life-principle, even through the entire period of gestation, (51, 56,
and 58,) is rendered probable by many facts related by unimpeached
authorities, which go to prove that when the whole intact Ovum has been
expelled at an advanced period of gestation, or at the natural
termination of that period, the fœtus has continued to live, and the
circulation of the blood has not ceased for an instant during a space of
time of from nine minutes to a quarter of an hour. (Roederer, Wrisberg,
Osiander, and Meckel, who repeated the experiments of the latter.) It
has been asserted by a venerated authority that in an intact Ovum,
expelled at seven months, the fœtus lived upwards of an hour. (Harvey.)
The truth of this assertion is confirmed by very recent observers
(Green, Velpeau, Gardien, Dr. Campbell)[9]. I once destroyed a female
cat by prussic acid near the time of parturition; and having removed
from the horns of the uterus the entire Ova, with their beautiful
annular placentæ, while the fœtus in each of them was still perfectly
lively, and could distinctly be seen, through the membranes, to move, I
found that at the end of thirty-five, forty, and even forty-two minutes,
some of them were still alive, the Ova remaining entire all the time,
and upon the table[10].
60. When the Ovulum has made good its fastening to the adventitious
lining of the womb (decidua), the circulation of the blood in it is as
yet imperfect. The Ovulum does not—cannot—receive the blood of the
mother. How could such a gossamer-like being, organized as the Ovulum
has been proved to be, during the first days after fecundation, be made
a part of so impetuous a torrent as the circulation of the blood of the
mother, without instant destruction to the produce of conception? No.
The blood of the embryo is first formed within itself. (Prevost, Home,
Magendie, Adelon, Serres, Rolando.)
61. The newly-engendered being passes through two striking metamorphoses
previously to the enjoyment of its extra-uterine life. These are the
Embryonic and the Fœtal states. The latter succeeds immediately to the
former; beginning at the moment when the new being is grafted on the
maternal womb, and continuing until its expulsion from thence at the
full period of gestation. It follows, therefore, that the Embryonic or
former state is that in which the new being is as yet, without any
direct or indirect communication with the mother, and still less so with
external objects. This state persists for about two weeks after
fecundation, during which the Embryo continues to derive its nourishment
from the cortical membrane of the Ovum. (Boer, Soemmering, Plagge,
myself.)
62. The growth and progress of the Embryo or Fœtus follow a very
irregular march. Up to the second month the increase is somewhat slow—it
is accelerated during the third—it slackens again at the fourth and
fifth months—between which and the last month the increase is more
rapid, until it has acquired its proper maturity. (Autenrieth,
Soemmering.)[11]
63. The Embryo may be perceived, with the naked eye, at the fourteenth
day after conception. It measures then 1–12th of an inch in length. (Dr.
Pockels.) On the third week, it is 1–10th of an inch long. It is as
large as a house-fly at four weeks, and as a horse-fly at six weeks. At
two months it weighs twenty grains, and is one inch long. It weighs an
ounce and a half at three months, and measures three inches; between
which time and the sixth month it increases in dimensions from three to
nine inches, and in weight from one ounce and a half to one pound. The
relative weights of augmentation of length for the seventh, eighth, and
ninth months stand thus:—from two to four pounds, and twelve inches;
from four to five pounds, and seventeen inches: from five to eight
pounds and twenty-two inches. (Averages of minute and accurate
observations made by Autenrieth, Soemmering, Bichat, Pockels, Carus,
&c.—confirmed by my own observations made on several early ova, and many
fœtuses examined in the course of seventeen years obstetrical practice.)
64. Towards the end of the first month it is easy to distinguish the
head of the fœtus, which has the appearance of a vesicle composed of
thin membranes, and is as large as the rest of the body. The latter is
straight—and there is in one part of the head a black dot, marking the
spot for the eyes. (Plate I. fig. 5.)[12] But it is during the second
month that the various parts of the face, as well as the superior and
inferior extremities, become visibly delineated in the fœtus. The eyes
are indicated by two black spots of considerable size, compared to the
volume of the fœtus. The eyelids are not spread over them until the
tenth week, at which time the external concha of the ear, as well as the
profile form of the nose, become properly defined. At this same period
we find the mouth, which was at first a simple opening of no mean size,
becoming more distinctly delineated, owing to the formation of the lips.
