other objects that had escaped our notice. But how many other
objects are there in every object discovered by the microscope which
the microscope itself cannot discover? What should not we see if we
could still subtilise and improve more and more the instruments that
help out weak and dull sight? Let us supply by our imagination what
our eyes are defective in; and let our fancy itself be a kind of
microscope, and represent to us in every atom a thousand new and
invisible worlds: but it will never be able incessantly to paint to
us new discoveries in little bodies; it will be tired, and forced at
last to stop, and sink, leaving in the smallest organ of a body a
thousand wonders undiscovered.


SECT. XXII. Of the Structure or Frame of the Animal.


Let us confine ourselves within the animal's machine, which has
three things that never can be too much admired: First, it has in
it wherewithal to defend itself against those that attack it, in
order to destroy it. Secondly, it has a faculty of reviving itself
by food. Thirdly, it has wherewithal to perpetuate its species by
generation. Let us bestow some considerations on these three
things.


SECT. XXIII. Of the Instinct of the Animal.


Animals are endowed with what is called instinct, both to approach
useful and beneficial objects, and to avoid such as may be noxious