SMELLING is the act by which we perceive smells, or become sensible of the presence of odorous bodies. The[7:20:404] sensations of smell are excited by certain effluvia, which, in the open air, are always issuing from the surfaces of most bodies, and striking on the extremities of the olfactory nerves, give them a peculiar sort of impression, which is communicated to the brain. The particles which issue thus from bodies are extremely volatile, and produce sensation by a degree of contact, which, though insensible, is still more efficient than if it were more gross and palpable. It is by a similar species of insensible contact that the eyes and ears are affected by external objects; while, in the excitation of the sensations of touch and of taste, an actual and sensible contact of the object with the organ is necessary. The organs of smelling are the nostrils and olfactory nerves; the minute ramifications of the latter being distributed throughout the whole concavity of the former.

The effluvia from odorous bodies are constantly floating about in the atmosphere, and must of course be drawn into the nostrils along with the air in inspiration; “so that there is,” as Dr. Smith observes, “a manifest appearance of design in placing the organ of smell in the inside of that canal through which the air is continually passing in inspiration and expiration.” It has been affirmed by Boerhaave, that the matter in animals, vegetables, fossils, and the like, which chiefly affects the sense of smelling, is that attenuated substance, inherent in their oily parts, called spirits; because, when this is taken away from the most fragrant bodies, what remains has scarcely any smell at all; but this, he says, if poured on the most inodorous bodies, gives them a fragrancy.^[1. See also Sir William Drummond’s Academical Questions, book i. chap. 9. ] ’ We cannot however enter at present upon this inquiry.

The sense of smell has a close alliance with that of taste; and it seems probable from the proximity in the situation of their organs in all animals, that both are principally intended to guide them in the choice of their food; so that from this close connection, they are better enabled to choose what is good for them, and to reject what would be injurious. This is the opinion of Dr. Reid, as it was, in a very early period of the history of philosophy, that of Socrates and of Cicero.^[2. ’ “Ut gustus," says a learned physiologist, “cibi itineri, sic olfactus ostio viarum, quas aer subire debet, custos praeponitnr, moniturus ne quid noxii, via quse semper patet, in corpus admittatur. Porro, ut gustus, sic quoque olfactus ad salutarem cibum invitat, a noxio aut corrupto, putrido imprimis vel rancido, deterret.” “When thou seest the moutb, through which animals take in whatever they desire, always placed near the nose and eyes, thinkest thou not, say Socrates to Aristodemus, that this is the work of a providence." (Xenophon’s Memorabilia, book i. chap. 4.) ] Dr. Reid also remarks, that the sense of smell probably serves the same purpose in the natural state of man; but it is not always a sure guide for this purpose. The organs of smell differ, like those of the other senses, according to the destination of the animals to which they belong; and we know, that this sense is in man much less acute, than in many other animals. We see, that in the choice of their food, they are guided by the senses of smell and of taste, except when man has brought them into a sort of unnatural state by domestication. And this circumstance renders it probable, that both these senses were intended to serve the same purpose in the natural state of our species, although less calculated for this end than they were in the brutes, on account of the great superiority of their smelling organs. Besides, since it is probable that man, in the natural state, acts more by instinct than when civilized in society, so also it is reasonable to think, that he may possess some of the senses, this of smell tor instance, in greater acuteness than we do. This indeed we are assured to be a fact; for we are told in the Histoire des Antilles, that there are negroes who, by the smell alone, can distinguish the footsteps of a Frenchman from those of a negro.

The sense of smell is much more obtuse in man than in some of the lower animals. Dogs we know possess a power of smelling, of which we can scarcely form a conception, and which it is happy for us we do not possess;^[3. • “The excessive eagerness which dogs express on smelling their game, seems to be but little connected with the appetite for food, and wholly independent of any preconceived ideas of the objects of their pursuit being tit for it. Hence several kinds of them will not eat the game which they pursue with such wild impetuosity; and of which the scent seems to animate them to a degree of ecstacy far beyond what the desire of food can produce.” (Knighton Taste.) ] and birds of prey are said to possess this sense in still greater acuteness. But although this be more perfect, still the sense of smelling in man, who has other means of judging of his food, is such as to fit him for deriving enjoyment from a diversity of scents, particularly those of flowers and perfumes, to which dogs and other animals seem perfectly insensible. It has been said, we are aware, that some animals, the elephant for instance, are capable of this enjoyment;^[4. • There is an animal to which, naturalists say, perfume is so agreeable and so necessary, that nature has provided it with a little bag stored with an exquisite odour. “On pretend,” says Buffon, “que la mangouste ouvre cette poche, pour se rafraichir lorsqu' elle a trop chaud.” ] but of this fact we cannot help being very doubtful.

