the one to the other. It is by these means that the blood circulates in the foetus, without entering the lungs, which it does in children, in adults, and in all animals who respire. [326]
It has been imagined by some, that the blood of the mother passes into the body of the foetus, by means of the placenta and umbilical cord: They supposed, that the blood-vessels of the uterus opened into the lacunae, and those of the placenta into the papillae, and that they inosculated with one another. But this opinion is contradicted by experiment. When the arteries of the umbilical cord are injected, the liquor returns by the veins, without any of it escaping externally. Besides, the papillae can be drawn out of the lacunae in which they are lodged, without any extravasation of blood either from the uterus or placenta; from both there oozes out a milky matter, which, we have already remarked, serves for the nourishment of the foetus. It is probable that this liquor enters the veins of the placenta in the same manner as the chyle enters the subclavian vein; and the placenta, perhaps, performs the office of the lungs in maturating the blood. One thing is certain, that the blood appears much sooner in the placenta than in the foetus; and I have often observed, in eggs which had been sit upon for a day or two, that the blood appeared first in the membranes, and that their blood-vessels are numerous and large, while the whole body of the foetus, excepting the point where these blood-vessels terminate, is only a white transparent matter, in which there is not the least vestige of blood. [327]
It has been imagined that the liquor of the amnios is a nourishment received by the mouth of the foetus. Some have even pretended to have found this liquor in the stomach, and to have seen several fetuses who wanted the umbilical cord entirely, and others who had only a small portion of it, which had no connection with the placenta. But, in this case, may not the liquor have passed into the body of the foetus by the portion of the cord that remained, or even by the navel itself? Besides, other facts may be opposed to these: Foetuses have been found, whose lips were not separated; and others whose oesophagus had no aperture. To reconcile these facts, some anatomists have maintained, that the aliment passed into the foetus partly by the umbilical cord, and partly by the mouth. But none of these opinions seem to have any foundation. The question is not, how the foetus alone, but how the whole apparatus of generation, receive their growth and nourishment? for [sic] the placenta, the liquor, and the membranes, increase in bulk as well as the foetus; and, consequently, those instruments and canal employed for receiving and transporting nourishment to the foetus, are themselves endowed with a species of life. The expansion of the placenta and membranes is equally difficult to conceive as that of the foetus; and, it may be said, with equal propriety, that the foetus nourishes the placenta, as that the placenta [328] nourishes the foetus. At the commencement of growth, the whole mass floats in the uterus, without any adhesion; and, of course, the nourishment can only be conveyed by an absorption of the lacteous fluid contained in the uterus. The placenta appears first to attract this fluid, which it converts into blood, and transports by the veins into the foetus. The liquor amnii seems to be nothing but this milky fluid in a purified state, the quantity of which is augmented, by a similar absorption, in proportion to the growth of the membranes; and the foetus probably absorbs this liquor, which seems to be necessary for its growth and nourishment: For, it is worthy of remark, that the foetus, during the first two or three months, contains very little blood: It is as white as ivory, and appears like a congeries of lymph somewhat consolidated; and, as the skin is transparent, and all the parts extremely soft, the body of the foetus may be easily penetrated by the fluid in which it swims, and thus receive the matter necessary for its growth and expansion. It may indeed be supposed that the foetus afterwards receives nourishment by the mouth; because we find a liquor, similar to that of the amnios, in the stomach, urine in the bladder, and meconium, or excrement, in the intestines; and, as neither urine nor meconium appear in the amnios, it is natural to conclude, that no excrements are voided by the foetus, especially as some are born without having the [329] anus perforated, and yet large quantities of meconium are found in their intestines.
