SOMNAMBULISM.
Our history of sleep would be incomplete without some account of a state which is closely allied to it, though differing from it in several important particulars. The pheno mena of somnambulism are so varied, that it is very difficult to frame any definition capable of including them all ; and we prefer charac terising the state by saying that it may be con sidered as an acted dream,—differing from or dinary dreaming in the two following points. In the first place, the train of thought is more under the direction of sensations derived from without; and, secondly, the muscular system is so completely under the control of the mind, as not merely to give expression to its emotional states, but also to act in respon dence to its volitions. As in dreaming, there would seem to be, in true somnambulism, a complete want of voluntary control over the current of thought, but there is not the same degree of mental activity; and in particular the operation of the associative principle is so much more restricted, that there is little or none of that incoherence or incongruity in the ideas brought up, which is so peculiar in ordi nary dreaming. On the contrary, reasoning processes are often carried out with extraor dinary clearness and correctness; the mind being intently fixed upon them to the exclu sion of all other considerations. This exclu siveness, indeed, is one of the most remarkable characteristics of the condition. Whilst the attention of the mind remains fixed upon any object, either perceived by the senses or brought up by the act of conception, nothing else is felt. Thus there may be complete in sensibility to bodily pain, the somnambulist's whole attention being given to that which is passing within the mind. Yet, in an instant, by directing the attention to the organs of sense, the anxsthesia may be succeeded by the most acute sensibility. So, again, when the attention is fixed upon a certain train of thought, whatever is spoken in harmony. with it is heard and appreciated by the somnam bulist ; but whatever is in discordance with it is entirely disregarded. The character of the intellectual operations partakes of this pecu liarity. AS just now stated, the reasoning processes are usually accurately and definitely carried on, so that the conclusion will be sound, provided that the data have been cor rect. Thus, a mathematician will work out a
difficult problem, or an orator will make a speech appropriate to a given subject. But the usual defect of the intellectual operations carried on in this condition is, that, owing to their very intensity, the attention is drawn off' from the considerations which ought to modify them ; and thus it happens that the result is often palpably inconsistent with the teachings of ordinary experience, and will be admitted to be so by the somnambulist when the former are brought to his mind.
The state of somnambulism may pass, on the one hand, into that of ordinary dreaming, so that it is difficult to draw the line between the two. Thus, the ordinary " talking in the sleep" may be referred to one or the other condition, according to the definition of each that we may adopt. In our own arrangement, they fall under the second head: because the vocal movements are expressions of the intel lectual processes that are taking place in the mind ; and because, in most cases of this kind, the sleep-talker hears and comprehends what is said to him, provided that this harmonises with what is going on within, and will answer rationally, so as to sustain a conversation. Thus, we knew a young lady at school, who frequently began to talk after having been asleep an hour or two ; her ideas almost always ran upon the events of the previous day ; and if encouraged by leading questions addressed to her, she would give a very distinct and co herent account of them ; frequently disclosing her own peccadilloes and those of her school fellows, and expressing great penitence for the former, whilst she seemed to hesitate about making known the latter. To all ordinary sounds, however, she seemed perfectly insen sible. A loud noise would awake her, but was never perceived in the sleep-talking state; and if the interlocutor addressed to her any questions or observations that did not fall in with her train of thought, they were completely disregarded. By a little adroitness, however, she might be led to talk upon almost any subject; a transition being graduallymade front one to another by means of leading questions.