scale. Take the
house cat and follow her through the life of a single day, observing
her actions. She washes her face and makes her toilet in the morning
by instinct. She has her peculiar instinctive ways of catching the
mouse for breakfast. She whets her appetite by holding back her meal
possibly for an hour, in the meantime playing most cruelly with the
pitiful mouse, letting it run and catching it again, and doing this
over and over. If she has children she attends to their training in
the details of cat etiquette and custom with the utmost care, all by
instinct; and the kittens instinctively respond to her attentions. She
conducts herself during the day with remarkable cleanliness of life,
making arrangements which civilized man follows with admiration. She
shows just the right abhorrence of water for a creature that is not
able to swim. She knows just what enemies to fly from and when to turn
and fight, using with inborn dexterity her formidable claws. She
prefers nocturnal excursions and sociabilities, having eyes which
make it safe to be venturesome in the dark. She has certain vocal
expressions of her emotions, which man in vain attempts to eradicate
with all the agencies of domestication. She has special arts to
attract her mate, and he in turn is able to charm her with songs which
charm nobody else. And so on, almost _ad infinitum_.

Observe the dog, the birds of different species, the monkeys, the
hares, and you find wonderful differences of habit, each adapting the
animal differently, but with equal effectiveness, to the life which he
in particular is called upon to lead. The ants and bees are
notoriously expert in the matter of instinct. They have colonies in
which some of the latest principles of social organization seem to
find analogues: slavery, sexual regulations, division of labour,
centralization of resources, government distribution of food, capital
punishment, etc.

All this--not to stop upon details which the books on animal life give
in great abundance--has furnished grounds for speculation for
centuries, and it is only in the last generation that the outlines of
a theory of instinct have been filled in with substantial knowledge. A
rapid sketch of this theory may be drawn in the following pages.

1. In instinct in general there is a basis of inherited nervous
tendency toward the performance of just the sort of action which the
instinct exhibits. This nervous tendency shows itself independent