There is a very great sympathy between the organs of smell and of taste; tor any defect or disease of one is generally attended with some corresponding defect or disease of the other. There is also a greater similarity between the sensations of both these, than between those of any other two senses; and hence it is, that we can sometimes tell the taste of an object from its smell, and vice versa. Hence also the reason why we apply the same epithets to the names of both these classes of sensations; as a sweet smell or taste.

It deserves also to be remarked, that both these senses seem subservient to the preservation of the animal existence, rather than to any other purpose. They accordingly constitute an object of the natural history of man, rather than of intellectual or of moral philosophy. The other three senses, on the contrary, seem rather intended for, as they certainly are essential to, our intellectual improvement, and become, of course, a proper object of investigation in the sciences of moral philosophy, or metaphysics.

The advantages derived by man and the other animals from the sense of smelling are not confined to the assistance which it affords them in the choice of their food. Most bodies in nature, when exposed to the open air, are constantly sending forth emanations or effluvia of such extreme minuteness as to be perfectly invisible. These diffuse themselves through the air, and however noxious or salutary, would not be perceived without the sense of smelling, which, if not vitiated by unnatural habits, is not only a faithful monitor when danger is at hand, but conveys to us likewise the most exquisite pleasures. The fragrance of a rose, and of many other flowers, is not only pleasant, but gives a refreshing and delightful stimulus to the whole system, while the odours proceeding from hemlock, or any noxious vegetable, or other substance, are highly offensive to our nostrils. Hence we are naturally led to seek the one class of sensations, and to avoid the other.

In some species of animals the sense of smell seems to be connected with certain mental sympathies, as those of hearing and sight are in all that possess them in any high degree; for not only their sexual desires appear to be excited by means of it, but other instinctive passions, which, according to the usual system of nature, should be still more remote from its influence. Dogs, although wholly unac[7:20:405] quainted with lions, will shudder at their roar; and an elephant that has never seen a tiger, will in the same manner show the strongest symptoms of horror and affright at the smell of it. “The late Lord Clive,” says an ingenious writer, “exhibited a combat between two of these animals at Calcutta; but the scent of the tiger had such an effect upon the elephant, that nothing could either force or allure him to go along the road, where the cage in which the tiger was inclosed, had passed, until a gallon of arrack was given him. Upon this, his horror suddenly turning into fury, he broke down the paling to get at his enemy, and killed him without difficulty.”

If riding along a road, near which a dead horse, or part of its carcass, happens to be lying, we know, that our horse although he sees it not, cannot be made to pass the place but with difficulty. Where blood has been shed, particularly that of their own species, oxen will assemble, and upon smelling it, roar and bellow, and show the most manifest signs of horror and distress; and yet these symptoms could not arise from any associated notions of danger or death, since they appear in such as never had any opportunities of acquiring them. They must therefore be instinctive like other instinctive antipathies and propensities. But although in their mutual intercourse, animals make much use of the sense of smell, still it does not seem to be further concerned in exciting their sexual desires, than in indicating their object.

Some of those splenetic philosophers, who are ready upon all occasions to quarrel with the constitution of nature, have taken the liberty of condemning their Maker, because it has pleased his unfathomable wisdom to bestow in some instances upon the brutes senses and instincts more perfect than he has given to man, without reflecting that he has given to man an ample equivalent; for it may be asked with the poet,

Is not bis reason all these powers in one?

Is Heaven unkind to man and man alone? Shall be alone, whom rational we call. Be pleased with nothing if not blessed with all?

