There is much difference of opinion among anatomists as to the fibrous structure of the uterus. The majority however agree as to the presence of muscular fibres,[9] some considering that they always exist, while others, and by far the greater number, consider them as appearances peculiar to pregnancy: they are, it is true, extremely indistinct in the unimpregnated state, but they are far from being peculiar to pregnancy, as they are frequently developed by any circ.u.mstances by which the formative powers of the uterus are excited. Thus in cases where the uterus has been much distended by some anormal growth, its fibres become much developed and distinctly fasciculated. Lobstein observed them very distinctly in a uterus which had been distended to the size of a seven months' pregnancy by a fatty tumour.

The uterine fibres have been usually considered as fleshy, but they differ from the red fibres of voluntary muscles, in being of a paler colour, flatter, and remarkably interwoven with each other: nevertheless they appear to be really muscular fibres from the powerful contraction with which they expel the foetus and placenta, and nearly obliterate the cavity of the uterus. In the unimpregnated state they resemble the fibrous coat of an artery, whereas, those of the gravid uterus are more like the fibres of muscle. Most anatomists agree in describing two sets of fibres, viz.

longitudinal and transverse. The external layer of fibres appears to form the round ligaments, which seem to have the same relation with them as tendon and muscle. "The fibres arise from the round ligaments, and regularly diverging spread over the fundus until they unite and form the outmost stratum of the muscular substance of the uterus. The round ligaments of the womb have been considered as useful in directing the ascent of the uterus during gestation, so as to throw it before the floating viscera of the abdomen: but in truth it could not ascend differently; and on looking to the connexion of this cord with the fibres of the uterus, we may be led to consider it as performing rather the office of a tendon than that of a ligament."[10] "On the outer surface and lateral part of the womb, the muscular fibres run with an appearance of irregularity among the larger blood-vessels, but they are well calculated to constringe the vessels, whenever they are excited to contraction. The substance of the gravid uterus is powerfully and distinctly muscular, but the course of the fibres is less easily described than might be imagined: this is owing to the intricate interweaving of the fibres with each other--an intermixture however which greatly increases the extent of their power in diminishing the cavity of the uterus. After making sections of the substance of the womb in different directions, we have no hesitation in stating that towards the fundus the circular fibres prevail, that towards the orifice the longitudinal fibres are most apparent, and that on the whole, the most general course of the fibres is from the fundus towards the orifice.

"This prevalence of longitudinal fibres is undoubtedly a provision for diminishing the length of the organ, or for drawing the fundus towards the orifice. At the same time these longitudinal fibres must dilate the orifice and draw the lower part of the uterus over the head of the child.

"In making sections of the uterus while it retained its natural muscular contraction, I have been much struck in observing how entirely the blood-vessels were closed and invisible, and how open and distinct the mouths of the cut blood-vessels became when the same portions of the uterus were distended or relaxed. This fact of the natural contraction of the substance of the uterus closing the smallest pore of the vessels, so that no vessels are to be seen, where we nevertheless know that they are large and numerous, demonstrates that a very princ.i.p.al effect of the muscular action of the womb is the constringing of the numerous vessels which supply the placenta, and which must be ruptured when the placenta is separated from the womb."

"Upon inverting the uterus, and brushing off the decidua, the muscular structure is very distinctly seen: the inner surface of the fundus consists of two sets of fibres, running in concentric circles round the orifices of the Fallopian tubes; these circles at their circ.u.mference unite and mingle, making an intricate tissue. Ruysch, I am inclined to believe, saw the circular fibres of one side only; and not adverting to the circ.u.mstance of the Fallopian tube opening in the centre of these fibres, which would have proved their lateral position, he described the muscle as seated in the centre of the fundus uteri. This structure of the inner surface of the fundus of the uterus is still adapted to the explanation of Ruysch, which was that they produced contraction and corrugation of the surface of the uterus, which, the placenta, not partaking of, the cohesion of the surface was necessarily broken. Farther, I have observed a set of fibres on the inner surface of the uterus, which are not described: they commence at the centre of the last described muscle, and having a course in some degree vortiginous, they descend in a broad irregular band towards the orifice of the uterus: these fibres co-operating with the external muscle of the uterus, and with the general ma.s.s of fibres in the substance of it, must tend to draw down the fundus in the expulsion of the foetus, and to draw the orifice and lower segment of the uterus over the child's head." (C. Bell, _op. cit._)

