utter, though
counted as a pure fat, is in reality made up of at least six fatty
principles, there being sixty-eight per cent of margarine and thirty per
cent of oleine, the remainder being volatile compounds of fatty acids. In
the best specimens of butter there is a slight amount of caseine, not over
five per cent at most, though in poor there is much more. It is the only
fat which may be constantly eaten without harm to the stomach, though if
not perfectly good it becomes an irritant.

The _Drippings_ of roasted meat, more especially of beef, rank next in
value; and _Lard_ comes last on the list, its excessive use being a
serious evil. Eaten constantly, as in pastry or the New-England doughnut,
it is not only indigestible, but becomes the source of forms of scrofulous
disease. It is often a convenient substitute for butter, but if it must be
used, would better be in connection with the harmless fat.

Eggs come last; and as a young animal is developed from them, it follows
that they contain all that is necessary for animal life, though in the
case of the chicken the shell also is used, all the earthy matter being
absorbed. In a hundred parts are found fourteen of nitrogen, ten and a
half of fatty matter, one and a half of saline matter, and seventy-four of
water. Of this water the largest part is contained in the white, which is
almost pure albumen, each particle of albumen being enclosed in very
thin-walled cells; it is the breaking of these cells and the admission of
air that enables one to beat the white of egg to a stiff froth. The fat is
accumulated in the yolk, often amounting to thirty per cent. Raw and
lightly-boiled eggs are easy of digestion, but hard-boiled ones decidedly
not so. An egg loses its freshness within a day or so. The shell is
porous; and the always-feeding and destroying oxygen of the air quickly
gains admission, causing a gradual decomposition. To preserve them, they
must be coated with lard or gum, or packed in either salt or oats, points
down. In this way they keep good a long time, and while hardly desirable
to eat as boiled eggs, answer for many purposes in cooking.

CHAPTER XI.

THE CHEMISTRY OF VEGETABLE FOOD.

We come now to the vegetable kingdom, the principal points that we are to
consider arranging themselves somewhat as follows:--

Farinaceous seeds,
Oleaginous seeds,
Leguminous seeds,
Tubers and roots,
Herbaceous articles,
Fruits,
Saccharine and farinaceous prepara