Though the foetus has no immediate connection with the uterus, but is only attached to it by the small external papillae of the placenta; though it has no communication with the blood of the mother, but, in some measure, is equally independent of her as the egg is independent of the hen which covers it; yet it has been maintained, that, whatever affects the mother, produces a similar effect upon the foetus, and that the impressions received by the former are communicated to the sensorium of the latter. To this imaginary influence have been attributed all those resemblances, monstrosities, and peculiar marks which appear on the skin of particular children. Many of these marks I have examined, and they uniformly appeared to be occasioned only by a derangement in the texture of the skin. Every mark must necessarily have a faint resemblance to something or other: But such resemblances, I am persuaded, depend more on the imagination of those who see them, than upon that of the mother. On this subject, the marvellous [sic] has been pushed to an extreme degree. The foetus has not only been said to bear the real representations of the appetites of the mother, but that, by a singular sympathy, the marks which represent strawberries, cherries, &c. assumed a deeper colour during the season of these fruits. A little attention, however, will [330] convince us, that these changes of colour are more frequent, and that they happen whenever the motion of the blood is accelerated, whether it be occasioned by the heat of summer, or by any other cause. The marks are always either yellow, or red, or black; because the blood gives these colours to the skin when it enters in too great quantities into the vessels. If these marks were occasioned by the appetites of the mother, why are not their forms and colours as various as the objects of her desires? What a multitude of strange figures would be exhibited, if all the whimsical longings of a mother were written upon the skin of the child?
As our sensations have no resemblance to the objects which excite them, it is impossible that desire, fear, horror, or any other passion or emotion, can produce real representations of the objects by which they are occasioned. An infant being, in this respect, equally independent of the mother, as the egg is independent of the hen that sits upon it, I should be equally induced to believe, that the imagination of a hen, which saw by accident a cock’s neck twisted, should produce wry-necked chickens from the eggs she was hatching, as that a woman, who saw a man broke upon the wheel, should produce, by the mere force of imagination, a child with all its limbs broken.
But, supposing this fact to be well attested, I still maintain that the imagination of the mother [331] could not be the cause of it: For, what is the effect of horror? An internal movement, or, if you please, a convulsion of the mother’s body, which might alternately compress and stretch the uterus. What would be the result of this commotion? Nothing similar to its cause; for, if the commotion was very violent, the foetus might be killed, wounded, or have some of its parts deranged: But how is it possible to imagine that this commotion should produce in the foetus any thing similar to the thoughts of the mother, unless we suppose, with Harvey, that the uterus possesses the faculty of conceiving ideas, and of realising [sic] them upon the foetus?
But, if the imagination of the mother has no effect upon the foetus, it may still be demanded, Why did this child come into the world with its members broken? Though a direct solution of a fact, which is both extraordinary and uncertain, is not to be expected; yet, I think, this question admits of a satisfactory answer. Phaenomena of the most uncommon kind, and which are but rarely exhibited, as necessarily happen, as those that are usual and frequent [sic]. Among the infinite combinations of which matter is capable of forming, arrangements of the most peculiar and extraordinary species must sometimes take place. Hence, out of the numberless children which daily come into the world, one may sometimes appear with two heads, with four legs, or with all its members broken. It is, [332] therefore, within the circle of nature, that a child, without the aid of the mother’s imagination, may be born with its arms and legs broken. This phaenomenon may have been exhibited oftener than once; the mother of this child may, during her pregnancy, have seen a man broken on the wheel; and the defects of conformation in the child may have been attributed to the impulse made, by this dreadful spectacle, upon the imagination of the woman. But, independent of this general solution, the fact may be explained in a more direct manner. The foetus, as formerly remarked, has nothing in common with the mother. Its functions, its organs, its blood, its movements, are all peculiar, and belong to itself alone. The only matter it derives from the mother, is the liquor or nutritive lymph which distills from the uterus. If this lymph suffers any change, if it be infected with the venereal virus, the infant is infected with same disease; and it is reasonable to think that all the diseases which proceed from viciated [sic] humours may be communicated from the mother to the child. We know that the small pox is communicated in this manner; and we have too many examples of children, immediately after birth, becoming victims of the debauchery of their parents. The venereal virus attacks the most solid parts of the bones; and it appears to act with more force upon the middle of the bones, which is the part where the [333] ossification first commence, and is, of course, the most hard and solid part. I conceive, therefore, that the infant in question has been affected with the venereal disorder while in the womb of its mother, and that this was the reason why it came into the world with its bones broken through the middle.
