3. The _third_ thing which makes up the secundine is the alantois, of which there is a great dispute among anatomists. Some say, there is such a thing, and others that there is not. Those that will have it to be a membrane, say it is white, soft, and exceeding thin, and just under the placentia, where it is knit to the urachos, from whence it receives the urine; and its office is to keep it separate from the sweat, that the saltness may not offend the tender skin of the child. 4. The _fourth_ and last covering of the child is called amnios; and it is white, soft, and transparent, being nourished by some very small veins and arteries. Its use is not only to enwrap the child, but also to retain the sweat of the child. Having thus described the parts proper to a child in the womb, I will next proceed to speak of the formation of the child therein, as soon as I have explained the hard terms of this section, that those for whose help it is designed, may understand what they read. A _vein_ is that which receives blood from the liver, and distributes it in several branches to all parts of the body. _Arteries_ proceed from the heart, are in continual motion, and by their continual motion quicken the body. _Nerve_ is the same with _sinew_, and is that by which the brain adds sense and motion to the body. _Placentia_ properly signifies a _sugar cake_; but in this section it is used to signify a spongy piece of flesh, resembling a cake, full of veins and arteries, and is made to receive the mother’s blood appointed for the infant’s nourishment in the womb. The _chorion_ is the outward 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 _allantois_. I now proceed to SECT. II. _Of the Formation of the Child in the Womb._ The woman having conceived, the first thing which is operative in the conception is the spirit whereof the seed is full, which nature quickening by the heat of the womb, stirs up to 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 the seed is circled round, and the membranes made, in which that seed which is most pure is wrapped round, and kept close together, that it may be defended from cold and other accidents, and operate the better.