What are you sniffing about? The mysterious sense of smell, now less mysterious

September 21, 1997|By MICHAEL PAKENHAM

The number of olfactory sensory cells in an average human being totals between 6 million and 10 million. A fox terrier has 150 million of them. You can lunch out on such Olympian trivia. So try this for dinner: The world champion smeller is the male silkworm, which is able to find a sexually available female miles away through the scent of bombykol.

There are miles to go before I would exhaust the incidental and illustrative facts about smell that are readily to be found in "Smell: The Secret Seducer," by Piet Vroon, with Anton van Amerongen and Hans de Vries. (Translated from the Dutch by Paul Vincent. Farrar Straus Giroux. 226 pages. $23). But there is much more to it, to smell, than rhinestone factoids.

Smell is, in truth, taste. Except for the mouth's capacity to sense acidity, saltiness, sweetness and bitterness, all "taste" happens in the nose.

I first became acutely aware of the complexity of smell and the challenge of disciplining it about 25 years ago, when in my off moments I began writing a weekly newspaper column about wine. I knew wines and wine making well, but in reading even the respected writing about it then, I found there was little if any satisfactory description of what the experience of tasting wine was actually like.

Aromatic life

Talking then with neurologists and other technical experts, I learned a good deal -the most dramatic discovery being that precious little serious medical and scientific work had been done about it, in relative terms to, say, sight or hearing.

I ended up coining a set of aroma associations of my own. This was at the beginning of the great American wine-consciousness revolution, and lots of other earnest people began writing descriptively as well. Together, we managed a small step for ornamenting self-indulgence.

But, even in the face of such minor disciplining, the mysteries remained. The Vroon book does not solve them all, but it brings together the accumulated scientific understanding of the process more comprehensively and comprehendably than any other volume I have found.

Its prose is relatively dense, but not highly technical. There are passages that will be ignored or skimmed by many readers because of the limits of their own interests and knowledge.

For anyone interested, however, it is an indispensable volume, a fine, sweeping survey of the state of knowledge about the most mysterious and elusive of senses. I would suggest strongly that anyone professionally involved in wine, food, cosmetics or commercial scent would be well advised to read it.

For physicians who are interested in the process and the phenomenon - including the legendary capacity to diagnose certain diseases by smell - the book contains substantially valuable guidance. The bibliography goes on for 15 pages. The medical contents include a sweeping inventory of major olfactory disorders and suggestions of sources of guidance for treatment.

The book was written in Dutch, a collaboration among Vroon, a psychology professor at Utrecht University, van Amerongen, a biologist, and de Vries, a psychologist. It declares right out that there has been a "reprehensible and strange" lack of scientific research and attention to the olfactory process and its consequences.

The history of consciousness of smell is rich and well surveyed. In pre-scientific medicine, there were all sorts of assumptions and guesswork and superstitions about medical, diagnostic and therapeutic consequences. The olfactory sense has well-developed connections to the older part of the brain structure, the limbic system, the neural chassis - the hormonal and pituitary systems. The connection with the "newer" part of the brain - the left neocortex, which contains language and the like - is much fainter. This may or may not account for the tendency for it to be hard to verbalize and rationalize smell.

Power and discrimination

The scientists estimate that 400,000 odors can be distinguished by an average human nose. The trouble is only a tiny number of these can be named or identified. There have been lots of efforts through history and especially through the 18th and 19th centuries to categorize or classify smells. One still accepted text defines more than 2,000 smells in terms of familiar scents and combinations.

The precise way in which an "oderant" stimulates the sensory cells is not entirely clear. The best estimate is that the smell sensation comes from the shape of the molecule that reaches the receptors in the nasal passages. This is totally unlike the senses of sight and sound, which familiarly are matters of wave length frequencies.

The sense of smell is the earliest to develop in the embryo. Acuity increases through childhood and shifts radically in puberty. Some research indicates it becomes most competent or complex between the age of 30 and 40 and stays stable into the 60s. In old age, after 80 particularly, the sense of smell has often virtually disappeared.

Smoking does very significantly lower smell sensations. Women have a slightly more acute sense of smell than men do, in general.

The brain is complicated. Smell is complicated. The two together multiply each other's complexity. The book contends that it appears that smell has played an important role in the sexual and reproductive and sexual lives of virtually all animal forms, from insects to humans - thus accounting, perhaps, for its pre-eminent power and discrimination in spite of the fact that it is really not as useful today as, say, sight or hearing.

Oh, yes. The size of your nose has absolutely nothing to do with the acuteness of your sense of smell.

Pub Date: 9/21/97

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