ay be possible for you to secure more
benefit from three to four hours' sleep than a shallow sleeper may
secure in eight hours of a lighter degree of sleep. This extreme depth
of sleep means complete rest for the brain, absolute loss of
consciousness, and, to a certain extent, loss of sensibility in respect
to our senses. In the lighter degree of sleep certain parts of the brain
may be at rest, while others are more or less active. Dreaming
represents a state of partial consciousness rather than a condition of
complete rest, inasmuch as various parts of the brain are active. One
may thus be conscious of his dreams. There is no doubt, however, that in
other cases various parts of the brain may be active though we may not
be conscious of their activity. We have all heard of instances where
mathematical problems appear to have been worked out during sleep, and
we have heard of musical compositions and poems being produced
during sleep. All these phenomena represent a condition in which one
is partly asleep and partly awake; in other words, some parts of the
brain are active and others are asleep. In extreme depth of sleep when
all the mental faculties are at rest, the energies are relaxed, and the
activities of the body are at a low ebb; it is such sound sleep that
makes for rapid recuperation. The deepest sleep generally occurs within
the first few hours after falling to sleep, and it gradually becomes
lighter and lighter in degree until consciousness is reached. Dreams,
therefore, represent partial consciousness and usually appear in the
earlier hours of the morning. When one states that he dreams all night
he is invariably mistaken. One may seem to live over periods of days
and even years in a dream, the actual duration of which may be measured
in minutes. The chances are that the dreamer enjoyed a sound
sleep before his dreaming commenced.

Although I have said that depth of sleep is more important than the
duration of sleep, yet it is true that when one sleeps very soundly
he usually sleeps longer. In other words, when one reaches great depth
of sleep the transition to the period of wakefulness is only gradual,
and it requires a longer time to complete the sleep and wake up than it
would if one did not sleep so deeply, or, as we would say, so soundly.
It will be found that healthy children, who unquestionably sleep very
soundly, also sleep for many hours at a time. They may have dre