CHAPTER II.

STRUCTURE OF THE PRINCIPAL ORGANS AND PARTS.

[Illustration: PLATE IV.

Vertical Section of the Womb and Vagina, natural size.

_a. a. a._ The solid walls of the Womb cut through. _b._ That part of the cavity, or hollow of the Womb, which is in the fundus, or top. _c._ That part of the cavity which is in the lower part, or neck, of the Womb. _d._ The Vagina. _e. e._ The cut edges of the Vagina. _f. f._ The positions of the Fallopian Tubes, which are cut off, and down the passages of which two needles are passed. _g._ The Os Tincæ, or Mouth of the Womb.]

In addition to the general explanation already given, there are some of the Female organs whose peculiar structure requires to be more fully noticed, on account of its important influence on some of the processes hereafter to be described.

THE WOMB.

The external appearance of the womb, viewed in front, and in connection with its appendages, is shown in Plate III. It is placed in the Pelvis, between the bladder and the Rectum, and at the top of the Vagina, as seen in Plates I and II. Its internal structure is represented in Plate IV.

The length of the Womb, after puberty, is about three inches; its breadth at the upper part, or fundus, about two inches; and at the cervix, or neck, about one inch. The cavity in the interior is small, owing to the thickness of the walls, and its form is triangular. The shape of the Womb resembles a pear, somewhat flattened, from before backward. Previous to puberty its size is much smaller, and with those who have had children it often exceeds the dimensions we have given.

The _Neck_, or narrow part, (_c._ Plate IV.) is much changed by pregnancy. In virgins it is long and pointed, and somewhat enlarged in the middle. In those who have borne children it is considerably shorter, more obtuse, and less regular in its form. The cavity in the Neck is larger in the middle than at either end, as will be seen in Plate IV.

The _Os Tincæ_, or mouth of the Womb, also undergoes considerable change from the same cause. In the young person it is merely like a small slit, scarcely to be felt, but after pregnancy it much enlarges, and remains more or less permanently open. The anterior lip, or the one in front, is somewhat larger than the posterior one.

The body of the Uterus is formed of a very dense, gray colored, muscular substance, possessing astonishing contractile power. The interior is lined, like the Vagina, with a mucus membrane, and the whole organ is plentifully supplied with arteries, veins, and nerves.

One of the most remarkable properties of the Womb is that of being able to distend to an extraordinary degree, and then retract again to nearly its original size. The force which it sometimes exhibits during its contraction is very great, being sufficient to separate, and even break, the bones of the mother's pelvis, and paralyze the hand of the operator when introduced. The Muscular Fibres on which this contractile force depends are most obvious during gestation; they then appear very numerous, and very curiously disposed, some of them ramifying in almost every direction, as will be seen by Plates V, VI. It is owing to this that the Womb contracts in every conceivable direction, and thus presses, during labor, on every part of the child's body.

PLATE V.

Figures 1 and 2.

Fig. 1. In this plate represents the Muscular Fibres a little exaggerated, so that they can be more distinctly seen.--_a. a._ are the orifices of the Fallopian Tubes.

Fig. 2. Represents the natural appearance, the fibres not being quite so distinct, though sufficiently obvious.--_a. a._ The orifices of the Fallopian Tubes.

In both Figures the Womb is supposed to be turned inside out, its peculiar structure being more readily seen interiorly than exteriorly.

[Illustration: Plate V.

The Muscular Fibres of the Womb.]

PLATE VI.

Figures 1 and 2.

Fig 1. This represents the appearance of the Fibres externally, and shows how they terminate in the round ligament a. b.

Fig. 2. The lines _a. b._ represent the direction of the force of the Fundul Fibres; _c. d._ That of the Circular Muscles of the body of the Uterus; _d. e._ The combined force of the Muscles.

The dotted lines represent the force reflected by the liquor amnii. The dotted curved lines the direction of the circular fibres of the body of the Uterus.

[Illustration: Plate VI.

The Muscular Fibres of the Womb.]

THE VAGINA.

The Vagina (_c._ Plate I.) is a membranous canal, lined with a mucus membrane like the Uterus. By its upper part it is attached to the neck of the Womb, at about two-thirds of its height--so that two-thirds of the neck hang within the Vagina. Below, it terminates in the Vulva, or external mouth. The upper part of the Vagina is much larger than the lower part, particularly in those who have borne children. It is capable of considerable distension, and after retraction, to allow of the child passing down it from the Womb. The external mouth is called the _Vulva_, and is usually partly closed, in the virgin state, by the membrane called the Hymen, (_n._ Plate I.) The length of the Vagina is from three to five inches, and its diameter from one inch to one and a half, or even two inches in those who have borne many children.

THE VULVA.

This is the external opening, or mouth of the Vagina, through which the child has to pass at the termination of delivery. The external and internal lips, with the muscular and membranous tissue surrounding it, are all capable of great distension, without injury, to allow of the passage of the child.

THE PERINEUM.

