Chapter XIV.
Of Dreaming, Incubus, or Night Mare, and Somambulism.
To enumerate all the phenomena of dreams, and to attempt an explanation of their proximate cause, would require a previous account of the theory of sleep, and this would render it necessary to introduce several physiological principles, all of which would be foreign to the practical objects of this work ; for which reason I shall barely remark, that dreaming is the effect of unsound or imperfect sleep. That this is the case is obvious, from its being uncommon among persons who labour, and sleep soundly afterwards, and from its causes to be mentioned presently. It is always; influenced by morbid or irregular action in the blood-vessels of the brain, and hence it is accompanied with the same erroneous train, or the same incoherence of thought, which takes place in delirium. This is so much the case, that a dream may be considered as a transient paroxysm of delirium, and delirium as a permanent