There are other circ.u.mstances which prove the muscularity of the uterus, beyond the mere evidence of its fibres, as seen during pregnancy. "In the quadruped," as Dr. Hunter observes, "the cat particularly and the rabbit, the muscular action or peristaltic motion of the uterus is as evidently seen as that of the intestines, when the animal is opened immediately after death." It is also proved by the powerful contraction which it exerts during labour, and "by the thickness of the fibres corresponding with their degree of contraction." (_Ibid._)

The inner surface of the uterus is lined by a smooth or somewhat flocculent membrane of a reddish colour, which is continued superiorly into the Fallopian tubes; inferiorly it becomes the lining membrane of the v.a.g.i.n.a.

Mucous follicles are only found in the cervix, especially at its lower part: when by chance these become inflamed, the orifice closes, and the follicle becomes more or less distended by a collection of thin fluid. The mucous casts of these follicles have been known by the name of _ovula Nabothi_, having been mistaken by an old anatomist for Graafian vesicles, which had been detached from the ovary, and conveyed into the cavity of the uterus.

The mucous membrane which lines the cervix uteri is corrugated into a number of rugae, between which the mucous follicles are chiefly found.

[Ill.u.s.tration: Uterus duplex.]

Before quitting this subject, it will be necessary to point out the changes which the uterus presents at different periods of foetal life, and the great resemblance it has at these periods to the uterus, as it appears in the lower cla.s.ses of the mammalia. We may, however, observe in the first place, that the uterus is not found to exist as a separate organ until we come to the cla.s.s mammalia; and even in the lower genera of this cla.s.s it bears a strong resemblance to the tubular character of the generative organs in the inferior cla.s.ses of animal life. The nearest to the tubular uterus, and where the transition from the oviduct in birds, &c. to the uterus in mammalia is least distinctly marked, is in the _uterus duplex_. Although the uterus is double, there is but one v.a.g.i.n.a into which the two ora uteri open; its low grade of development is marked by the resemblance which each uterus bears to an intestinal tube: there are as yet no traces of a cervix, each os uteri merely forming a simple opening at the lower end of what is little more than a cylindrical ca.n.a.l.

We do not find that thickening at the lower extremity of the uterus which distinguishes the cervix in the higher mammalia. This species of uterus is found among a large portion of the rodentia, and is also occasionally met with as an abnormal formation in the human subject. The next grade of uterine development appears under the form of the _uterus bicollis_. The double os uteri here ceases to exist, and the division begins a little higher up, so that the two cavities of the uterus communicate for a short s.p.a.ce: the ova, however, do not reach the common cavity, but remain each in its separate cornu. In this form of uterus, the os uteri is not only single, but the lower portion is thickened, although it has not yet formed a distinct neck or cervix; it is met with among some of the rodentia, and also certain carnivora.

[Ill.u.s.tration: Uterus bicollis.]

[Ill.u.s.tration: Uterus bicorporeus.]

In the _uterus bicorporeus_, the union of the cornua is higher up, so that the lower portion is single, while the upper part alone is double, consisting of two strongly curved cornua. This conformation is peculiar to ruminating animals. If two ova be present they are separate from each other, each being contained in its own distinct body or cornu, but a portion of the membranes extends along the common cervix, from one body to the other.

[Ill.u.s.tration: Uterus bifundalis.]

