warm. Till towards morning many people become so warm, as to find it
necessary to throw off some of their bed-clothes, as soon as they awake;
and in others sweats are so liable to occur towards morning during their
sleep.

Thus those, who are not accustomed to sleep in the open air, are very
liable to take cold, if they happen to fall asleep on a garden bench, or in
a carriage with the window open. For as the system is warmer during sleep,
as above explained, if a current of cold air affects any part of the body,
a torpor of that part is more effectually produced, as when a cold blast of
air through a key-hole or casement falls upon a person in a warm room. In
those cases the affected part possesses less irritability in respect to
heat, from its having previously been exposed to a greater stimulus of
heat, as in the warm room, or during sleep; and hence, when the stimulus of
heat is diminished, a torpor is liable to ensue; that is, we take cold.
Hence people who sleep in the open air, generally feel chilly both at the
approach of sleep, and on their awaking; and hence many people are
perpetually subject to catarrhs if they sleep in a less warm head-dress,
than that which they wear in the day.

16. Not only the sensorial powers of irritation and of sensation, but that
of association also appear to act with greater vigour during the suspension
of volition in sleep. It will be shewn in another place, that the gout
generally first attacks the liver, and that afterwards an inflammation of
the ball of the great toe commences by association, and that of the liver
ceases. Now as this change or metastasis of the activity of the system
generally commences in sleep, it follows, that these associations of motion
exist with greater energy at that time; that is, that the sensorial faculty
of association, like those of irritation and of sensation, becomes in some
measure accumulated during the suspension of volition.