DREAMING. 623 



dream is the result of memory, and thus have revelations which 

 appear singular, but which are merely revived knowledge, 

 utterly forgotten. <i Dreaming being only excitement of some 

 portion or portions of the brain while the rest are asleep, the 

 causes of dreaming, no less than their mode of operation, must 

 be analogous to those of excitement in any other organ. These 

 exciting causes will produce their effect, like all other exciting 

 causes, not only according to their own intensity, but ac- 

 cording to the predisposition and present degree of excitement 

 of the brain ; having, unless powerful, no effect if the brain has 

 no undue irritability or present excitement, and having, though 

 feeble, great effect if the brain is very irritable or already much 

 excited: and, where either of the latter circumstances exists, 

 dreaming will occur without any adventitious cause of excitement. 

 We may dream from an external impression upon any of our 

 nerves or from feelings produced in any internal part : from 

 light being let into the eyes, external heat or cold, titillation, an 

 uncomfortable bed, motion, pain, uneasiness of the digestive 

 organs, &c. We may dream from the brain being excited sym- 

 pathetically with the condition of any other organ, just as all 

 other organs may sympathise with each other: as the state of 

 the kidney or the brain may produce vomiting, the state of the 

 stomach produce headach, though productive of no uneasy 

 sensation in the stomach itself, so the administration of substances 

 possessed of the power of stimulating the brain in particular, 

 as certain narcotics in doses not sufficient to overpower the organ 

 and cause sleep, may induce dreams. Whatever excites the 

 blood-vessels of the brain will do the same : the ingurgitation 

 of stimulants, blows, great functional excitement, and any cause of 

 an inflammatory state or an approach to it. When the brain is 

 irritable by disease, as in fever, dreaming occurs ; and, sleep 

 taking place with difficulty, the delirium of approaching sleep 

 continues so long and sleep is so often interrupted, that nurses 

 tell us that the patient wandered greatly at night. But, inde- 

 pendently of its excitement of such a state, the functional ex- 

 citement of the brain in the waking state may be too great for 

 complete sleep, by not easily subsiding, so that, if not too 

 great to prevent sleep, it may continue sufficiently to prevent the 



q See a curious instance of the discovery of legal papers by a dream, in Sir 

 Walter Scott's notes to the Antiquary. 



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