And out of these same forms of
ordinary matter, and from none which are simpler, the vegetable world
builds up all the protoplasm which keeps the animal world a-going.
Plants are the accumulators of the power which animals distribute and
disperse.
But it will be observed, that the existence of the matter of life
depends on the pre-existence of certain compounds; namely, carbonic
acid, water, and certain nitrogenous bodies. Withdraw any one of these
three from the world, and all vital phenomena come to an end. They are
as necessary to the protoplasm of the plant, as the protoplasm of the
plant is to that of the animal. Carbon, hydrogen, oxygen, and nitrogen
are all lifeless bodies. Of these, carbon and oxygen unite in certain
proportions and under certain conditions, to give rise to carbonic acid;
hydrogen and oxygen produce water; nitrogen and other elements give rise
to nitrogenous salts. These new compounds, like the elementary bodies of
which they are composed, are lifeless. But when they are brought
together, under certain conditions, they give rise to the still more
complex body, protoplasm, and this protoplasm exhibits the phenomena of
life.
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