ll. On the other
hand, the definition thus amended will exclude all ordinary vegetable
organisms.

Cuvier himself practically gives up his second distinctive mark when he
admits that it is wanting in the simpler animals.

The third distinction is based on a completely erroneous conception of
the chemical differences and resemblances between the constituents of
animal and vegetable organisms, for which Cuvier is not responsible, as
it was current among contemporary chemists. It is now established that
nitrogen is as essential a constituent of vegetable as of animal living
matter; and that the latter is, chemically speaking, just as complicated
as the former. Starchy substances, cellulose and sugar, once supposed to
be exclusively confined to plants, are now known to be regular and normal
products of animals. Amylaceous and saccharine substances are largely
manufactured, even by the highest animals; cellulose is widespread as a
constituent of the skeletons of the lower animals; and it is probable
that amyloid substances are universally present in the animal organism,
though not in the precise form of starch.

Moreover, although it remains true that there is an inverse relation
between the green plant in sunshine and the animal, in so far as, under
these circumstances, the green plant decomposes carbonic acid and exhales
oxygen, while the animal absorbs oxygen and exhales carbonic acid; yet,
the exact researches of the modern chemical investigators of the
physiological processes of plants have clearly demonstrated the fallacy
of attempting to draw any general distinction between animals and
vegetables on this ground. In fact, the difference vanishes with the
sunshine, even in the case of the green plant; which, in the dark,
absorbs oxygen and gives out carbonic acid like any animal.[1] On the
other hand, those plants, such as the fungi, which contain no chlorophyll
and are not green, are always, so far as respiration is concerned, in the
exact position of animals. They absorb oxygen and give out carbonic acid.

[Footnote 1: There is every reason to believe that living plants, like
living animals, always respire, and, in respiring, absorb oxygen and give
off carbonic acid; but, that in green plants exposed to daylight or to
the electric light, the quantity of oxygen evolved in consequence of the
decomposition of carbonic acid by a special apparatus which green plants
possess exceeds that absorbed in the concurrent respir