rganised Beings into
Animals and Vegetables," in which the question is treated with that
comprehensiveness of knowledge and clear critical judgment which
characterise his writings, and justify us in regarding them as
representative expressions of the most extensive, if not the profoundest,
knowledge of his time. He tells us that living beings have been
subdivided from the earliest times into _animated beings_, which possess
sense and motion, and _inanimated beings_, which are devoid of these
functions and simply vegetate.

Although the roots of plants direct themselves towards moisture, and
their leaves towards air and light,--although the parts of some plants
exhibit oscillating movements without any perceptible cause, and the
leaves of others retract when touched,--yet none of these movements
justify the ascription to plants of perception or of will. From the
mobility of animals, Cuvier, with his characteristic partiality for
teleological reasoning, deduces the necessity of the existence in them of
an alimentary cavity, or reservoir of food, whence their nutrition may be
drawn by the vessels, which are a sort of internal roots; and, in the
presence of this alimentary cavity, he naturally sees the primary and the
most important distinction between animals and plants.

Following out his teleological argument, Cuvier remarks that the
organisation of this cavity and its appurtenances must needs vary
according to the nature of the aliment, and the operations which it has
to undergo, before it can be converted into substances fitted for
absorption; while the atmosphere and the earth supply plants with juices
ready prepared, and which can be absorbed immediately. As the animal body
required to be independent of heat and of the atmosphere, there were no
means by which the motion of its fluids could be produced by internal
causes. Hence arose the second great distinctive character of animals, or
the circulatory system, which is less important than the digestive, since
it was unnecessary, and therefore is absent, in the more simple animals.

Animals further needed muscles for locomotion and nerves for sensibility.
Hence, says Cuvier, it was necessary that the chemical composition of the
animal body should be more complicated than that of the plant; and it is
so, inasmuch as an additional substance, nitrogen, enters into it as an
essential element; while, in plants, nitrogen is only accidentally joined
with he three other fund