A System of Midwifery
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Title: A System of Midwifery
Author: Edward Rigby
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A SYSTEM OF MIDWIFERY.
by
EDWARD RIGBY, M. D.,
Physician To the General Lying-In Hospital, Lecturer on
Midwifery, at St. Bartholomew's Hospital, etc. etc.
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* * * * * *
A SYSTEM OF MIDWIFERY.
With Numerous Wood Cuts.
by
EDWARD RIGBY, M. D.,
Physician to the General Lying-In Hospital, Lecturer on
Midwifery, at St. Bartholomew's Hospital, etc. etc.
With Notes and Additional Illustrations.
Philadelphia:
Lea & Blanchard.
1841.
Entered, according to the Act of Congress, in the year 1841, by Lea &
Blanchard, in the District Court for the Eastern District of Pennsylvania.
Griggs & Co., Printers.
THE EDITOR'S PREFACE.
This System of Midwifery, complete in itself, was published in London, as
a part of Dr. Tweedie's "_Library of Medicine_." The first series of the
Library, that on "_Practical Medicine_," recently completed, has been
received with extraordinary favour on both sides of the Atlantic, and the
character of the publication is fully sustained in the present
contribution by Dr. Rigby, and will secure for it additional patronage.
The late Professor Dewees, into whose hands this volume was placed, a few
weeks before his death, in returning it, expressed the most favourable
opinion of its merits; and the judgment of such high authority renders it
supererogatory to add a word farther of commendation.
It is only necessary for the editor to say that the production of the
author is so complete as to have rendered his labour a light one. He has
restricted himself mainly to such additions and references as he conceived
would render the work more useful to American practitioners. The object of
the publication being to present the most condensed view of each subject,
he believed it to be inexpedient to depart from the plan by making
extensive additions, and entering into the discussion of controversial
points, most of which are of minor practical importance.
CONTENTS.
INTRODUCTION, Page 13
PART I. THE ANATOMY AND PHYSIOLOGY OF UTERO-GESTATION.
CHAPTER I. THE PELVIS.
Ossa innominata.--Sacrum.--Coccyx.--Distinction between the
male and female pelvis.--Diameters of the pelvis.--Pelvis
before puberty.--Axes.--Inclination, 15
CHAPTER II. FEMALE ORGANS OF GENERATION.
Internal and external.--Ovaria.--Ovum.--Corpus luteum.--
Fallopian tubes.--Uterus.--Vagina.--Hymen.--Clitoris.--
Nymphæ.--Labia, 22
CHAPTER III. DEVELOPMENT OF THE OVUM.
Membrana decidua.--Chorion.--Amnion.--Placenta.--Umbilical
cord.--Embryo.--Foetal circulation, 48
PART II. NATURAL PREGNANCY AND ITS DEVIATIONS.
CHAPTER I. SIGNS OF PREGNANCY.
Difficulty and importance of the subject.--Diagnosis in the
early months.--Auscultation.--Changes in the vascular and
nervous systems.--Morning sickness.--Changes in the appearance
of the skin.--Cessation of the menses.--Areola.--Sensation of
the child's movements.--"Quickening."--Auscultation.--Uterine
souffle.--Sound of the foetal heart.--Funic souffle.--Sound
produced by the movements of the foetus.--Ballottement.--State
of the urine.--Violet appearance of the mucous membrane of the
vagina.--Cases of doubtful pregnancy.--Diagnosis of twin
pregnancy, 80
CHAPTER II. TREATMENT OF PREGNANCY.
Sympathetic affections of the stomach during pregnancy.--
Morning sickness.--Constipation.--Flatulence.--Colicky
pains.--Headach.--Spasmodic cough.--Palpitation.--Toothach.--
Diarrhoea.--Pruritus pupendi.--Salivation, 101
CHAPTER III. SIGNS OF THE DEATH OF THE FOETUS.
Difficulty of the subject.--Signs before labour.--Motion of
the foetus.--Sound of the foetal heart.--Uterine souffle.--
Signs during labour where the head presents--where the face,
the nates, the arm, or the cord, present.--Fetid liquor
amnii.--Discharge of meconium, 107
CHAPTER IV. MOLE PREGNANCY.
Nature and origin.--Varieties.--Diagnostic symptoms.--
Treatment, 112
CHAPTER V. EXTRA-UTERINE PREGNANCY.
Tubarian, ovarian, and ventral pregnancy.--Pregnancy in the
substance of the uterus, 117
CHAPTER VI. RETROVERSION OF THE UTERUS.
History.--Causes.--Symptoms.--Diagnosis.--Treatment.--
Spontaneous terminations, 126
CHAPTER VII. DURATION OF PREGNANCY, 136
CHAPTER VIII. PREMATURE EXPULSION OF THE FOETUS.
Abortion.--Miscarriage.--Premature labour.--Causes.--
Symptoms.--Prophylactic measures.--Effects of repeated
abortion.--Treatment, 141
PART III. EUTOCIA, OR NATURAL PARTURITION.
CHAPTER I. STAGES OF LABOUR.
Preparatory stage.--Precursory symptoms.--First
contractions.--Action of the pains.--Auscultation during the
pains.--Effect of the pains upon the pulse.--Symptoms to be
observed during and between the pains.--Character of a true
pain.--Formation of the bag of liquor amnii.--Rigour at the
end of the first stage.--Show.--Duration of the first stage.--
Description of the second stage.--Straining pains.--Dilatation
of the perineum.--Expulsion of the child.--Third stage.--
Expulsion of the placenta.--Twins, 156
CHAPTER II. TREATMENT OF NATURAL LABOUR.
State of the bowels.--Form and size of the uterus.--True and
spurious pains.--Treatment of spurious pains.--Management of
the first stage.--Examination.--Position of the patient during
labour.--Prognosis as to the duration of labour.--Diet during
labour.--Supporting the perineum.--Treatment of perineal
laceration.--Cord round the child's neck.--Birth of the child,
and ligature of the cord.--Importance of ascertaining that the
uterus is contracted after labour.--Management of the
placenta.--Twins.--Treatment after labour.--Lactation.--Milk
fever and abscess.--Excoriated nipples.--Diet during
lactation.--Management of lochia.--After-pains, 169
CHAPTER III. MECHANISM OF PARTURITION.
Cranial presentations--first and second position.--Face
presentations--first and second positions.--Nates
presentations, 199
PART IV. MIDWIFERY OPERATIONS.
CHAPTER I. THE FORCEPS.
Description of the straight and curved forceps.--Mode of
action.--Indications.--Rules for applying the forceps.--
History of the forceps, 216
CHAPTER II. TURNING.
Turning.--Indications.--Circumstances most favourable for this
operation.--Rules for finding the feet.--Extraction with the
feet foremost.--Turning with the nates foremost.--Turning with
the head foremost.--History of turning, 230
CHAPTER III. CÆSAREAN OPERATION.
Indications,--Different modes of performing the operation.--
History of the Cæsarean operation, 243
CHAPTER IV. ARTIFICIAL PREMATURE LABOUR.
History of the operation.--Period of pregnancy most favourable
for performing it.--Description of the operation, 250
CHAPTER V. PERFORATION.
Variety of perforators.--Indications.--Mode of operating.--
Extraction.--Crotchet.--Embryulcia, 256
PART V. DYSTOCIA, OR ABNORMAL PARTURITION.
CHAPTER I. FIRST SPECIES OF DYSTOCIA.
Malposition of the child.--Arm or shoulder the only faulty
position of a full-grown living foetus.--Causes of
malposition.--Diagnosis before and during labour.--Results
where no assistance is rendered.--Spontaneous expulsion.--
Malposition complicated with deformed pelvis or spasmodically
contracted uterus.--Embryulcia.--The prolapsed arm not to be
put back or amputated.--Presentation of the arm and head.--
Presentation of the hand and feet.--Presentation of the head
and feet.--Rupture of the uterus.--Usual seat of laceration.--
Causes.--Premonitory symptoms.--Symptoms.--Treatment.--
Gastrotomy.--Rupture in the early months of pregnancy, 264
CHAPTER II. SECOND SPECIES OF DYSTOCIA.
Size and form of the child.--Hydrocephalus.--Cerebral
tumours.--Accumulation of fluid and tumours in the chest or
abdomen.--Monsters.--Anchylosis of the joints of the foetus, 281
CHAPTER III. THIRD SPECIES OF DYSTOCIA.
Difficult labour from faulty condition of the parts which
belong to the child.--The membranes.--Premature rupture of the
membranes.--Liquor amnii.--Umbilical cord.--Knots upon the
cord.--Placenta, 286
CHAPTER IV. FOURTH SPECIES OF DYSTOCIA.
Abnormal state of the pelvis.--Equally contracted pelvis.--
Unequally contracted pelvis.--Rickets.--Malacosteon, or
mollities ossium.--Symptoms of deformed pelvis.--Funnel-shaped
pelvis.--Obliquely distorted pelvis.--Exostosis.--Diagnosis of
contracted pelvis.--Effects of difficult labour from deformed
pelvis.--Fracture of the parietal bone.--Treatment.--Prognosis, 292
CHAPTER V. FIFTH SPECIES OF DYSTOCIA.
_Obstructed Labour from a Faulty Condition of the Soft Passages._
Pendulous abdomen.--Rigidity of the os uteri.--Belladonna.--
Edges of the os uteri adherent.--Cicatrices and callosities.--
Agglutination of the os uteri.--Contracted vagina.--Rigidity
from age.--Cicatrices in the vagina.--Hymen.--Fibrous bands.--
Perineum.--Varicose and oedematous swellings of the labia and
nymphæ.--Tumours.--Distended or prolapsed bladder.--Stone in
the bladder, 308
CHAPTER VI. SIXTH SPECIES OF DYSTOCIA.
_Faulty Labour from a Faulty Condition of the expelling Powers._
I. Where the uterine activity is at fault--functionally or
mechanically--from debility--derangement of the digestive
organs--mental affections--the age and temperament of the
patient--plethora--rheumatism of the uterus--inflammation of
the uterus--stricture of the uterus.--Treatment. II. Where the
action of the abdominal and other muscles is at fault.--Faulty
state of the expelling powers after the birth of the child.--
Hæmorrhage.--Treatment, 324
CHAPTER VII. INVERSION OF THE UTERUS.
Partial and complete.--Causes.--Diagnosis and symptoms.--
Treatment.--Chronic inversion.--Extirpation of the uterus, 345
CHAPTER VIII. ENCYSTED PLACENTA.
Situation in the uterus.--Adherent placenta.--Prognosis and
treatment.--Placenta left in the uterus.--Absorption of
retained placenta, 354
CHAPTER IX. PRECIPITATE LABOUR.
Violent uterine action.--Causes.--Deficient resistance.--
Effects of precipitate labour.--Rupture of the cord.--
Treatment.--Connexion of precipitate labour with mania, 361
CHAPTER X. PROLAPSUS OF THE UMBILICAL CORD.
Diagnosis.--Causes.--Treatment.--Reposition of the cord, 368
CHAPTER XI. PUERPERAL CONVULSIONS.
Epileptic convulsions with cerebral congestion.--Causes.--
Symptoms.--Tetanic species.--Diagnosis of labour during
convulsions.--Prophylactic treatment.--Treatment--Bleeding.--
Purgatives.--Apoplectic species.--Anæmic convulsions.--
Symptoms.--Treatment.--Hysterical convulsions.--Symptoms, 376
CHAPTER XII. PLACENTAL PRESENTATION, OR PLACENTA PRÆVIA.
History.--Dr. Rigby's division of hæmorrhages before labour
into accidental and unavoidable.--Causes.--Symptoms.--
Treatment.--Plug.--Turning.--Partial presentation of the
placenta.--Treatment, 393
CHAPTER XIII. PUERPERAL FEVERS.
Nature and varieties of puerperal fever.--Vitiation of the
blood.--Different species of puerperal fever.--Puerperal
peritonitis.--Symptoms.--Appearances after death.--
Treatment.--Uterine phlebitis.--Symptoms.--Appearances after
death.--Treatment.--Indications.--False peritonitis.--
Treatment.--Gastro-bilious puerperal fevers.--Symptoms.--
Appearances after death.--Treatment.--Contagious or adynamic
puerperal fevers.--Symptoms.--Appearances after death.--
Treatment, 415
CHAPTER XIV. PHLEGMATIA DOLENS.
Nature of the disease.--Definition of phlegmatia dolens.--
Symptoms.--Duration of the disease.--Connexion with crural
phlebitis.--Causes.--Connexion between the phlegmatia dolens
of lying-in women and puerperal fever.--Anatomical
characters.--Treatment.--Phlegmatia dolens in the
unimpregnated state, 463
CHAPTER XV. PUERPERAL MANIA.
Inflammatory or phrenitic form.--Treatment.--Gastro-enteric
form.--Treatment.--Adynamic form.--Causes and symptoms.--
Treatment, 473
INDEX, 483
A SYSTEM OF MIDWIFERY.
INTRODUCTION.
By the term Midwifery is understood the knowledge and art of treating a
woman and her child during her pregnancy, labour, and the puerperal state.
We employ it in this extended sense, because most systematic writers of
later times have adopted this arrangement. The terms, _Art des
Accouchemens_ of the French, the _Ostetricia_, and _Arte della Parteria_,
of the Italians and Spaniards, and the _Geburtshülfe_ of the Germans, are
restricted to the process of parturition, although they have been and
continue to be, used in the same extended sense as that in which we
propose to use the term Midwifery.
Although pregnancy and parturition, strictly speaking, are perfectly
natural functions, yet they involve such a complication and variety of
other processes, and also changes of such extent, that the whole system is
rendered more or less subservient to them during the periods of their
existence: hence, therefore, their number and variety must ever render
them more or less liable to deviations and irregularities of action, which
will necessarily be aggravated by the effects of civilized life, and in
many instances are productive of derangement in the general economy of the
system. Under such circumstances the irritability of the system increases
at the expense of its strength and vigour, and not only increases its
liability to these derangements, but diminishes its power of resisting
their effects.
In order that we may render the nature and treatment of the changes
and phenomena, which take place in the human system during the
periods above alluded to, more intelligible, we shall take a short
anatomico-physiological view of the structure, form, arrangement, and
function of the parts and organs which are more or less directly
concerned in these important processes. This will embrace the subject of
embryology, a department of physiological knowledge, which, though it has
lately been much enriched by valuable discoveries, still affords a rich
field of investigation and research.
The diagnosis and course of healthy pregnancy, and its various diseases,
terminating with the subject of healthy parturition and its treatment will
form the subject of the succeeding part.
Parturition properly speaking, will come under two separate heads
_eutocia_ and _dystocia_; the one signifying natural or favourable labour,
the other, unnatural, faulty, or unfavourable labour.
The concluding part will contain a short account of some of the more
important diseases which occur to the female during the first month after
parturition.
PART I.
THE ANATOMY AND PHYSIOLOGY OF UTERO-GESTATION.
CHAPTER I.
THE PELVIS.
_Ossa innominata.--Sacrum.--Coccyx.--Distinction between the male and
female pelvis.--Diameters of the pelvis.--Pelvis before puberty.--
Axes.--Inclination._
The Pelvis, as the frame-work which, in great measure, contains, supports,
and protects, the complicated apparatus of the generative organs, first
claims our attention; since an accurate knowledge of the form, size, and
uses, of its different parts is indispensably necessary, not only to
understand the situation of the viscera it contains, but also to form a
correct view of the mechanism upon which the process of parturition
depends.
This osseous canal or circular archway, consists essentially of three
bones, the right and left os innominatum, which form the sides of the
arch, with the sacrum between them, acting as a keystone, and supporting
the whole weight of the trunk above.
_Ossa innominata._ The ossa innominata in early life consists of three
distinct bones, the _iliac_ or _hip bones_ at the sides, the _ischia_ or
lower portion upon which we sit, and the _ossa pubis_ which meet each
other anteriorly to form the front part of the pelvis. In the adult these
are consolidated into one bone, merely leaving irregular lines and ridges
here and there to mark their previous existence.
These bones present several striking points of resemblance with those
which belong to the upper extremities, viz. the scapula and clavicle; and
in the early stages of development, this similarity is much more
distinctly seen: it is remarkable, that although the ischia and ossa pubis
are formed later than the ilia, yet they unite with each other much sooner
than with the ilia, so that the two consolidated bones bear the same
relation to the ilium which is separated from them, that the clavicle does
to the scapula: many other points of resemblance between the bones of the
shoulder and pelvis might be noticed if necessary. (Meckel, _Anat._ vol.
ii. p. 239.) The ossa innominata meet each other in front, forming the
_symphysis pubis_, having layers of fibro-cartilage interposed between
their extremities, and bound together by ligamentous fibres constituting
the _ligamentum arcuatum_, or _annulare ossium pubis_, and by which a more
rounded appearance is given to the pubic arch. They are united to the
sacrum posteriorly, one on each side of it, forming the _right and left
sacro-iliac symphysis_ or _synchondrosis_; this differs in many respects
from the symphysis pubis, the cartilaginous coverings of the opposing
bones being much thinner, especially those of the ossa innominata; the
surfaces are extremely uneven from the deep indentations which each bone
presents at this part, locking, as it were, into each other, and thus
contributing greatly to increase the firmness of the joint, which is also
still farther strengthened by the support of powerful ligaments.
