waste is attendant on action applies to both
dead and living bodies; but beyond this point a remarkable difference
between them presents itself. In the physical or inanimate world, what
is once lost or worn away _is lost forever_; but _living_ bodies,
whether vegetable or animal, possess the distinguishing characteristic
of being able to _repair their own waste_ and add to their own
substance. The possession of such a power is essential to their
existence. But there is a wide difference between them in other
respects. In surveying the respective modes of existence of vegetables
and of animals, we perceive the fixity of position of the one, and the
free locomotive power of the other. The vegetable grows, flourishes, and
dies, fixed to the same spot of earth from which it sprang. However much
external circumstances change around it, it must remain and submit to
their influence. At all hours and at all seasons, it is at home, and in
direct communication with the soil from which its nourishment is
extracted. But it is otherwise with animals: these not only enjoy the
privilege of locomotion, but are compelled to use it, and often to go a
distance in search of food and shelter. The necessity for a constant
change of place being imposed on them, a different arrangement became
indispensable for their nutrition. The method which the Creator has
provided is not less admirable than simple. To enable animals to move
about, and at the same time to maintain a connection with their food,
they are provided with a stomach. In this receptacle they can store up a
supply of materials from which sustenance may be gradually elaborated
during a period of time proportioned to their necessities and mode of
life. Animals thus _carry with them_ nourishment adequate to their
wants; and the small nutritive vessels imbibe their food from the
internal surface of the stomach and bowels, where it is stored up, just
as the roots or nutritive vessels of vegetables do from the soil in
which they grow. The possession of a stomach or receptacle for food is
accordingly a distinguishing characteristic of the animal system.

The sole objects of nutrition being to repair waste and to admit of
growth, the Creator has so arranged that within certain limits it is
always most vigorous when growth or waste proceeds with the greatest
rapidity. Even in vegetables this provision is distinctly observable. It
is also strikingly apparent in animals. Whenever growth is proc