This is the part situated between the Vulva and the Rectum. (_p._ Plate I.) It is composed of a somewhat dense and firm substance, chiefly muscular, and, like all the other parts mentioned, is capable of great distension. It is important, in many of the manipulations during labor, to be well acquainted with it; and when the child's head is passing the perineum requires supporting, to prevent its being lacerated or broken through, an accident which often happens from want of due attention, and which leads to the most serious consequences.

THE PELVIS.

The Pelvis is that part of the bony structure, or skeleton, of the female, in which the generative organs are placed, and through which the process of parturition is effected. An acquaintance with its natural structure, and with the changes which may be produced in its form and size, by disease and other accidents, is indispensable to those who wish to practise or understand midwifery.

In early life the Pelvis is composed of several bones, many of which, after puberty, grow together. In the adult female it is customary to speak of but _four_ bones, the sacrum, the coccygis, and the two innominata, or hip bones, (see Plates VII, VIII.) In the young female these are divided into several distinct parts.

PLATE VII.

_Bones of the Pelvis._

_The four principal bones, as found in Mature life._--A. A. The Ossa Ilii, or Ossa Innominata, commonly called the haunch, or hip bones.--B. The Os Sacrum, or lower part of the back bone.--C. The extreme termination of the back bone, called the Os Coccygis.

_The divisions into parts, as in Early life._--The Ilium, A, on each side, is in three parts; the Ilium, properly so called, marked _a. a._; the Pubis, marked _b. b._; and the Ischium, marked _c. c._ The Sacrum is in five parts, marked 1, 2, 3, 4, 5.

_d._ Is the last bone of the spine, which joins the Sacrum.--_e. e._ Are the Sockets in which the upper parts of the thigh bones fit, forming the hip joints.--_g. g._ The two rings, formed by the bones of the Pubis and Ischium, each called the Foramen Magnum.

[Illustration: Plate VII.

Bones of the Pelvis.]

[Illustration: PLATE VII.--_a._

This represents the Male Pelvis, to show the difference in structure.

The letters correspond with those in Plate VII.]

[Illustration: PLATE VIII.

Section of the Pelvis, to show the shape and connection of those parts not distinctly visible in the full view. The section is made down the middle of the back bone, and through the symphysis pubes, in front. The letters correspond with those in Plate VII.

A. The right Ilium.--B. The Sacrum.--C. The Coccygis.--_b._ The Os Pubis.--_c._ The Os Ischinum.--_g._ The Foramen Magnum.--_o._ shows the manner in which the coccygis is bent back through labor.]

These bones are all firmly bound together by a cartilaginous substance, which is placed between where they touch, and is firmly attached to each one. This union is called a _symphysis_. The one at front which joins the pubic bones is called the symphysis pubis; the two which join the Ossa Illii to the Sacrum are called the sacro iliac symphyses; and that which joins the Coccygis to the Sacrum, is called the Sacro coccygeal symphysis. The two pubic bones are separated a little in Plate VIII, simply to show them better. The reader will bear in mind that they are naturally connected by the cartilaginous substance which forms the symphysis.

These articulations, or joinings, become much softened during labor, and give way a little, but not to any extent sufficient to assist delivery. It is a mistake to suppose that the bones separate at that time. The only part which gives way is the sacro coccygeal symphysis, which does relax, and allows the Os Coccygis to be pushed back by the child's head a full inch or more, thus enlarging the inferior strait.--(See _c._ and _o._ Plate VIII.) Sometimes this little bone will be even broken off, when there is great disproportion between the head and the strait. I have heard it snap like a stick breaking. There is nothing serious nor alarming in this, however, unless it be _a first delivery late in life_, though it may cause some pain at the time, and a little difficulty in _sitting_ for some time after. In young persons the symphysis is soft, and gives way easily, so that they have little difficulty during delivery from this cause; but if a female marry late in life, after it becomes hardened, she may suffer considerably. In this case the coccygis is usually curved inwards considerably, and being firmly fixed the head cannot push it back, and on that account cannot pass, without great difficulty, and with the risk of rupturing some of the soft parts, or breaking the coccygis completely off. There is in fact great difficulty, and some danger, if the first pregnancy takes place late in life.

The Pelvis is usually divided into two parts,--the _great pelvis_, or upper part, enclosed between the wide flanges of the Ossa illii and the upper part of the sacrum; and the _small pelvis_, or basin, which is enclosed between the lower part of the sacrum and coccygis behind, and the ossa ischii and ossa pubes in front. The basin is nearly cylindrical, larger in the middle, and curved towards the front.

_The Straits of the Pelvis._--The bones of the Pelvis, it will be seen, form a kind of broad ring, or cylinder, particularly in the basin; and the straits are two passages, one by which the child passes into the basin from the upper Pelvis, and the other by which it passes out from the basin into the world.

In Plate VIII. the line marked † is the antero posterior diameter of the _upper strait_, through which the child first passes, called also the brim, or entrance to the Pelvis. The line marked ‡ is the diameter of the _lower_ strait, through which the child passes into the world, called also the outlet of the Pelvis. In Plate VII. the line marked † crosses the upper strait, or brim of the Pelvis.