Between the ligamento-and cartilaginous layers which cover the surfaces of
the bones at the pubic and sacro-iliac symphyses, a minute collection of
synovial fluid may be detected, like that found in the fibro-cartilages
between the vertebræ; it serves to lubricate their surfaces, and separates
them more or less, thereby increasing the thickness of the intervening
cartilaginous structure; and separating also the edges of the bones, to a
certain extent, more especially at the symphysis pubis. (Portal, _Anat.
Méd._) These laminæ of intervening fibro-cartilage are thicker in the
female than in the male, although of smaller extent; and this is still
more remarkable during pregnancy, this ligamento-cartilaginous structure
becoming now more cushiony and elastic, while in the latter months we can
easily distinguish blood-vessels ramifying through it, which are branches
of the pudic arteries and veins.
_Sacrum._ The sacrum, which forms the upper and posterior portion of the
pelvis, contributes greatly to the general solidity of the whole bony
circle. From its wedge-like shape, it is admirably adapted to support the
entire weight of the trunk, and acts, as we have before observed, as a
kind of keystone to the arch which is formed by the ossa innominata. It is
of a triangular shape, being concave before and convex behind. In the
foetus it consists of five distinct pieces of bone separated by
intervening layers of cartilage, like the vertebræ of the spinal column,
and from their resemblance to those bones they have been called false
vertebræ. These cartilages, after a time, gradually disappear; bony matter
is deposited in their place; so that by the period of puberty the five
sacral vertebræ become united into one solid bone, although they may be
distinguished, until an advanced period of life, by the ridges which their
edges form.
The upper surface of the sacrum, having to sustain the whole weight of the
spinal column, is broad and flat, and corresponds to the lower surface of
the last lumbar vertebra. Its anterior surface forms with that of the
other mentioned bone a considerable angle, which projects forwards and
more or less downwards towards the symphysis pubis, and is called the
_promontory of the sacrum_. Beneath this point, the sacrum takes a
considerable sweep backwards as it descends, gradually advancing again
forwards, as we approach its inferior extremity, forming an extensive
concavity upon its anterior surface: this is termed _the hollow of the
sacrum_.
_Coccyx._ The lower end is prolonged by a small bone, called _Coccyx_ or
_os Coccygis_, from its supposed resemblance to a cuckoo's beak. It
usually consists of four, and sometimes (especially in women) of five
portions; they are much smaller than the bones of the sacrum, and are very
imperfect rudiments of vertebral formation; like these, they are at an
early period little else than cartilage, and even when the bones are fully
formed, they are united by intermediate cartilage, and thus retain so much
mobility upon each other, as well as upon the lower end of the sacrum, as
to admit of being forced backwards to the extent of a full inch, thus
contributing greatly to increase the capacity of the outlet.
The sacrum not only serves to form the posterior parietes of the pelvis,
but by the curve which its lower portion takes forwards, together with the
coccyx, it gives a powerful support to the pelvic viscera.
When we take a general view of the bones which collectively form the
pelvis, we find that it is evidently divided into two portions--an upper
and a lower one. On the Continent these have been called the large and the
small pelvis; in Britain we merely speak of the pelvis above or below the
_brim_, the line of demarcation being the linea ilio-pectinea at the
sides, the crista of the os pubis in front, and the promontory of the
sacrum behind. The alæ of the ilia form a prominent feature in the upper
pelvis, and not only afford an attachment for numerous muscles, but
furnish a powerful and ample means of protection and support to the pelvic
and lower abdominal viscera. In the female pelvis this is remarkably the
case, the cavitas iliaca being well expanded and of greater extent than in
the male, the crista of the ilium thrown more outwards; hence the distance
between the antero-superior processes is much more considerable.
_Distinction between the male and female pelvis._ At the brim, the female
pelvis presents several well-marked points of distinction from that of the
male. The male pelvis has a contracted brim of a rounded or rather
triangular form, with the promontory of the sacrum considerably
projecting; whereas, that of the female is spacious, of an oval shape, and
with a slightly prominent sacrum, thus affording more room for the passage
of the child through the brim. The cavity of the male pelvis is deep,
while in the female pelvis it is shallow, a circumstance which is very
strikingly seen in comparing the length of the symphysis pubis in each,
that of the male pelvis being nearly double the length of the female. This
is an important point of difference as regards parturition, because in a
shallow pelvis, the extent of surface exposed to the pressure of the head
will be much less than where it is deep, and hence the resistance to the
passage of the child will be proportionably diminished: in confirmation of
this, we find that tall women, in whom the pelvis is usually deep, do not,
on the whole, bear children so easily as women of middling stature in whom
the pelvis is more shallow. The capacious hollow of the sacrum in the
female pelvis adds also greatly to the extent of its cavity, and
peculiarly adapts it for parturition, the injurious pressure of the head
upon the soft linings of the pelvis being thus prevented, and every
facility afforded for its quick and easy transit through the cavity. This
applies especially to the neck of the bladder, which would almost
inevitably suffer in every labour, were it not for the ample hollow of the
sacrum relieving the pressure of the head against the anterior portions of
the pelvis. The bones of the female pelvis being more slender and
delicately formed, the foramina ovalia and sacro-ischiatic notches are
wider, and thus add still farther to the capacity of the cavity.
In no part of the pelvis is the difference between the sexes more strongly
marked than at the outlet. The spacious and well-rounded arch of the pubes
in the female of the slender rami, is a striking contrast to the
contracted angular arch of the male pelvis; and the tuberosities of the
ischium being much wider apart, the head is enabled to pass under the arch
with greater facility, and thus still farther to relieve the anterior of
the pelvis from its pressure. The length of the sacro-sciatic ligaments,
and the mobility of the coccyx upon the sacrum, by which it can be forced
backwards to the extent of an inch by the pressure of the head during
labour, not merely serve to distinguish it from the male pelvis, but
afford a beautiful instance of design and adaptation.
The greater width of the pubic arch in the female pelvis is seen by
comparing its angle with that of the arch in the male pelvis. In the
female it has been estimated to form an angle varying between 90° and
100°, whereas in the male it is not more than between 70° and 80°.
(Osiander, _Handbuch der Embindungs-kunst_, cap. iv. p. 58.)
From the greater width of the female pelvis, the acetubula are farther
apart, and the great trochanters of the thigh-bones more projecting; hence
the greater motion of the hips in the female when she walks, which is
still more visible when she runs, for the motion is communicated to the
whole trunk, so that each shoulder is turned more or less forwards as the
corresponding foot is advanced. The thigh-bones, which are so far apart at
their upper extremities, approach each other at the knees, contributing to
produce that unsteady gait which is peculiar to the sex. "The woman," says
Mr. John Bell, "even of the most beautiful form, walks with a delicacy and
feebleness which we come to acknowledge as a beauty in the weaker sex."
(_Bell's Anat._ vol. i.)
These characteristic marks of the female figure, upon which its beauty in
great measure depends, are well seen in all great works of art, whether of
sculpture or painting. "The ancients," as Mr. Abernethy has observed, "who
had a clear and strong perception of whatever is beautiful or useful in
the human figure, and who, perhaps, delicately exaggerated beauty to
render it more striking, have represented Venus as measuring one-third
more across the hips than the shoulders, whilst, in Apollo, they have
reversed these measurements." (_Physiological Lectures._)
_Diameters of the pelvis._ It is of the utmost importance to the
obstetrician, that he should be thoroughly acquainted with the various
dimensions of the female pelvis, for, without this, he can form no correct
idea of the manner in which the presenting part of the child passes
through its brim, cavity and outlet during labour; indeed, unless he be
thoroughly versed in this necessary point of obstetric knowledge, he will
remain in almost total ignorance of the whole mechanism of parturition,
which must, in great measure, be looked upon as the basis of practical
midwifery. The dimensions of the brim cavity and outlet of the pelvis may
be given with sufficient correctness for all practical purposes, by
measuring three of their diameters,--1. the _straight_,
_antero-posterior_, or _conjugate_; 2. the _transverse_; and 3. the
_oblique_. At the brim they are as follow:--the straight diameter, drawn
from the middle of the promontorium sacri to the upper edge of the
symphisis pubis, 4·3 inches; the transverse diameter, from the middle of
the linea-ilio-pectinea of one ilium to that of the other, 5·4 inches; and
the oblique diameter, from one sacro-iliac synchondrosis to the opposite
acetabulum, 4·8 inches. The oblique diameters are called right and left,
according to the sacro-iliac symphysis from which they are drawn.
[Illustration: _Fig. 1. Fig. 2._
In the annexed representations of the superior and inferior aspects of the
female pelvis are shown the three diameters of its brim and outlet; those
of the former in _fig. 1._, and those of the latter in _fig. 2._ The same
letters of reference are used in each figure to indicate the several
diameters; thus _a p_ refers to the antero-posterior, _t t_ to the
transverse, _o o_ to the right oblique, and _o' o'_ to the left oblique
diameters.
In _fig. 2._ the coccyx is represented in situ.]
In the cavity these dimensions vary more or less. The straight diameter,
measured from the centre of the hollow of the sacrum to that of the
symphysis pubis, is 4·8 inches; the transverse, from the point
corresponding to the lower margin of the acetabulum on one side to that of
the other, 4·3; and the oblique, drawn from the centre of the free space
formed by the sacro-ischiatic notch and ligaments on one side of the
foramen ovale of the other, 5·2.
At the inferior aperture or outlet the alteration is still more
remarkable. The straight diameter, from the point of the coccyx to the
lower edge of the symphysis pubis, measures only 3·8 inches; but from the
mobility of the coccyx enabling it to be pushed back during labour to the
extent of a whole inch, it is capable of being extended to 4·8 inches. The
transverse diameter from one tuberosity of the ischium to the other,
measures 4·3 inches: and the oblique, from the middle of the lower edge of
the sacro-sciatic ligament of one side, to the point of union between the
ischium and descending ramus of the pubes on the other 4·8 inches.
Although these are the proportions of the brim cavity and outlet of the
female pelvis in the skeleton state, their real dimensions during life,
when the pelvis is thickly lined with muscular and other structures, are
very different. The large masses of the psoas magnus and iliacus internus,
besides other muscles of inferior size, contribute to alter materially the
relations of the pelvic diameters to each other; hence we find that, so
far from being the longest, the transverse diameter is one of the
shortest, being little more than the antero-posterior. This holds good,
especially during labour, because these muscles being thrown into powerful
contraction, their bellies swell, and thus tend still farther to diminish
its length. The oblique diameters are, in fact, the longest during life,
because not only are the parietes of the pelvis at the brim covered by a
very thin layer of soft tissues in these directions; but as the
extremities of these diameters, in the cavity and outlet, correspond to
free spaces which are merely filled up with soft yielding structure, it
follows that their length can be somewhat increased when pressure is
applied in these directions; the antero-posterior diameter of the outlet
can alone be compared with the oblique diameters in this respect, and then
only when the coccyx is forced backwards to its full extent by the
pressure of the head.
_Pelvis before puberty._ The proportions of the adult female pelvis are no
longer what they were during childhood; before the age of puberty they
resemble those of the male pelvis, the brim being contracted and more or
less triangular, and the antero-posterior diameter equalling or even
exceeding the transverse. Indeed, at a still earlier period, it presents
many points of resemblance even to the pelvis of animals; as, however,
growth and development advance, and the various changes which constitute
puberty take place, the transverse diameters of the brim, cavity, and
outlet increase at the expense of the antero-posterior, until at length,
it has assumed the proper proportions of the adult female pelvis.
_Axes._ Of not less importance is it that the obstetrician should be
thoroughly acquainted with the direction which the central line or axis of
the entrance and outlet of the pelvis takes. The axis of the superior
aperture has been considered to form with the horizon an angle varying
between 50° and 60°; this was noticed long ago by Dr. Smellie: "when the
body of a woman," says this valuable author, "is reclined backwards, or
half sitting half lying, the brim of the pelvis is horizontal; and an
imaginary straight line, descending from the navel, would pass through the
middle of the cavity; but in the last month of pregnancy such a line must
take its rise from the middle space between the navel and scrobiculus
cordis in order to pass through the same point of the pelvis." (_Treatise
of Midwifery_, book i. chap. i. sect. 2.)
_Inclination of the pelvis._ The angle which the axis of the superior
aperture of the pelvis forms with the horizon, when a woman is in the
upright posture, necessarily marks what has been called _the inclination
of her pelvis_, and varies, of course, in proportion to the angle which
the above mentioned axis forms. In a tall woman of slender figure, where
the different curves of the spinal columns are slight, the inclination of
the pelvis is much less than in a short thick set woman, where the spine
is much more strongly curved. Where the inclination is slight, the hollow
of the sacrum is generally small, and the vulva directed more forwards;
where, on the other hand, the pelvis is much inclined, the hollow of the
sacrum is generally observed to be deep, and the vulva directed more or
less backwards. The axis of the lower aperture or outlet appears to
depend, in great measure, on the curve which the lower part of the sacrum
takes downwards and forwards; but, as a general rule, we think it will be
found to form, more or less, a right angle with the axis of the brim. The
greater the angle which the axis of the brim forms with the horizon, the
less will be that which the axis of the outlet forms, and _vice versâ_;
or, in other words, the angle with the horizon which the axis of the one
forms is inversely to that of the other.
The consideration of the various deviations, as to size and form, from the
natural proportions which the female pelvis occasionally presents,
belongs, more strictly speaking, to that species of faulty labour which
arises from these conditions. We, therefore, refer to the fourth species
of dystocia, viz. _Dystocia Pelvica_, where the different pelvic
anormalities are described.
CHAPTER II.
FEMALE ORGANS OF GENERATION.
_Internal and external.--Ovaria.--Ovum.--Corpus luteum.--Fallopian
tubes.--Uterus.--Vagina.--Hymen.--Clitoris.--Nymphæ.--Labia._
The female organs of generation have been usually classed by the English
authors under the two heads of _internal_ and _external_; a similar
arrangement has also been followed by the Continental writers, but with
the advantage of using distinctive terms which are more expressive of
their peculiar functions, viz. the _formative_ and _copulative_ organs.
Under the first are included the ovaria, Fallopian tubes, and uterus:
under the second, the vagina and external parts. We propose to give a
short description of these in the unimpregnated state, and then to
describe the changes which they present during pregnancy, labour, and the
puerperal condition. In point of situation and arrangement they bear a
considerable resemblance to the generative organs in the male, being
situated at the lower portion of the trunk, and arranged in symmetrical
order, so that they either occur in pairs, one on each side the median
line of the body, or singly, being equally divided by it throughout their
whole length. Although there is in many points considerable difference
between the male and female organs, still there is sufficient resemblance
to entitle them to be considered as being formed upon the same fundamental
type, a resemblance which is seen still more strikingly in the early
periods of foetal life. They differ essentially from all the other organs
of the system, being in activity during a portion of a woman's life only,
and then only at intervals.
_Ovaria._ The ovaries are situated in the upper part of the cavity of the
pelvis, one on each side, near to the uterus, to which they are merely
attached by a ligament (the _ligamentum ovarii_) which is a portion of
that duplicature of the peritoneum which connects the uterus to the
pelvis, and is known by the name of ligamentum latum, or broad ligament.
They are of an oval figure; their anterior and posterior surface is
convex, the superior margin is also convex, while their lower edge is
straight or somewhat concave: towards their inner and outer extremities
they become thinner.
Their external surface in the virgin state is usually smooth, but in
advanced age they become uneven and shrivelled; when fully developed they
are about an inch and a half in length: their greatest breadth, which is
at that portion of the ovary which is farthest from the uterus, is half an
inch; their thickness is somewhat less.
[Illustration: Convoluted arteries of the ovary, crossing it in nearly
parallel lines.]
The ovaries are supplied with blood by the spermatic arteries, which are
of course considerably shorter in the female; they pass between the two
layers of the broad ligament to the ovarium, assuming there a beautifully
convoluted arrangement, very similar to the convoluted arteries of the
testis. These vessels traverse the ovary nearly in parallel lines, forming
numerous minute twigs, which have an irregular knotty appearance from
their tortuous condition, and appear to be chiefly distributed to the
Graafian vesicles. The external covering of the ovaries is formed by
peritoneum, which here receives the name of _Inducium_; it envelopes the
parenchymatous tissue of the gland called _stroma_, which is a dense
laminar cellular tissue of a reddish colour; its external portion which is
in contact with and firmly adherent to the indusium, is condensed into a
species of covering of a firm structure and whitish colour, and is called
the _tunica albuginea of the ovary_. In the substance of the stroma are
embedded a number of vesicles of various sizes, which, although previously
described by Vesalius and Fallopius, have been called Graafian vesicles,
after De Graaf. These do not commonly become visible until the seventh
year, from which period they gradually enlarge until puberty, when the
ovaries increase in size, become softer and more vascular, and one or two
of these vesicles may be observed to be larger, more developed, and
projecting considerably from the surface of the gland.
The proper capsule of the Graafian vesicle is composed of two layers. The
outer is formed of dense cellular tissue, in which are ramified many blood
vessels; the inner layer is thicker, softer, and more opaque than the
preceding, to which it is closely united, and from which it receives
vascular twigs.
_Ovum._ The contained part or nucleus of the vesicle of De Graaf consists
of, first, a granulary membrane, enclosing, secondly, a coagulable
granular fluid; thirdly, connected with the granulary membrane on one side
is a circular mass or disc of granulary matter, in the centre of which is
embedded, fourthly, the ovum.