A still higher grade is the _uterus bifundalis_, where the fundus alone is double, the cornu being formed only by this portion. This formation is observed in the horse, a.s.s, &c.: the common cavity is here the receptacle of the ovum, so that in the unimpregnated state, the cornua appear only as appendices, into which a portion of the membranes extend.

In the _uterus biangularis_, the double formation has nearly disappeared, except at the fundus, where the uterus imperceptibly pa.s.ses into the tubes: this is the case among the edentata, and some of the monkey tribes.

The highest grade is the _uterus simplex_: every trace here of the double form is lost; the fundus no longer forms an acute angle, where it bifurcates into two cornua; but is convex. We now for the first time see the divisions of the uterus into body and cervix distinctly marked.

[Ill.u.s.tration: Uterus biangularis.]

The human uterus presents a similar variety of forms, as it gradually rises in the scale of development during the different periods of utero-gestation. It is at first divided into two cornua, and usually continues so to the end of the third month, or even later; the younger the embryo the longer are the cornua, and the more acute the angle which they form; but even after this angle has disappeared, the cornua continue for some time longer.

[Ill.u.s.tration: Uterus simplex.]

The uterus is at first of an equal width throughout; it is perfectly smooth and not distinguished from the v.a.g.i.n.a either internally or externally by any prominence whatever. This change is first observed when the cornua disappear and leave the uterus with a simple cavity. The upper portion is proportionably smaller, the younger the embryo is. The body of the uterus gradually increases, until at the period of p.u.b.erty it is no longer cylindrical, but pyriform: even in the full-grown foetus the length of the body is not more than a fourth part of the whole uterus; from the seventh even to the thirteenth year it has only a third, nor does it reach a half until p.u.b.erty has been fully attained. The os tincae or os uteri externum first appears as a scarcely perceptible prominence projecting into the v.a.g.i.n.a; it increases gradually, in size until the latter months of gestation, when the portio v.a.g.i.n.alis is relatively much larger than afterwards.

The parietes of the uterus are thin in proportion to the age of the embryo. They are of an equal thickness throughout at first: at the fifth month, the cervix becomes thicker than the upper parts; between five or six years of age, the uterine parietes are nearly of an equal thickness, and remain so until the period of p.u.b.erty, when the body becomes somewhat thicker than the cervix.

As the function of menstruation with its various derangements will be considered among the diseases of the unimpregnated state, we proceed to consider these changes which the uterus undergoes during pregnancy as well as during and after labour: these are very remarkable both as regards its structure, form, and size.

Shortly after conception, and before we can perceive any traces of the embryo, the uterus becomes softer and somewhat larger, its blood-vessels increased in size, and the fibrous layers of which its parietes are composed looser and more or less separated. The internal surface when minutely examined has a flocculent appearance, and very quickly after conception becomes covered with a whitish paste-like substance, which is secreted from the vessels opening upon it; this pulpy effusion soon becomes firmer and more dense; it bears a strong a.n.a.logy to coagulable lymph, and forms a membrane which lines the whole cavity of the uterus, and which in the course of a few weeks (from changes to be mentioned hereafter) crosses the os uteri and thus closes it. The uterine cavity in a short time becomes still farther closed by the ca.n.a.l of the cervix being completely sealed, as it were, by a tough plug of gelatinous matter which is secreted by the glandules of that part.

The structure of the uterus becomes remarkably altered; its fibrous structure is much more apparent; in fact, it is only during pregnancy, or when the uterus has been distended by some anormal growth, that we are able to detect the uterine fibres with any degree of certainty. This has led some anatomists to consider that they are only formed at such periods, a supposition which is not very probable; at any rate they now become very distinct: hence the uterus does not owe its increasing size to mere extension, but it evidently acquires a considerable increase of substance, a fact which is not only proved by examining the contracted uterus after labour at the full period, but also by comparing its weight with that of the unimpregnated organ. The adult virgin uterus weighs about one ounce, whereas the gravid uterus at the full term of pregnancy, when emptied of its contents, weighs at least twenty-four ounces, showing that there has been an actual increment of substance in the proportion of one to twenty-four. Having ascertained this point, it next becomes a question, whether the parietes of the gravid uterus increase in thickness during pregnancy, or whether they become thinner. Meckel, who is one of the greatest modern authorities on these subjects, states that from careful admeasurement of sixteen gravid uteri at different periods of gestation, he finds the parietes become thicker during the first, second, or third months, but after this period they become gradually thinner up to the full time: they are thicker in the upper parts of the uterus, whereas inferiorly they are a third or nearly a half less.

