The difference in the nature of various bodies depends, as I have often
observed to you, rather on their state of combination, than on the
materials of which they are composed. Thus, in considering the chemical
nature of the creation in a general point of view, we observe that it is
throughout composed of a very small number of elements. But when we
divide it into the three kingdoms, we find that, in the mineral, the
combinations seem to result from the union of elements casually brought
together; whilst in the vegetable and animal kingdoms, the attractions
are peculiarly and regularly produced by appropriate organs, whose
action depends on the vital principle. And we may further observe, that
by means of certain spontaneous changes and decompositions, the elements
of one kind of matter become subservient to the reproduction of another;
so that the three kingdoms are intimately connected, and constantly
contributing to the preservation of each other.

EMILY.

There is, however, one very considerable class of elements, which seems
to be confined to the mineral kingdom: I mean metals.

MRS. B.

Not entirely; they are found, though in very minute quantities, both in
the vegetable and animal kingdoms. A small portion of earths and sulphur
enters also into the composition of organised bodies. Phosphorus,
however, is almost entirely confined to the animal kingdom; and
nitrogen, but with few exceptions, is extremely scarce in vegetables.

Let us now proceed to examine the nature of the three principal
materials of the animal system.

_Gelatine_, or _jelly_, is the chief ingredient of skin, and of all the
membranous parts of animals. It may be obtained from these substances,
by means of boiling water, under the forms of glue, size, isinglass, and
transparent jelly.

CAROLINE.

But these are of a very different nature; they cannot therefore be all
pure gelatine.

MRS. B.

Not entirely, but very nearly so. Glue is extracted from the skin of
animals. Size is obtained either from skin in its natural state, or from
leather. Isinglass is gelatine procured from a particular species of
fish; it is, you know, of this substance that the finest jelly is made,
and this is done by merely dissolving the isinglass in boiling water,
and allowing the solution to congeal.

EMILY.

The wine, lemon, and spices, are, I suppose, added only to flavour the
jelly?

MRS. B.

Exactly so.

CAROLINE.

But jelly is often made of h