This disc, called by Baer the _proligerous disc_, presents in its centre
on the side towards the interior of the vesicle, a small rounded
prominence, called the _cumulus_, and on the opposite side a small
cup-like cavity hollowed out in the cumulus. The cavity is for the
reception of the ovum.[1]
[Illustration: _Diagram of a section of the Graafian Vesicle and its
contents, showing the situation of the Ovum._
_a_ The granulary membrane. _b_ The proligerous disc. _c_ Ovum. _d_ The
inner and outer walls of the Graafian vesicle. _e_ Indusium of the ovary.
_From T. W. Jones._]
From the very minute size of the human ovum, and the difficulty of
detecting it, the existence of this little corpuscule was not
satisfactorily ascertained until modern times. Although De Graaf had
observed ova in the Fallopian tube so early as 1668, which fact had been
confirmed by the researches of Dr. Haighton and Mr. Cruickshank, still, as
no traces of such ova had been discovered in the Graafian vesicle, and as
it was evident that the Graafian vesicle, from its size, &c. could not
pass along the Fallopian tube, it was concluded that the inner surface of
the vesicle was a species of glandular structure which secreted the fluid
with which it was filled, and which was analogous to the semen of the male
testicle; hence, in former times, the ovaries were known by the name of
_testes muliebres_. The celebrated anatomist Steno[2] first pointed out
the analogy between these organs and the ovaries of the fish tribe: this
view was afterwards supported by De Graaf,[3] and they have since
continued to retain the name of ovaries.
To Professor von Baer, now of St. Petersburg, is due the merit of having
first pointed out the distance of the ovum in the Graafian vesicle, and of
thus putting beyond all doubt the accuracy of De Graaf's observations, as
well as those of Dr. Haighton and Mr. Cruickshank.
_Corpus luteum._ Upon impregnation taking place, one or more of the most
prominent Graafian vesicles begins to show marks of considerable
vascularity, both in its external capsule and in the surrounding stroma of
the ovary. The vesicle swells, and at length bursts, discharging its
contents into the funnel-shaped extremity of the Fallopian tube, which
firmly grasps the ovary at this point by means of its fimbriæ.
These changes begin to take place immediately after impregnation; the
inner lining of the vesicle, which Professor von Baer considers to be a
mucous membrane, appears to undergo a rapid development, much more so than
the external capsule which contains it. It is, therefore, thrown into a
number of corrugations by which the cavity of the vesicle is greatly
diminished; it becomes much thicker, and assumes a yellow colour. As its
growth proceeds, the cavity of the vesicle becomes still farther
contracted, until being unable longer to retain its contents, it bursts
and discharges them as above described.
[Illustration: Corrugation of the lining membrane of the Graafian capsule
after impregnation. _From Baer._]
The remains of the ruptured vesicle form a round glandular yellow coloured
body, called _corpus luteum_: it projects considerably from the surface of
the ovary, attaining the size of a small mulberry. In the middle of this
projection there is a little irregular and generally triangular depression
or indentation, which is the opening through which the ovum was discharged
from the Graafian vesicle: this after a short time closes, forming a
little cicatrix on the surface of the ovary.
[Illustration: Corpus luteum in the third month. _From Dr. Montgomery._]
"Upon slitting the ovarium at this part, the corpus luteum appears a round
body, of a very distinct nature from the rest of the ovarium. Sometimes it
is oblong or oval, but more generally round. Its centre is white, with
some degree of transparency; the rest of its substance has a yellowish
cast, is very vascular, tender and friable, like glandular flesh. Its
larger vessels cling round its circumference, and these send their smaller
branches inwards through its substance: a few of these larger vessels are
situated at the cicatrix or indentation on the outer surface of the
ovarium, and are there so little covered as to give that part the
appearance of being bloody when seen at a little distance."[4] Upon making
a section of a corpus luteum, we observe that its cavity has an angular
form, from which, as from a centre, white lines radiate to the
circumference of the vesicle; an appearance which is evidently produced by
the corrugation of the inner membrane of the vesicle, as above alluded to.
To a similar cause we may also attribute the lobular appearance, which the
structure of the corpus luteum presents when a section is made of it. The
number of these corpora lutea corresponds exactly with the number of newly
formed ova. Meckel, after having examined no less than two hundred
pregnant animals of the class mammalia, found that the number of corpora
lutea corresponded exactly with that of the young produced. "When there is
only one child," says Dr. W. Hunter, "there is only one corpus luteum, and
two in the case of twins. I have had opportunities of examining the ovaria
with care in several cases of twins, and always found two corpora lutea.
In some of these cases there were two distinct corpora lutea in one
ovarium, in others there was a distinct corpus luteum in each ovarium."
A Graafian vesicle cannot be converted into a corpus luteum except by
actual and effective sexual intercourse; and the strange and discrepant
accounts which have every now and then been published, even by authors of
considerable repute, of corpora lutea having been found in the ovaries of
virgin and even newly-born animals merely prove that the true
characteristics of the corpus luteum were not sufficiently known. The
irregular cysts, cavities, or deposites of whitish or yellowish structure
which are frequently found in the ovary, independent of impregnation, and
which have been improperly enough called virgin corpora lutea, present
points of difference so marked that they can scarcely be mistaken by an
experienced eye. The angular cavity opening externally, the stellated,
radiated, cicatrix-like appearance, which a section of the corpus luteum
presents, its soft and delicate structure as described by Dr. Hunter, and
above all its vascularity, and the facility with which its vessels can be
injected from the general tissue of the ovary, are characters only found
in a true corpus luteum. Virgin corpora lutea frequently occur under
circumstances of disease, especially those of a tubercular character. They
frequently appear as distinct cysts, the walls of which are
semi-cartilagenous; at other times they seem to be nothing more than a
coagulum of blood: they seldom project much from the ovary, and in no
instance have they the peculiar structure of the corpus luteum, nor the
external cicatrix, nor are they capable of being injected.
After awhile the cavity of the corpus luteum contracts, and the opening
into it closes. The surrounding stroma loses its vascularity, the
prominence at this part of the ovary gradually subsides, and the ovary
returns to its former size. The periods at which these changes take place
vary, but with the exception of those first mentioned they proceed slowly
whilst pregnancy lasts, after which time, now that the increased activity
of the pelvic circulation peculiar to that period has ceased, they advance
more rapidly.
[Illustration: Corpus luteum at the end of the ninth month. _From Dr.
Montgomery._]
"If an examination be made within the first three or four months after
conception, we shall, I believe, always find the cavity still existing,
and of such a size as to be capable of containing a grain of wheat at
least, and very often of much greater dimensions: this cavity is
surrounded by a strong white cyst (the inner coat of the Graafian
vesicle,) and as gestation proceeds the opposite parts of this
approximate, and at length close together, by which the cavity is
completely obliterated, and in its place there remains an irregular white
line, whose form is best expressed by calling it radiated or
stelliform."[5] Dr. Montgomery adds, "I am unable to state exactly at what
period the central cavity disappears, or closes up to form the stellated
line. I think I have invariably found it existing up to the end of the
fourth month. I have one specimen in which it was closed in the fifth
month, and another in which it was open in the sixth: later than this I
never found it."
When pregnancy is over, the corpus luteum gradually diminishes and
disappears. Dr. Montgomery states that "the exact period of its total
disappearance I am unable to state, but I have found it distinctly visible
so late as at the end of five months after delivery at the full time, but
not beyond this period." Hence it will be seen that in a few months after
the termination of pregnancy, all traces of the corpus luteum are lost,
and that, therefore, it will be impossible to decide as to how frequently
impregnation has taken place, merely by examining the ovaries, as has been
supposed. There is also another point to which Dr. Montgomery has alluded,
which is well worthy of notice: in mentioning the fact that a vesicle may
contain two ova, and thus a woman be delivered of twins, and yet there be
but one corpus luteum, he observes that "the presence of a corpus luteum
does not prove that a woman has _borne a child_, although it would be a
decided proof that she has been impregnated, and had conceived, because it
is quite obvious that the ovum, after its vivification, may be, from a
great variety of causes, blighted and destroyed, long before the foetus
has acquired any distinct form. It may have been converted into a mole or
hydatids: thus, however paradoxical it may at first sight appear, it is
nevertheless obviously true, that a woman may conceive and yet not become
truly with child, a fact already alluded to, as noticed by Harvey; but the
converse will not hold good. I believe no one ever found a foetus in utero
without a corpus luteum in the ovary; and that the truth of Haller's
carollary, 'nullus unquam conceptus est absque corpore luteo' remains
undisputed."
During childhood, the ovaries present a perfectly smooth surface, and
their structure appears to be homogeneous, consisting of a dense cellular
tissue. About the seventh year, the first traces of the Graafian vesicles
make their appearance; as the period of puberty approaches, the whole
gland enlarges, becomes softer and more vascular; the Graafian vesicles
are more numerous, and generally one or two will be found larger and more
prominent than the rest. After repeated impregnations, and especially
towards that time of life when the catamenia are about to disappear, the
ovary becomes more or less flabby and corrugated, and at a still more
advanced age presents a shrivelled appearance.
The ovaries are liable to inflammation and its consequences, more
especially abscess, general enlargement, and induration: the malignant
changes of structure, viz. cephaloma, hæmatoma, and cancer, rarely have
their origin in the ovaries, but extend to these organs from the adjacent
parts. Lipomatous or fatty tumours are occasionally met with, containing
hair, rudiments of teeth, &c. Cysts not unfrequently occur in the ovaries,
and attain a very considerable size; they are simple or compound,
sometimes consisting of several cysts one within the other, and distended
with fluids, which vary considerably in their character. These tumours
come under the general head of OVARIAN DROPSY. The ovaries are also liable
to many remarkable morbid changes in the puerperal state, such as
softening and complete disorganization, the natural structure of the organ
being entirely broken down and converted into a bloody pulpy mass; in some
cases the whole gland is apparently dissolved away, so as scarcely to
leave a trace of its previous existence.
_Fallopian tubes._ The Fallopian tubes, which act as excretory ducts to
the ovaries, take their course through the upper portion of the broad
ligaments, running from without inwards, towards the superior margin of
the uterus, the ovaries being situated behind and somewhat above them.
They are somewhat contorted, and are considerably more dilated at their
abdominal extremity where they are unattached, than where they are
connected to the uterus, being as much as from three to four lines at the
former point; whereas, at the latter, they are not more than half a line.
Their abdominal extremity, which is like the mouth of a funnel, has its
edge strongly fimbriated, and has hence been called the _morsus diaboli_.
Their other extremity opens into the cavity of the uterus at the angle
which the fundus forms with its sides, and the whole of the tube is about
five inches.
The Fallopian tubes receive their external covering from the peritoneum,
which becomes connected at their open extremity with the membrane which
lines them. Between the external and internal membrane is the proper
tissue of the tubes, and which, except in very muscular subjects, seldom
display the fibrous structure; still, nevertheless, two layers of fibres
have been observed--an outer or longitudinal, and an inner or circular
layer. The Fallopian tubes are lined with mucous membrane, forming
numerous longitudinal rugæ. The canal is not pervious during the early
months of foetal life, the abdominal extremity being closed and rounded;
this appears to open about the fourth month. The canal is relatively
larger, the younger the embryo is, and may, therefore, be easily
demonstrated at this time.
At the period of impregnation, the Fallopian tubes implant themselves by
means of their fimbriated extremity upon that part of the ovary where the
Graafian vesicle is about to burst; they become remarkably engorged with
blood, assuming a deep purple colour, and are now much thicker; the canal
enlarges, so that a tolerably-sized probe can be introduced, whereas, at
other periods it will scarcely admit a large bristle. The uterine
extremity of the tube is closed by a continuation of that pulpy coagulable
lymph-like secretion which now lines the cavity of the uterus, forming the
membrana decidua of Hunter, and which, especially on the side where the
corpus luteum is found, extends into the tube to nearly the distance of an
inch. The tubes are now observed to be in a state of distinct peristaltic
motion, "like writhing worms," as Mr. Cruickshank has well expressed it;
"the fimbriæ were also black and embraced the ovaria (like fingers laying
hold of an object) so closely and so firmly, as to require some force and
even slight laceration to disengage them."[6] From the great degree of
vascularity which is observed in the Fallopian tubes at this period, some
anatomists have been induced to consider that their proper tissue was
vascular, analogous to the corpora cavernosa penis. Besides the
peristaltic motion already mentioned, other movements called ciliary have
been observed in the Fallopian tubes at this period, consisting of minute
portions of mucous membrane moving briskly and whirling round their axis,
apparently for the purpose of propelling the ovum.[7]
As pregnancy advances, the Fallopian tubes undergo other changes as
respects their situation, which are worthy of notice. The broad
ligaments, in the upper parts of which the Fallopian tubes take their
course, are well known to be merely expansions of peritoneum from each
side of the uterus, and therefore become gradually unfolded and shorter as
the uterus increases in size. "In proportion as the fundus uteri rises
upwards and increases in size, the upper part of the broad ligament is so
stretched that it clings close to the side of the uterus, so that in
reality the broad ligament disappears, no more of it remaining than its
very root, viz. its upper and outer corner, where the group of spermatic
vessels pass over the iliacs immediately to the side of the uterus. In
this state, though the small end of the tube opens in the same part of the
uterus as before impregnation, yet the tube has a very different
direction. Instead of running outwards in the horizontal direction, it
runs downwards, clinging to the side of the uterus. And behind the fimbriæ
lies the ovarium, for the same reason clinging close to the side of the
uterus."[8]
_Uterus._ The uterus is a hollow fibrous viscus situated in the
hypogastric region between the bladder and the rectum, below the
intestinum ileum and above the vagina, and is by far the largest of the
generative organs. It is of a pyriform figure: its upper portion which is
the largest is triangular, becoming gradually smaller inferiorly; that
portion of it which is above the spot where the Fallopian tubes enter is
called the _fundus uteri_; the lower and cylindrical portion receives the
name of _cervix_; that between the cervix and fundus is called the _body
of the uterus_.
The parietes of the adult uterus are nearly half an inch in their greatest
thickness, which is about the middle of the body, the body being slightly
thicker than the cervix, which is of a somewhat harder structure. Near the
point at which the Fallopian tubes enter the uterus the parietes become
thinner, gradually diminishing from four or five to only one line in
thickness.
The cavity of the uterus is triangular, its base being directed upwards,
the superior angles corresponding to the points where the Fallopian tubes
enter it. The cavity of the uterus is so small, owing to the thickness of
its parietes, that they are nearly in contact: it is only four lines in
breadth; the fundus, which forms the base of the triangle, is convex both
internally as well as externally; whereas, the sides which form the body
are convex internally, but somewhat concave externally.
The cavity of the uterus is most contracted at the point where the cervix
is united to the body, which here forms the _os uteri internum_; from this
point the cervix gradually dilates as far as its middle portion, when it
again contracts; its lower extremity terminates in the upper part of the
vagina by an anterior and posterior cushion-like projection, of which the
posterior is usually the longest, although from the direction of the
uterine axis the anterior is commonly felt lowest in the pelvis. Between
these there is a transverse fissure known by the name of _os tincæ_ or _os
uteri externum_, the lips or labia of which are formed by the two
above-mentioned prominences. The internal surface of the body of the
uterus is smooth, whereas that of the cervix is uneven, forming upon its
anterior and posterior wall a number of delicate rugæ diverging obliquely
in an arborescent form, and hence called the _arbor vitæ_. The lips of the
os uteri are smooth, except when slight lacerations have taken place
during labour.
In the virgin state the uterus is about two inches long, of which the
cervix occupies the smaller half: the greatest breadth of the body is
sixteen lines; that of the cervix from nine to ten. The uterus which has
been impregnated, especially when this has been frequently the case,
scarcely ever regains its original dimensions, and the fissure which the
os tincæ forms becomes broader from before backwards. The weight of an
adult virgin uterus is from seven to eight drachms, but the uterus which
has been once impregnated is seldom less than an ounce and a half. It lies
between the bladder and rectum, its upper half being covered by
peritoneum, which closely adheres to it. In the adult state it is situated
entirely in the cavity of the pelvis; the fundus, which is below the upper
edge of the symphysis pubis, is turned forwards and upwards, while its
mouth is directed downwards and backwards, so that its long axis is nearly
parallel to the axis of the superior aperture of the pelvis.
The uterus is connected to the neighbouring parts by several duplicatures
of peritoneum, which are continuous with that portion of it which covers
the fundus. The most considerable are the _broad_ or _lateral ligaments_:
these arise from the sides of the uterus, which is enclosed between their
anterior and posterior layers or laminæ; they proceed transversely
outwards towards the sides of the pelvic cavity, which is thus divided
into two portions, and are then continued into that portion of the
peritoneum which lines the cavity.
The _round ligaments_ arise from the sides of the uterus close beneath and
a little anterior to the uterine extremity of the Fallopian tubes. They
pass between the two layers of the broad ligaments, behind the umbilical
arteries, and before the iliac vessels, in a direction upwards and
outwards to the external opening of the inguinal canal; they then make a
turn round the epigastric artery downwards, inwards, and forwards, and
pass through the abdominal ring, and dividing into numerous fasciculi and
fibres are gradually lost in the cellular substance of the mons Veneris
and upper portion of the labia. Besides consisting of cellular substance
and blood-vessels, the round ligaments contain some very distinct bundles
of muscular fibres, of which the upper arise from the external layer of
uterine fibres, and the lower from the inferior edge of the internal
oblique muscle, and pass upwards.
