When we wish to smell anything—for example, a flower—we close our lips and draw in our breath, and the air which is thus made to enter the nose carries with it the odorous matter, and brings it in contact with the ramifications of the nerve of smell. Every inspiration of air, whether the mouth is closed or not, causes any odorous substance present in that air to touch the expanded filaments of the nerve.
In virtue of this contact or touching of the nerve and the volatile scent, the mind becomes conscious of odor, though how it does so we know as little as how the mind sees or hears; we are quite certain, however, that if the olfactory nerve be destroyed, the sense of smell is lost.
Besides its endowment by the olfactory nerve, or nerve proper of smell, the nostril, especially at its lower part, is covered by branches of another nerve (known to anatomists as the fifth), of the same nature as those which are found endowing every part of the body with the susceptibility of heat, cold, smoothness, roughness, pleasure, and pain. It is on this nerve that pungent vapors, such as those of smelling-salts, strong vinegar, mustard, and the like, make the sharp impression with which all are familiar.
Can the Sense of Smell be Educated?—The extent to which the sense of smell may be educated far exceeds what most imagine can be realized from this sense. There are probably as many odors as there are colors or sounds; and the compass of one nostril in reference to the first, likely differs as widely from that of another, as the compass of the eye or the ear does in reference to the last two. The wine merchant, the distiller of perfumes, the manufacturer of drugs, the grower of scented plants, the epicure in things savory, the tobacco dealer, and many others, have by long training educated themselves to distinguish differences of odor which escape an uneducated and unpracticed nostril, however acute by natural endowment.
Perfumes.—Much importance attaches to the use of perfumes by both ancient and modern civilized nations. But all the ancient nations who had attained to civilization, were addicted to the use of perfumes to an extent to which no modern people at the present day affords any parallel. Not merely as contributing to the luxury of the body were perfumes so prized. They were used at every sacred ceremonial; lavishly expended at the public religious services; and largely employed at the solemn rites which were celebrated at the burial of the dead.
THE TONGUE: THE ORGAN OF TASTE
The organ of taste is generally held to be synonymous with the tongue, but, in reality, the throat and the nostril are as much concerned as the tongue in the perception of taste. The power of these portions of the body to distinguish savors mainly depends, as in the case of the eye and the ear, upon their connection with the brain through those fine white nerves which have been already referred to. The tongue and the auxiliary organs of taste are largely supplied with nerves, and through them those sensations are experienced which we connect with the words taste, savor, sapidity; sweet, salt, sour, bitter, and the like.
Membrane of the Tongue.—At certain points the membrane of the tongue forms distinct folds, containing fibrous or muscular tissue, which act to a certain extent as ligaments to the tongue. The most considerable of these folds is termed the frœnum (or bridle) of the tongue, and connects its anterior free extremity with the lower jaw. Other folds of mucous membrane pass from the base of the tongue to the epiglottis; while from the sides of the base, passing to the soft palate, are seen two folds on either side, the “pillars of the fauces.”
The upper surface of the tongue is divided into two parts by a long furrow, commencing at the tip, and extending back about two-thirds of the tongue’s length.