Olfaction

“ I am acquainted with people—English people—who are able to recognise by olfaction not only different races and the two sexes, but even different persons. One of those sensitives informs me that to her the personal olfactory atmosphere is every whit as characteristic and unmistakable as the play of features or the carriage of the figure.
Another remarkable feat within the capacity of human macrosmatics, and one that seems almost incredible to the ordinary individual, is that of being able to distinguish the clothing of different persons by its aroma. ”

“ When you would rather not hear you can be inattentive. A proffered handshake you can ignore. A dish you dislike you may decline. But you can’t help smelling—no, not even if you turn up your nose.
Olfaction is thus the great leveller among the senses, equality having here a reality but rarely found elsewhere. For odour makes its way into the nose of king and cadger, duke and drayman, 80lady and lout, indifferently. Nay, by an ironical law of olfaction the fœtors are more powerful than the fragrances, and vervain the feeble turns tail before the onslaught of scatol (as well it might, indeed!) ”

“ Now, this act of judgment seems to us to be quite independent of any olfactory evidence. We rely upon our predominant senses just as the dog relies upon his. Yet I sometimes catch myself wondering whether olfaction, olfaction rarefied and refined beyond imagining, does not without our knowledge play some part in our estimate of the pros and cons in character.
What is conveyed to us by the “personality” of a man ? Here we have apparently a complex of sense-impressions, for the most part vague, which we are seldom able to analyse, even to ourselves. ”

“ When the physicist can control the vibrations of his electrons and make them rotate in accordance with his will, then he may be able to synthesise new odours—till then we have no means of testing his theories.”
The older view of olfaction—and many modern scientists, as we see, still adhere to it—is that the odorous molecule acts as a chemical reagent upon the olfactory hairs. ”

“ But, as we have already seen, of all the senses none so quickly becomes inert under stimulation as olfaction. Why it would be hard to say, unless, like the exhaustion of colour-vision, it is due to the using up of some chemical reagent in the sense-organ. At all events, if you wish to appreciate the full intensity of a smell, you should arrange to come upon it from the open air.
I wonder if this, or something like it, is the reason why England was the first country in the world to wage war against its stenches. For the English are of all races the most addicted to fresh air. ”

“ A recent development of the theory which we owe to Heyninx, a Belgian scientist, brings the process very closely into harmony with what occurs in the eye. According to this authority, olfaction is in reality a perception of ethereal undulations of the same character as the undulations of light, these undulations being provoked by the intra-molecular vibrations of the odorous vapour in the nasal mucus and transmitted to the olfactory hairs not by immediate contact, but through the medium of the ether. ”

“ Zwaardemaker’s is the classification most usually followed at present, and as it is to him we owe most of our knowledge of scientific olfaction, we shall detail it here :
(1) Ethereal or fruity odours; (2) aromatic, including as sub-classes camphrous, herbaceous, anisic and thymic, citronous, and the bitter almond group; (3) balsamic, with sub-groups floral, liliaceous, and vanillar; (4) ambrosial or muscous ; (5) garlicky (including garlic) , oniony, fishy, and the bromine type of odour; (6) empyreumatic (guaiacol) ; (7) caprylic (valerianic acid) ; (8) disgusting ; and (9) nauseating. ”

“ It seemed, to quote his words, as though in these experiments we were assisting at the formation of the odorous molecules. Those delicate atoms emitted from odorous substances and diffused through the atmosphere are, in fact, the very same that impinge on our pituitary membrane, and give us the sensation of odors. Moreover, facts long ago observed display this revealing action, so to call it, of water upon odors. At morning, when the verdure is moist and the flowers covered with sparkling pearls of dew, a fresher and balmier fragrance exhales from every plant. ”