Upon a superficial examination, the structure of the uterus would almost
seem to be homogeneous, nevertheless a number of reddish yellow strata
interspersed with whitish streaks running from behind forwards may be
perceived even in the unimpregnated state; between these strata the
vessels of the uterus take their course, forming numerous anastomoses.
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 circumstances 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 principal 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 circumference
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 circumstance 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
mass 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 circumstances 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
vagina.
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 rugæ, between which the mucous follicles are chiefly found.
[Illustration: 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 classes 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 class mammalia; and even in the lower genera of this
class it bears a strong resemblance to the tubular character of the
generative organs in the inferior classes 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 vagina
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 canal.
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
space: 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.
[Illustration: Uterus bicollis.]
[Illustration: 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.
[Illustration: 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, ass, &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 passes 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.
[Illustration: 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.
[Illustration: Uterus simplex.]
The uterus is at first of an equal width throughout; it is perfectly
smooth and not distinguished from the vagina 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 puberty 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 puberty has been fully attained. The os tincæ or os uteri
externum first appears as a scarcely perceptible prominence projecting
into the vagina; it increases gradually, in size until the latter months
of gestation, when the portio vaginalis 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 puberty, 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 analogy 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 canal 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 mass 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 rugæ, 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 circumstance 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 quantity of blood, and the
greatest number both of the large and small arteries at that part pass
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 vertebræ, 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
vaginalis 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
vaginalis 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 canal being closed by the gelatinous plug already mentioned.
In primiparæ, or women pregnant for the first time, the margin of the os
uteri thus closed is not only circular but perfectly smooth; whereas in
multiparæ, 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 pubes; 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 superincumbent 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 rectum, 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 vaginalis 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 vaginalis has lost half its
length, being scarcely half an inch in length.
[Illustration: 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 primiparæ; 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 vaginalis 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.
[Illustration: 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 primiparæ
has entirely disappeared. The portio vaginalis 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.
[Illustration: 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 primiparæ: 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 multiparæ, 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 vaginalis 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.
The fundus is now lower than it was in the preceding month, being about
half way between the scrobiculus cordis and umbilicus; the abdomen has, as
it is called, _fallen_; and from the diaphragm being now able to resume
its functions the breathing becomes more easy, and the female feels more
comfortable and capable of moving about. On examination per vaginam the
anterior portion of the inferior segment of the uterus will be felt still
deeper in the pelvis: if the head presents it distends this part of the
uterus, so that, in many cases, we have to pass the finger round it before
we can reach the os uteri, which is now in the upper part of the hollow of
the sacrum. All traces of the cervix have now disappeared, it having been
required to complete the full development of the uterus; the situation of
the os uteri itself is marked merely by a small depression or dimple;
there is no longer any distinction between the os uteri internum and
externum; the edges of the opening are so thin as to be nearly membranous,
but remain closed in primiparæ until the commencement of labour.[16]
In women who have had several children, a considerable difference is
observed as regards the state of the cervix and os uteri: the cervix does
not undergo that shortening during the latter half of pregnancy, which is
the case in a primipara, a portion of it at least remaining up to the full
term of utero-gestation: in many cases, especially where the female has
had a large family, it is nearly an inch long at this period; nor is the
lower portion of the uterus so spherical as in the primipara; to this
circumstance may probably be attributed the fact of the head not
descending so deep into the pelvis just before labour. In multiparæ the os
uteri is also very different: instead of being perfectly round with its
edges smooth, it is irregular and uneven, and seldom loses altogether the
lip-like shape of the unimpregnated state in consequence of the greater
thickness and elongation of its lips from former labours; its edges here
and there is uneven and knotty, from little callous cicatrices, where it
has been torn; moreover it does not remain closed till the commencement of
labour, but the os uteri externum (commonly called os tincæ,) and
sometimes even the os uteri internum will be more or less open during the
last three or four weeks of pregnancy. These peculiarities are of great
importance in coming to a conclusion as to whether a patient be in her
first pregnancy or not: although not invariable in the utmost sense of the
word, still their occurrence, even after a single labour, is sufficiently
frequent to make them worthy of careful observation. Indeed, on more than
one occasion, we have known them occur even after a miscarriage, a
circumstance on the strength of which the patient had ventured to deny
that she was pregnant. On the other hand, we sometimes meet with the os
uteri in a second pregnancy so little altered by the effects of the
previous labour, that it would be extremely difficult to come to a
decision.
When labour is over, the uterus contracts very considerably, and, in a few
days after, its parietes will be found at least an inch in thickness. It
now gradually diminishes in size, and continues to do so for some weeks;
the blood-vessels contract, and losing the peculiarly loose spongy
structure of pregnancy it becomes harder, firmer, and more compact. It
nevertheless remains softer and larger than in the virgin state, and does
not attain its original size and hardness until an advanced period of
life.
The os uteri, which in the latter months of pregnancy had formed a
circular opening, resumes its former shape, except that its lips,
especially the posterior one, which are more or less irregular and uneven,
are thicker and longer than in the virgin state. For the first weeks after
labour, the os uteri is high in the pelvis, soft, and easily admits the
tip of the finger; at the end of the second week it is much lower in the
pelvis, and no longer permits the finger to pass. Immediately after
labour, the contracted uterus forms a hard solid ball, the size of a
new-born child's head; this state of contraction is not, however, of long
continuance: in the course of half an hour, or even less, it begins to
increase in size, becoming softer and larger, and continuing to increase
slowly for some hours, when it again gradually diminishes, until, as
before observed, it approaches its original size in the unimpregnated
state. The state of powerful contraction in which the uterus is felt
immediately after labour, after a time gradually relaxes; its spongy
texture, from which the blood had been forcibly expelled by the violent
action of its fibres, becomes again filled with blood; the organ swells
and becomes softer and more bulky, and the orifices of the vessels which
open into the cavity of the uterus are again partly pervious, and emit a
sanious fluid called the _lochia_. This state lasts for two or more days
after delivery, when the vessels begin to recover their former caliber,
and lose that degree of dilatation peculiar to the gravid state. The
lochia become less and less coloured, and now, and not before the uterus
undergoes that gradual diminution of size and bulk which we have just
alluded to.
The copulative or external organs of generation are the _vagina_, _hymen_,
_clitoris_, _nymphæ_, and _labia_, the three last being known by the term
_vulva_.
_Vagina._ The vagina is a canal of about four inches in length and one in
breadth, broader above than below; its parietes are thin and are
immediately connected with the uterus. It envelopes the portio vaginalis
of the uterus at its upper or blind extremity (fundus vaginæ,) and is
continuous with its substance; inferiorly, where it is narrowest, it
passes into the vulva. It is situated between the bladder and rectum, and
attached to each by loose cellular tissue. Its direction differs from that
of the uterus, for its axis corresponds very nearly with that of the
pelvic outlet, running downwards and forwards. Posteriorly it is somewhat
convex, anteriorly concave.
The vagina consists of two layers; the external, which is very thin, firm,
of a reddish-white colour, and continuous with the fibrous tissue of the
uterus; and a lining mucous membrane which is closely united to it. This
latter is much corrugated, especially in the virgin state, the rugæ
running transversely in an oblique direction, and gathered together on its
anterior and posterior surface, forming the _columna rugarum anterior and
posterior_, which appear to be a continuation of the corrugations which
form the arbor vitæ of the cervix.
In the upper part of the vagina there are considerable mucous follicles,
which moisten the canal with their secretion, and which during sexual
intercourse, and particularly during the first stage of labour, pour forth
an abundant supply of colourless mucus for the purpose of lubricating the
vagina, and rendering it more dilatable. Near its orifice, especially at
the upper part, the veins of the vagina form the _plexus retiformis_, a
congeries of vessels which has almost a cellular appearance, and from this
reason has been called the _corpus cavernosum_ of the vagina; it appears
to be capable of considerable swelling from distension with blood, like
the corpus cavernosum penis, and by this means serves to contract still
farther the os externum during the presence of venereal excitement. A
similar disposition to form plexuses of vessels is seen in the venous
circulation of the nymphæ, bladder, and rectum.
_Hymen._ The lining membrane of the vagina is of a reddish-gray colour,
interspersed here and there, especially at its upper part, with livid
spots like extravasation. At the os externum it forms a fold or
duplicature called _hymen_, running across the sides of the posterior part
of the opening, and usually of a crescentic figure, the cavity looking
upwards. The duplicatures of membrane are united by cellular tissue. In
some instances, the hymen arises from the whole circumference of the os
externum, having a small orifice in the centre for the escape of the
menses and vaginal secretions: in some rare cases it is cribriform; and in
others it completely closes the vaginal entrance. When torn in the act of
sexual intercourse, it generally forms three or four little triangular
appendages, called _carunculæ myrtiformes_, arising from the posterior and
lateral portions of the os externum.
From the identity of its fibrous coat with that of the uterus, the vagina
possesses considerable powers of contraction, when excited by the presence
of any body which distends it; hence it is a valuable assistance to the
uterus during labour: it also stands in the same relation to the abdominal
muscles that the rectum does, so that as soon as it is distended by the
head, &c. it calls them into the strong involuntary action, which
characterizes the bearing down pains of the second stage of labour. The
orifice of the vagina (os externum) is surrounded by a thin layer of
muscular fibres, which arise from the anterior edge of the sphincter ani;
they enclose the outer margin of the vagina, cover its corpus cavernosum,
and are inserted into the crura clitoridis at their union. It has been
called the sphincter or constrictor vaginæ, and assists the corpus
cavernosum still farther in contracting the os externum.
_Clitoris._ The clitoris is an oblong cylindrical body, situated beneath
the symphysis pubis, arising from the upper and inner surface of the
ascending rami of the ischium, by means of two crura of about an inch
long, and uniting with each other at an obtuse angle. It terminates
anteriorly in a slight enlargement, called the _glans clitoridis_, which
is covered with a thin membrane or a loose fold of skin, viz. the
_preputium clitoridis_. It is a highly nervous and vascular organ, and
like the penis of the male, is composed of two crura and corpora
cavernosa, which are capable of being distended with blood; they are
contained in a ligamentous sheath, and have a septum between them. The
clitoris is also provided with a suspensory ligament, by which it is
connected to the ossa pubis. Like that of the penis, the glans clitoridis
is extremely sensible, but has no perforation. Upon minute examination, it
will be found that the gland is not a continuation of the posterior
portion of the clitoris, but merely connected with it by cellular tissue,
vessels, and nerves; the posterior portion terminates on its anterior
surface in a concavity which receives the glans. In the glans itself there
is no trace of the septum, which separates the corpora cavernosa. On the
dorsum of the clitoris several large vessels and nerves take their course,
and are distributed upon the glans, and upon its prepuce are situated a
number of mucus and sebaceous follicles.
The crura clitoridis at their lower portion are surrounded by two
considerable muscles, called the erectores clitoridis, arising by short
tendons close beneath them from the inner surface of the ascending ramus
of the ischium, and extending nearly to their extremity.
_Nymphæ._ The _nymphæ_ or _labia pudendi interna_, are two long corrugated
folds, resembling somewhat the comb of a cock, arising from the prepuce
and glans clitoridis, and remaining obliquely downwards and outwards along
the inner edge of the labia, increasing in breadth, but suddenly
diminishing in size. At their lower extremity they consist of a spongy
tissue, which is more delicate than that of the clitoris, but resembles
considerably that of the glans, of which it appears to be a direct
continuation. It has been called the _corpus cavernosum nympharum_, and is
capable of considerable increase in size when distended with blood. The
two crura of the prepuce terminate in their upper and anterior
extremities; they are of a florid colour, and in their natural state they
are contiguous to, and cover the orifice of the urethra. The skin which
covers them is very thin and delicate, bearing a considerable resemblance
to mucous membrane, especially on their inner surface, where it is
continuous with the vagina; externally it passes into the labia.
The space between the nymphæ and edge of the hymen is smooth, without
corrugation, and is called _vestibulum_.
Close behind the clitoris, and a little below it, is the orifice of the
urethra, lying between the two nymphæ: it is surrounded by several lacunæ
or follicles of considerable depth, secreting a viscid mucus; its lower or
posterior edge is, like the lower portion of the urethra, covered by a
thick layer of cellular tissue, and a plexus of veins, which occasionally
become dilated and produce much inconvenience; it is this which gives the
urethra the feel of a soft cylindrical roll at the upper part of the
vagina; and in employing the catheter, by tracing the finger along it, the
orifice will be easily found.
_Labia._ The labia extend from the pubes to within an inch of the anus,
the space between the vulva and anus receiving the name of _perineum_.
The opening between the labia is called the _fossa magna_: it increases a
little in size and depth, as it descends, forming a scaphoid or boat-like
cavity, viz. the _fossa navicularis_.
The labia are thicker above, becoming thinner below, and terminate in a
transverse fold of skin, called the _frænulum perinei_, or _fourchette_,
the edge of which is almost always slightly lacerated in first labours.
They are composed of skin cushioned out by cellular and fatty substance,
and lined by a very vascular membrane, which is thin, tender, and red,
like the inside of the lips; they are also provided with numerous
sebaceous follicles, by which the parts are kept smooth and moist.
CHAPTER III.
DEVELOPMENT OF THE OVUM.
_Membrana decidua.--Chorion.--Amnion.--Placenta.--Umbilical
cord.--Embryo.--Foetal circulation._
_Membrana decidua._ The earliest trace of impregnation which is to be
observed in the cavity of the uterus, and even before the ovum has reached
it, is the presence of a soft humid paste-like secretion, with which the
cavity of the uterus is covered, and which is furnished by the secreting
vessels of its lining membrane. This is the _membrana decidua_ of Hunter:
properly speaking, it should be called the _maternal membrane_, in
contra-distinction to the chorion and amnion, which, as belonging
peculiarly to the foetus, are called the _foetal_ membranes.[17]
Although at first in a semi-liquid state, it soon becomes firmer and more
compact, assuming the character of a membrane: it appears to be nothing
else than an effusion of coagulable lymph on the internal surface of the
uterus, having "scarcely a more firm consistence than curd of milk or
coagulum of blood." (Hunter, _op. cit._ p. 54.) Hence, although much
thicker than the other membranes, it is weaker; it is also much less
transparent.
It is not of an equal thickness, being considerably thicker in the
neighbourhood of the placenta than elsewhere; inferiorily, and especially
near the os uteri, it becomes thinner: during the first weeks of pregnancy
it is much thicker than afterwards, becoming gradually thinner as
pregnancy advances, until it is not half a line in thickness. In the
earlier months its external surface is rough and flocculent, but
afterwards it becomes smoother as its inner surface was at an earlier
period.
It is much more loosely connected with the uterus during the first months
of pregnancy than afterwards, and this is one reason why premature
expulsion of the ovum is more liable to take place at this period than
during the middle and latter part of utero-gestation. It is more firmly
attached to the uterus in the vicinity of the placenta than any where
else, which is owing to the greater number of blood-vessels it receives
from the uterus at this point; whereas commonly "it has no perceptible
blood-vessels at that part which is situated near the cervix uteri,"
(_Ibid._,) this portion being much more loosely connected with the uterus.
The course which the decidual vessels take on coming from the inner
surface of the uterus is admirably adapted to render the attachment of
this membrane to it as firm as possible.
[Illustration: Vascularity of the decidua. _From Baer._]
Upon examining the lining membrane of the uterus at a very early period,
when the decidua was still in a pulpy state, Professor v. Baer
observed[18] that its villi, which in an unimpregnated state are very
short, were remarkably elongated: between these villi, and passing over
them, was a substance, not organized but merely effused, and evidently the
membrana decidua at an extremely early age. The uterine vessels were
continued into this substance, and formed a number of little loops round
the villi, thus anastomosing with each other. On account of this reticular
distribution it was impossible to distinguish arteries from veins; there
is evidently the same relation between the uterus and the decidua as
between an inflamed surface and the coagulable lymph effused upon it.
[Illustration: Decidual cotyledons. _From Dr. Montgomery._]
Professor v. Baer considers that at a later period the connexion between
the decidua and mucous membrane becomes so intimate, that it is impossible
to separate the former without also separating the latter from the fibrous
tissue of the uterus. This, we apprehend, is the stratum which, as Dr.
Hunter observes, "is always left upon the uterus after delivery, most of
which dissolves and comes away with the lochia." He does not appear to
have been fully aware of the close connexion between the decidua and
lining membrane of the uterus, although he evidently observed the fact
from the following sentence: "in separating the membranes from the uterus
we observe that the adhesion of the decidua to the chorion, and likewise
its adhesion to the _muscular fibres of the uterus_, is rather stronger
than the adhesion between its external and internal stratum, which, we may
presume, is the reason that in labour it so commonly leaves a stratum
upon the inside of the uterus." According to the observations of Dr.
Montgomery, a great number of small cup-like elevations may be seen upon
the external surface of the decidua vera, "having the appearance of little
bags, the bottoms of which are attached to, or embedded in, its substance;
they then expand or belly out a little, and again grow smaller towards
their outer or uterine end, which, in by far the greater number of them,
is an open mouth when separated from the uterus: how it may be while they
are adherent, I cannot at present say. Some of them which I have found
more deeply embedded in the decidua were completely closed sacs. They are
best seen about the second or third month, and are not to be found at the
advanced periods of gestation."[19]
[Illustration: _a_ Uterus. _d_ Decidua reflexa. _b_ Fallopian tube. _e_
Ovum. _c_ Decidua.]
