not only is all flesh grass, but grass is air. In
the vital processes of the body they are again
reduced to their primitive state, and pass
again into the air to renew their round of
fresh existence; revolving through a never-
ending series of material metamorphoses.
This sublime cycle of an ever-renewed life
arrests and fascinates our intelligence. But
we are compelled to recur—not without some
doubt and trouble—to the Biblical declaration,
from earth was man made, and to dust he
shall return. We ask for reconciliation of
human with divine truth; although we know
well that the one can never contradict the
other. The interpretation is often above our
power; but a faithful study of structure and
nutrition leads us to the solution of this
problem also.

According to Quetelet, a full-grown man
weighs on an average one hundred and fifty-
four pounds. Subtract from this the water
which lies everywhere, giving pliancy and
suppleness, there remain thirty–eight pounds;
of which one-fourth is constituted by earthy
that is, mineral matter. If we remember
that the dust of the earth is mineral, we shall
see a glimmering of light. Let us track these
mineral matters at once to their source:—

Man, we have said, directly or indirectly,
feeds upon the vegetable kingdom. Quod
facit per alium, facit per se [who acts by
another acts for himself],—and, although it
is not generally acknowledged that a man
can get his eating done for him by an agent;
yet we have shown that, practically, we do
avail ourselves of the greater digestive powers
of oxen, sheep, and herbivorous animals
generally, to obtain grass in the more palatable and
assimilatable form of beef and mutton. What
then is the food of plants? No modern
discovery in chemical science promises to exercise
a more immense influence over the welfare of
nations than this observation of Liebig,—that
plants, although feeding upon air, take, each
of them from the earth, mineral substances.
They will not nourish without them; they
thrive only on a soil affording them that
mineral aliment which they specially require.
The impoverishment of fields by successive
crops means only the exhaustion of the
mineral components of the soil, and the
whole business of the agriculturist is to restore
continually to the fields, in a proper form,
those minerals which his crops withdraw. It
took a long time to get a reception, for this
doctrine; nay, is not even yet everywhere
acknowledged. The farmer thought his crops
fed on charcoal and mould, or humus. The
man of science backed the farmer's opinion,
by endeavouring to prove the absorption of
humus, and by examining the qualities of
humic acid and chrenic acid. Decandolle
said that the refusal of the earth to yield a
succession of similar crops, arose from the
fact that plants expelled from their rootlets
a fluid, poisonous to themselves and other
individuals of their kind. This monstrous
theory, throws upon the gentlest plant the
odium of distilling venomous compounds, and
accuses it of poisoning for others the very fount
of its own life. Such a theory is not less untrue
than horrible. Liebig and his followers
conclusively showed that the plant was innocent
of any other process than that of continually
absorbing, from the earth, those mineral
products which are essential to its existence; so
that, at length, it leaves the field devoid of the
elements of nutrition. Fleets traverse the
ocean, labourers hew at the beds of coprolite,
or fossil dung, which marvellously retains its
fertilising powers after countless ages; and
cunning chemists compound various forms
of superphosphate, that the fields may receive
this needed nutriment. The full solution
of the problem is not yet worked out; but
its successful demonstration will restore to
our exhausted lands and famished population,
the agricultural riches and plenty which smile
upon the virgin plains of the New World,
and beckon away our lean and hungry paupers
to fresh fields and pastures new.

These minerals, which are interwoven with
the living structure of the plant, are taken
up into the fabric of the animal. And, to us,
they are as important as to the meanest
vegetable that grows. I, who write this,
boast myself living flesh and blood. But
lime strengthens my bones; iron flows in my
blood; flint bristles in my hair; sulphur and
phosphorus quiver in my flesh. In this
human frame the rock moves, the metal
flows, and the materials of the earth,
snatched by the divine power of vitality
from the realms of inertia, live and move,
and form part of a soul-tenanted frame.
In the very secret chamber of the brain
there lies a gland, gritty with earthy mineral
matter, which Descartes did not scruple, with
a crude scientific impiety, to assign as the
residence of the soul. You could no more
have lived and grown, and flourished without
iron, and silica, and potash, and sodium, and
magnesium, than wheat can flourish without
phosphorus, grass without silica, cress without
iodine, or clover without lime. We are all of
us indeed of earth, earthy.

The relations between the mineral and
vegetable kingdoms do not wholly resemble
those which exist between mineral and
animal. Among plants, we find that each
class has a special predilection for some one
particular metal, because it is essential to its
well-being, nay, to its existence. Liebig,
therefore, went so far as to divide cultivated
vegetables into:—

1. Alkali plants, to which belong potatoes and
    beets.
2. Lime plants, which include clover and peas.
3. Silex plants, grasses, &c.
4. Phosphorus plants, as rye, wheat, &c.

But we cannot make out a like ground for
classification among animals or men. A
lobster shows, to be sure, a marked affection
for carbonate of lime; because he needs it to