“ Odors, to be perceived, must be taken up by oxygen, and borne by it to the organ of smell. In a word, odor is the odoriferous particle itself, while light is not the light-giving body.
Does oxygen exert a chemical influence on those atoms of which it robs odorous substances? We do not know, neither do we know of what kind is the action which occurs on the contact of odor with the olfactory nerve, whether the phenomenon is a mere mechanical agitation, or whether some chemical decomposition takes place in the case. ”

“ The physical theory of odour, then, refers that quality to the vibration of the molecule. It suggests that the molecules of an odorous body passing in the gaseous or, in fishes, the liquid state into the olfactory region of the nose, are there received by the film of mucus in which the olfactory hairs lie, and stimulate these hairs by their molecular vibration. No chemical change is supposed to take place, only, as it were, a mechanical stimulation, comparable to the mechanical stimulation of the retina by the waves of light. ”

“ Gleg has estimated that the reaction time for auditory sensation is from 0’12 to 0’15 of a second, whereas the reaction time for smell is as much as 0’5 of a second, only one sensory stimulus being slower, that of pain, namely, which occupies 0’9 of a second.
Odours are conveyed to the olfactory end-organ in the air we breathe. Before they can rise into the air from the odorivector (the odorous body) and be transported they must, it is clear, pass into the vaporous or gaseous state. (In the case of fish, of course, the odour must undergo solution, that is pass into the liquid state.) ”

“ Secondly, almost all particular virtues act according to the greater or less quantity of the body. Large quantities of water corrupt slowly, small ones quickly. Wine and beer ripen and become fit to drink much more quickly in bottles than in casks. If an herb be steeped in a large quantity of liquid, infusion takes place [p. 214] rather than impregnation; if in a small, impregnation rather than infusion. Thus in its effect on the human body a bath is one thing, a slight sprinkling another. Light dews again never fall in the air, but are dispersed and incorporated with it. ”

“ The paste is prepared by stirring crushed barley with hot water to a thick paste and adding small portions of hot water, so that the temperature of the mass is kept at between 86° to 104° F. In a few days the mass commences to develop gas, which shows at first no odor, but soon the development of gas becomes stronger and an acid odor is perceptible, which in a short time is replaced by a terrific stench which, as before mentioned, affects the olfactory organs in a most unpleasant manner. ”

“ All the essential oils which have a higher boiling-point than spirit, remain in the retort, whilst the spirit passes into the receiver with only a trace of the oil, where the alcohol may be recognized by the smell and taste. Should, however, a doubt exist, add to the distillate a little acetate of potash and strong sulphuric acid, and heat the mixture in a test-tube to the boiling-point, when the characteristic odor of acetic ether will be manifest, if any alcohol be present. ”

“ When the inner tube, which is graduated, is slipped into the outer one so as to cover completely its inner face, and air is drawn into the nostril through the tube, the odorous surface, being covered, gives out no particles, and no odour is perceived. By adjusting the inner tube in relation to the outer one, whereby more or less of the oderous surface is exposed, a point can be found where minimum stimulation occurs. The amount of odorous substance delivered under these circumstances to the air current has been designated by Zwaardemaker as an olfactie, the unit of olfactory stimulation. ”

“ The taste-bulbs are capable of appreciating four sensations only, and these quite simple, while the capacity of the olfactory organ, as we shall see more fully later on, is practically unlimited. All the subtlety of “taste,” all that we call “flavour,” is an olfactory sensation. Thus, people devoid of the sense of smell cannot discern the finer savours. ”

“ Water in lead pipes takes up some of the lead. Lead is a poison. You should let the water run off from a pipe a little while before you use it. Good water is clear and has no smell or taste. Dirty or yellow water, or water with a taste or smell, is not fit for use.
39. Tea and coffee.—Tea and coffee are steeped in water and used as a drink. The drink is the water. The tea and coffee are neither food nor drink. ”