The membrana decidua does not envelope the ovum with a single covering,
but forms a double membrane upon it, somewhat like a serous membrane; in
fact, the descent of the ovum through the Fallopian tube is very similar
to that of the testicle through the inguinal canal into the scrotum. The
ovum pushes before it that portion of the decidua which covers the uterine
extremity of the Fallopian tube, and enters the cavity of the uterus,
which is already lined with decidua, covered by the protruded portion
which forms the _decidua reflexa_. It must not be supposed that this
reflexion of the decidua is completed as soon as the ovum enters the
uterine cavity; the ovum usually remains at the mouth of the Fallopian
tube, from which it has emerged, covered by the plastic mass of soft
decidua, and the reflexion of this membrane will take place in proportion
as the ovum gradually increases in size. The external layer of decidua is
called _decidua vera_; the internal or reflected portion is called the
_decidua reflexa_, having received this appellation from its discoverer,
Dr. Hunter. These membranes would, as Dr. Baillie has correctly observed,
be more correctly named the _decidua uteri_ and _decidua chorii_: the
decidua chorii or reflexa is reflected inwardly from above downwards; it
is connected on its inner surface with the chorion: externally it is
unattached, whereas, the decidua uteri or vera is unconnected on its inner
surface, but attached to the uterus externally.
The membrana decidua differs in its arrangement from that of a serous
membrane, inasmuch, as it is not only reflected so as to cover the
chorion, but at the point of reflexion it is continued over the chorion
externally, where it forms the placenta, so that the chorion is enclosed
in all directions by the decidua: this latter portion, however, is not
formed till about the middle of pregnancy. The decidua uteri or vera does
not extend farther than the os uteri internum, which is filled up by the
plug of tough gelatinous substance above described; the decidua chorii or
reflexa, from its forming the outer covering of the chorion, of course
passes over the os uteri.
[Illustration: _Membrana decidua._
The lower orifice corresponds to the os uteri, the two upper ones to the
Fallopian tubes. _From Dr. Hunter._]
According to Mr. John Hunter, the decidua vera is continued some little
way into the Fallopian tubes, more especially, on that side where the
corpus luteum has been formed; it is perforated at the points where the
Fallopian tubes enter, as well as at the os uteri, a fact which is
beautifully shown in Dr. Hunter's last plate: but this does not continue
long, for, as Mr. John Hunter observes, the inferiour opening becomes
closed in the first month, and, according to Lobstein's observations, the
openings of the Fallopian tubes are closed after the second month. "Where
the decidua reflexa is beginning to pass over the chorion, there is, at an
early period of pregnancy, an angle formed between it and the decidua,
which lines the uterus; and here the decidua is often extremely thin and
perforated with small openings so as to look like a piece of lace.
"In proportion as pregnancy advances, the decidua reflexa becomes
gradually thinner and thinner, so that at the fourth month it forms an
extremely fine layer covering the chorion; it comes at the same time more
and more closely in contact with the decidua, which lines that part of the
uterus to which the placenta is not fixed, till at length they adhere
together."[20] That portion of the decidua which passes between the
placenta and uterus during the latter half of gestation, is called the
_placental decidua_, the description of which will be given with that of
the placenta.
To Dr. W. Hunter are we indebted for the first correct description of the
decidua; indeed, so excellent is it, that the membrane has been called
after him, the _decidua of Hunter_. Although he was the undoubted
discoverer of the reflexa, the existence of the decidua was distinctly
noticed by Burton, in 1751. In stating the _post mortem_ examination of a
woman, who died undelivered at the full time of pregnancy, he says, "Upon
wiping the inside of the uterus very gently with a sponge, there seemed to
be pieces of a very tender thin transparent membrane adhering to it in
such parts of the uterus where the placenta did not stick to it; but as
the womb was somewhat corrupted, and the membrane so very tender, we could
not raise any bulk of it so as to be certain what it was." (Burton's
_Midwifery_.)
The decidua seems chiefly intended to form the maternal part of the
placenta: (see _Placenta_:) hence in all those quadrupeds when the
maternal part of the placenta is permanently appended to the internal
surface of the uterus, no decidua is found.
Having described the maternal membranes of the ovum, we come now to the
membranes which form the parietes of the ovum. These are called the
_foetal membranes_, for they are essentially connected with the origin of
the foetus itself. They are the _chorion_ and the _amnion_; besides which,
there are two others that require notice, viz. the _vesicula umbilicalis_
and _allantois_.
_Chorion._ The chorion is the proper covering of the ovum, and corresponds
to the membrane lining the shell of an egg, in oviparous animals. It is a
thin and transparent membrane, and presents on its external surface a
ragged tufted appearance, being covered externally with groups of
arborescent villous processes, which after a time unite into trunks to
form the umbilical vessels, which, according to Lobstein's observations,
are merely veins during the early period of gestation. These loose tufts
of venous radicles appear to absorb nourishment for the ovum, much in the
same manner as the roots of a plant. Although the chorion is so thin and
transparent, it consists nevertheless of two laminæ or layers, between
which the villi, which produce this shaggy appearance, take their course.
Although the chorion on its external surface is nothing but a net-work of
villi, which in process of time become vascular, anatomists have been
unable to detect blood-vessels in the structure of the membrane itself.
Its vascularity, however, has been asserted chiefly on the ground of the
known vascularity of the decidua, it being supposed that the vessels of
the decidua penetrate into the chorion. The chorion, however, belongs so
essentially and exclusively to the foetus, that it appears extremely
improbable that any maternal vessels should ramify in its structure for
the purposes of its nourishment and growth, and the more so when we
reflect that the nutrition of the foetus itself at this early period is
obtained in so different a manner. It is, moreover, extremely difficult to
distinguish between the venous absorbing radicles of the chorion, which
form the early rudiments of the umbilical vessels, and any vessels which
may take their course in the structure of the membrane itself; and the
more we consider the relation between the chorion and the decidua, the
less are we inclined to accept Meckel's explanation of the vascularity of
the chorion, viz. that the vessels of the decidua have the same relation
to those of the chorion as the blood-vessels of the maternal part of the
placenta have to those of the foetal part.
Neither nerves nor lymphatics have been discovered in the structure of the
chorion, unless, indeed, those white filaments, which are observed here
and there about the edge of the placenta, perform the office of
lymphatics. This has been hinted at by Dr. Hunter, where he says, "these
are the remains of those shaggy vessels which shoot out from the chorion
in a young conception, and give the appearance of the ovum being
altogether surrounded by the placenta at that time. With a magnifying
glass, they appear to be transparent ramifying vessels, which run in
corresponding furrows upon the internal surface of the decidua, and a good
deal resemble lymphatics." (W. Hunter, _op. cit._ p. 53.)
The chorion undergoes various changes during the different periods of
pregnancy, and forms a very important part of the physiology of
utero-gestation. Its thickness, which in the earlier months of pregnancy
is more considerable than afterwards, at this period is uniform in every
part of the ovum: its external surface covered with those villous
prolongations which have already been alluded to. In the second month of
pregnancy these become larger, and much more arborescent; after the third
month a considerable portion of them gradually disappears, generally from
below upwards, so that the greater part of its external surface becomes
nearly smooth, except at that point where the umbilical cord has its
origin, at which spot the villous prolongations become more developed, and
unite to form the umbilical vessels. This part of the chorion, together
with the corresponding portion of the membrana decidua, forms a flat
circular mass, which at the end of pregnancy covers nearly one-third of
the surface of the ovum, and constitutes the placenta or after-birth. At
this point the chorion, which forms its inner surface, is considerably
thicker than elsewhere.
At the commencement of pregnancy the chorion is but loosely connected with
the decidua, but by degrees it becomes so closely connected by fibres,
which are the remains of the little vascular prolongations, especially
where these two membranes combine to form the placenta, that in the latter
months of pregnancy, they can scarcely, if at all, be separated.
For the more minute consideration of the formation, development, and
functions of the chorion, we must refer to the description of the placenta
and foetus.
_Amnion._ The amnion is the inner membrane of the ovum. It is transparent,
and of great tenuity, "yet its texture is firm, so as to resist laceration
much more than the other membranes." (W. Hunter, _op. cit._ p. 50.) It is
loosely connected with the chorion on its external surface, except when
this membrane unites with the decidua to form the placenta at which spot
it adheres to the chorion much more firmly. Its inner surface, which is in
immediate contact with the liquor amnii, is very smooth; whereas
externally, from being connected with the chorion by an exceedingly fine
layer of cellular tissue, its surface is not so smooth. Dr. W. Hunter
considers that this intervening tissue, is a gelatinous substance: it
seems, however, to possess too much elasticity for such a structure; and,
from the reticular appearance which it generally presents upon the
membranes to which it adheres, we are inclined to adopt the opinion of
Meckel in considering it cellular. "In the very early state of an ovum the
amnium forms a bag, which is a good deal smaller than the chorion, and,
therefore, is not in contact with it." (_Ibid._ p. 75:) hence, therefore,
a space is formed between the two membranes which is filled with a fluid
called the _liquor amnii spurius_, or more correctly the _liquor
allantoidis_. "In the course of some weeks, however, it comes nearly into
contact with the chorion, and through the greater part of pregnancy the
two membranes are pretty closely applied to each other." (_Ibid._)
Lobstein, in his admirable _Essai sur la Nutrition du Foetus_, observes,
that the membranes continues separate from each other so late as the third
and fourth month. Cases every now and then occur where a considerable
quantity of fluid is found between the chorion and amnion in labour at the
full period of pregnancy.
We shall defer the minute description of the amnion and its relations,
during the very early periods of utero-gestation, until we describe the
embryo. The amnion is reflected upon the umbilical cord at its insertion
into the placenta, envelopes the umbilical vessels, the external covering
of which it forms, and is continued to the anterior surface of the child's
abdomen, passing into that projecting portion of the skin which forms the
future navel.
Blood-vessels and nerves have not as yet been discovered in the structure
of the amnion, but Meckel considers it extremely probable that the fine
layer of cellular tissue by which it is connected with the chorion
contains vessels for its nutrition.
_Liquor amnii._ The amnion contains a fluid known by the name of liquor
amnii. In the earlier months of pregnancy it is nearly, if not quite
transparent; as pregnancy advances it becomes turbid, containing more or
less of what appears to resemble mucus: it has a distinctly saline taste;
its specific gravity is rather more than that of water. Its relative and
absolute quantity vary considerably at different periods of pregnancy:
thus the relative weight of liquor amnii to that of the foetus is very
considerable at the beginning of pregnancy, at the middle they are nearly
equal, but towards the end, the weight of fluid to that of the child,
diminishes considerably, so that during the last weeks of pregnancy it
scarcely equals a pound, and seldom more than eight ounces, whereas the
medium weight of the child is usually between six and seven pounds: the
quantity, however, varies considerably, sometimes amounting to several
quarts. In the early months the absolute quantity increases, so that
between the third and fourth months it sometimes equals as much as
thirty-six ounces. Chemically it consists chiefly of water, a small
quantity of albumen and gelatine, a peculiar acid called amniotic, with a
little muriate of soda and ammonia, and a trace of phosphate of lime.
The source of the liquor amnii is still unknown. Dr. Burns asserts that
"it is secreted from the inner surface of the membrane by pellucid
vessels," but as he confesses that "these have never been injected or
traced to their source (_Principles of Midwifery_, by J. Burns, M. D. p.
222.,) little weight can be attached to such a view." Meckel considers
(_Handbuch der Menschlichen Anatomie_, vol. iv. p. 707,) that the greater
part of it, especially in the early months, is a secretion from the
maternal vessels, but that afterwards, as pregnancy advances, it becomes
mingled with the excretions of the foetus. It appears to be a means of
nourishment to the foetus during the first part of pregnancy, from the
fact that it contains more nutritious matter in the early than in the
latter months, since at that time a considerable coagulation is produced
by alcohol, &c. The disappearance of this coagulable matter of the liquor
amnii, towards the end of pregnancy, may be attributed to its having been
absorbed at an earlier period, and to the process of nutrition being now
carried on by other means. Besides being a source of nourishment to the
foetus, it serves many useful purposes; it secures the foetus against
external pressure or violence, and supports the regular distension of the
uterus; on the other hand it diminishes and equalises the pressure of the
foetus upon the uterus; during labour by distending the membranes into an
elastic cone, it materially assists to dilate the os uteri; it also serves
to lubricate and moisten the external passages.
_Placenta._ The placenta is formed essentially by the chorion and
decidua; it is a flat, circular, or more or less oval mass, soft, but
becoming firmer towards its edge. It is the most vascular part of the
ovum, and by which it is connected most intimately with the uterus. Its
longest diameter is generally about eight, its shortest about six inches;
its greatest thickness is at that spot where the umbilical cord is
inserted, which is usually about the middle of the placenta, although it
occasionally varies considerably in this respect, the cord coming off
sometimes at the edge. The placenta, as ordinarily seen after labour, is
barely an inch in its thickest part, but when filled with blood or
injection it swells very considerably, and is then little short of two
inches. It is generally attached to the upper part of the uterus in the
neighbourhood of one of the Fallopian tubes, and more frequently on the
left side than on the right; its inner or foetal surface is smooth, being
covered by the chorion, which at this part is much thicker.
The placenta cannot be distinguished from the other parts of the ovum
until the end of the second month, at which period it covers nearly half
the surface of the ovum, gradually diminishing in relative size, but
increasing in thickness and absolute bulk up to the full period of
utero-gestation. It forms a spongy vascular mass, its uterine surface
being divided unequally into irregular lobes called _cotyledons_.
The uterine surface of a full-grown placenta is covered by a pulpy
membrane, resembling in structure the decidua which covers the chorion,
and of which it seems to be a continuation. This is always found present
at the end of pregnancy: it covers the lobes of the uterine surface of the
placenta, descending into the sulci which runs between them: in some parts
it is thicker than in others, especially where it is connected with, or in
fact becomes, the decidua of the chorion or decidua reflexa. This
membrane, which has been called the _placenta decidua_, is pretty firmly
attached to the vessels of the placenta, so as not to be separated without
rupture; but by maceration, its texture is more or less destroyed, so that
we may easily distinguish the extremities of these vessels. "This decidua,
or uterine portion of the placenta," says Dr. Hunter, "is not a simple
thin membrane expanded over the surface of the part: it produces a
thousand irregular processes, which pervade the substance of the placenta
as deep as the chorion or inner surface; and are every where so blended
and entangled with the ramifications of the umbilical system, that no
anatomist will perhaps be able to discover the nature of their union.
While these two parts are combined, the placenta makes a pretty firm mass,
no part of it is loose or floating; but when they are carefully separated,
the umbilical system is evidently nothing but loose floating ramifications
of the umbilical vessels, like that vascular portion of the chorion, which
makes part of the placentula in a calf; and the uterine part is seen
shooting out into innumerable floating processes and rugæ, with the most
irregular and minutely subdivided cavities between them that can be
conceived. This part answers to the uterine fungus in the quadrupeds: it
receives no vessels demonstrable by the finest injection from those of the
navel string; yet it is full of both large and small arteries and veins:
these are all branches of the uterine vessels, and are readily filled by
injecting the arteries and veins of the uterus, and they all break through
in separating the placenta from the uterus, leaving corresponding orifices
on the two parted surfaces." (Hunter, _op. cit._ p. 42.)
According to Lobstein's observations, although this membrane appears to be
a continuation of the decidua which covers the chorion, it nevertheless
does not exist during the earlier months. During the first months of
pregnancy the placenta does not present a solid mass, with its uterine
surface covered with projecting lobuli, as it does at the full term of
pregnancy; but the vessels of which it is composed (foetal) are loose and
floating, as if it had been subjected to maceration. It has been supposed,
that this irregular lobulated appearance of the uterine surface of the
placenta was produced at the moment of its separation from the uterus
during labour; this, however, is not the case, for Lobstein having opened
the uterus of a woman who died in the fifth month of pregnancy, and
separated the placenta with great care, found these lobular prominences,
although not yet covered by the membrane of which we have just spoken.
Wrisberg, professor of anatomy at Göttingen, considered that this membrane
was distinct from the decidua reflexa, since with care the two membranes
can be easily separated.
[Illustration: _Uterine surface of the Placenta._]
In examining the uterine surface of a full grown placenta it is necessary
to place it upon something convex, in order that it may resemble, as
nearly as possible, the form which it had when attached to the concave
surface of the uterus; the cotyledons are thus rendered prominent and
separated from each other; the sulci, which run between them, are wide and
gaping: whereas, when the placenta is laid upon a flat surface, its
cotyledons are closely pressed together, and the sulci more or less
completely concealed. On minute examination of these sulci a number of
openings may be observed, varying in size and shape, but usually more or
less oval, their edges distinct, smooth, and thin; on directing a strong
light into some of the larger ones a number of smaller apertures may be
observed opening into them, in much the same way as is observed when
looking down a large vein. Some of these canals do not immediately lead to
smaller orifices as above described, but open at once into an
irregular-shaped cell or cavity, in the parietes of which numerous small
apertures may be observed, through which blood oozes when the adjacent
parts of the placenta are slightly pressed upon. Besides these openings at
the bottom of the interlobular sulci, others may be seen here and there
upon the cotyledons; these are generally smaller, their edges thicker, and
in most instances they are round; but they are not so invariably met with
as the openings between the cotyledons, these lobular projections being
sometimes very thickly covered with placental decidua. The openings
observed on the uterine surface of the placenta correspond to the mouths
of the uterine veins and arteries, which, in the unimpregnated state, open
into the cavity of the uterus, but which now, by means of the decidua,
convey maternal blood to and from the placenta. "Any anatomist," says Dr.
