el. 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 with ammonia,
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 ammonia, which certainly possess no properties but
those of ordinary matter. 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 ammonia. Withdraw any one of these three from the
world and all vital phaenomena come to an end. They are related 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 hydrogen give rise to ammonia. 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.

I see no break in this series of steps in molecular complication, and I
am unable to understand why the language which is applicable to any one
term of the series may not be used to any of the others. We think fit to
call different kinds of matter carbon, oxygen, hydrogen, and