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inherent in, and originally and unalterably essential to himself.

It is not so, as we have reason to believe, with any other beings, and certainly not with man. Although a great part of his knowledge relates to material things, he is so formed, and his constitution is so ordered, that he is wholly dependent for it on the senses.-Deprive him of the ear, and all nature becomes voiceless and silent; deprive him of the eye, and the sun and moon withdraw their light, and the universe becomes darkened like sackcloth; deprive him of the sense of touch, and he is then entirely insulated, and as much cut off from all communication with others, as if he were the only being in existence.

§. 153. Of the connection of the brain with sensation and perception.

It may perhaps be asked, Whether these views are intended to exclude the brain, as having a connection with the senses in the results, which are here ascribed to them? And this inquiry leads us to observe, (what has been before alluded to,) that the brain is a prominent organ in the material part of the process of sensation and of external perception. The senses evidently cannot be separated from the nervous system. But the substance, which is found in the nerves, excepting the coat in which it is enveloped, is the same as in the brain, being of the same soft and fibrous texture, and in continuity with it. As a general statement, when the brain has been in any way injured, the inward sensation, which would otherwise be distinct on the presence of an external body, is imperfect. Also if the nerve be injured, or if its continuity be disturbed by the pressure of a tight ligature, the effect is the same; a circumstance which goes to confirm the alleged identity of substance in the two.

The brain, therefore, and whatever of the same substance in continuity with it, particularly the nerves, constitute the sensorial organ, which, in the subordinate organs of taste, smell, sight, touch, and hearing presents it

self under different modifications to external objects. On this organ, the sensorial, as thus explained, an impression must be made, before there can be sensation and perception.

An impression, for instance, is made on that part of the sensorial organ called the auditory nerve, and a state of mind immediately succeeds, which is variously termed, according to the view in which it is contemplated, either the sensation, or the perception of sound.

An impression is made by the rays of light on that expansion of the optic nerve, which forms what is called the RETINA of the eye, and the intellectual principle is immediately brought into that new position, which is termed visual perception or a perception of sight.

The hand is impressed on a body of an uneven and rough surface, and immediately consequent on this application and pressure, is that state of mind, which is termed a sensation or perception of roughness.

§. 153. Order in which the senses are to be considered.

In considering those ideas, which we become possessed of by means of the senses, it is natural to begin with that sense, which will cause us the least difficulty in the analysis of its results; and to proceed to others successively, as we find them increasing in importance. It may not be altogether easy to apply this principle with strictness, but it will answer all the purpose, for which it is here introduced, if we consider the senses in the following order, the smell, taste, hearing, touch, and sight.

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The mind holds a communication with the material 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 subtility. These small particles are rapidly and widely scattered abroad in the neighbourhood of the body, from which they proceed. No sentient being can come within the circumference, occupied by these continually moving and volatile atoms, without experiencing effects from it.

§. 151. Of the sense and sensations of smell.

The medium, through which we have the sensation 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 some 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 connection between the smell and the external objects, than that there exists a connection between the emotions of joy and sorrow and the same ob jects. 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 learnt 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.

§. 155. 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 utterly unable to mark the mind's progress from the inward feeling to the conception of the outward cause. Nor is this inability surprizing, 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.

§. 156. Of the sense and the sensations of taste.

The tongue, which is covered with numerous nervous papillae, forms essentially the organ of taste; although the papillae 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 that 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 connection 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 connection between them.

§. 157. 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 importance, than the other senses, and other parts of the animal economy, it is not without its ends. There is evidently design in

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