The same effect might be produced by the rickets: In the royal cabinet, there is a skeleton of a rickety child, the bones of whose legs and arms are joined in the middle by a callus: From inspecting this skeleton, it appears that its bones had been broken before birth, and afterwards reunited by a callus.
But we have dwelt too long upon a fact which credulity alone has rendered marvellous. Prejudice, especially that species of it which is founded in wonder, will always triumph over reason. It is needless to attempt to persuade women that the marks on their children have no connection with their ungratified longings. I have sometimes asked them, before the birth of a child, of what particular longings they had been disappointed, and, of course, what marks the child would bear? But I had only the satisfaction of perplexing, without convincing them.
The time of gestation is generally about nine months; but it is sometimes longer and sometimes shorter. Many children are born in the seventh and eighth, and some not till after the ninth month: But, in general, the births before [334] the ninth month are more frequent than those that exceed that term.
It is generally believed, that children born in the eighth month cannot live, or, at least, that more of them die than of those who come into the world in the seventh moth. This opinion appears to be paradoxical; and, if we consult experience, I believe it will be found to be erroneous. A child born in the eight month is more perfectly formed, and consequently more vigorous and lively, than one who is born in the seventh. This opinion, however, is very commonly received, and is founded on the authority of Aristotle: “Caeteris animantibus ferendi uteri unum est tempus, homini vero plura sunt; quipped et septimo mense et decimo nascitur, atque etiam inter septimum et decimum positis; qui enim mense octavo nascuntur, etsi minus, tamen vivere possunt.”* The beginning of the seventh month is the earliest term of delivery. If the foetus be rejected sooner, it dies, and is denominated an abortion. Thus the time of gestation is more various in the human species than in other animals; for it extends from the 7th to the 10th, and, perhaps, to the eleventh month.
We are assured by women who have had many children, that females remain longer in the womb than males. If this be true, it is not surprising that female children should sometimes be [335] born in the 10th month. When infants come into the world before the 9th month, they are neither so large nor so well formed as those who appear not till a later period. Those, on the contrary, who remain in the womb till the 10th month, are larger and better made; their hair is longer; the growth of the teeth, though still concealed within the gums, is more advanced; and the tone of their voice is deeper and more distinct.
With regard to the occasional causes of delivery, there is much uncertainty. It is imagined by some writers, that, when the foetus has acquired a certain size, the capacity of the uterus becomes too small for its retention, and that the restraint felt by the child obliges it to exert every effort to break its prison. Others alledge, which amounts nearly to the same thing, that the foetus becomes too heavy to be supported by the uterus, which, therefore, opens to be discharged of its load. Neither of these reasons appear to be satisfactory: The uterus has always sufficient capacity and strength to contain and support the weight of a child of nine months; for it is often loaded with two, during the same period; and it is certain, that the weight and size of two children of eight months, for example, exceed those of a single infant of the same age. Besides, it is not unfrequent that a child of nine months is less than another at eight months, though it still remains in the womb. [336]
Galen pretends that the foetus continues in the uterus till it is able to take nourishment by the mouth, and that the want of proper food makes it restless, and anxious to escape. It has been said by others, that the foetus is originally nourished by the mouth, but that, in process of time, the liquor amnii is so contaminated with the urine and transpiration of the foetus, that is becomes perfectly disgustful, and obliges the child to use every method to effect its escape from the womb.
These reasons seem not to be more satisfactory than the former; for from them it would follow, that the smallest and weakest fetuses would necessarily remain longer in the womb than those of large and more robust bodies; which is by no means the case. Besides, it is not for nourishment that the child, immediately after birth, seems to be anxious; for it can dispense with the want of it for a considerable time after: It appears, on the contrary, to be extremely desirous of easing itself of the superfluous load of nourishment (the meconium) received in the womb. This circumstance induced Drelincourt, and some other anatomists, to think, that the acrimony and uneasiness, arising from an accumulation of excrement in the bowels, is the reason why they become restless, and use every effort to escape from the womb. I am not, I acknowledge, more satisfied with this explication [337] than the others. If the child is pressed with faeces, why does it not evacuate them in the liquor amnii? But this never happens. It appears, on the contrary, that the necessity of evacuating the meconium is not felt till after birth, when the motion of the diaphragm, occasioned by respiration, compresses the intestines, and gives rise to this evacuation; especially since no meconium was found in the amnios of a foetus of ten months, who had not respired, and since an infant of six or seven months discharges the meconium soon after respiration.
