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. 59. Of the sense and sensation of smell. any 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 odoriferous particles, sent from external objects, affect this 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. Of 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 immediately causes in it a change or affection; and this is at once followed by a mental affection or a new state of the mind. In this way we have the sensations and perceptions, to which we give the names sweet, bitter, sour, acrid, &c. Having experienced the inward sensation, the affections of the mind are then referred by us to something external as their cause. We do not, however, always, nor even generally, distinguish the qualities which constitute this cause by separate and appropriate designations; but express them by the names that are employed for the internal feeling, viz., sweetness, bitterness, sourness, &c. This reference of what is internally experienced to its external cause, is very rapidly made; so that we at once say of one apple it is sweet, and of another it is sour. Still it is to be kept in mind, that, in point of fact, it is subsequent, both in the order of nature and of time, to the mere sensation; although we may not be able, in consequence of its rapidity, to mark distinctly the progress of the mental action from the one to the other. As in the case of smells, which have already been remarked upon, the reference is the result of our former experience. We say of one body it is sweet, and of another it is sour, because we have ever observed that the mental states indicated by those terms have always existed in connexion with the presence of those bodies. Whenever, therefore, we say of any bodies that they are sweet, bitter, sour, or apply any other epithets expressive of sapid qualities, we mean to be understood to say, that such bodies are fitted in the constitution of things to cause in the mind the sensations of sweetness, bitterness, and sourness, or other sensations expressed by denominations of taste. Or, in other words, that they are the established antecedents of such mental states, as there is, further than this, no necessary connexion between them. 62. Design and uses of the senses of smell and taste. It is not unprofitable to delay oftentimes, and contemplate the designs and uses which nature has in view in her works. Although the sense of smell may appear (and perhaps with sufficient reason) to be of less impor tance than the other senses and the other parts of the animal economy, it is not without its ends. There is evidently design in the position of the organ in reference to the effluvia, which are the direct subjects of its action, it being placed in the inside of the canal, where the air is continually forced in and out with every breath we draw. The organ is precisely adapted, both in its nature and its place, to its appointed medium of communication with other bodies; nor is this the only mark of design attending it. This sense is frequently a source of gratification; and although it is less keen and powerful in men than in many inferior animals, it still has power enough to afford much assistance in this respect, that it often warns us of the presence of objects which experience has found to be injurious to us. The remark has been justly made, that the senses both of taste and smell are of great use in distinguishing bodies that cannot be distinguished by our other senses. They are peculiarly quick and exact in their judgments, especially in discerning, before we can ascertain it in any other way, the beginning and progress of those changes which all bodies are constantly undergoing. But in both of these senses design and utility are discoverable in reference to food in particular. While the sense of smell guards the entrance of the canal for breathing, the sense of taste has its station at the entrance of the alimentary canal. Hence the food which we consume undergoes the scrutiny of both; an intentional and benevolent provision for protecting men and the animal creation generally against the introduction of what would be noxious to them. CHAPTER IV. THE SENSE OF HEARING. 63. Organ of the sense of hearing. FOLLOWING the order which has been proposed, we are next to consider the sense of HEARING. And, in proceed ing to the consideration of this subject, the remark is a very obvious one, that we should be unable to hear if we had not a sense designed for and appropriate to that result. The air, when put strongly in motion, is distinctly perceived by the touch; but no impression which it could make on that sense would cause that internal feeling which is termed a sensation of sound. Our Creator, therefore, has taken care that these sensations shall have their own organ; and it is obviously one of precise and elaborate workmanship. The ear is designedly planted in a position where, with the greatest ease, it takes cognizance of whatever is going on in the contiguous atmosphere. When we examine it externally, we not only find it thus favourably situated, but presenting a hollowed and capacious surface, so formed as to grasp and gather in the undulations of air continually floating and in motion around it. Without, however, delaying to give a minute description of the internal construction of the ear, which belongs rather to the physiologist, it will answer our present purpose merely to add, that these undulations are conducted by it through various windings, till they are brought in a state of concentration, as it were, against the membrane called the TYMPANUM. It is worthy of notice, that on the internal surface of this membrane (the drum, as it is popularly called) there is a nerve spread out in a manner analogous to the expansion of the optic nerve at the bottom of the eye. Whether this nervous expansion be indispensably necessary to the result or not, it is certain that a pressure upon or affection of the tympanum by the external air is followed by a new state of the mind, known as the sensation or perception of sound. 64. Nature of sonorous bodies, and the medium of the communication of sound. When we leave the bodily organ, and, looking outward, inquire still further for the origin of the sensations which we have by means of the ear, we find them attributable ultimately to the presence and influence of the substances around us. Those undulations of air, which impinge upon the tympanum, and without which there is no sensation of sound, are caused by the vibrations or oscilla |