signify a spongy piece of flesh resembling a cake, full of veins and
arteries, and is made to receive a mother's blood appointed for the
infant's nourishment in the womb. The _chorion_ is an outward skin which
compasseth the child in the womb. The _amnios_ is the inner skin which
compasseth the child in the womb. The _alantois_ is the skin that holds
the urine of the child during the time that it abides in the womb. The
_urachos_ is the vessel that conveys the urine from the child in the
womb to the _alantois_. I now proceed to

SECT. II.--_Of the Formation of the Child in the Womb._

To speak of the formation of the child in the womb, we must begin where
nature begins, and, that is at the act of coition, in which the womb
having received the generative seed (without which there can be no
conception), the womb immediately shuts up itself so close that the
point of a needle cannot enter the inward orifice; and this it does,
partly to hinder the issuing out of the seed again, and partly to
cherish it by an inward heat, the better to provoke it to action; which
is one reason why women's bellies are so lank at their first conception.
The woman having thus conceived, the first thing which is operative in
conception is the spirit whereof the seed is full, which, nature
quickening by the heat of the womb, stirs up the action. The internal
spirits, therefore, separate the parts that are less pure, which are
thick, cold and clammy, from those that are more pure and noble. The
less pure are cast to the outside, and with these seed is circled round
and the membrane made, in which that seed that is most pure is wrapped
round and kept close together, that it may be defended from cold and
other accidents, and operate the better.

The first thing that is formed is the amnios; the next the chorion; and
they enwrap the seed round like a curtain. Soon after this (for the seed
thus shut up in the woman lies not idle), the navel vein is bred, which
pierceth those skins, being yet very tender, and carries a drop of blood
from the veins of the mother's womb to the seed; from which drop the
vena cava, or chief vein, proceeds, from which all the rest of the veins
which nourish the body spring; and now the seed hath something to
nourish it, whilst it performs the rest of nature's work, and also blood
administered to every part of it, to form flesh.

This vein being formed, the navel arteries are soon after formed; then
the great artery,