fountain; while the cavities of the brain
are the central office. Moreover, respiration and other such
actions as are natural and usual in the body, and which depend on
the course of the spirits, are like the movements of a clock, or of
a mill, which may be kept up by the ordinary flow of the water.

"The external objects which, by their mere presence, act upon the
organs of the senses; and which, by this means, determine the
corporal machine to move in many different ways, according as the
parts of the brain are arranged, are like the strangers who,
entering into some of the grottoes of these waterworks,
unconsciously cause the movements which take place in their
presence. For they cannot enter without treading upon certain
planks so arranged that, for example, if they approach a bathing
Diana, they cause her to hide among the reeds; and if they attempt
to follow her, they see approaching a Neptune, who threatens them
with his trident; or if they try some other way, they cause some
monster who vomits water into their faces, to dart out; or like
contrivances, according to the fancy of the engineers who have made
them. And lastly, when the _rational soul_ is lodged in this
machine, it will have its principal seat in the brain, and will
take the place of the engineer, who ought to be in that part of the
works with which all the pipes are connected, when he wishes to
increase, or to slacken, or in some way to alter, their
movements."[72]

And again still more strongly:--

"All the functions which I have attributed to this machine (the
body), as the digestion of food, the pulsation of the heart and of
the arteries; the nutrition and the growth of the limbs;
respiration, wakefulness, and sleep; the reception of light,
sounds, odours, flavours, heat, and such like qualities, in the
organs of the external senses; the impression of the ideas of these
in the organ of common sense and in the imagination; the retention,
or the impression, of these ideas on the memory; the internal
movements of the appetites and the passions; and lastly, the
external movements of all the limbs, which follow so aptly, as well
the action of the objects which are presented to the senses, as the
impressions which meet in the memory, that they imitate as nearly
as possible