n an
immense variety of food. The flesh and the blood of other animals of
all kinds, warm or cold, the leaves, twigs, fruits, juices of plants,
putrid carcases, hair, feathers, skin, bran, sawdust, the vegetable
mould or "humus" of the earth's surface, the sand of the sea, with its
minute particles of organic detritus, all serve as food to different
kinds of animals. Some are very little fettered in their tastes, and
are called "omnivorous," others are bound in the strictest way to a
diet consisting of the leaves of some one species of plant or the
juices of one species of animal. Some of the latter class, under
stress or privation, can accommodate themselves to a new food very
different in character and origin from that which is habitual to them;
others have no elasticity in this respect, and must have their exact
habitual food-plant or food-animal, unless they are to die of
starvation.

Man exhibits his great powers of accommodation to changed
circumstances in respect of food as well as in other matters. If we
are to suppose, as is probable, that our original ape-like ancestors
fed exclusively upon fruits and an occasional egg or juicy grub, how
vast are the changes in diet to which man has habituated himself! Man
is sometimes said to be omnivorous, but this is not a sufficient
description of the state of things which has grown up as he has spread
over the earth's surface. Every race--and even many a small group of
men--has its accustomed diet, to depart from which is a pain and a
difficulty, even though new kinds of food may be gradually accepted
and even become popular. Man has in this, as in so many other things,
a large range of possible accommodation, but he has at the same time
habits the continuance of which are necessary for the healthy working
of the nervous system. The psychical element in the matter of
food-habit is important in all higher animals, but most of all in man.
The digestive organs are controlled by the nervous system, and the
brain acts upon the latter in such a way as to favour or to restrain
the "appetite" and the secretion of the elaborate digestive juices, so
that fear, surprise, disgust, and "nausea" (that strange product of
mental and physical reactions) may destroy appetite and inhibit the
digestive process. There are vast populations of men who live on rice,
or beans, or meal, and never eat animal food, not even milk (after
babyhood), nor cheese, and would be, at a first attempt to eat