With respect to that unknown peculiarity of bodies, which is the cause of our sensations of smell, the opinions of philosophers have been very various. Until of late, the doctrine of Des Cartes and Locke on this subject was pretty generally received; but, since the publication of Dr. Reid’s works, his opinion, which we deem the most correct and satisfactory, has become very popular. We will endeavour to abridge his account of this matter. For this purpose, let us suppose a person, who has grown up without the sense of smell, to be immediately endowed with the use of this organ, and placed near some flowers of an exquisite savour. When he examines what he feels in such a situation, he can find no resemblance between this new sensation, and any thing with which he is already acquainted. He finds himself unable to explain its nature, and cannot ascribe to it figure, extension, or any known property of matter. It is a simple affection, or feeling of mind, and, considered abstractedly, can have no necessary connection with the nerves, the nostrils, or effluvia, or with any thing material whatever. By the nature of his constitution he is however led to refer this peculiar sensation to the nostrils, as its organ; and when, from experience, and by means of touch, he learns that external objects have the power of exciting this sensation, he concludes, that there must exist in bodies some unknown cause by which it is excited. In the first part of this process he considers the feeling, or sensation, abstractedly. As such, it exists in the mind only; and cannot exist there but when the mind is conscious of it. His consciousness soon enables him to distinguish different sorts of smells, all of them very distinct from one another, but, conformably to the nature of all sensation, extremely simple. He concludes, that each of these must have a distinct cause; and finding, by experience, that this cause is an unknown something in bodies, he concludes, that it must be a property of matter, and, for want of another, gives it the name of smell. When he removes an odorous body from the organ, the sensation vanishes; when the body is again applied, the sensation is excited; and hence it is, that he is led naturally to connect the sensation with this unknown peculiarity of bodies by which it is produced. But since we see, that the sensation is, in a great degree, related to other objects besides its unknown cause, to the mind in which it exists, for instance, and to the organ which is its instrument, it may be asked why it becomes associated in the mind with its cause only? The reason seems pretty obvious. No single sensation, or class of sensations, is more connected with the mind, than any other of which it is susceptible. Nor is the connection subsisting between the organ and any of the sensations peculiar to it, greater than that which subsists between it and every other sensation of which it is the inlet. Hence the connection between the smell of an orange and the mind, or between it and the nostrils, is very general, and cannot, in the former instance, distinguish it from any other sensation of whatever kind, nor, in the latter, from any other particular smell. But the connection between this sensation and the orange is peculiar and permanent; and we accordingly find them always associated in the mind, just as we associate the notion of fire with the sensation of burning. The relation which a sensation of smell, or any sensation, bears to the mind, to an organ, or to the memory and conception of itself, is common to all sensations. The relation which any sensation bears to its own cause, suppose of the sensation of smell to a particular virtue or quality of bodies, is common to it with every other sensation, when considered with respect to its peculiar cause. And finally, a sensation of any kind bears the same sort of relation to the memory and conception of itself, that any other feeling or operation of mind bears to the conception and memory of that particular feeling or operation.

Whatever then be the nature of the minute particles of bodies by which our sensations of smell are excited, we cannot help considering their unknown cause as a virtue or quality of matter. Like all other modifications of material substance, it must be confessed, that this can have no resemblance to the sensations of mind. But we are not therefore to conclude with the followers of Des Cartes and Locke, that this secondary quality is a mere sensation; especially as we can readily conceive it existing where it is not smelled, or even after supposing the annihilation of every sentient being throughout the universe. The existence of the sensation we know to be momentary and fugitive; but in the existence of its cause we can, without difficulty or inconsistency, conceive a permanency independent of mind and of its sensations.

The doctrine which we have been illustrating has of late been called in question by a sceptical writer, who, it appears to us, has upon this occasion been entirely deficient in his accustomed acuteness. Dr. Reid’s speculations seem so frill, so clear and convincing, that we are at a loss to conceive how his meaning can be misunderstood; and yet the argument and objections of the writer to whom we allude, derive all their plausibility from a misinterpretation of Dr. Reid’s meaning, and from a deviation from the established use of language. “An eminent metaphysician,” says this author, “has declared that he has not the least difficulty in conceiving the air perfumed with aromatic odours in the deserts of Arabia; and he has decided, that the man who maintains smells to exist only in the mind must be mad, or must abuse language and disgrace philosophy. There are some authors, nevertheless, who differ widely on this subject from the learned metaphysician. Is it possible for a sensation to exist where there is no sentient? The authors to whom I allude think it impossible.” And so, we may tell this learned author, does Dr. Reid, if he will take his word for it. Of the sensation of smell he remarks, “It[7:20:406] is indeed impossible, that it can be in any body; it is a sensation, and a sensation can be in a sentient thing only.”^[5. Reid’s Inquiry, ch. ii. sect. 2. ] Again, “I can think of the smell of a rose when I do not smell it; and it is possible that when I think of it, there is no rose any where existing; but, when I smell it, I am necessarily determined to believe that the sensation really exists. This is common to all sensations, that, as they cannot exist but in being perceived, so they cannot be perceived but they must exist.”^[6. ’ Reid’s Inquiry, chap. ii. sect. 3. ] ® But, continues this acute metaphysician, “a smell is nothing else than a sensation. It is a feeling, which may be agreeable or disagreeable; which may, as some think, be excited by various combinations of elements; but which, since it is a feeling, cannot be those elements which are said to cause it, and cannot exist where there is no creature to perceive it. What is to be understood, in philosophical strictness, by the perfumes of the desert? We can excuse the poet when he makes the ocean smile,^[7. Milton ] ’ the winds dance,^[8. ' Cowley. ] and the flowers respire;^[9. Thomson. . ] or even were he to perfume the desert. But the philosopher is no such magician, and had better not wander through the regions of fancy in search of sensations where there is no sentient.” And is it then true that the word smell means only a sensation? A sensation is no more than an effect; it is a transient modification of the mind, which the mind itself can never produce. It must then have some cause which is external to the mind. Now, it is to this cause, and not to the sensation, that the name smell is most frequently applied in all languages; and it is this cause which Dr. Reid supposes capable of existing in the deserts of Arabia, where there is no sentient being to perceive it. But let us hear himself. “We have considered smell as signifying a sensation, feeling, or impression upon the mind; and in this sense it can only be in a mind or sentient being; but it is evident that mankind give the name of smell much more frequently to something which they conceive to be external, and to be a quality of body; they understand by it something which does not at all infer a mind, and have not the least difficulty in conceiving the air perfumed with aromatic odours in the deserts of Arabia, or some uninhabited island where the human foot never trod.”^[10. Inquiry, chap ii. sect. 8 ] “The faculty of smelling is something very different from the actual sensation of smelling; for the faculty may remain when we have no sensation. And the mind is no less different from the faculty, for it continues the same individual being when the faculty is lost. What is smell in the rose? It is a quality or virtue of the rose, or of something proceeding from it, which we perceive by the sense of smelling; and this is all we know of the matter. But what is smelling? It is an act of the mind, but is never imagined to be a quality of the mind. Again, the sensation of smelling is conceived to infer necessarily a mind or sentient being; but smell in the rose infers no such thing. We say, this body smells sweet, and that stinks; but we do not say, this mind smells sweet, and that stinks; therefore smell in the rose, and the sensation which it causes, are not conceived, even by the vulgar, to be things of the same kind, although they have the same name.”^[11. ! Inquiry, chap. ii. sect. 9. ]