Other anatomists, and particularly Fabricius ab Aquapendente, imagined that the foetus left the uterus, from a desire of being refreshed by respiration. But this cause seems to be as chimerical as any that has been mentioned. It is impossible that a foetus can have any idea of respiration; and far less can it have any conception whether respiration would be agreeable or disagreeable.
After considering all these hypotheses, I suspect that the delivery of the foetus depends on a cause of a very different nature. The menstrual flux returns at stated intervals. Though its appearance can be interrupted by impregnation, its cause is not destroyed; and, though no blood is exhibited at the accustomed period; yet a revolution in the system, similar to what happens before impregnation, must take place. It is for [338] this reason, that, in some women, the menses are not entirely suppressed during the first two or three months after conception. I imagine, therefore, that this periodic revolution happens as regularly after a woman has conceived as before; but that the blood is prevented from flowing, by the excretories of the uterus being swelled and shut up, unless when it arrives in such large quantities, and acts with such force, as to overcome the resistance which is opposed to it. In this case, a great quantity of blood rushes out, and an abortion is the consequence. But it frequently happens, that a small quantity of blood appears, without producing this effect; because the blood has only been able to open a few of the canals or excretories of the uterus, while the rest remain entirely obstructed.
Though no blood appears, which is generally the case, the first revolution fails not to be accompanied with the same painful symptoms. During the first suppression of the menses, therefore, the uterus is affected with a considerable agitation, which, when a little augmented, entirely destroy the product of generation. Hence, we may reasonably conclude, that few of those conceptions, which happen a short time before the accustomed return of the menses, are successful; because the action of the menstrual blood easily destroys the feeble roots of a germ so tender and so delicate. Those conceptions, on the contrary, which take place immediately [339] after this periodic discharge, succeed much better; because the foetus is allowed more time to grow, and to fortify itself against the action of the blood, when the next revolution happens in the system.
After the foetus has been enabled to resist the action of the first revolution, the increase of its growth, and of its attachment to the uterus, render it still more capable of resisting any of the subsequent revolutions: Abortions, indeed, sometimes happen during every revolution; but they are more rare in the middle period of gestation, than either at the beginning or near the end of it. Why they are more frequent at the beginning, has already been explained: It only remains to show why they are likewise more frequent towards the end.
The foetus generally comes into the world during the tenth revolution of the menses. When it is born at the ninth or eighth, it lives, and is not, therefore, regarded as an abortion. Some have pretended to have seen instances of children born at the seventh, and even at the sixth revolution, who, notwithstanding this unfavourable circumstance, continued to live. There is no difference between abortion and birth, but what relates to the living powers of the child. In general, the number of abortions in the first, second, and third moths, for the reasons already assigned, is very great; and the number of premature births, in the seventh and eighth months, [340] is also very great, in proportion to the abortions in the fourth, fifth, and sixth months; because, during this middle term of gestation, the product of generation having acquired strength and solidity sufficient to resist the action of the first four periodic revolutions, a more violent effort than any of the former is necessary to destroy it. For the same reason, an abortion is more difficult during the fifth and sixth months. But the foetus, which till now was weak, and could only exert is own force in a feeble manner, begins to move with more vigour; and, when the eighth revolution takes place, the efforts of the foetus uniting with those of the uterus, and facilitating its exclusion, the foetus may come into the world in the seventh month, and be in a capacity of living, whenever it happens to be unusually strong at this period. But, if the foetus be excluded solely from a weakness of the uterus, which renders it unable to resist the action of the blood during the eighth revolution, the birth of it is considered as an abortion, and the child dies. But such cases are uncommon; for, if the foetus has resisted the first seven revolutions, nothing but particular accidents can prevent it from resisting the eighth, unless it has acquired more vigour than is common at this period. A foetus which has acquired the same degree of strength, but at a later period, will be excluded at the ninth revolution; and those which require nine months in obtaining this degree of [341] strength, will be born at the tenth revolution, which is the most usual term. But, when the foetus acquires not this degree of strength and perfection in nine months, it will remain in the uterus till the eleventh, or even the twelfth revolution, that is, till the tenth or eleventh month: Of such late births many examples are recorded.