_The diameters of the Pelvis_ are the distances between the prominent points of each strait, and are four in number for each, _those for the upper_ strait being represented below.

PLATE IX.

_Diameters of the Upper Strait._

A B, which extends from the most prominent point of the Sacrum, to the top of the Symphysis pubes, is called the _antero posterior_ diameter, or that from before to behind.--C D, and E F, are called the two _oblique diameters_; they extend from each sacro iliac symphysis, to the most prominent point of the Os Ilium on the opposite side.--G H, is called the Transverse, or _bis iliac_ diameter, it crosses the Pelvis nearly from one hip joint to the other.

The Sacro Antero posterior diameter measures _four inches_. The two oblique diameters _four inches and a half_ each. The bis iliac diameter measures _five inches_.

(By comparing this with Plate VII. the various points will be still more apparent.)

The inferior strait has also four diameters, represented in Plate X.

[Illustration: Plate IX.

Diameters of the Upper Strait.]

PLATE X.

The Bones of the Pelvis viewed from below, looking through the inferior strait, to show its diameters.

A B, which extends from the end of the Coccygis to the lower part of the Symphysis Pubis, is called the _antero posterior_ diameter; it measures _four inches_, like that of the upper strait, but is increased a little by the bending back of the Coccygis.--C D, and E F, are the two _oblique diameters_, also corresponding to those in the upper strait; they measure _four inches_, but are increased a little by the giving way of the soft parts.--G H, is the transverse, or bis-ischiatic diameter; it measures _four inches_.

[Illustration: Plate X.

The Bones of the Pelvis viewed from below, looking through the inferior strait, to show its diameters.]

It will thus be seen that the diameters only average from four to five inches, but it must be remembered that the soft parts, and even one of the bones, very readily give way, and thus they are slightly increased.

When we come to describe the form and size of the fœtal child's head, it will be found that its diameters correspond very nearly with those of the pelvic straits through which it has to pass, so that ordinarily labor presents no serious difficulty. If the head be larger than natural, from any cause, or if the Pelvis be too small, or deformed, this mutual adaptation does not exist, and delivery of course becomes difficult, or dangerous, and sometimes impossible. The only obstacle therefore, which can seriously impede the expulsion of the fœtus, or prevent it altogether, is this want of conformity, in size and shape, between its head and the bones of the Pelvis. The _soft parts_ may retard labor considerably, by being contracted or rigid, but can generally be made to give way, either by the efforts of nature or by manual assistance; and the fœtal head can be reduced in size if necessary; but insufficient size, or faulty form, in the _bones_, is irremediable.

The various causes which produce deformity, or imperfect development, in the Pelvis, and unnatural growth of the child's head, will be stated in a subsequent section. For the present, we have only to do with both in the normal state.

The importance of an accurate knowledge of the structure of the Pelvis, and of the changes which may be induced in it, will now be obvious; neither the theory nor the practice of Midwifery can in fact be understood without such knowledge. It is also frequently of the first importance to know, _previous to marriage_, whether the pelvis of a young person is so formed that delivery can be safely effected! Inattention to this has sacrificed the lives of many, and caused others to live for years suffering and helpless. In another place we shall give some plain rules and directions by which this important point may be determined.

_The floor of the Pelvis._--The soft parts at the bottom of the basin of the Pelvis, consisting of the perineum and various muscles, are called the floor of the Pelvis--the only passage through which is by the Vulva, or mouth of the Vagina. As the head of the child descends to the bottom of the basin, it presses upon this floor, and gradually distends it, until the Vulva is sufficiently enlarged. This delay is advantageous, for if the passage was always large enough, or increased in size without any difficulty, the child would pass too suddenly, and much mischief might often result from its sudden expulsion--such as pulling down of the womb, flooding, and the falling of the child upon the ground.

_Direction of the passage of the Pelvis._--In most of the lower animals the passage of the Pelvis is straight, and on a line with the body, the two straits being opposite each other, which makes delivery much more easy with them. Even in the negroes, and other inferior races, the passage is much straighter than in the whites. The more perfect the organization therefore, the more difficult is parturition; and the more imperfect or simple the organization, the more easy is parturition. The dotted line in Plate XI. shows the direction of the passage of the Pelvis, in the human female, to be a curve, so that the child has to move, during its passage, in a circle.

[Illustration: PLATE XI.

The axis, or direction, of the upper strait is denoted by the line A, that of the lower strait by the line B, and that of the Vulva by the line C. The force of expulsion tending to push the child in _each_ direction, it has to traverse a path intermediate with them all, or compounded of them all, not being able to move in either alone. This aggregate direction is denoted by the dotted curved line, which shows the direction in which the child passes, and in which the hand must be passed when introduced.

I is the Perineum.--The dotted line which crosses A denotes the upper strait, and the line I the lower strait.]