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, of which all the others are but branches; and then the heart, for the liver furnisheth the arteries with blood to form the heart, the arteries being made of seed, but the heart and the flesh, of blood. After this the brain is formed, and then the nerves to give sense and motion to the infant. Afterwards the bones and flesh are formed; and of the bones, first of all, the vertebrae or chine bones, and then the skull, etc. As to the time in which this curious part of nature's workmanship is formed, having already in Chapter II of the former part of this work spoken at large upon this point, and also of the nourishment of the child in the womb, I shall here only refer the reader thereto, and proceed to show the manner in which the child lies in the womb. SECT. III.--_Of the manner of the Child's lying in the Womb._