EMBRYOLOGY--THE DEVELOPMENT OF LIFE
You remember I mentioned that at various times during the month an ovum
or egg leaves the ovary and passes along the tube to the uterus. Here it
remains if it is impregnated or fertilized by a union with the
spermatozoon or male element. The whole body of the babe is developed
from the ovum or female element after it has been fertilized by the
spermatozoon or male element. The union usually takes place in the tube.
The spermatozoon, after being deposited in the vagina, travels to the
mouth of the womb, then up through the womb into one of the tubes. Here
it meets the ovum and unites with it, then the impregnated ovum
continues on its way to the uterus. It attaches itself to the lining of
the womb by little thread-like filaments which it projects. The ovum
then begins to grow, dividing itself into portions that go to make the
different parts of the body. Before I continue, let me remind you that
the ovum in the beginning is only about as large as the point of a pin,
being about 1-125 of an inch in diameter, while the spermatozoon is so
tiny it cannot be seen without the aid of a miscroscope. Therefore, it
can be realized how much the ovum has to grow before it becomes a fully
formed babe.
During the time the ovum is developing into the babe we speak of it
first as the embryo, then the foetus. It takes about nine calendar
months or ten lunar months before the foetus is fully developed and
ready to be expelled from the womb. During the process of development
the foetus resembles various animals. It seems it must pass through
about the same stages of evolution that our primitive ancestors did.
By the end of the third week, the dividing has progressed so far that
the body is quite well indicated. By the end of the seventh week the
body and limbs are quite well defined. One peculiar thing is that, at
this time, the foetus has a tail which disappears during the next two
weeks. During the third month the foetus increases in size and weight
so that by the end of the month the weight is four ounces and the
length two and three-fourths inches. It now is not directly attached to
the lining of the womb but is attached by means of the cord to the
placenta or afterbirth which has been forming slowly. This placenta
consists of fatty tissue surrounding a great many little blood vessels.
The tiny blood vessels lie so close to the blood vessels of the lining
of the womb that the blood passes from one to the other. To do this, it
must pass through the walls of the blood vessels, as the vessels of the
mother and those of the placenta are not directly united. The blood
vessels of the placenta unite to form two veins and one artery which lie
very close to each other and are surrounded by a membrane. These three
blood vessels united together form what we call the cord. The other end
of the cord is attached to the foetus so that the blood can flow back
and forth between the foetus and placenta.
By the end of the third month the limbs have definite shape, the nails
being almost perfectly formed. During the next month the sexual
distinctions of the external organs become well marked.
By the last of the fifth month the weight has increased to one pound and
the length to eight inches. Active foetal movements begin, that is,
the foetus begins to move around and not lie quietly as before. This
is what is usually spoken of as "feeling life," or as "quickening."
There is life from the very beginning but during the first four or five
months the foetus does not move about and so the mother does not "feel
life." This has caused the erroneous idea that there is no life before
the fifth month.
By the end of the sixth month the weight is two pounds and the length
twelve inches. The eyebrows and eyelashes have begun to grow and the
lobule of the ear is more characteristic.
By the end of the seventh month the weight is three pounds and the
length fourteen inches. The surface of the body, which has appeared
wrinkled, now appears more smooth owing to the increase of fat
underneath.
By the end of the eighth month the weight is four to five pounds and the
length twenty inches. The nails have grown to project beyond the finger
tips. Up to this time the body has been covered with a fine hair called
lanugo. This now has begun to disappear and the skin becomes brighter
and is covered with a white, cheesy material called the vernix caseosa.
This almost entirely disappears during the next month, but frequently
there are portions of it remaining on the body at the time of birth. The
foetus is fully developed by the end of the ninth month. Then its
average weight is six or seven pounds and the length twenty inches.
If we could look into the womb just before the time of labor we would
find the foetus attached by the cord to the placenta and floating in a
sac of water. This sac is formed partly of the placenta and partly of
the membrane; the side of the placenta opposite to the child being
attached to the womb. Just before labor the child takes a position with
its head downward, its lower limbs flexed and its arms folded upon its
breast. This allows it to come in the usual way, head first. But
sometimes, for various reasons, it does not take this position and some
part other than the head, for instance, the feet, may be born first.
Labor pains are caused by the contraction of the muscles of the womb in
an effort to expel the foetus. The muscles, contracting, push the
foetus downward to the mouth of the womb but push ahead of it a
portion of the membrane enclosing some of the water. This is called the
"bag of waters." As it presses against the mouth of the womb it causes
it to dilate so as to allow the foetus to pass through into the
vagina. The foetus, preceded by the bag of waters, then descends
through the vagina or birth canal until it comes to the external opening
of the vagina. This it must dilate before it can pass through it. The
bag of waters should rupture normally while it is being pushed through
the external opening. Sometimes the bag does not rupture directly in
front of the descending head but further up along the side. Then a
portion of the membrane may be over the face of the child when it is
born. This is what is called being "born with a veil" or "born with a
caul."
The bag of waters helps dilate the parts much easier than the foetus
could do it alone. When the bag breaks the water lubricates the parts so
as to make the passage of the child easier. When it breaks, as it
sometimes does, at the beginning of labor we have what is termed a "dry
labor." This usually is much slower than it would be otherwise. The
majority of the cases of labor extend over a period of from twelve to
twenty-four hours.
Sometimes the external opening of the vagina does not dilate enough to
allow the passage of the child. As the head presses hard against the
perineum it tears it. This tear should be repaired immediately after
completion of labor.
When the baby is born it is fully formed but its lungs have never
contained air. At the first cry the air rushes into the lungs and
expands them. At birth there is a change in the circulation of the blood
of the baby. Before this time, the blood has passed to and from the
placenta through the cord but now this is stopped. Before birth there
was an opening between the right and left sides of the heart but this
closes during the first few days of the child's life. To assist in this
closure, it is wise to keep the child on its right side for a few days.
Rarely, this opening never closes and we have what is called a "blue
baby," which seldom lives very long.
In a great many cases, painless childbirth could be a possibility by a
little attention to diet, exercise and other hygienic measures during
the last few months of pregnancy. Knowing this, it seems inconceivable
that any woman would neglect to so fully inform herself on these matters
that both she and her child could have all benefit of the investigations
of science.