the act whereby we perceive smells, or whereby we become sensible of odorous bodies, by means of certain effluvia thereof; which, striking on the olfactory organ, briskly enough to have their impulse propagated to the brain, excite a sensation in the foul. The principal organs of smelling are the nostrils and the olfactory nerves; the minute ramifications of which latter are distributed throughout the whole convolute of the former. For their descriptions, see Anatomy.

Smelling is performed by drawing into the nostrils the odorous effluvia floating in the air in inspiration, which strike with such force against the fibrilae of the olfactory nerves, which the figure of the nose, and the situation of the little bones, render opposite thereto, as to shake them, and give them a vibratory motion; which action, being communicated hence to the common sensory, occasions an idea of a sweet, or fetid, or sour, or an aromatic, or a putrefied object, &c. The matter in animals, vegetables, fossils, &c., which chiefly affects the sense of smelling, Boerhaave observes, is that subtle substance, inherent in their oily parts, called called spirits; because, when this is taken away from the most fragrant bodies, what remains has scarce any smell at all; but this, poured on the most inodorous bodies, gives them a fragrance.

Willis observes, that brutes have generally the sense of smelling in much greater perfection than man: by this alone they distinguish the qualities of bodies, which could not otherwise be known; hunt out their food at a great distance, as hounds and birds of prey; or hid among other substances, as ducks, &c. Man, having other means of judging of his food, &c. did not need so much sagacity in his nose; yet have we instances of a great deal even in man. In the Histoire des Antilles, we are assured there are negroes who, by the smell alone, can distinguish between the footsteps of a Frenchman and a negro. It is found, that the laminae, where-with the upper part of the nostrils is fenced, and which serve to receive the divergencies of the olfactory nerves, are always longer, and folded up together in greater numbers, as the animal has this sense more acute: the various windings and turnings of these laminae detaining the odoriferous particles.

The sense of smelling may be diminished or destroyed by dilacres; 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 mucus when it is too dry, some recommend snuff made of the leaves of marjoram, mixed with oil of amber, marjoram, and aniseed; or a tincture 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 mucus, 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 freezing, may be applied to the nose; the forehead may likewise be anointed with balm of Peru, to which may be added a little oil of amber.