_The mental Process obvious._--So far as regards the purely mental part of the phenomena, the operations of the mind in somnambulism, there is nothing which is not easily explained. In somnambulism, as indeed in all these states so closely connected--sleep, dreams, the mesmeric process, and even insanity--_the will loses its controlling power over the train of thought, and, consequently, the thought or feeling that happens to be dominant gives rise to, and entirely shapes, the actions that may in that state be performed_. This dominant thought or feeling, in the case of the somnambulist, is, for the most part, probably, the result of previous causes; a continuation of the former mental action, which, when the influence of the will is suspended and the senses closed, by a sort of inherent activity keeps on in the same channel as before. Of such action, the soul is itself probably conscious at the moment, but afterward no recollection of it lingers in the mind. § IV.--DISORDERED MENTAL ACTION. _Relation to other mental Phenomena._--Closely allied to somnambulism, dreaming, etc., are certain forms of disordered mental condition commonly termed insanity; having this one element in common with the former, the loss or suspension of all voluntary control over the train of thought. This must be regarded as the characteristic feature and essential ground-work of the various phenomena in all these various states. _Classification._--The forms of disordered mental action are various, and admit of some classification. Some are transient, others permanent, arising from some settled disorder of the intellect, or the sensibilities. I. _Transient Forms._--Of these, some are artificially produced, as by exciting drugs, stimulants, intoxicating drinks, etc., others by physical and natural causes, as disease, etc.