e clay of the potter: which, bake it and paint it as he will, remains
clay, separated by artifice, and not by nature, from the commonest brick
or sun-dried clod.

Thus it becomes clear that all living powers are cognate, and that all
living forms are fundamentally of one character. The researches of the
chemist have revealed a no less striking uniformity of material
composition in living matter.

In perfect strictness, it is true that chemical investigation can tell
us little or nothing, directly, of the composition of living matter,
inasmuch as such matter must needs die in the act of analysis,--and upon
this very obvious ground, objections, which I confess seem to me to be
somewhat frivolous, have been raised to the drawing of any conclusions
whatever respecting the composition of actually living matter, from that
of the dead matter of life, which alone is accessible to us. But
objectors of this class do not seem to reflect that it is also, in
strictness, true that we know nothing about the composition of any body
whatever, as it is. The statement that a crystal of calc-spar consists
of carbonate of lime, is quite true, if we only mean that, by
appropriate processes, it may be resolved into carbonic acid and
quicklime. If you pass the same carbonic acid over the very quicklime
thus obtained, you will obtain carbonate of lime again; but it will not
be calc-spar, nor anything like it. Can it, therefore, be said that
chemical analysis teaches nothing about the chemical composition of
calc-spar? Such a statement would be absurd; but it is hardly more so
than the talk one occasionally hears about the uselessness of applying
the results of chemical analysis to the living bodies which have yielded
them.

One fact, at any rate, is out of reach of such refinements, and this is,
that all the forms of protoplasm which have yet been examined contain
the four elements, carbon, hydrogen, oxygen, and nitrogen, in very
complex union, and that they behave similarly towards several reagents.
To this complex combination, the nature of which has never been
determined with exactness, the name of Protein has been applied. And if
we use this term with such caution as may properly arise out of our
comparative ignorance of the things for which it stands, it may be truly
said, that all protoplasm is proteinaceous; or, as the white, or
albumen, of an egg is one of the commonest examples of a nearly pure
protein matter, we may say that all li