Another disease, the periods of which generally commence during our sleep,
is the asthma. Whatever may be the remote cause of paroxysms of asthma, the
immediate cause of the convulsive respiration, whether in the common
asthma, or in what is termed the convulsive asthma, which are perhaps only
different degrees of the same disease, must be owing to violent voluntary
exertions to relieve pain, as in other convulsions; and the increase of
irritability to internal stimuli, or of sensibility, during sleep must
occasion them to commence at this time.

Debilitated people, who have been unfortunately accustomed to great
ingurgitation of spirituous potation, frequently part with a great quantity
of water during the night, but with not more than usual in the day-time.
This is owing to a beginning torpor of the absorbent system, and precedes
anasarca, which commences in the day, but is cured in the night by the
increase of the irritability of the absorbent system during sleep, which
thus imbibes from the cellular membrane the fluids, which had been
accumulated there during the day; though it is possible the horizontal
position of the body may contribute something to this purpose, and also the
greater irritability of some branches of the absorbent vessels, which open
their mouths in the cells of the cellular membrane, than that of other
branches.

As soon as a person begins to sleep, the irritability and sensibility of
the system begins to increase, owing to the suspension of volition and the
exclusion of external stimuli. Hence the actions of the vessels in
obedience to internal stimulation become stronger and more energetic,
though less frequent in respect to number. And as many of the secretions
are increased, so the heat of the system is gradually increased, and the
extremities of feeble people, which had been cold during the day, become