These soon approach each other, leaving a simple transversal slit or
depression between them. (Plate II. fig. 11 and 12.)
65. The extremities appear in the form of globular tubercles at first;
the superior preceding the inferior by a short period of time. Until
between the third and fourth month, the lower are smaller than the
superior extremities. Even at the latter month they are shorter than the
projection of the os coccygis. The parts of reproduction may then be
distinctly seen. In the male as well as in the female, these parts are
exceedingly prominent. (Plate V. fig. 18 and 19.) But the difference of
the sexes may be deduced from other circumstances besides the sexual
organs. Such as the particular structure of the thorax and abdomen, the
form of the head, the extremities, and the dorsal spine. (Autenrieth,
Soemmering, Meckel, Velpeau.)
66. The external organs of the fœtus are all well defined at the end of
the fourth month. The abdomen is fully covered in; the intestines are no
longer visible. By the sixth month the fœtus is perfect in its shape and
formation. In the seventh, eighth, and ninth months, its successive
development is limited to mere size, volume, or amplitude, and a
proportionate increase in weight. It is well to keep in mind, that
although the growth of the various parts of the fœtus bears a proportion
to the general development of its body, that part of the body which is
above the navel, measures in length more than the part below it, until
the full and complete period of gestation, when the navel marks the
precise middle of the length of the fœtus. This circumstance assists us
materially in forming our opinion respecting the age of any fœtus,
either as a matter of curiosity, or as a guide in questions of forensic
medicine. (Foderé, Chaussier.)
67. It was supposed, until within the last fifteen years, that the
nervous system was the first to be formed in the human embryo; but
recent discoveries have proved that the vascular system has precedence
of the former. The nerves invariably appear after the arteries which
they are intended to accompany. The spinal marrow appears before the
brain, and the latter before the cerebellum, and accordingly it is found
that the arteries of the spinal marrow shew themselves before those of
the brain, and the arteries of the brain become manifest before those of
the cerebellum. In this respect the organogenesy of the human fœtus is
analogous to that of birds. (Serres, Desmoulins, Adelon.)[13]
68. The blood is formed independently of the heart, and appears at two
distinct points from it, and acquires a motion independently of it.
(Prevost, Dumas, Baer.) The veins are formed first—next, the
heart—lastly, the arteries, &c. (French Physiologists.) The arteries
are, by an Italian physiologist, said to be the first to appear.
(Rolando.)[14]
69. The nervous system is not developed, beginning at the centre and
proceeding towards the circumference of the embryo, but the reverse.
Thus the lateral nerves of the head, trunk, and pelvis, are already
formed, when the cerebro-spinal system is yet in a liquid state. It
follows hence that those nerves cannot be considered (as it has all
along been supposed) in the light of emanations from, but as distinct
bodies proceeding to, that particular portion of the nervous system.
(Serres.)
70. Of the apparatus for digestion, the intestinal canal is the first to
appear. It consists, during the first days of its formation, of an open
gutter, extending the whole length of the embryo, placed before the
vertebral column, and gently curved like a canoe. It is in communication
with the _vesicula umbilicalis_, or intestinal vesicle. (Wolf, Meckel,
Oken, Baer.) The gutter, without losing altogether its communication
with that vesicle or chamber during the first ten or twelve weeks,
becomes closed at last, and extends, lengthens, and expands in a variety
of ways. One of its extremities, the mouth, appears between the fourth
and fifth week. It is open on the sixth. The other extremity, the anus,
opens on the seventh week. About the ninth week, the outlines of a
stomach are visible. (Meckel., Adelon, Velpeau.)[15]
71. The VESICULA UMBILICALIS (intestinal vesicle) corresponds to the
vitelline sac of birds. The discovery is due to Bojanus. In the human
embryo it measures about half an inch in diameter. It is situated
immediately against the anterior surface of the embryo (Lobstein); but
it gets further from it at the end of the first month, when it is found
on the outside of the sheath of the cord. (Meckel.) It is composed of a
granular membrane of considerable tenacity. It contains a whitish
liquid, which gradually diminishes—becomes thicker, and ultimately,
hardened; while the vesicle itself withers, and becomes opaque. It
receives the blood vessels called omphalo-mesenteric. (Pockels.) It
disappears generally about the third month. (Meckel.) It has been
observed, though extremely rarely, at the full period of
gestation—placed at a short distance from the insertion of the cord into
the placenta, but not larger than when seen at between two and three
months. (Hunter, Meckel.) It is connected, as stated before, by a short
neck, and by vessels, with the smaller intestines at the termination of
the ileum (Meckel)—or at the cæcum, which is, in reality, the
representative of the vesicula vitellaria drawn into the abdomen as in
birds. (Oken.)