Nothing proves the actual increase of bulk and substance in the uterus more than its appearance when contracted immediately after labour at the full term; it forms a fleshy ma.s.s as large as the head of a new-born child, the parietes of which are at least an inch in thickness.

"The spongy or cellular tissue (says M. Leroux) becomes considerably developed during pregnancy, and its porous cells increase in proportion as the uterus dilates, more especially at the fundus and the spot where the placenta is attached, where they become so large as to admit a goosequill.

The internal membrane is pierced with numerous orifices, of which some are the mouths of arteries, and others communicate with the cells already mentioned. This membrane also during pregnancy forms those irregular tufted rugae, which serve to give a more intimate connexion between the uterus and the placenta. In the unimpregnated uterus and in the intervals between the menstrual periods the little orifices which are observed in the lining membrane of the uterus contain only a transparent lymph, which lubricates the interior of the uterus; during the appearance of the menses they contain blood, and during pregnancy they are connected with the vessels of the placenta and chorion."[11]

There is no circ.u.mstance in which the gravid uterus differs more from the unimpregnated than in the size and termination of its blood-vessels. The arteries, both spermatic and hypogastric, are very much enlarged. The hypogastric is commonly considerably larger than the spermatic, and we very often find them of unequal sizes in the different sides. They form a large trunk of communication all along the side of the uterus, and from this the branches are sent across the body of the uterus both before and behind. The cervix uteri has branches only from the hypogastrics, and the fundus only from the spermatics; or, in other words, the hypogastric artery gives a number of branches to the cervix, besides sending up the great anastomosing branch, and the spermatic artery supplies the tube and fundus uteri before it gives down the anastomosing branch on the lateral parts of the uterus. All through the substance of the uterus there are infinite numbers of arteries large and small, so that the whole arterial system makes a general network, and the arteries are convoluted or serpentine in their course.[12] Hardly any of the larger arteries are seen for any length of way upon the outside of the uterus. As they branch from the sides where they first approach the uterus, they disappear by plunging deeper and deeper into its substance.

The arterial branches which are most enlarged are those which run towards the placenta, so that wherever the placenta adheres, that part appears evidently to receive by much the greatest quant.i.ty of blood, and the greatest number both of the large and small arteries at that part pa.s.s through to the placenta, and are necessarily always torn through upon its separation. The veins of the uterus would appear to be still more enlarged in proportion than the arteries. The spermatic and hypogastric veins in general follow the course of the arteries, and like them anastomose on the side of the uterus. From thence they ramify through the substance of the uterus, running deeper and deeper as they go on, and without following precisely the course of the arterial branches. They form a plexus of the largest and most frequent communications which we know of in the vessels of the human body, and this they have in common with the arteries that their larger branches go to, or rather come from, that part of the uterus to which the placenta adheres: so that when the venous system of the uterus is well injected, it is evident that that part is the chief source of returning blood. Here, too, both the large and small veins are continued from the placenta to the uterus, and are always necessarily broken, upon the separation of these two parts. As I know no reason for calling the veins of the uterus sinuses, and as that expression has probably occasioned much confusion among the writers upon this subject, I have industriously avoided it.[13]

The form of the uterus changes considerably during pregnancy: the upper part appears to increase in greater proportion than the lower, a fact which appears to be proved from the alteration which takes place in the relative position of the Fallopian tubes, which are situated much lower down the sides of the uterus at full term than in the unimpregnated state, nor do they entirely regain their former position after labour, until the female has attained an advanced age; hence as the cervix diminishes in length during the latter half of pregnancy, it follows that the difference in point of size between the fundus and the body of the uterus, and this part will be continually increasing.

