_Theory of a general Sense._--The only theory that seems to offer even a plausible solution is that advanced by some German psychologists, and by Rauch in this country, of a _general sense_. The several special senses, they say, are all resolvable into one general sense as their source, viz., that of feeling. They refer us in illustration to the ear of the crab, to the eye of the fly and the snail, to the scent of flies, in which cases, respectively, we find no _organ_ of hearing, or vision, or smell, but simply an expansion of the general nerve of sensation, or some filament from it, connecting with a somewhat thinner and more delicate membrane than the ordinary skin. This shows that our ordinary way of perceiving things is not the only way; that special organs of vision, etc., are not needed in order to all perception, much less to sensation. It has been found by experiment that bats, after their eyes have been entirely removed, will fly about as before, and avoid all obstacles just as before. In these cases, it is contended, perception is merely _feeling heightened_, the exercise of the general sense into which the special senses are severally merged. And this, it is said, may be the case with the somnambulist. _Remarks on this Theory._--There is doubtless truth in the general statement now advanced. I do not see, however, that it accounts for all that requires explanation in the case. It explains, perhaps, how, without the organ of vision, a certain dim, confused perception of objects might be furnished by the general sense, but not for a _clearer_ vision and a _nicer_ operation than the waking eye can give. This, to me, remains yet unexplained. Is there an inner consciousness, a hidden soul-life not dependent on the bodily organization, which at times comes forth into development and manifests itself when the usual relations of body and soul are disturbed and suspended? So some have supposed, and so it may be for aught we know to the contrary, but this is only to solve one mystery by supposing another yet greater. _Must admit what._--Whatever theory we adopt, or even if we adopt none, we must admit, I think, in view of the facts in the case, that in certain disordered and highly excited states of the nervous system, as, _e. g._, when weakened by disease, so that ordinary causes affect it more powerfully than usual, _it can, and does sometimes, perceive what, under ordinary circumstances, is not perceptible to the eye, or to the ear; nay, even dispenses with the use of eye and ear, and the several organs of special sense_. This occurs, as we have seen, in somnambulism, or natural magnetic sleep. We meet with the same thing also in even stranger forms, in the mesmeric state, and in some species of insanity.