the young of all viviparous animals whilst in the womb, and of oviparous animals before being hatched: the name is transferred by botanists to the embryos of vegetables.

Strictly, the name is applied to the young after it is perfectly formed; previous to which it is usually called EMBRYO. See ANATOMY Index.

In the human fetus are several peculiarities not to be found in the adult; some of them are as follow.

1. The arteries of the navel string, which are continuations of the hypogastrics, are, after the birth, shrivelled up, and form the ligamenta umbilic. infer.

2. The veins of the navel string are formed by the union of all the venous branches in the placenta, and passing into the abdomen become the falciform ligament of the liver.

3. The lungs, before being inflated with air, are compact and heavy, but after one inspiration they become light, and as it were spongy; and it may be noted here, that the notion of the lungs sinking in water before the child breathes, and of their swimming after the reception of air, are no certain proofs that the child had or had not breathed, much less that it was murdered: for the uninflated lungs become specifically lighter than water as soon as any degree of putrefaction takes place in them; and this soon happens after the death of the child; besides, where the utmost care hath been taken to preserve the child, it hath breathed once or twice and then died.

4. The thymus gland is very large in the fetus, but dwindles away in proportion as years advance.

5. The foramen ovale in the heart of a fetus, is generally closed in an adult.