the current of ideas in sleep, are
not so numerous as those in operation in our waking state.

The principal, indeed in general the exclusive, impulse to our dreaming
thoughts, is our past experience and existing character, from and in
obedience to which, imagination moulds our dreams.

Not that sensation is suspended in sleep. On the contrary, it appears to
have its usual acuteness; and impressions made upon our senses--the
feelings produced by an uneasy posture, for instance, or the
introduction of sudden light into the room, or a loud and unusual noise,
or even whisperings in the ear--will give a new and corresponding
direction to the dreaming thoughts. Sensation is only commonly not
called into play in sleep: we shut our eyes; we even close the pupils;
we cover up our ears; court darkness and quiet; knowing that the more we
exclude sensible impressions the better we shall sleep.

But the great difference between sleeping and waking, that which indeed
constitutes the essence of the former state, psychically considered, is
the suspension of the attention--all the leading phenomena of sleep are
directly traceable to this cause: for example--

In sleep we cease to support ourselves, and fall, if we were previously
standing or sitting. That is, we cease to attend to the maintenance of
our equilibrium. We forget the majority of our dreams: attention is the
soul of recollection.

Our dreams are often nonsense, or involve absurdities or ideas which we
know to be false. The check of the attention is absent.

Our ideas whirl with unwonted rapidity in our dreams; the fly-wheel of
the attention has been taken off.

When we are being overcome with sleep, we are conscious of not being
able to fix our attention.

When we would encourage sleep, we endeavour to avoid thoughts which
would arouse the attention.

Though the sensibility of our organs is really undiminished, _it seems
to be lowered_ in sleep, because then no attention is given to common
sensation.

Sleep, however, it should be added, may be either profound, or light, or
imperfect; in the two latter cases, the attention seems to be less
completely suspended.

So, in sleep, it is the attention alone that really sleeps; the rest of
the mental powers and impulses are on the contrary in motion, but free
and unchecked, obtaining their refreshment and renovation from
gambolling about and stretching themselves. The inspector only slumbers;
or, to use a closer figur