“Somnambulists are insensible to external impressions, except those which are in relation with their ideas, their thoughts, and their feelings. It is thus that persons, the subjects of somnambulism, will pass before objects or individuals without seeing them, although they may have their eyes open. This phenomenon occurs often to individuals who are fully awake, although in a less degree. Thus when we are strongly preoccupied with any subject, the objects which surround us make no impression on our senses or our mind. Archimedes while meditating on a discovery, was an entire stranger to all that was going on around him. A part only of his brain was awake and active. While thus engaged, Syracuse was taken by the enemy, and he was not diverted from his thoughts either by the chant of victory by the conqueror, or by the cries and groans of the wounded and the dying.” As regards the sense of hearing, it is doubtless true that somnambulists rarely exercise it. There have been cases in which replies have been made to questions; but such answers have been given automatically, and not as if the mind took cognizance of the subject. A person intently engaged in reading, will often answer questions without suffering his train of thought to be interrupted. When he has ceased his study, he is surprised when told that he has been conversing. The sense of taste appears to be very inactive in general, though in a few cases it has been manifested. The same is true in even a greater degree with the sense of smell. The sense of touch is very differently affected, for so far from being diminished in its action, it is invariably unduly exalted. Though the eyes do not see, the ears hear, the tongue taste, or the nose smell, the somnambulist has one sense which is fully awake, and by which he is enabled to guide himself through the most devious passages in dangerous paths. In this fact it appears to me we have a strong argument in favor of the theory of somnambulism which I have already referred to, and which appears to me to be supported by much additional evidence. I propose this view not without hesitation; but much study of the phenomena of somnambulism, and of analogous states of the nervous system, has certainly tended to convince me of its general correctness, and I am not without the hope that other students of neurology will find it reconcilable with their observations and experiments. In my opinion, somnambulism is a condition of the organism in which through profound sleep the action of the encephalic ganglia is so materially lessened that the spinal cord becomes able to control and direct the body in its movements.