on cooling.
This colour, therefore, may be called the soot produced by the burning
of ivory or bone.

CONVERSATION XXIV.

ON THE ANIMAL ECONOMY.

MRS. B.

We have now acquired some idea of the various materials that compose the
animal system; but if you are curious to know in what manner these
substances are formed by the animal organs, from vegetable, as well as
from animal substances, it will be necessary to have some previous
knowledge of the nature and functions of these organs, without which it
is impossible to form any distinct idea of the process of
_animalisation_ and _nutrition_.

CAROLINE.

I do not exactly understand the meaning of the word animalisation?

MRS. B.

Animalisation is the process by which the food is _assimilated_, that is
to say, converted into animal matter; and nutrition is that by which the
food thus assimilated is rendered subservient to the purposes of
nourishing and maintaining the animal system.

EMILY.

This, I am sure, must be the most interesting of all the branches of
chemistry!

CAROLINE.

So I think; particularly as I expect that we shall hear something of the
nature of respiration, and of the circulation of the blood?

MRS. B.

These functions undoubtedly occupy a most important place in the history
of the animal economy. --But I must previously give you a very short
account of the principal organs by which the various operations of the
animal system are performed. These are:

The _Bones_;
_Muscles_,
_Blood vessels_,
_Lymphatic vessels_,
_Glands_, and
_Nerves_.

The _bones_ are the most solid part of the animal frame, and in a great
measure determine its form and dimensions. You recollect, I suppose,
what are the ingredients which enter into their composition?

CAROLINE.

Yes; phosphat of lime, cemented by gelatine.

MRS. B.

During the earliest period of animal life, they consist almost entirely
of gelatinous membrane having the form of the bones, but of a loose
spongy texture, the cells or cavities of which are destined to be filled
with phosphat of lime; it is the gradual acquisition of this salt which
gives to the bones their subsequent hardness and durability. Infants
first receive it from their mother's milk, and afterwards derive it from
all animal and from most vegetable food, especially farinaceous
substances, such as wheat-flour, which contain it in sensible
quantities. A portion of the phosphat, after the bo