f all animals endowed with feeling
have the least perfect nervous system,[185] have perceptions of
objects which affect them, and seem to have memory of them when they
are repeated. Yet they can vary their actions and change their
habits, though they do not possess the organ whose acts could give
them the means.

"_On the Instincts of Animals._

"We define instinct as the sum (_ensemble_) of the decisions
(_determinations_) of animals in their actions; and, indeed, some
have thought that these determinations were the product of a
rational choice, and consequently the fruit of experience. Others,
says Cabanis, may think with the observers of all ages that several
of these decisions should not be ascribed to any kind of reasoning,
and that, without ceasing as for that to have their source in
physical sensibility, they are most often formed without the will of
the individuals able to have any other part than in better directing
the execution. It should be added, without the will having any part
in it; for when it does not act, it does not, of course, direct the
execution.

"If it had been considered that all the animals which enjoy the
power of sensation have their inner feeling susceptible of being
aroused by their needs, and that the movements of their nervous
fluids, which result from these emotions, are constantly directed by
this inner sentiment and by habits, then it has been felt that in
all the animals deprived of intelligence all the decisions of action
can never be the result of a rational choice, of judgment, of
profitable experience--in a word, of will--but that they are
subjected to needs which certain sensations excite, and which awaken
the inclinations which urge them on.

"In the animals even which enjoy the power of performing certain
intelligent acts, it is still more often the inner feeling and the
inclinations originating from habits which decide, without choice,
the acts which animals perform.

"Moreover, although the executing power of movements and of actions,
as also the cause which directs them, should be entirely internal,
it is not well, as has been done,[186] to limit to internal
impressions the primary cause or provocation of these acts, with the
intention to restrict to external impressions that which provokes
intelligent acts; for, from what few facts are known bearing on
these considerations, we are convin