72. At the lower end of the anal intestines, there projects another
vesicle or sac, to which the name of Allantoid has been given. It exists
in birds—in all the mammalia—and in the human embryo. In the latter it
appears about the fourth week, and by the sixth week it has almost
disappeared. Its existence is therefore but short, while the size it
attains is always trifling. Not so with the mammalia, in which it
acquires great amplitude. The communication of this sac with the
bladder, by a canal called the urachus, and which canal is found
impervious after the first three or four months of gestation, is
admitted by all observers. (Meckel, Baer, Dutrochet.)
73. The umbilical cord or navel string, in man, has been found to spring
from a vesicle to which the discoverer has given the name of Erythroid.
(Dr. Pockels.) This vesicle had been before observed in the mammalia.
(Oken.) The cord appears at the end of the third week. (Pockels.) It
then consists of a vein and two arteries, the urachus, a species of
gelatine of a ropy nature, called the _gelatine of Wharton_, a portion
of the intestinal canal, (larger in proportion as the embryo is
younger,) the vesicula umbilicalis, in part, and the omphalo-mesenteric
vessels, the whole enveloped by a sheath proceeding from the involucra
of the ovum already described. The last three constituent elements of
the cord, however, become obliterated or disappear after the third or
fourth month of gestation—the others remain permanent throughout that
period.
74. The umbilical vein and the arteries are spirally twisted together
and in the majority of cases they are so from left to right. (Hunter.)
The former contrivance is evidently intended for the purpose of giving
the greatest possible extension of tubular passage for the blood
compatible with the smallest increase in the length of the cord. The
cord which is very short at five or six weeks, becomes at the conclusion
of gestation from one foot six to two feet long. (Chaussier.)
75. The umbilical arteries, two in number, are a continuation of the
primitive iliac arteries; they pass over the lateral regions of the
bladder, ascend along the internal surface of the anterior abdominal
covering of the fœtus, approaching each other as they get nearer to the
navel, through which they emerge in order to enter the sheath of the
cord, winding round the vein in their way to the placenta. (77) The vein
on the contrary which proceeds from the placenta is of a larger calibre
than that of the two arteries taken together. It is soft and
extensible—and after having slightly meandered within the umbilical
sheath penetrates through the navel into the abdomen of the fœtus,
directs its course towards the inferior surface of the liver, enters the
antero-posterior fissure of that viscus, unites with the left branch of
the hepatic and vena portarum, and reaches under the name of the venous
duct, the inferior cava. It has no valves, except one at its
intro-abdominal bifurcation. This vessel, throughout its course, becomes
obliterated after birth.
76. The omphalo-mesenteric vessels consist of a vein and an artery, the
ramifications of which, externally to the fœtus, are seen distinctly on
the umbilical vesicle (vesicula intestinalis). They accompany the cord
as far as the navel through which they pass into the abdomen. They then
separate, the former proceeding on the right to join the trunk or one of
the branches of the mesenteric vein, and the latter on the left to join
the superior mesenteric artery. These vessels are obliterated, as the
vesicula umbilicalis to which they belong disappear, and lastly
disappear in their turn. They have, however, been observed sometimes in
the cord of the full grown fœtus, like whitish solid filaments.
(Chaussier, Beclard.) In the recent case of an individual twenty years
of age, who died of consumption, these vessels were found as pervious as
when existing in the embryonic state, and contained blood.