“ Thus in the opening paragraph of this book we encountered a large number of olfactory words. But they are all vague ; some applying to pleasant, some to unpleasant, odours. Many of them are very expressive, for disgust begets strong language. But although our olfactory vocabulary may be forceful, it is not discriminative. In other words, it is an emotional, not an intellectual, vocabulary,
These considerations will become more obvious as we deal with olfactory epithets in detail.
Thus smells may be faint or “strong,” but so may any other sensation. ”

“ Odour, strong, fragrant, and aromatic. Taste, acrid, aromatic and permanent. Benzoic acid has lately been discovered in them.
Solubility. Water extracts their odour, but little of their taste; alcohol and ether take up both completely. Medicinal Uses. They are more stimulant than any of the other aromatics; they are sometimes given alone, but more generally as a corrigent to other medicines. Officinal Preparations. Infusum Caryophyllorum. L. Spir. Lavand. co. D. (B) Frauds. The Dutch frequently mix the best cloves with those from which the oil has been drawn. ”

“ The first scent of a flower is the strongest and sweetest; and after a few minutes' exposure the intensity of even a foetid odour may not be perceived. This fact may be accounted for on the supposition that the olfactory membrane becomes quickly coated with a thin layer of matter, and that the most intense effect is produced when the odoriferous substances are applied to a clean surface. The intensity of smell depends on (1) the area of olfactory surface affected, and (2) the degree of concentration of the odoriferous matter. ”

“ We know that the flavour of things tasted is an olfactory sensation, Now while language attains to precision in characterising the sensations of pure taste, as we have just seen, it is significant that flavours are left unnamed, except in the manner we have just explained for olfactory epithets. ”

“ And in any case we are here dealing with that obscure region where chemistry and physics meet and mingle.
134We have now come to the end of our discourse upon the theories of odour, and it must be confessed that we are still very much in the dark as to the nature of the odorous, and as to the manner in which it excites the olfactory organ to activity.
Still more mysterious, however, is the process by which the physical quality of odour becomes the sensation of the mind we call smell.
The transmutation of a physical quality into a sensation is indeed the great mystery of all our senses. ”

“ After a long refusal, he hastened home at the dead of night, and returned with a little glass of crystallised dry salt, which was dissolved in water, and swallowed by the patient. It had a decidedly alkaline taste. The salt was scarcely taken than my situation appeared relieved; and from that moment the disease took a turn which, by degrees, led to my recovery. I need not say how much this strengthened and heightened our faith in our physician, and our industry to share in such a treasure. ”

“ This arises from the fact, that so long as there is the vapor of alcohol, mixed with oxygen-air, passing over red-hot platinum, certain definite products always result, namely, acetic acid, aldehyde, and acetal, which are formed more or less and impart a peculiar and rather agreeable fragrance to the vapor, but which overpowers any other odor that is present. ”

“ These are obtained from animal matter by fusion, and from vegetable by expression, or decoction with water. Qualities. Odour, none; Taste, mild; they boil at 600°, but undergo decomposition, becoming acrid and empyreumatic; the oil, in this state, was formerly used in medicine under the name of philosopher’s oil. [576] By exposure to air they absorb oxygen and become rancid; they congeal at a temperature of 32°, and some even above that. ”

“ Having thus learned what physiologists think of the sense of smell and the conditions of the perception of odors, let its see what naturalists and chemists have ascertained respecting the latter as viewed in themselves, what place they give to odorous bodies, and what character they attribute to them all. The three kingdoms possess odors. Among mineral substances, few solids, but quite a number of liquids and gases, are endowed with more or less powerful scents, in most cases not very pleasant ones, and usually characteristic. ”

“ Volatile oils, from continued exposure to the air, absorb oxygen, and become resinous, by which they lose their volatility, fragrance, and pungency, hence they should be preserved in small opaque phials, completely full and well stopped. Med. Uses. They act as powerful stimulants and aromatics; they remove nausea and flatulence, correct the griping of certain purgatives, and cover the offensive taste of various remedies. See Aquæ destillatæ. They, moreover, have the property of defending certain animal and vegetable preparations from mouldiness. ”