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Smells and Smellers
Nature Bulletin No. 720   June 1, 1963
Forest Preserve District of Cook County
Seymour Simon, President
Roberts Mann, Conservation Editor

SMELLS AND SMELLERS
Did you ever take a long look at your nose in a mirror and think about what a remarkable, what an essential feature it is? Without it, and with merely two holes in the upper middle of your face, you would be a freak -- an object of pity and aversion. There would be nothing to intercept the dirt and dust in the air we breathe. And even if it were replaced by a miracle of plastic surgery you would be deprived of many pleasures in life.

You would have no sense of smell -- none at all. And, as a result of that, your sense of taste would be limited to the four primary sensations: sweet, sour, bitter, and salty. It could distinguish between them but no further, because the sense of taste depends largely upon the sense of smell. The so-called "taste" of fruits and wine, for example, is really an aroma or smell.

That can be demonstrated by holding your nose tightly shut while chewing coffee beans -- they will be tasteless -- or by eating an onion and a raw potato or a carrot -- there will be scarcely any difference in their tastes. That is why food doesn't "taste right" when you have a bad head cold.

In the uppermost chamber of each nostril there is a patch, about the size of a dime, containing vast numbers of sense cells -- nerve endings connected with the brain. Odors, as we explained in Bulletin No. 568, are detected as the air passes over those patches when we breathe or sniff.

Your proboscis is described by scientists as a protective shell housing a delicate mechanism which is so sensitive that "a small area within each nasal passage is able to receive and identify an unlimited number of dissimilar odor stimuli, sometimes from remote distances and sometimes in dilutions as weak as one part in billions of parts of air. .

Odors come to us in the form of extremely small particles in gases given off by volatile oils or from solutions of organic materials, and these produce distinctive reactions in the sense cells of the nose. Some authorities believe that the similarity or difference of odors is due to the character of the odorous molecules -- the combinations of atoms within them.

Somehow, even in the stillest air, such molecules may travel considerable distances in all directions. The fragrance of a wild grape vine in bloom may be detected many yards away when there is no wind at all; the smell of a field of newly mown hay, or of burning leaves in autumn, will travel farther. Also, of course, odors are carried by winds so that the stench of a stockyard, a slaughterhouse, or a garbage dump can be smelled several miles away.

Evidently there is an infinite number of odors. For instance, each person has a basic odor. A dog recognizes it and can find his master, even at night and in a crowd, by following his footsteps. That basic odor has a different "flavor" sometimes, depending upon a person's health, food, occupation, cleanliness, and even his emotional state such as grief and fear. Dogs and horses can sense when people are afraid of them.

Fundamentally, there are two kinds of odors -- good and bad; agreeable and disagreeable -- but there is no general agreement on how they should be classified. Henning, a German scientist, grouped them in six categories: spicy, flowery, fruity, resinous, burnt or scorched, and foul. Other authorities have nine or more categories including titles such as pungent, fragrant, cloying, stuffy, clean, damp and nauseating.

As stated in our previous bulletin, we need nasal education as much as audio-visual education, a d a vocabulary for smells. Would you like to see a bulletin about how other animals smell?


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