240 ON THE EFFECTS OP CERTAIN MENTAL 



whilst the remainder are in profound repose, and some physiologists 

 have supposed that those which do slumber, do this more profoundly 

 from the activity of those which are awake. The senses may sleep 

 independently of the brain ; and portions of the latter without the 

 former. When all the senses are asleep, and the communication 

 with external objects has entirely ceased — when colours of the most 

 brilliant and varied hue, or of the most dazzling brightness, cease 

 to provoke the action of the eye — when the most melodious sounds 

 are lost upon the ear — when the fragrancy of the rose and the 

 daintiest viands affect not the taste and the smell — the intellectual 

 faculties may be in full activity, and all these may be present to the 

 Imagination, to the Memory, or even to the Judgment. In this 

 manner we have dreaming produced ; but if the Imaginations of 

 our dreams are of a certain character, or of sufficient degree of vivid- 

 ness, we have called into play the actions of the locomotive organs 

 or the senses, and, in conformity with the Imagination of our dream, 

 we may walk, sing, hear, smell, or taste, according to its character, 

 and the sense, or senses, which are in action. 



The endless variety of dreaming and the somnambulatory state 

 can only be explained on the supposition that some parts of the 

 brain wake whilst others sleep, and the opposite ; thus forming an 

 endless combination which, like the notes of an octave in different 

 states of combination, afford us music which, at one time, melts to 

 tears, at another excites to love, or at a third, rouses to anger. 

 Somnambulism is comparatively a rare affection, at least in its more 

 marked and singular forms, and is generally connected with a mor- 

 bid mental or corporeal constitution, commonly preceding or con- 

 nected with epilepsy, catalepsy, the various forms of lunacy or ma- 

 nia, and other maladies which have their seat principally in the 

 nervous system. It will be recollected that, in my lecture on the 

 Imagination of dreamers, I endeavoured to trace the connexion be- 

 tween the wanderings of the fancy and the variations in the condi- 

 tion of the bodily health ; and we shall find that a recurrence to 

 this subject will throw some li'^ht on the causes of sleep-walking. 

 The state of our health is hardly the same two hours together; the 

 infinitely various modifications which this undergoes can never be 

 appreciated by us, but may be ascertained, in some measure, by the 

 variable state of the mind. We are troubled with ennui, listless 

 and unhappy we know not why, and again are cheerful, gay, and 

 merry, and are just as ignorant of the cause. The variations in the 

 condition of the body are, in great measure, the origin of this, and the 

 extension of this influence to sleep is the cause of by far the greater 