W. Hunter, "who has once seen and understood them, can readily discover
them upon the surface of any fresh placenta; the veins, indeed, he will
find have an indistinct appearance from their tenderness and frequent
anastomoses, so as to look a good deal like irregular interstitial void
spaces: the arteries which generally make a snake-like convolution or two,
on the surface of the placenta, and give off no anastomosing branches, are
more distinct." (Hunter, _op. cit._ p. 46.) From the observations of
Messrs. Mayo and Stanley, and from their examination of the original
preparations in the Hunterian museum at the College of Surgeons, London,
illustrating this subject, it appears that, in all probability, most of
the large thin-edged apertures at the bottom of the interlobular sulci are
connected with the uterine veins; whereas, the smaller orifices, the
margins of which are thicker, and which are chiefly observed upon the
cotyledons, are continuations of the uterine arteries.
These openings were also pointed out by the late Dr. Hugh Ley, in
describing the _post mortem_ examination of a woman who had died at the
full term undelivered (_Med. Gaz._ June 1, 1833:) "The uterine surface (of
the placenta) thus detached from the uterus, exhibited its lobules with
their intersecting sulci, even more distinctly than they are seen in the
uninjected placenta; and in several parts there could be perceived, with
the naked eye, small apertures of an oval form, with edges perfectly
smooth, regularly defined, and thicker, as well as more opaque, than the
contiguous parts which they penetrated." The communication between the
openings of the placental cells, and the mouths of the uterine veins and
arteries, which convey their blood to the placenta, as before observed,
is effected by means of the placental decidua. The connecting portion of
canal is of a flattened shape, runs obliquely between the uterus and
placenta, and appears to be formed entirely of decidua. The manner in
which the arteries pass to the placenta is very different to that of the
veins: "the arteries," as Dr. W. Hunter observes, "are all much convoluted
and serpentine; the larger, when injected, are almost of the size of
crow-quills: the veins have frequent anastomoses." Mr. J. Hunter has
described this point more minutely, and gives still more precise notions
of the manner in which the arteries pass to the placenta. "The arteries of
the uterus which are not immediately employed in conveying nourishment to
it, go on towards the placenta, and, proceeding obliquely between it and
the uterus, pass through the decidua without ramifying: just before they
enter the placenta, making two or three close spiral turns upon
themselves, they open at once into its spongy substance, without any
diminution of size, and without passing beyond the surface as above
described.
The intention of these spiral turns would appear to be that of diminishing
the force of the circulation as it approaches the spongy substance of the
placenta, and is a structure which must lessen the quick motion of the
blood in a part where a quick motion of this fluid was not wanted. The
size of these curling arteries at this termination is about that of a
crow's quill. The veins of the uterus appropriated to bring back the blood
from the placenta, commence from this spongy substance by such wide
beginnings as are more than equal to the size of the veins themselves.
These veins pass obliquely through the decidua to the uterus, enter its
substance obliquely, and immediately communicate with the proper veins of
the uterus; the area of those veins bear no proportion to their
circumference, the veins being very much flattened."[21]
On examining these vessels in an injected uterus to which the placenta is
attached, we shall therefore find that all traces of a regular canal or
tube are suddenly lost upon their entering the placenta; each vessel
(whether artery or vein) abruptly terminating in a spongy cellular tissue.
If a blow-pipe be introduced into a piece of sponge, we shall have a very
simple but correct illustration of the manner in which the uterine blood
circulates through the placenta. The cell into which each vessel
immediately opens is usually much larger than the rest, so that when the
cellular structure of the placenta is filled with wax, a number of
irregular nodules[22] are found continuous with these vessels and passing
into an infinity of minute granules, which are merely so many casts of
smaller cells. That this cellular tissue pervades the whole mass of the
placenta, and communicates freely with the uterine vessels by which it is
filled with blood, is proved by repeating a very simple experiment of Dr.
Hunter, viz. "if a blow-pipe be thrust into the substance of the placenta
any where, the air which is blown into the cellular part opens, and rushes
out readily by, the open mouths both of the arteries and veins." (Hunter,
_op. cit._ p. 46.) That it also envelopes the umbilical vessels of the
cord is shown by the fact, that if a pipe be inserted beneath the outer
covering of the cord near to its insertion into the placenta, we shall be
able to "fill the whole placenta uniformly in its cellular part, and
likewise all the venous system of the uterus and decidua, as readily and
fully as if we had fixed the pipe in the spermatic or hypogastric vein; so
ready a passage is there reciprocally between the cells of the placenta
and the uterine vessels." (_Ibid._ p. 47.)
The maternal portion of the placenta therefore consists of a spongy
cellular tissue, which is filled by the uterine vessels, and also of those
trunks which pass through the decidua, and which form the communication
between these vessels and the placental cells.
[Illustration: _Foetal surface of the placenta._]
The foetal surface of the placenta is smooth and glossy, being covered by
the amnion and chorion; it is much harder than the uterine surface, and is
streaked over by the larger branches of the umbilical vein and arteries,
which radiate irregularly from the point where the cord is inserted; and
which pass beneath the amnion, and between the two layers of which the
chorion is composed, to which they are intimately connected. These vessels
supply the various lobuli of which the placenta is composed, so that each
lobulus receives at least one of these branches; for, although the
umbilical cord consists of two arteries and one vein, this arrangement
does not continue into the body of the placenta. "Every branch of an
artery," as Dr. Hunter observes, "is attended with a branch of a vein:
these cling to one another, and frequently in the substance of the
placenta entwine round one another, as in the navel string." (_Ibid._ p.
40.) Each cotyledon receives its own vessels, so that the vessels of one
cotyledon have no direct communication with those of the adjacent ones, as
proved by Wrisberg's examinations; for if we inject the vessel or vessels
of one of these lobuli, the injection will not pass into those of the
others. When the vessels have reached the cotyledons, they are divided and
subdivided _ad infinitum_; they are connected together by a fine cellular
membrane, which may be very easily removed by maceration, and then they
may be seen ramifying in the most beautiful and delicate manner possible;
the main branches having no communication or anastomosis with each other.
The umbilical arteries anastomose freely with each other upon the foetal
surface of the placenta, before dividing into the branches
above-mentioned; hence, if an injection be thrown into one umbilical
artery it will return almost immediately by the other; but if this be tied
also, the injection, after a time, will return by the umbilical vein, but
not until all the vessels of the placenta have been filled, proving that
there is a free passage of blood from the arteries into the veins.
From these remarks, founded chiefly on the admirable observations of the
Hunters, and repeated examinations of the placenta, which we have made
with the greatest care and impartiality, it may be stated with confidence,
that the placenta consists of two portions--a maternal and a foetal. The
maternal portion consists, as we have before observed, of a spongy
cellular tissue; and also of those trunks which pass through the decidua,
and which form the communication between the uterine vessels and the
placental cells. The foetal part is formed by the ramifications of the
umbilical vessels: "that each of those parts has its peculiar system of
arteries and veins, and its peculiar circulation, receiving blood by its
arteries, and returning it by its veins; that the circulation through
these parts of the placenta differs in the following manner: in the
umbilical portion the arteries terminate in the veins by a continuity of
canal; whereas, in the uterine portion there are intermediate cells into
which the arteries terminate, and from which the veins begin." (Hunter,
_op. cit._ p. 48.)
Although various observations and anatomical injections show that to a
certain degree, there is a communication between the uterus and the
placenta, inasmuch as the blood of the former is received into the sinuses
or cells of the latter, we possess no proof that the blood can pass from
these sinuses into the umbilical vessels: on the contrary, every thing
combines to prove that the circulation of the foetus is altogether
independent of that of the mother. We know from daily experience that in
labour at the full term of pregnancy, the placenta is easily expelled
from the uterus: that, upon examining the surface which had been attached
to the uterus we find no laceration, and that a discharge of more or less
blood takes place for some days afterwards. We know, also, that when the
placenta becomes detached from the uterus during the progress of
gestation, it is followed by a considerable hemorrhage, which greatly
endangers the life of the mother. These facts prove that there is a
circulation of uterine blood in the placenta, which is destroyed upon its
being separated from the uterus. That this uterine circulation in the
placenta is unconnected with the circulation of foetal vessels in the
placenta is proved by the fact first pointed out by Wrisberg, viz. that,
where the mother has died from loss of blood, and the maternal vessels
therefore drained of their contents, those of the foetus have been full of
blood. Still farther to illustrate this fact, he killed several cows big
with calf, by a large wound through the heart or great vessels, so as to
ensure the most profuse and sudden loss of blood possible, and never found
that the vessels of the calf were deprived of blood, although those of the
mother were perfectly empty; moreover, no anatomist has ever yet succeeded
in making injections pass from the foetal into the uterine vessels, or
_vice versâ_. Lobstein has mentioned a mode of illustrating this fact
(_Essai sur la Nutrition du Foetus_,) which is both simple and striking.
Upon examining the uterine surface of a placenta which has been expelled
at the full term, it presents the appearance of a spongy mass gorged with
blood, which may be removed by washing or maceration, and if a placenta
thus prepared be injected, the fluids will pass with the greatest facility
from the umbilical arteries into the umbilical vein, but not one drop into
its cellular structure; it is evident, therefore, that the blood which had
filled the intervals between the vessels, and which had been removed by
washing and maceration, could not have belonged to the foetus, but must
have come from the mother; for if any of the vessels had been ruptured the
injection would not have succeeded.
In concluding these observations upon the placenta, we may briefly state,
that there is the same relation between the umbilical vessels and the
maternal blood, which fills the placental cells, as there is between the
branches of the pulmonary artery, and the air which fills the bronchial
cell.[23]
_Umbilical cord._ The umbilical cord, funis, or navel string, is a
vascular rope extending between the foetus and placenta, by which they are
connected together. It usually arises, as we have before observed, from
about the middle of the placenta, and terminates at the umbilical ring of
the foetus; it consists of two umbilical arteries and one umbilical vein;
the former conveying the blood from the common iliac arteries of the
foetus to the cotyledons of the placenta; the latter formed by the union
of the collected umbilical veins, on the inner surface of the placenta,
and returning this blood to the foetus. In the early periods of pregnancy
it also consists of the duct and vessels of the vesicula umbilicalis, the
urachus, and more or less of the intestinal canal. The umbilical cord does
not present the same form or appearance at every period of gestation; the
younger the embryo, the shorter and thicker is the cord; in fact, there
are no traces whatever of a cord at first, the embryo adhering, by its
lower or caudal extremity, directly to the membranes. By the fifth or
sixth week it becomes visible; at this early period the vessels of which
it is composed pass from the foetus in a straight direction, but as
pregnancy advances they become more or less spiral, winding round each
other, and usually from left to right: according to Meckel, they take the
opposite direction much less frequently, viz. in the proportion of one to
nine.
The vessels of the umbilical cord are imbedded in a thick viscid
substance; upon minute examination, it will be found to consist of a very
fine cellular tissue, containing an albuminous matter which slowly exudes,
when pressed between the fingers. This cellular tissue itself may be
demonstrated by the inflation of air or injection with mercury: it seems
to accompany the umbilical vessels as far as the posterior surface of the
peritoneum; and Lobstein is of opinion that it is a continuation of the
cellular tissue, which covers this membrane. (Lobstein, _sur la Nutrition
du Foetus_. § 75.)
Externally, the umbilical cord is covered by a continuation of the amnion,
which, although it be the inner membrane of the ovum, is the outer
covering of the cord: in some places it is very thick and strong, and not
easily ruptured. From repeated observations, the weakest part of the cord
seems to be at about three or four inches distant from the umbilicus, this
being the spot where it has invariably given way in every case we have
seen, where the cord has been broken at the moment of the child's birth.
From the time of the commencement to the full time of utero-gestation, the
cord becomes gradually longer, so that it attains an average length of
from eighteen to twenty inches; this, however, varies remarkably. We have
known the cord exceed forty inches; and a case is described by
Baudelocque, where it was actually fifty-seven inches long: on the other
hand, it is sometimes not more than four or five inches in length.
It is remarkable that the cord, which at the end of pregnancy is usually
of about the same length as the foetus, is relatively much longer during
the sixth month; hence we may conclude, that in those cases where knots
have been found upon the cord, the knot must have been formed at this
period when the foetus was small enough to pass through a coil of it.
Neither blood-vessels nor lymphatics have as yet been found in the
structure of the cord itself. A filament of nerve from the solar plexus
has been occasionally seen passing through the umbilical ring, and
extending to a distance down the cord.
The vesicula umbilicalis and allantois, being essentially connected with
the earliest grades of foetal development, will be considered under that
head.
_Embryo._ There is, perhaps, no department of physiology which has been so
remarkably enriched by recent discoveries, as that which relates to the
primitive development of the ovum and its embryo. The researches of Baer,
Rathke, Purkinje, Valentin, &c. in Germany; of Dutrochet, Prevost, Dumas,
and Coste, &c. in France; and of Owen, Sharpey, Allen Thomson, Jones, and
Martin Barry in England, but more especially those of the celebrated Baer,
have greatly advanced our knowledge of these subjects, and led us deeply
into those mysterious processes of Nature which relate to our first origin
and formation.
These researches have all tended to establish one great law, connected
with the early development of the human embryo, and that of other
mammiferous animals, viz, that it at first possesses a structure and
arrangement analogous to that of animals in a much lower scale of
formation: this observation also applies of course to the ovum itself,
since a variety of changes take place in it after impregnation, before a
trace of the embryo can be detected.
At the earliest periods, the human ovum bears a perfect analogy to the
eggs of fishes, amphibia, and birds; and it is only by carefully examining
the changes produced by impregnation in the ova of these lower classes of
animals, that we have been enabled to discover them in the mammalia and
human subject.
As the bird's egg, from its size, best affords us the means of
investigating these changes, and as in all essential respects they are the
same in the human ovum, it will be necessary for us to lay before our
readers a short account of its structure and contents, and also of the
changes which they undergo, after impregnation. In doing this we shall
merely confine ourselves to the description of what is applicable to the
human ovum.
[Illustration: _Section of a hen's egg within the ovary._
_a_ The granulary membrane forming the periphery of the yelk. _b_ Vesicle
of Purkinje imbedded in the cumulus. _c_ Vitellary membrane. _d_ Inner and
outer layers of the capsule of the ovum. _e_ Indusium of the ovary.]
The egg is known to consist of two distinct parts, the vitellus or yelk
surrounded by its albumen or white; to the former of these we now more
particularly refer. The yelk is a granular albuminous fluid, contained in
a granular membranous sac (the _blastodermic membrane_) which is covered
by an investing membrane called the _vitelline membrane_ or _yelk-bag_.
The impregnated vitellus is retained in its capsule in the ovary,
precisely as the ovum of the mammifera is in the Graafian vesicle. The
whole ovary in this case has a clustered appearance, like a bunch of
grapes, each capsule being suspended by a short pedicle of indusium.
[Illustration: _a_ Vitelline membrane _b_ Blastoderma. _From T. W.
Jones._]
In those ova which are considerably developed before impregnation, the
granular blastermodic membrane is observed to be thicker, and the granules
more aggregated at that part which corresponds to the pedicle, forming a
slight elevation with a depression in its centre, like the cumulus in the
proligerous disc of a Graafian vesicle. This little disc is the
blastoderma, germinial membrane or cicatricula; in the central depression
just mentioned is an exceedingly minute vesicle first noticed by Professor
Purkinje of Breslau, and named after him: in more correct language it is
the _germinal vesicle_.
According to Wagner, the germinal vesicle is not surrounded by a disc
before impregnation; and it is only after this process that the
above-mentioned disc of granules is formed. By the time the ovum is about
to quit the ovary the vesicle itself has disappeared, so that an ovum has
never been found in the oviduct containing a germinal vesicle, nothing
remaining of it beyond the little depression in the cumulus of the
cicatricula.
The rupture of the Purkinjean or germinal vesicle has been supposed by Mr.
T. W. Jones to take place before impregnation; but the observations of
Professor Valentin seem to lead to the inference that it is a result of
that process, and must be therefore looked upon as one of the earliest
changes which take place in the ovum or yelk-bag upon quitting the
ovary.[24]
During its passing through the oviduct (what in mammalia is called the
Fallopian tube,) the ovum receives a thick covering of albumen, and as it
descends still farther along the canal the membrane of the shell is
formed.
On examining the appearance of the ovum in mammiferous animals, and
especially the human ovum, it will be found that it presents a form and
structure very analogous to the ova just described, more especially those
of birds. It is a minute spherical sac, filled with an albuminous fluid,
lined with its blastodermic or germinal membrane, in which is seated the
germinal vesicle or vesicle of Purkinje. When the ovum has quitted the
ovary the germinal vesicle disappears, and on its entering the Fallopian
tube it becomes covered with a gelatinous, or rather albuminous covering.
This was inferred by Valentin, who considered that "the enormous swelling
of the ova, and their passage through the Fallopian tubes," tended to
prove the circumstance. (_Edin. Med. and Surg. Journ._ April, 1836.) It
has since been demonstrated by Mr. T. W. Jones in a rabbit seven days
after impregnation. The vitellary membrane seems, at this time, to give
way, leaving the vitellus of the ovum merely covered by its spherical
blastoderma, and encased by the layer of albuminous matter which surrounds
it.
From what we have now stated, a close analogy will appear between the ova
of the mammalia and those of the lower classes, more especially birds,
which from their size afford us the best opportunities of investigating
this difficult subject.