(Spakenberg.)[16]
77. When the Ovum is advanced to the second or third month of its
fecundated existence (for the period varies in different examples I have
had under my observation); its attachment to the Uterus, is firm and
complete. Many of the vessels of the external surface of the chorion,
which by this time have increased in size, while their free ends have
luxuriantly branched out in innumerable minute vessels, have clustered
together and formed what are in reality cotyledons—by means of which the
said attachment is principally effected. (Personal observations and
experiments.) The congeries of these clusters of vessels constitute the
principal part of what has been called the Placenta, which grows in size
and expands as the gravid uterus expands progressively during gestation.
78. The Cotyledons sometimes consist of only one short and very thick
principal trunk—dividing itself, at a short distance from the surface
whence it springs, into two, three, sometimes more, lesser trunks, and
then again subdividing into thousands of smaller tubes;—at other times
the cotyledons consist of two or three distinct straight trunks of
different calibre springing from the chorion close to each other (as
insulated clusters of lofty and straight trees are often seen here and
there on a plain); in which case, the corresponding subdivisions being
more numerous, the cotyledon is necessarily larger. (Personal
observations, 1825, 1826.)
79. The main trunks of these cotyledons are ramifications of the
umbilical vein and arteries, seen to spring from the subdivision of
those vessels which are observed to run horizontally on the fœtal
surface of the placenta, and which are the termination of the umbilical
cord. Between these cotyledons there are spaces of various sizes in
which the surface of the Chorion is clear of all filaments, vessels, or
any other attachment or projection whatever,—such surfaces are smooth
and shining. (Personal experiments, 1825, 1826.)[17]
80. The trunks of the cotyledons and their subdivisions whether
springing from the vein or from the arteries of the cord have their
coats made of the Chorion and amnion which accompany each cluster so as
to form the thinnest pellicular receptacle for their ramifications. It
follows hence, that when a coloured liquid, or even air is injected
through the arteries of the cord, no escape of the injection takes
place, nor can take place, from the terminal vessels of the clusters or
cotyledons—and as it is found also that the same injection, if projected
long enough (without lacerating any part of the gossamer-like structure
we act upon) is brought back by the vein of the cord (which has no
valves to prevent such a return) another conclusion is inevitable,
namely that the terminal arterial vessels become, by a continuous
arrangement, incipient radicles of the venous tubes. (Personal
experiments, 1825, 1826.)
81. Now in as much as in the human placenta, expelled at the full period
of gestation, before any experiment be undertaken to disturb its
integrity, the lobes which it presents have each the appearance of a
continuous mass, without any intervening spaces (79); and as these
appear only clear, smooth, and shining, after maceration and much
patient dissection that leaves nothing rough, or lacerated or divided by
violence, behind; it follows that a something must have been removed,
during the process of maceration and dissection, which before the
employment of those processes occupied the spaces in question. (79.)
82. That something consists in a congeries of blood-vessels, arterial as
well as venous, proceeding from the longitudinal vessels of the decidua
covering the placenta (Dr. Hunter, Chaussier, Meckel, Lesauvages,
myself). These vessels ramify in a manner analogous to that in which
those of the fœtus have been described to ramify, (78, 79.) They
penetrate between the interstices left by the minutest branches of the
umbilical cotyledons. Their direction is lateral, perpendicular,
oblique, and variously tortuous, in reference to the plane of the
decidua whence they originate. Wherever they form a thick cluster, they
are found to occupy one of the spaces already described (79). To
facilitate this arrangement, and to render the distribution of the
decidual vessels throughout the masses of the umbilical cotyledons more
effectual—the membrane itself (decidua) is found to dip among the
latter, dividing the general mass into lobes of various sizes, by which
contrivance the decidua acquires an additional extension. (Personal
Observations and Experiments.)
83. The decidual vessels are formed by continuous arterio-venous tubes.
They reach, but do not connect themselves with the chorion. In the same
manner as the terminal vessels of the umbilical cotyledons reach, but do
not connect themselves with the superimposed decidua. When an attempt is
made to remove (peel off) the latter from the surface of the placental
mass, we notice certain attachments between them which are torn in the
removal. These are the decidual vessels (82) and not as stated
incorrectly by some, the terminal vessels of the umbilical system.
