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'world by means of the sense of smelling. All animal and vegetable bodies (and the same will probably hold good of other bodies, though generally in a less degree) are continually sending out effluvia of great subtilty. These small particles are rapidly and widely scattered abroad in the neighbourhood of the body from which they proceed. No percipient being can come within the circumference occupied by these continually moving and volatile atoms, without experiencing effects from it.
0 59. Of the sense and sensation of smell. The medium through which we have the sensations and perceptions of smell, is the organ which is termed the olfactory nerve, situated principally in the nostrils, but partly in some continuous cavities. When any odoriferous particles, sent from external objects, affect th's organ, there is a certain state of mind produced, which varies with the nature of the odoriferous bodies. But we can no more infer, from the sensation itself merely, that there exists any necessary connexion between the smell and the external objects, than that there exists a connexion between the emotions of joy and sorrow and the same objects. It might, indeed, be suggested to us by the change in our mental states, that there must be some cause or antecedent to the change ; but this suggestion would be far from implying the necessity of a corporeal cause.
How, then, does it happen that we are not merely sensible of the particular sensation, but refer it at once to some external object, to the rose or the honeysuckle? In answer, it may be remarked, if we had always been destitute of the senses of sight and touch, this reference never could have been made; but, having been furnished with them by the beneficent Author of our being, we make this reference by experience. When we have seen the
rose, when we have been near to it and handled it, we have uniformly been conscious of that state of mind which we term a sensation of smell. When we have come into the neighbourhood of the honeysuckle, or when it has been gathered and presented to us, we have been reminded of its fragrance. And thus, having learned by experience that the presence of the odoriferous body is
always attended with the sensations of smell, we form the habit of attributing the sensations to that body as their cause.
$ 60. Of perceptions of smell in distinction from sensations. The mental reference spoken of in the last section is made with almost as much promptness as if it were necessarily involved in the sensation itself. It is at least so rapid, that we find ourselves unable to mark the mind's progress from the inward feeling to the conception of the outward cause. Nor is this inability surprising, when we consider that we have repeated this process, both in this and in analogous cases, from our earliest childhood. No object has ever been present to us, capable of operating on the senses, where this process has not been gone through. The result of this long-continued and frequent repetition has been an astonishing quickness in the mental action, so much so that the mind leaps outward with the rapidity of lightning, to be present with, and to comprehend the causes of the feeling within.
This view, it will be seen, helps in illustrating the nature of PERCEPTION, as distinguished from sensation. The outlines of that distinction have already been given; and every one of the senses, as well as that now under consideration, will furnish proofs and illustrations of it. Accordingly, when we are said to perceive the smell, or to have perceptions of the smell of a body, the rapid process which has been described is gone through, and the three things which were involved in the definition of Perception already given are supposed to exist : (1.) The presence of the odoriferous body, and the affection of its appropriate organ ; (2.) The change or sensation in the mind; and (3.) The reference of the sensation to the external body as its cause.
$ 61. Or the sense and the sensation of taste. The tongue, which is covered with numerous nervous papillæ, forms essentially the organ of taste, although the papillæ are found scattered in other parts of the cavity of the mouth. The application of any sapid body to this
organ inninediately causes in it a change or affection: