SMELL; this word has in most languages two meanings, signifying either that sensation of mind of which we are conscious, in consequence of certain impressions made on the nostrils, and conveyed to the brain by the olfactory nerves; or that unknown virtue, or quality in bodies, which is the cause of our sensations of smell.

SMELLING is the act by which we perceive smells, or become sensible of the presence of odorous bodies. The 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; whilst, 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. For a description of these, see Anatomy.

The effluvia from odoriferous 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 Reid 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, &c., 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 fragrance*. 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 (a).

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 it is 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 for 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 (b); 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, &c., 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 (c); but of this fact we cannot help being very doubtful.

There is a very great sympathy between the organs of smell and of taste; for 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 those classes of sensations; as a sweet smell or taste, &c.

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.

(a) "Ut gustus (says a learned physiologist) cibi itineri, sic olfactus ostio viarum, quas aer subire debet, custos praeponitur, moniturus ne quid noxi, via qua semper patet, in corpus admittatur. Porro, ut gustus, sic quoque olfactus ad salutarem cibum invitat, a noxio aut corrupto, putrido imprimis vel rancido, deterrit."

"When thou seest the mouth, through which animals take in whatever they desire, always placed near the nose and eyes, thinkest thou not, says Socrates to Aristodemus, that this is the work of a providence." Xenophon's Memorables, book i. chap. 4.

(b) "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 fit 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 ecstasy far beyond what the desire of food can produce." Knight on Taste.

(c) 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 mangoustre ouvre cette poche, pour se refraîchir lorsqu'elle a trop chaud." 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, whilst 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 unacquainted 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 his reason all these powers in one? "Is Heaven unkind to man and man alone? "Shall he 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 Descartes and Locke on this subject was pretty generally received; but, since the publication of Doctor 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 others 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 connexion 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 Smelling 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 Descartes 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 we have been illustrating has of late been called into question by a sceptical writer, who, it appears to us, has upon this occasion been entirely deficient in his accustomed acuteness. Dr Reid's account of this affair seems so full, so clear and convincing, that we are at a loss to conceive how his meaning can be misunderstood; and yet the arguments 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 is indeed impossible, that it can be in any body: it is a sensation; and a sensation can be in a sentient thing only." 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 anywhere 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."

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, the winds dance, and the flowers respire; 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." "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."

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 permitted to say so, altogether different from each other. Is not smell sensation when the spaniel finds sport in the field for 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 odor; 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 for his master 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 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 deserts? "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*. 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, if that there were no odour or external cause of smell, no animal would have this sensation.

The sense of smell becomes sometimes too acute, either in consequence of some defect or disease of the organ, or from too great a sensibility of the whole nervous system, such as we sometimes observe in fevers, in phrenitis, and in hysterical diseases. It is however more frequently blunted in consequence of affections of the brain and nerves, arising from blows on the head, or from internal causes; or this may happen on account of too great a dryness of the organ, owing to a suppression of the accustomed humours, or to their being conveyed off by some other channel: or it may arise from too great a quantity of tears and of mucus choking up the nostrils. We have instances of both in cases of common cold, in which, at the beginning of the disease, the nostrils are dry, but as it advances, begin to discharge a great deal of humour, or become obstructed by a thick mucus. Whatever hinders the free entrance of the air into the nostrils or its passage through them, must also injure the sense of smell. It is also sometimes so depraved as to perceive smells when there is no odorous body present, or to perceive smells different from those that are really present. Some of the particles of the odorous effluvia, after having remained for some time in the caverns of the nostrils, issuing forth again and affecting the organ, will sometimes cause this species of false perception, even in the most healthy persons.

The sense of smelling may be diminished or destroyed by diseases; as by the moisture, dryness, inflammation, or suppuration of the olfactory membrane, the compression of the nerves which supply it, or some fault in the brain itself at their origin. A defect, or too great a degree of solidity of the small spongy bones of the upper jaw, the caverns of the forehead, &c. may likewise impair this sense; and it may be also injured by a collection of fetid matter in these caverns, which is continually exhaling from them, and also by immoderate use of snuff. When the nose abounds with moisture, after gentle evacuations, such things as tend to take off irritation and coagulate the thin sharp serum may be applied; as the oil of anise mixed with fine flour, camphor dissolved in oil of almonds, &c. the vapours of amber, frankincense, gum-mastic, and benjamin, may likewise be received into the nose and mouth. For moistening the mucous when it is too dry, some recommend snuff made of the leaves of marjoram, mixed with oil of amber, marjoram, and aniseed; or a sternutatory of calcined white vitriol, twelve grains of which may be mixed with two ounces of marjoram water and filtrated. The steam of vinegar upon hot iron, and received up the nostrils, is also of use for softening the mucous, removing obstructions, &c. If there be an ulcer in the nose, it ought to be dressed with some emollient ointment, to which, if the pain be very great, a little laudanum may be added. If it be a venereal ulcer, 12 grains of corrosive sublimate may be dissolved in a pint and a half of brandy, a table spoonful of which may be taken twice a-day. The ulcer ought likewise to be washed with it, and the fumes of cinnabar may be received up the nostrils.

If there be reason to suspect that the nerves which supply the organs of smelling are inert, or want stimulating, volatile salts, or strong snuffs, and other things which occasion sneezing, may be applied to the nose; the forehead may likewise be anointed with balsam of Peru, to which may be added a little oil of amber.