(Recent German, and French, and Personal Experiments.) In the same
manner as the umbilical vessels are accompanied by the chorion, the
decidual vessels are accompanied by a membrane peculiar to the placenta,
which I have called the _membrana propria_.
84. If we take a placenta which has been expelled from the womb, in all
its integrity, between the fifth and seventh month, when the vascularity
of the decidua is considerable, and after carefully washing its surface
in tepid water, we plunge it in a weak solution of alcohol, so as to
harden the decidua in some degree, we shall be able to slice off the
latter from the surface of the placenta, at the depth of about the tenth
of an inch, without injuring the delicate texture of the membrane. This
should then be carefully macerated by turning the under surface upwards,
under water, when, after a time, much of the tomentous attachment seen
floating, will gradually be detached, and leave part of a smooth surface
behind. If the membrane be then viewed with a strong magnifying glass,
on its upper surface several orifices, with regular edges, but of
various aperture, will be observed, through which, if we introduce a
slender pipe and blow air into them, not only the longitudinal vessels
in the decidua will be seen to fill with that fluid; but the short
fragments of their ramifications pendent from the under surface of the
membrane, will be distended, and the air will pass through them bubbling
up through the water, thus denouncing their own vascular nature and
arrangement. This is _an experimentum crucis_. (Original, 1826–27).
85. The orifices in the decidua have been denied by one or two recent
writers, particularly by Professor Lauth; but they are admitted by all
the rest of the modern physiologists and anatomists, from Dr. Hunter
down to the latest experimentalist on the subject. It is through these
that the injection, thrown into the uterine vessels, while the placenta
is still adhering to the uterus, passes into that part of the placental
mass which is formed by the decidual ramifications. In a very beautiful
and most accurately conducted experiment made at the Middlesex hospital,
by Dr. H. Ley, (March, 1833,) the particulars of which, I hope, to see
published by that able physician; a red injection was pushed, without
any difficulty,—laceration,—or extravasation, towards the adherent
placenta, from the uterine vessels of a pregnant woman, who died of a
disease of the heart, undelivered; when it was found to have penetrated,
in the most regular and uniform manner, to the very remotest terminal
ramifications of the decidual vessels. The placenta was then carefully
detached, the decidual surface was carefully examined with magnifying
glasses, no laceration could be detected, except what had been made by
accident or violence in a small part of its circumference while the
placenta was being detached from the womb. Orifices, as distinct and as
properly organized as orifices can be in membranous textures, were seen
in many parts of it by more than one competent and unbiassed person; and
air was blown through some of them, or a small silver pipe introduced,
without effort or laceration. Not the slightest vestige of
extravasation, or lump of injection, was observed in any part of the
intact placenta when cut into. This same result has been obtained, it is
understood, in a recent injection by Sir A. Cooper, but the nature of
the experiment is not yet known. The same result was obtained by Dr.
Hunter, whose positive affirmation has been so recently questioned. The
same result has been obtained by Lobstein. The same result has been
obtained by Chaussier. Such a result is believed to be correct by
Magendie. Professor Mende, in a report to the Obstetrical Society of
Gottingen, states having made the experiment of injecting the uterine
vessels with air—and with milk, in the case of a woman who died (1830)
after the Cæsarean operation, the placenta remaining firmly adherent to
the uterus, and he obtained the like result—as Hunter and others. Can
we, therefore, refuse credence to such a host of eminent men and
experimenters?
86. The decidual vessels derive their fluid from the uterine vessels.
The arteries which convey uterine blood to the decidual vessels, are
tortuous and very small; they are the adventitious produce of the
_membrana propria_ of the womb acting under the influence of a peculiar
stimulation which produces the decidual membrane, as inflamed surfaces
produce organized exudations. Though the latter be formed in the uterus,
even when the embryo is lodged, by aberration, in some other part of the
abdomen, its presence must not be deemed, on that account, unessential
to the embryo; for a vascular membrane, as nearly alike to it in texture
as can be, has invariably been found to connect, by blood-vessels, the
embryo to some vital part nearest to where that embryo has been casually
deposited, that part having, at the same time, its circulation and
vascularity greatly increased, and becoming, in fact, the parent of the
connecting vascular membrane in question.