As the uterus increases, the fundus of course rises and can be felt through the distended abdominal parietes: its anterior surface, especially in the latter month of pregnancy, lies immediately behind the anterior wall of the abdominal cavity, and pushes the small intestines upwards, backwards, and to the sides.

The form of the gravid uterus differs also from that in the unimpregnated state in other respects, and this difference appears to depend in great measure upon its increase of size, and upon the form of the cavities which it occupies. Thus in the unimpregnated state when it occupies the cavity of the pelvis, its anterior surface which corresponds to the bladder is flattened; whereas its posterior surface, which is turned towards the hollow of the sacrum, is convex; it is however the reverse during the latter half of pregnancy. The anterior surface is now strongly convex, being merely covered by the yielding anterior wall of the abdomen; whereas posteriorly the uterus is nearly concave, corresponding to the solid convexity of the lumbar vertebrae, a fact which may be easily ascertained by examining the abdomen of a patient in the last month of pregnancy while lying down. The situation and position of the uterus are also changed in the unimpregnated state; the fundus is inclined somewhat backwards, the os uteri being nearly in the centre of the pelvic cavity, but the gravid uterus during the latter half of pregnancy has its fundus strongly inclined forwards and the os uteri directed backwards towards the upper part of the hollow of the sacrum.[14]

A minute and intimate knowledge of the changes and appearances which the uterus presents at every period of pregnancy, is essential to the diagnosis and treatment of the various derangements to which this process is subject. The numerous and important questions in medical jurisprudence connected with pregnancy can alone be determined by its means; and it is only by more close and attentive observation of every step in the gradual development of the uterus up to the full term of gestation, that we can expect to increase our means of forming a correct and certain diagnosis in those cases of doubtful pregnancy, where not merely professional reputation is more or less at stake, but the character, happiness, and even life of the individual upon whose case we are required to decide.

During the first month of pregnancy the changes are not very appreciable upon examination during life. The uterus has become larger, softer, and more vascular, much as it does during a menstrual period. The portio v.a.g.i.n.alis of the cervix, which in the unimpregnated state is hard and almost cartilaginous to the feel, becomes softer and larger:[15] the transverse fissure which the os uteri forms is more oval.

In the second month, the abdomen becomes somewhat flat: the portio v.a.g.i.n.alis can be now reached by the finger with greater ease than at any time of pregnancy, which is not from the uterus itself being lower in the pelvis, but from not yet having altered its position; any increase of its size therefore will cause its inferior extremity to be felt lower down and nearer to the os externum. The os uteri has undergone a considerable change, inasmuch as its edges have lost their lip-like figure; they now form a ring or rather dimple-like concavity at the lower end of the cervix, its ca.n.a.l being closed by the gelatinous plug already mentioned.

In primiparae, or women pregnant for the first time, the margin of the os uteri thus closed is not only circular but perfectly smooth; whereas in multiparae, not only is the cervix usually larger in every direction, but the os uteri itself is larger, thicker, and of an irregular shape; it is also knotty here and there from little callous cicatrices, where its edge has been torn in former labours.

In the third month of pregnancy the uterus rises above the brim of the pelvis. A slight protrusion of the abdomen may be sometimes observed above the p.u.b.es; the os uteri is not reached so easily as in the preceding month. The alteration which takes place in the situation of the uterus during the third month appears to result from gradual shortening of the broad ligament as it increases in size. As the uterus rises it pushes up that portion of the small intestines which rests upon it; these however being confined by the mesentery to the spine, and therefore prevented ascending before the uterus, at length slip down behind it, and the fundus being freed from the superinc.u.mbent pressure rises in a direction upwards and forwards into the cavity of the abdomen. The direction of the uterus becomes much altered; the os uteri is no longer in the middle of the pelvic cavity, but inclines towards the upper part of the hollow of the sacrum, whereas the fundus approaches more and more to the anterior parietes of the abdomen.

