h, by the situation of the former on or
near the moist and aerated surface of the earth, and of the latter in the
ever-changing and ventilated water, may not be in need of an apparatus for
the oxygenation of their first blood, before the leaves of one, and the
gills of the other, are produced for this purpose.

III. 1. There are many arguments, besides the strict analogy between the
liquor amnii and the albumen ovi, which shew the former to be a nutritive
fluid; and that the fetus in the latter months of pregnancy takes it into
its stomach; and that in consequence the placenta is produced for some
other important purpose.

First, that the liquor amnii is not an excrementitious fluid is evinced,
because it is found in greater quantity, when the fetus is young,
decreasing after a certain period till birth. Haller asserts, "that in some
animals but a small quantity of this fluid remains at the birth. In the
eggs of hens it is consumed on the eighteenth day, so that at the exclusion
of the chick scarcely any remains. In rabbits before birth there is none."
Elem. Physiol. Had this been an excrementitious fluid, the contrary would
probably have occurred. Secondly, the skin of the fetus is covered with a
whitish crust or pellicle, which would seem to preclude any idea of the
liquor amnii being produced by any exsudation of perspirable matter. And it
cannot consist of urine, because in brute animals the urachus passes from
the bladder to the alantois for the express purpose of carrying off that
fluid; which however in the human fetus seems to be retained in the
distended bladder, as the feces are accumulated in the bowels of all
animals.

2. The nutritious quality of the liquid, which surrounds the fetus, appears
from the following considerations. 1. It is coagulable by heat, by nitrous
acid, and by spirit of wine, like milk, serum of blood, and other fluids,
which daily experience evinces to be nutritious. 2. It has a saltish taste
according to the accurate Baron Haller, not unlike the whey of milk, which
it even resembles in smell. 3. The white of the egg which constitutes the
food of the chick, is shewn to be nutritious by our daily experience;
besides the experiment of its nutritious effects mentioned by Dr. Fordyce
in his late Treatise on Digestion, p. 178; who adds, that it much resembles
the essential parts of the serum of blood.

3. A fluid similar to the fluid, with which the fetus is surrounded, except
what little