Other reasons, to confirm the opinion, that the menstrual flux is the occasional cause of births at different periods, may be produced. The females of all animals which have no menses, bring forth very nearly at the same terms: The difference in the times of gestation is extremely small. We may, therefore, conclude, that this variation, which is very great in women, proceeds from the action of the menstrual blood, which is exerted at every periodic revolution.
We have already remarked, that the placenta adheres to the uterus only by the papillae; that there is no blood either in these papillae, or in the lacunae in which they are inserted; and that, when they are separated, an operation which requires no great effort, a milky liquor only issues from them. Why, therefore, is the birth of a child uniformly followed by a considerable haemorrhage, first of pure blood, and afterwards of blood mixed with a watery fluid? This blood proceeds not from the separation of the placenta; for the papillae are drawn out of the lacunae [342] without any effusion of blood. Delivery, therefore, which is nothing more than this separation, ought to produce no haemorrhage. Is it not more natural, on the contrary, to think, that the action of the blood is the cause of the birth: and that it is this menstrual blood alone which forces the vessels of the empty uterus, and begins to flow immediately after delivery, in the same manner as it did before conception?
We know, that, for some time after conception, the sack which contains the product of generation, adheres not to the uterus. We have seen, from the experiments of De Graaf, that, by blowing upon the small globule, it is made to change its position. The adhesion to the uterus is never strong: In the early periods of gestation, the placenta is slightly applied to the uterus; and those parts are only contiguous, or joined by a mucilaginous matter which has hardly any adhesion. How, then, should it happen, that, in abortions of the first or second month, this globule never escapes without being attended with a great effusion of blood? This effusion cannot be occasioned by the passage of the globule, which has no adhesion to the uterus. It is by the action of the blood, on the contrary, that the globule is extruded. Should we not, therefore, conclude, that this is the menstrual blood, which, by forcing the canals through which it was accustomed to flow before impreg- [343] nation, destroys the product of conception, and resumes its ordinary course?
The pains of child-bearing are principally occasioned by this action of the blood; for, it is well known, that they are equally violent in abortions of two or three moths, as in ordinary births; and that many women feel, without having conceived, very acute pains, whenever the menstrual flux is about to appear. These pains are of the same kind with those which accompany abortions or births. Ought we not, therefore, to ascribe them to the same cause?
It appears, then, that the periodic revolution of the menstrual blood has great influence in child-bearing, and that it is the cause why the terms of delivery in women are more various than in other animals which are not subject to this discharge, and which always bring forth at the same times. It is also apparent, that the revolution occasioned by the action of the menstrual blood is not the only cause of birth: The action of the foetus itself contributes greatly to this end; for there are instances of children having made their escape from the uterus after the death of the mother, which could only happen from an exertion peculiar to the foetus.
The terms of gestation in cows, sheep, and other animals, are always the same, and no haemorrhage attends their delivery. May we not, therefore, conclude, that the blood discharged by women after delivery is the menstrual blood, and that the action of this blood upon the uterus, during every period revolution, is the reason why the human foetus is excluded at so many different terms? It is natural to imagine, that, if the females of viviparous animals had menses like women, their deliveries would be followed by an effusion of blood, and be equally various in their terms. The fetuses of animals are brought forth covered with their membranes; and it is seldom that the membranes are broken, or the waters flow before their delivery. But the birth of a child, with its membranes entire, is a rare phaenomenon. This circumstance seems to evince, that human fetuses make greater efforts to escape from their prison than those of other animals, or that the uterus of a woman affords not so free a passage to the child; for it is by the struggles of the foetus against the resistance it meets with at the orifice of the uterus, that the membranes are torn. [345]
* Harvey de Generat. p. 257 [back to page 319].
* See Vegetable Statics, chap. 6 [back to page 326].
* Vide de Generat. anim. 1. p. 4. c. ult [back to page 335].