There are some other remarks on Dr. Reid’s opinion, in the work upon which we have been commenting, which we shall pass by; we may however notice the author’s concluding argument. After mentioning some examples, he observes, “Now, in these instances, we see men and animals, that must have perception of smell, if I may be per-mitte'd to say so, altogether different from each other. Is not smell sensation when the spaniel finds sport in the field tor his master; when the shark pursues through the ocean its expected victim; and when the camel conducts the thirsty wanderer to a fountain of fresh water, across the burning sands of the Arabian desert? If no animal had the sensation of smell, there would be no odour; for aroma and oils may be thought to be material compositions, but are neither agreeable nor disagreeable feelings.” If men and animals differ in their perceptions of smell, and, no doubt, difference of organization will cause them to do so, the conclusion should not be, we think, that smell is merely sensation, but that there is actually something external which is the cause of their sensations, and about which they differ. A rose put to the nostrils of a man, and then to those of a dog, may excite very different sensations; but we cannot think that the peculiarity of the rose, which excites those different sensations, varies by thus changing the position of the rose. If at table one person mistakes mutton for beef, and another thinks that it is venison, the conclusion may be, that it is neither venison nor beef; but no man in his senses, can conclude that there is no meat at the table. But, “is not smell sensation when the spaniel finds sport in the field ?” There is sensation no doubt; but we may be permitted to ask, what would become of the spaniel’s sensation of smell and of his master’s sport, were there no game in the field? What of the shark’s sensation of smell and pursuit, were there no victim in the ocean? and what of the camel and the thirsty wanderer, were there no fountain of fresh water in the Arabian desert? ‘The smell of a rose signifies two things,” says Dr. Reid; “first, a sensation which can have no existence but when it is perceived, and can only be in a sentient being or mind; secondly, it signifies some power, quality, or virtue in the rose, or in effluvia proceeding from it, which hath a permanent existence independent of the mind, and which, by the constitution of nature, produces the sensation in us. By the original constitution of our nature, we are both led to believe that there is a permanent cause of the sensation, and prompted to seek after it; and experience determines us to place it in the rose. The names of all smells, tastes, sounds, as well as heat and cold, have a like ambiguity in all languages; but it deserves our attention, that these names are but rarely, in common language, used to signify the sensations; for the most part, they signify the external qualities which are indicated by the sensations.”^[12. Inquiry, ch. ii. sect. 9. ] We have been induced thus to discuss this topic at some length, because we regretted to see Dr. Reid’s opinion and reasoning misrepresented; and we shall now conclude, not as this modern Berkleian does, “that if no animal had the sensation of smell, there would be no odour,” but, that if there were no odour or external cause of smell, no animal would have this sensation.