In the mean time, to accomplish the feats he performs, the most accurate _perception_ of sensible objects is required. Of what nature is that of which he so marvellously evinces the possession? You may adopt the simple hypothesis,--that the mind, being disengaged from its ordinary relations to the senses, does without them, and perceives things directly. Or you may suppose, if you prefer it, that the mind still employs sensation, using only impressions that in ordinary waking are not consciously attended to, for its more wonderful feats; and otherwise common sensation, which, however generally suspended, may be awakened by the dreaming attention to its objects.
The following case of somnambulism, in which the seizure supervened, in a girl affected with St Vitus's dance, and combined itself with that disorder, is given by Lord Monboddo:--
The patient, about sixteen years of age, used to be commonly taken in the morning a few hours after rising. The approach of the seizure was announced by a sense of weight in the head, a drowsiness which quickly terminated in sleep, in which her eyes were fast shut. She described a feeling beginning in the feet, creeping like a gradual chill higher and higher, till it reached the heart, when consciousness or recollection left her. Being in this state, she sprang from her seat about the room, over tables and chairs, with the astonishing agility belonging to St Vitus's dance. Then, if she succeeded in getting out of the house, she ran at a pace with which her elder brother could hardly keep up, to a particular spot in the neighbourhood, taking the directest but the roughest path. If she could not manage otherwise, she got over the garden-wall with surprising rapidity and precision of movement. Her eyes were all the time fast closed. The impulse to visit this spot she was often conscious of during the approach of the paroxysm, and, afterwards, she sometimes thought she had dreamed of going thither. Towards the termination of her indisposition, she dreamed that the water of a neighbouring spring would do her good, and she drank much of it. One time they tried to cheat her by giving her water from another spring, but she immediately detected the difference. Towards the end, she foretold that she would have three paroxysms more, and then be well--and so it proved.