14 LOVE AND ITS HIDDEN HISTORY.
substance from which they spring is thus clearly stated by Mr.
Herbert Spencer, in his 'Principles of Biology :' 'The doctrine
that all organisms are built up of cells, or that cells are the ele¬
ments out of which every tissue is developed, is but approximately
true. There are living forms of which cellular structure cannot be
asserted ; and in living forms that are, for the most part, cellular,
there are, nevertheless, certain portions which are not produced
by the metamorphosis of cells. Supposing that they were the only
material available for building, the proposition that all houses are
built of bricks would have about the same relation to the truth as
does the proposition that all organisms are composed of cells.
This generalization respecting houses would be open to two criti¬
cisms : first, that certain houses, of a primitive kind, are formed,
not out of bricks, but out of unmoulded clay ; and second, that,
though other houses consist mainly of bricks, yet their chimney-
pots^lrain-pipes, and ridge-tiles do not result from combinations
or metamorphosis of bricks, but are made directly of the original
clay ; and of like natures are the criticisms which must be passed
on the generalization that cells are the morphological (structural)
units of organisms. To continue the simile, the truth turns out
to be that the primitive clay or protoplasm out of which organ¬
isms are built may be moulded directly, or with various degrees of
indirectness, into organic structures.'
"Protoplasm consists of the four chemical elements, carbon,
oxygen, hydrogen, and nitrogen, which also compose the bulk of
the entire organic world. These elements are united in very com¬
plex union, the nature of which has never been determined with
exactness. It is albumenoid in aspect, that is, like white of egg.
A few years ago, the term protein was applied to a combination of
these four elements, which was supposed to be the common basis
of all albumenoid substances ; but no such principle has ever been
separated or proved to exist. The term, however, is still retained,
though with what vagueness may be inferred from the statement
of Professor Frankland, that so-called protein has probably more
than a thousand isometric forms.
" Professor Huxley aims to show that, as between protoplasm
and all the developed forms of life, there is an acknowledged unity
of composition, so there is also a unity of power and form.
" First, as regards unity of powers, by what property is it man-