In the fourth month, the fundus uteri has risen about two or three fingers' breadth above the symphysis pubis; this is not very easily ascertained even in a thin person, still less where the patient is stout and the parietes of the abdomen therefore thick. The directions which the celebrated Roederer has given for making an examination of the abdomen during the early months of pregnancy, are well worthy of notice. Having evacuated the bladder and r.e.c.t.u.m, the patient should be placed in a half-sitting posture with the knees drawn up, so as to relax the abdominal parietes as much as possible: she must then breathe slowly and deeply; and if the hand be suddenly pressed against the abdomen a little above the symphysis pubis, at the moment of her making a full expiration, we shall in all probability feel the hard globe of the uterus.

In the fifth month, the fundus will be felt half way, or a little more, between the symphysis pubis and umbilicus. The increased size of the abdomen cannot be concealed by the dress; the portio v.a.g.i.n.alis has become distinctly shorter, and the os uteri is situated higher in the pelvis and more posteriorly.

In the sixth month, the fundus has risen as high as the umbilicus; the irregular folds of the skin which form the fovia umbilici or navel depression begin to disappear; the first perceptible movements of the child may occasionally be felt; the portio v.a.g.i.n.alis has lost half its length, being scarcely half an inch in length.

[Ill.u.s.tration: Cervix uteri about the sixth or seventh month.]

In the seventh month, the fundus rises an inch or so above the umbilicus, the folds of which have nearly disappeared. In some cases it begins to protrude, forming a species of umbilical hernia: this varies a good deal in different individuals, being more marked in primiparae; whereas in women, whose abdomen has been distended in previous pregnancies, little or no convexity of the navel is produced until a later period, and not always even then, the umbilical depression being merely diminished in point of depth, and its folds not so strongly marked. The movements of the child are now perfectly distinct; the portio v.a.g.i.n.alis is still shorter, and approaches more and more to the upper part of the hollow of the sacrum.

The anterior portion of the inferior segment of the uterus, or that part which extends from the os uteri towards the symphysis pubis, is now considerably developed and convex, and on pressing the point of the finger against it, the presenting part of the child will be felt. When this is the head as is usually the case, it will feel like a light ball which rises when pushed by the finger, but which, if the finger be held still, in a few moments descends and may again be felt.

[Ill.u.s.tration: Cervix uteri in the eighth month.]

In the eighth month, the fundus has risen half way between the umbilicus and the scrobiculus cordis. The abdomen has increased considerably in size, and has become more convex; the umbilical depression in primiparae has entirely disappeared. The portio v.a.g.i.n.alis is still shorter, being barely a quarter of an inch in length. The os uteri is so high up as not to be reached without difficulty; the presenting part of the child can be distinctly felt.

[Ill.u.s.tration: Cervix uteri in the ninth month.]

In the ninth month, the fundus has reached nearly to the scrobiculus cordis, and by the end of the month is quite in it; this is more especially the case with primiparae: the anterior parietes of the abdomen not allowing the fundis to incline so strongly forwards, the oppression of breathing is therefore more marked in them than in multiparae, for the fundus uteri rising so high prevents in great measure the action of the diaphragm, so that the chest is expanded by other muscles; hence the shortness of breath and inability of moving, so frequently complained of at this period of utero-gestation. The portio v.a.g.i.n.alis is still shorter, and in the primipara forms little more than a soft cushiony ring which marks the os uteri. The inferior part of the uterus is becoming more spherical, and is usually occupied by the presenting part of the child: this latter is no longer so moveable as before, its size as also its weight being evidently increased. That portion of the uterus which extends between the symphysis pubis and os uteri is now not only more convex but lower in the pelvis than the os uteri itself.

During the last four weeks of pregnancy a considerable change is observed.