ementary bodies which enter into the composition of protoplasm;
but, as I need hardly say, a hogshead of that fluid would not keep a
hungry man from starving, nor would it save any animal whatever from a
like fate. An animal cannot make protoplasm, but must take it ready-made
from some other animal, or some plant--the animal's highest feat of
constructive chemistry being to convert dead protoplasm into that living
matter of life which is appropriate to itself.
Therefore, in seeking for the origin of protoplasm, we must eventually
turn to the vegetable world. A fluid containing carbonic acid, water,
and nitrogenous salts, which offers such a Barmecide feast [105] to the
animal, is a table richly spread to multitudes of plants; and, with a
due supply of only such materials, many a plant will not only maintain
itself in vigour, but grow and multiply until it has increased a
million-fold, or a million million-fold, the quantity of protoplasm
which it originally possessed; in this way building up the matter of
life, to an indefinite extent, from the common matter of the universe.
Thus, the animal can only raise the complex substance of dead protoplasm
to the higher power, as one may say, of living protoplasm; while the
plant can raise the less complex substances--carbonic acid, water, and
nitrogenous salts--to the same stage of living protoplasm, if not to the
same level. But the plant also has its limitations. Some of the fungi,
for example, appear to need higher compounds to start with; and no known
plant can live upon the uncompounded elements of protoplasm. A plant
supplied with pure carbon, hydrogen, oxygen, and nitrogen, phosphorus,
sulphur, and the like, would as infallibly die as the animal in his bath
of smelling-salts, though it would be surrounded by all the constituents
of protoplasm. Nor, indeed, need the process of simplification of
vegetable food be carried so far as this, in order to arrive at the
limit of the plant's thaumaturgy. Let water, carbonic acid, and all the
other needful constituents be supplied except nitrogenous salts, and an
ordinary plant will still be unable to manufacture protoplasm.
Thus the matter of life, so far as we know it (and we have no right to
speculate on any other), breaks up, in consequence of that continual
death which is the condition of its manifesting vitality, into carbonic
acid, water, and nitrogenous compounds, which certainly possess no
properties but those of ordinar
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