Of all animals

man is most given to dreaming. Children and infants
do not dream, but in most cases dreaming comes on at the age of four
or five years. Instances have been known of full-grown men and women
that have never dreamed at all; in exceptional cases of this kind,
it has been observed that when a dream occurs in advanced life it
prognosticates either actual dissolution or a general break-up of
the system.

So much then for sensation and for the phenomena of sleeping and
of awakening.