In birds, the covering of the vitellus is called _yelk-bag_; whereas, in
mammalia and man it receives the name of _vesicula umbilicalis_. Its
albuminous covering, which corresponds to the white and membrane of the
shell in birds, is called _chorion_: by the time that the ovum has reached
the uterus, this outer membrane has undergone a considerable change; it
becomes covered with a complete down of little absorbing fibrillæ, which
rapidly increase in size as development advances, until it presents that
tufted vascular appearance, which we have already mentioned when
describing this membrane.
The first or primitive trace of the embryo is in the cicatricula or
germinal membrane, which contained the germinal vesicle before its
disappearance. In the centre of this, upon its upper surface, may be
discovered a small dark line;[25] "this line or primitive trace is swollen
at one extremity, and is placed in the direction of the transverse axis of
the egg."
[Illustration: _a_ Transparent area. _b_ Primitive trace.]
As development advances, the cicatricula expands. "We are indebted to
Pander,"[26] says Dr. Allen Thomson in his admirable essay above quoted,
"for the important discovery, that towards the twelfth or fourteenth hour,
in the hen's egg the germinal membrane becomes divided into two layers of
granules, the serous and mucous layers of the cicatricula; and that the
rudimentary trace of the embryo, which has at this time become evident,
is placed in the substance of the upper-most or serous layer." "According
to this observer, and according to Baer, the part of this layer which
surrounds the primitive trace soon becomes thicker; and on examining this
part with care, towards the eighteenth hour, we observe that a long furrow
has been formed in it, in the bottom of which the primitive trace is
situated; about the twentieth hour this furrow is converted into a canal
open at both ends, by the junction of its margins (the _plicæ primitivæ_
of Pander, the _laminæ dorsales_ of Baer:) the canal soon becomes closed
at the cephalic or swollen extremity of the primitive trace, at which part
it is of a pyriform shape, being wider here than at any other part.
According to Baer and Serres, some time after the canal begins to close, a
semi-fluid matter is deposited in it, which on its acquiring greater
consistence, becomes the rudiment of the spinal cord; the pyriform
extremity or head is soon after this seen to be partially subdivided into
three vesicles, which being also filled with a semi-fluid matter, gives
rise to the rudimentary state of the encephalon." "As the formation of the
spinal canal proceeds, the parts of the serous layer which surrounds it,
especially towards the head, become thicker and more solid, and before the
twenty-fourth hour we observe on each side of this canal four or five
small round opaque bodies, these bodies indicate the first formation of
the dorsal vertebræ.
[Illustration: _a_ Transparent area. _b_ Laminæ dorsales. _c_ Cephalic
end. _d_ Rudiments of dorsal vertebræ. _e_ Serous layer. _f_ Lateral
portion of the primitive trace. _g_ Mucous layer. _h_ Vascular layer. _k_
Laminæ dorsales united to form the spinal canal.]
"About the same time, or from the twentieth to the twenty-fourth hour,
the inner layer of the germinal membrane undergoes a farther division, and
by a peculiar change is converted into the vascular mucous layers." (A.
Thomson, _op. cit._) It will thus be seen, that the germinal membrane is
that part of the ovum in which the first changes produced by impregnation
are observed. The rudiments of the osseous and nervous systems are formed
by the outer or serous layers; the outer covering of the foetus or
integuments, including the amnois, are also furnished by it. "The layer
next in order has been called _vascular_, because in it the development of
the principal parts of the vascular system appears to take place. The
third, called the _mucous_ layer, situated next the substance of the yelk,
is generally in intimate connexion with the vascular layer, and it is to
the changes which these combined layers undergo, that the intestinal, the
respiratory, and probably also the glandular systems owe their origin."
(A. Thomson, _op. cit._ p. 298.)
[Illustration: _a_ Serous layer. _b c_ Vascular layer. _d_ Mucous layer.
_e_ Heart.]
The embryo is therefore formed in the layers of the germinal membrane, and
becomes, as it were, spread out upon the surface of the ovum: the changes
which the ovum of mammalia undergoes appear from actual observation, to be
precisely analogous to those in the inferior animals. (_Baer_, _Prevost_
and _Dumas_.) From the primitive trace, which was at first merely a line
crossing the cicatricula, and which now begins rapidly to exhibit the
characters of the spinal column, the parietes of the head and trunk
gradually approach farther and farther towards the anterior surface of the
abdomen and head until they unite; in this way the sides of the jaws close
in the median line of the face, occasionally leaving the union incomplete,
and thus appearing to produce in some cases the congenital defects of
hare-lip and cleft palate. In some way the ribs meet at the sternum; and
it may be supposed that sometimes this bone is left deficient, and thus
may become one of the causes of those rare cases of malformation, where
the child has been born with the heart external to the parietes of the
thorax. In like manner the parietes of the abdomen and pelvis close in the
linea alba and symphysis pubis, occasionally leaving the integuments of
the navel deficient, or, in other words, producing congenital umbilical
hernia, or at the pubes a non-union of its symphysis with a species of
inversion of the bladder, the anterior wall of that viscus being nearly or
entirely wanting.
The cavity of the abdomen is therefore at first open to the vesicula
umbilicalis or yelk, but this changes as the abdominal parietes begin to
close in; in man and the mammalia merely a part of it, as above mentioned,
forms the intestinal canal, whereas, in oviparous animals the whole of the
yelk-bag enters the abdominal cavity, and serves for an early nutriment to
the young animal. Another change connected with the serous or outer layer
of the germinal membrane is the formation of the _amnion_. The foetal
rudiment which from its shape has been called _carina_, now begins to be
enveloped by a membrane of exceeding tenuity, forming a double covering
upon it; the one which immediately invests the foetus is considered to
form the future epidermis; the other, or outer fold, forms a loose sac
around it, containing the liquor amnii. Whilst these changes are taking
place in the serous layer of the germinal membrane, and whilst the
intestinal canal, &c. are forming on the anterior surface of the embryo,
which is turned towards the ovum, by means of the inner or mucous layer,
equally important changes are now observed in the middle or vascular
layer. "In forming this fold," says Dr. A. Thomson, "the mucous layer is
reflected farthest inwards; the serous layer advances least, and the space
between them, occupied by the vascular layer, is filled up by a dilated
part of this layer, the rudiment of the heart." (_Op. cit._ p. 301.)
Whilst this rudimentary trace of the vascular system is making its
appearance, minute vessels are seen ramifying over the vesicula
umbilicalis, forming, according to Baer's observations, a reticular
anastomosis, which unites into two vessels the vasa omphalo-meseraica.
(_British and Foreign Med. Rev._ No. 1.) These may be demonstrated with
great ease in the chick: the cicatricula increases in extent; it becomes
vascular, and at length forms a heart-shaped net-work of delicate vessels,
which unite into two trunks, terminating one on each side of the abdomen.
[Illustration: _b_ Is a portion of the convexity of the amnion, upon
which, at _a_ is the fundus of the diminutive human allantois.
_c_ The duct of the vesicula umbilicalis, dividing into two intestinal
portions; and besides this duct are two vessels which are distributed upon
the vesicula umbilicalis, and form a reticular anastomosis with each
other. _From Baer._]
The umbilical vesicle now begins to separate itself more and more from the
abdomen of the foetus, merely a duct of communication passing to that
portion of it which forms the intestinal canal. The first rudiment of the
cord will be found at this separation; its foetal extremity remains for a
long time funnel-shaped, containing, besides a portion of intestine, the
duct of the vesicula umbilicalis, the vasa omphalo-meseraica (the future
vena portæ,) the umbilical vein from the collected venous radicles of the
chorion, and the early trace of the umbilical arteries. These last-named
vessels ramify on a delicate membranous sac of an elongated form which
rises from the inferior or caudal extremity of the embryo, viz. the
_allantois_; whether this is formed by a portion of the mucous layer of
the germinal vesicle, in common with the other abdominal viscera, appears
to be still uncertain: in birds this may be very easily demonstrated as a
vascular vesicle, arising from the extremity of the intestinal canal; and
in mammalia, connected with the bladder by means of a canal called
_urachus_: from its sausage-like shape, it has received the name of
_allantois_.
The existence of an allantois in the human embryo has been long inferred
from the presence of a ligamentous cord extending from the fundus of the
bladder to the umbilicus, like the urachus in animals. But from the
extreme delicacy of the allantois, and from its function ceasing at a very
early period, it had defied all research, until lately when it has been
satisfactorily demonstrated in the human embryo by Baer and Rathke. It
occupies the space between the chorion and amnion, and gives rise
occasionally to a collection of fluid between these membranes, familiarly
known by the name of the liquor amnii spurius, which, strictly speaking is
the liquor allantoidis.
The function of the allantois is still in a great measure unknown. In
animals it evidently acts as a species of receptaculum urinæ during the
latter periods of gestation; but it is very doubtful if this be its use
during the earlier periods. It does not seem directly connected with the
process of nutrition, which at this time is proceeding so rapidly, first
by means of the albuminous contents of the vitellus, or vesicula
umbilicalis, and afterwards by the absorbing radicles of the chorion; but,
from analogy with the structure of the lower classes of animals, it would
appear that it is intended to produce certain changes in the rudimentary
circulation of the embryo, similar to those which, at a later period of
pregnancy, are effected by means of the placenta, and after birth by the
lungs, constituting the great functions of respiration.
In many of the lower classes of animals, respiration (or at least the
functions analogous to it) is performed by organs situated at the inferior
or caudal extremity of the animal: thus for instance, certain insect
tribes, as in hymenoptera, or insects with a sting, as wasps, bees, &c.;
in diptera, or insects with two wings, as the common fly; and also the
spider tribe, have their respiratory organs situated in the lower part of
the abdomen. In some of the crustacea, as, for instance, the shrimp, the
organs of respiration lie under the tail between the fins, and floating
loosely in the water. Again, some of the molusca, viz. the cuttle-fish,
have the respiratory organs in the abdomen. We also know that many
animals, during the first periods of their lives, respire by a different
set of organs to what they do in the adult state: the most familiar
illustration of this is the frog, which, during its tadpole state, lives
entirely in the water.
[Illustration: _a_ Bronchial processes. _b_ Vesicula umbilicalis. _c_
Vitellus. _d_ Allantois. _e_ Amnion. _From Baer._]
As the growth of the embryo advances, other organs whose function is as
temporary as that of the allantois, make their appearance: these also
correspond to the respiratory organs of a lower class of animals, although
higher than those to which we have just alluded,--we mean bronchial
processes or gills. It is to Professor Rathke (_Acta Naturæ Curios._ vol.
xiv,) that we are indebted for pointing out the interesting fact, that
several transverse slit-like apertures may be detected on each side the
neck of the embryo, at a very early stage of development. In the chick, in
which he first observed it, it takes place about the fourth day of
incubation: at this period the neck is remarkably thick, and contains a
cavity which communicates inferiorly with the oesophagus and stomach, and
opens externally on each side by means of the above-mentioned apertures,
precisely as is observed in fishes, more especially the shark tribe; these
apertures are separated from each other by lobular septa, of exceedingly
soft and delicate structure. Rathke observed the same structure in the
embryo of the pig and other mammalia; and Baer has since shown it
distinctly in the human embryo. It is curious to see how the vascular
system corresponds to the grade of development then present: the heart is
single, consisting of one auricle and one ventricle; the aorta gives off
four delicate, but perfectly simple branches, two of which go to the
right, and two to the left side; each of these little arteries passes to
one of the lobules or septa at the side of the neck, which correspond to
gills, and having again united with the three others, close to what is the
first rudiment of the vertebral column, they form a single trunk which
afterwards becomes the abdominal aorta. In a short time these slit-like
openings begin to close; the bronchial processes or septa become
obliterated, and indistinguishable from the adjacent parts; the heart
loses the form of a single heart; a crescentic fold begins to mark the
future division into two ventricles, and gradually extends until the
septum between them is completed. It is also continued along the bulb of
the aorta, dividing it into two trunks, the aorta proper and pulmonary
artery; at the upper part the division is left incomplete, so that there
is an opening from one vessel to the other, which forms the ductus
arteriosus.[27] A similar process takes place in the auricles, the
foramen ovale being apparently formed in the same manner as the ductus
arteriosus; these changes commence in the human embryo about the fourth
week, and are completed about the seventh.
At first the body of the embryo has a more elongated form than afterwards,
and the part which is first developed is the trunk, at the upper extremity
of which a small prominence less thick than the middle part, and separated
from the rest of the body by an indentation, distinguishes the head. There
are as yet no traces whatever of extremities, or of any other prominent
parts; it is straight, or nearly so, the posterior surface slightly
convex, the anterior slightly concave, and rests with its inferior
extremity directly upon the membranes, or by means of an extremely short
umbilical cord.
The head now increases considerably in proportion to the rest of the body,
so much so, that at the beginning of the second month, it equals nearly
half the size of the whole body: previous to, and after this period, it is
usually smaller. The body of the embryo becomes considerably curved, both
at its upper as well as its lower extremity, although the trunk itself
still continues straight. The head joins the body at a right angle, so
that the part of it which corresponds to the chin is fixed directly upon
the upper part of the breast; nor can any traces of neck be discerned,
until nearly the end of the second month.
The inferior extremity of the vertical column, which at first resembles
the rudiment of a tail becomes shorter towards the middle of the third
month, and takes a curviture forwards under the rectum, in the fifth week
the extremities become visible, the upper usually somewhat sooner than the
lower, in the form of small blunt prominences. The upper close under the
head, the lower near the caudal extremity of the vertebral column. Both
are turned somewhat outwards, on account of the size of the abdomen; the
upper are usually directed somewhat downwards, the lower ones somewhat
upwards.
[Illustration: _Diagram of the foetus and membranes about the fourth
week._
_a_ Vesicula umbilicalis already passing into the ventricular and rectum
intestine at _g_. _b_ Vena and arteria omphalo-meseraica. _c_ Allantois
springing from the pelvis with the umbilical arteries. _d_ Embryo. _e_
Amnion. _f_ Chorion. _From Carus._]
The vesicula umbilicalis may still be distinguished in the second month as
a small vesicle, not larger than a pea, near the insertion of the cord, at
the navel, and external to the amnion. From the trunk, which is almost
entirely occupied by the abdominal cavity, arises a short thick umbilical
cord, in which some of the convolutions of the intestines may still be
traced. Besides these it usually contains, as already observed, the two
umbilical arteries and the umbilical vein, the urachus, the vasa
omphalo-meseraica, or vein and artery of the vesicula umbilicalis, and
perhaps, even at this period, the duct of communication between the
intestinal canal and vesicula umbilicalis, the foetal extremity of which,
according to Professor Oken's views, forms the processus vermiformis.
[Illustration: _Diagram of the foetus and membranes about the sixth week._
_a_ Chorion. _b_ The larger absorbent extremities, the site of the
placenta. _c_ Allantois. _d_ Amnion. _e_ Urachus. _é_ Bladder. _f_
Vesicula umbilicalis. _g_ Communicating canal between the vesicula
umbilicalis and intestine. _h_ Vena umbilicalis. _i i_ Arteriæ
umbilicales. _l_ Vena omphalo-meseraica. _k_ Arteria omphalo-meseraica.
_n_ Heart. _o_ Rudiment of superior extremity. _p_ Rudiment of lower
extremity. _From Carus._]
The hands seem to be fixed to the shoulders without arms, and the feet to
adhere to the ossa illi; the liver seems to fill the whole abdomen; the
ossa innominata, the ribs, and scapulæ are cartilaginous.
In a short time the little stump-like prominences of the extremities
become longer, and are now divided into two parts, the superior into the
hand and the fore arm, the inferior into the foot and leg; in one or two
weeks later, the arms and thighs are visible. These parts of the
extremities which are formed later than the others, are at first smaller,
but as they are gradually developed they become larger. When the limbs
begin to separate into an upper and lower part, their extremities become
rounder and broader, and divided into the fingers and toes, which at first
are disproportionately thick, and until the end of the third month are
connected by a membranous substance analogous to the webbed feet of water
birds; this membrane gradually disappears, beginning at the extremities of
the fingers and toes, and continuing the division up to their insertion.
The external parts of generation, the nose, ears, and mouth appear after
the development of the extremities. The insertion of the umbilical cord
changes its situation to a certain degree; instead of being nearly at the
inferior extremity of the foetus as at first, it is now situated higher up
on the anterior surface of the abdomen. The comparative distance between
the umbilicus and pubis continues to increase, not only to the full period
of gestation, when it occupies the middle point of the length of the
child's body, as pointed out by Chaussier, but even to the age of puberty,
from the relative size of the liver becoming smaller.
Though the head appears large at first, and for a long time continues so,
yet its contents are tardy in their development, and until the sixth month
the parietes of the skull are in great measure membranous or
cartilaginous. Ossification commences in the base of the cranium, and the
bones under the scalp are those in which this process is last completed.
The contents of the scull are at first gelatinous, and no distinct traces
of the natural structure of the brain can be identified until the close of
the second month; even then it requires to have been sometimes previously
immersed in alcohol to harden its texture. There are many parts of it not
properly developed until the seventh month. In the medulla spinalis no
fibres can be distinguished until the fourth month. The thalami nervorum
opticorum, the corpora striata, and tubercula quadrigemina, are seen in
the second month; in the third, the lateral and longitudinal sinuses can
be traced, and contain blood. In the fifth we can distinguish the corpus
callosum; but the cerebral mass has yet acquired very little solidity, for
until the sixth month it is almost semi-fluid. (Campbell's _System of
Midwifery_.)
About the end of the third, during the fourth, and the beginning of the
fifth months, the mother begins to be sensible of the movements of the
foetus. These motions are felt sooner or later, according to the bulk of
the child, the size and shape of the pelvis, and the quantity of fluid
contained in the amnion, the waters being in larger proportionate quantity
the younger the foetus.
The secretion of bile, like that of the fat, seems to begin towards the
middle of pregnancy, and tinges the meconium, a mucous secretion of the
intestinal tube which had hitherto been colourless, of a yellow colour.
Shortly after this the hair begins to grow, and the nails are formed about
the sixth or seventh month. A very delicate membrane (membrana
pupillaris,) by which the pupil has been hitherto closed, now ruptures,
and the pupil becomes visible. The kidneys, which at first were composed
of numerous glandular lobules (seventeen or eighteen in number,) now
unite, and form a separate viscus on each side of the spine; sometimes
they unite into one large mass, an intermediate portion extending across
the spine, forming the horse-shoe kidney.
Lastly, the testes, which at first were placed on each of the lumbar
vertebræ, near the origin of the spermatic vessels, now descend along the
iliac vessels towards the inguinal rings, directed by a cellular cord,
which Hunter has called _Gubernaculum testis_: they then pass through the
openings carrying before them that portion of the peritoneum which is to
form their tunica vaginalis.
The length of a full-grown foetus is generally about eighteen or nineteen
inches; its weight between six and seven pounds. The different parts are
well developed and rounded; the body is generally covered with the vernix
caseosa;[28] the nails are horny, and project beyond the tips of the
fingers, which is not the case with the toes; the head has attained its
proper size and hardness; the ears have the firmness of cartilage; the
scrotum is rugous, not peculiarly red, and usually containing the testes.
In female children the nymphæ are generally covered entirely by the labia,
the breasts project, and in both sexes frequently contain a milky fluid.
As soon as a child is born, which has been carried the full time, it
usually cries loudly, opens its eyes, and moves its arms and legs briskly;
it soon passes urine and fæces, and greedily takes the nipple. (Naegelé's
_Hebammenbuch_.)
Thus, then, in the space of forty weeks, or ten lunar months, from an
inappreciable point, the foetus attains a medium length of about eighteen
or nineteen inches, and a medium weight of between six and seven pounds.
As these observations on the development of the ovum show that the
structural arrangement of the embryo undergoes a succession of changes, by
which it gradually rises from the lowest to the highest scale of
formation, so we shall find it furnished with a succession of means for
its nutrition, each corresponding more or less to the particular grade of
development which it may have attained. Its earliest source of nourishment
is doubtless the vitellus, or albuminous contents of the vesicula
umbilicalis. The radicle or primitive trace, in this respect, bears a
strong analogy to the seed of a plant; it brings with it its own supply of
nourishment for its first stage of growth; in the latter, the cotyledons
afford nourishment to the little plumula, until, by the formation of roots
and absorption of moisture from the surrounding soil, it is enabled to
support the early rudiment of the future plant. The early function of the
chorion is very analogous to that of roots; it is an absorbing apparatus,
collecting nourishment by means of its numerous absorbing fibrillæ: hence,
according to Lobstein, the umbilical vein exists for some time previous to
the umbilical arteries, and seems to perform an office in the foetus
similar to that of the thoracic duct at a later period; its radicles or
absorbing extremities seem to absorb a milky fluid, which after the first
two months is found in the placenta, and which must be looked upon as a
means of nourishment which does not exist in the latter months. This milky
fluid was noticed by Leroux, who even then expressed his doubts, whether
the radicles of the umbilical vein receive blood from the mother, or
whether they only serve to absorb a white fluid which resembles chyle. In
some manuscript notes of Dr. Young's lectures, which were taken by the
late Dr. Parry, of Bath, when a student at Edinburgh, we find the
following observation: "There is evidently in the placenta, besides
blood-vessels, some other substance, which serves to absorb juices from
the uterus, and to convert these into a chylous matter proper to nourish
the foetus, and this matter is absorbed by the umbilical veins. This seems
to be proved from the consideration of the placenta of animals which have
cotyledons; for, on squeezing these glandular substances, we force out a
sort of chylous liquor, and these are surrounded by the placenta, which
absorb their liquor and convey it to the foetus."
The absorbing power of the umbilical vein continues till the fifth month;
during the second or third, the foetus receives a good deal of nourishment
from the liquor amnii, which at this period contains a considerable
quantity of albuminous matter; this diminishes in the latter months of
pregnancy. Moreover the body of the foetus begins to be covered with the
vernix caseosa towards the seventh month, so that in the eighth and ninth
months the absorption of liquor amnii by the skin is considerably impeded.
How far the full formed placenta, as seen after the fifth month, serves as
a means of nutrition to the foetus, may still be a matter of doubt; its
chief use after this period is, as we have already shown, for the purpose
of producing certain changes in the blood of the foetus analogous to those
of respiration;[29] still, however, it would seem that its function of
nutrition is not entirely at an end, even at a late period of pregnancy.
The numerous little granules of phosphate of lime, which are frequently
found on the uterine surface of a full-grown placenta at a time when
ossification is rapidly advancing in the foetal skeleton, would surely
lead us to infer that the placenta in some way or other supplies the
materials for this process.
_Foetal circulation._ We have already shown, that, in the early stages of
development, the heart of the embryo is single, consisting of one auricle
and one ventricle; that a septum gradually divides these into two parts
until the double heart is formed, leaving two openings of communication
between the right and left sides, the one between the auricles called the
_foramen ovale_, the other between the pulmonary artery and aorta, viz.
the _ductus arteriosus_.
From these and other peculiarities it will be seen that the foetal
circulation differs essentially from that of a child after birth; and, in
order to comprehend the nature and mechanism of the changes which take
place in it when respiration first commences, it will be necessary that
these peculiarities should be thoroughly understood. The condition of the
foetus must also be remembered: surrounded by the liquor amnii, the foetus
does not respire; its lungs have as yet been unemployed; they are
therefore small and collapsed, and present a firm solid mass, nearly
resembling liver in appearance. In this state but little blood from the
pulmonary arteries can circulate through them; for, as the extreme
ramifications of these vessels are distributed upon the mucous membrane
lining the bronchi and air-cells, the free passage of blood through them
will in great measure depend upon a previous condition of the air-cells.
The pulmonary arteries in the foetal state are therefore small, and
transmit but a small quantity of blood into their numerous ramifications,
just sufficient to keep pervious these vessels which after birth are to be
so greatly distended: in this state the lungs when thrown into water sink.
Hence, as the pulmonary arteries do not afford a sufficiently free exit to
the contents of the right side of the foetal heart, nature has provided it
with a peculiar means for carrying off the overplus quantity of blood,
which is poured into the right auricle from the vena cava. This is
attained first by the _foramen ovale_, an oval-shaped opening in the
septum between the right and left auricles, and furnished with a semilunar
valvular flap, so constructed, as to allow a free passage for the blood
from the right to the left auricle, but none in the contrary direction. By
this means a considerable quantity of blood is transmitted at once from
the right to the left auricle, and, consequently, much less into the right
ventricle and pulmonary artery. Still, however, more blood passes into the
right ventricle than the pulmonary artery, in the collapsed state of the
foetal lungs, is capable of conveying away. The pulmonary artery is
therefore continued beyond its bifurcation into the aorta at its
curvature, by means of the _ductus arteriosus_, which, in the full-grown
foetus, forms a short thick passage between these two vessels; and in this
manner is the right ventricle enabled to get rid of its surplus quantity
of blood. Thus we see that the foetal heart although consisting of two
auricles and two ventricles, continues to perform the functions only of a
single heart, both ventricles assisting simultaneously to propel the same
column of blood, viz. that of the aorta, and thus enabling the heart to
act with considerable power.
The chief part of the blood, which flows through the iliac arteries,
instead of being sent to the inferior extremities, is carried into the
umbilical arteries, which passing up along the sides of the bladder meet
the umbilical vein at the navel, and thus form the vessels of the
umbilical cord. These arteries convey the blood of the foetus to the
placenta, where, having undergone changes to which we have already
alluded, it is returned by the umbilical vein. This vessel, which
afterwards forms the round ligament of the liver, passes through the
umbilicus along the anterior edge of the suspensory ligament; it supplies
the left lobe with blood, and having given off a communicating branch to
the vena portæ, which supplies the right lobe, it passes at once by a
short passage, called _canalis venosus_, into the vena cava.
Thus, then, the peculiarities of the foetal circulation may be considered
as four, viz. the _foramen ovale_, or passage from the right to the left
auricle; the _ductus arteriosus_, or communication from the bifurcation of
the pulmonary artery into the arch of the aorta; the _umbilical arteries_
arising from the iliac arteries, and carrying the blood along the cord
into the placenta; and, lastly, the _canalis venosus_, or passage between
the umbilical vein and vena cava.
Let us now examine the changes which take place in the foetal circulation
at the moment of the child's birth. The child, which had hitherto been
immersed in the bland and warm medium of the liquor amnii, is at once
exposed to the action of the external air. By means of the sympathy
existing between the skin and respiratory muscles, sudden and convulsive
efforts at inspiration take place; the air-cells of the lungs become
partially inflated, and, after a short time as the respiration increases
in power and activity, become distended throughout their whole extent. The
thorax rises; the flaccid diaphragm, which hitherto had been pushed up by
the large foetal liver, now contracts, pressing down the liver into its
natural situation. The lungs, from being a hard solid heavy substance,
resembling liver, at once become inflated, elastic, and crepitous, light
and permeable to air in every part.
The capillary terminations of the pulmonary artery, which ramify in the
mucous membrane, forming the parietes of the air-cells, and which
hitherto had been firmly compressed by the collapsed state of the foetal
lungs, are suddenly rendered pervious throughout their whole extent. By
this means, a vacuum, as it were, is formed in the ramifications of the
pulmonary artery; each inspiration is accompanied by a rush of blood from
the right ventricle into the newly-inflated structure. The pulmonary
artery, at its bifurcation, swells and becomes turgid: the blood is
carried off into its numerous ramifications as fast as the right ventricle
can supply it; this may be easily understood from the law, in anatomy,
viz. that the area of two arteries is greater than that of the trunk from
which they bifurcate. From this state of distension, the distance between
the pulmonary artery and the aorta is increased; the ductus arteriosus,
which has now become empty, is stretched, and thus partially closed; the
right auricle, which, but for the foramen ovale, could not have cleared
itself of the whole quantity of blood which was poured into it from the
vena cava, is now enabled to transmit its entire contents into the right
ventricle; the left auricle, which before birth was supplied only by the
foramen ovale from the right auricle, is now rapidly filled by the blood
brought into it by the four pulmonary veins;--the equilibrium between the
two auricles becomes altered;--the right, which hitherto had been somewhat
gorged with blood, is now able to clear itself with facility; whereas, the
left, which was but partially supplied, is now distended with a much
greater quantity: there is now rather a disposition for the blood to
regurgitate from the left to the right auricle; this, however, is
prevented by the semilunar fold of the foramen ovale, which now acts as a
valve, and generally becomes firmly attached to the septum. The
obliteration of the canalis venosus at the posterior margin of the liver,
and of the umbilical vein at the anterior edge, may, we think, be
explained by the changes which necessarily follow the inflation of the
lungs: the diaphragm, when it contracts, pulls down the liver into its
natural situation; the distance, therefore, between the liver and the
heart is increased, and the canalis venosus is consequently stretched, and
considerably pressed upon, and precisely the same results follow with the
umbilical vein.
PART II
NATURAL PREGNANCY AND ITS DEVIATIONS.
CHAPTER I.
SIGNS OF PREGNANCY.
_Difficulty and importance of the subject.--Diagnosis in the early
months.--Auscultation.--Changes in the vascular and nervous
systems.--Morning sickness.--Changes in the appearance of the
skin.--Cessation of the menses.--Areola.--Sensation of the child's
movements.--"Quickening."--Ausculation.--Uterine souffle.--Sound of
the foetal heart.--Funic souffle.--Sound produced by the movements of
the foetus.--Ballottement.--State of the uterine.--Violet appearance
of the mucous membrane of the vagina.--Cases of doubtful
pregnancy.--Diagnosis of twin pregnancy._
There is, perhaps, no subject connected with midwifery, which is of such
importance, or which, from its difficulty and the serious questions it
involves, demands such attentive consideration, and requires so familiar
an acquaintance with every part of it, as the diagnosis of pregnancy. The
responsibility which a medical man incurs in deciding cases of doubtful
pregnancy, and in thus giving an opinion which may not only affect the
fortune, happiness, character, but even life itself of the individual
concerned, is rendered more painful by the perplexing obscurity of the
circumstances under which these cases sometimes occur, being not
unfrequently complicated with diseases which add still farther to the
difficulty of coming at the truth, and occasionally rendered peculiarly
obscure by wilful and determined falsehood and duplicity.
To render this subject more intelligible to our readers, we propose first
to consider the general effects which pregnancy produces upon the system,
and then to describe those changes and phenomena which are _peculiar_ to
this state, and which may therefore be taken as so many means of
diagnosis.
Under all circumstances, the diagnosis of pregnancy must ever be difficult
and obscure during the early months; the development of the uterus is
still inconsiderable, and the effects which it may have produced upon the
system, although appreciable and even distinct, are nevertheless too
capable of being also produced by other causes, to warrant our drawing any
decided conclusion from them.
The effects over the whole animal economy, which result from the presence
and advance of this great process, are very remarkable, and show
themselves in every portion of it.
The vascular system undergoes a considerable change; the actual quantity
of blood in the circulation appears to be increased; the pulse is harder,
stronger, and more full; in many instances the blood, when drawn, exhibits
the buffy coat, as in cases of inflammation; the vagina is more vascular,
it is warmer, and the secretion of mucus considerably increased; there is
a disposition to headach, and occasional flushing of the face; the animal
heat over the whole body is increased. In the nervous system we also
observe distinct evidences of a change having taken place: the
irritability is increased; there is weariness, lassitude, and a peculiar
alteration of taste and disposition; women, who otherwise are of a
cheerful disposition, are now gloomy and reserved, and _vice versâ_; in
some the temper becomes fretful and hasty, and in those who are naturally
so, a most agreeable change for the better is sometimes observed.[30] Some
are liable to spasmodic affections, palpitations, spasmodic cough,
vomiting, fainting, headach, toothach, &c.: under this head will come the
"morning sickness," which is so commonly observed during the first weeks;
the nature and treatment of which will be considered under the DISEASES OF
PREGNANCY; on the other hand, women who are constantly suffering from
spasmodic affections, for instance, asthma, &c. are now entirely free from
them, and appear to be insensible to causes which, in the unimpregnated
state, would induce an attack. To changes in the nervous system must we,
in great measure, attribute not only the sickness just mentioned, but also
those extraordinary longings or antipathies for certain articles of food
or drink, and in some cases, as in chlorosis, for substances which, under
other circumstances, would excite disgust. In many, the changes in the
function of the digestive apparatus does not amount to actual disease, the
stomach merely refusing to digest articles of food which before had agreed
with it: but in others, producing severe cardialgia, acidity, or even
vomiting. Hence, we not unfrequently observe that women who had hitherto
enjoyed a good digestion, now suffer from dyspepsia, and are obliged to be
exceedingly careful in their diet; whereas those, in whom the digestion
had been previously weak, are now able to digest almost any thing. The
secretions of the whole alimentary canal are altered both in quality and
quantity; the saliva frequently becomes tenacious, white, and frothy
(_Dewees_,) and at times is so much increased in quantity as to amount to
actual salivation; the secretions of the stomach are remarkably altered,
as shown by the copious formation of acid in some cases during pregnancy;
the mucus is ropy, and frequently vomited up in considerable quantities.
The bowels are in some cases much relaxed; in others, constipated. This
latter condition, however, may in part be attributed to the pressure of
the gravid uterus obstructing the peristaltic motion.
The changes in the appearance of the skin during pregnancy are also worthy
of notice. Women, who are naturally pale and of a delicate complexion,
have frequently a high colour, and _vice versâ_; in some the skin assumes
a sallow or cadaverous hue; copper-coloured blotches appear on the face
and forehead: in others the skin appears loose and wrinkled, giving the
patient an aged haggard expression, and destroying her good looks. Mole
spots become darker and larger, and these, with a dark ring beneath the
eyes and the changes already mentioned, combine to alter the whole
appearance of the face. In some women a considerable quantity of hair
appears in those parts of the face where the beard is seen in the other
sex; it disappears after labour, when the skin resumes its natural
functions, but returns on every succeeding pregnancy. In others a similar
appearance takes place upon the breasts. The secretions of the skin are
more or less altered; women who perspire freely have now a dry, rough
skin; whereas those who at other times have seldom or never a moist skin,
have copious perspiration, which is not unfrequently of a peculiarly
strong odour. Cutaneous affections, also, which have been very obstinate,
or had even become habitual, sometimes disappear, or at least are
suspended during the period of utero-gestation. Similarly favourable
changes are observed for a time in severe structural diseases of certain
organs: the fact of well-marked phthisis apparently disappearing whilst
pregnancy lasts, is well known.
The breasts become larger, blue veins are seen ramifying beneath the skin,
and the circular disc of rose-coloured skin which surrounds the nipples
becomes remarkably changed in colour, &c.; appearances, the description
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