Monday, June 14, 2010

Sniff

My daughter, the editor, sent me an early copy of a book to be published soon, Remembering Smell: A Memoir of Losing -- and Discovering -- the Primal Sense, by Bonnie Blodgett. Blodgett, a gardening writer, attributes her loss of smell to a popular over-the-counter nasal spray she used to combat a cold. Not a happy turn of events for someone who writes about flowers.

Why did my daughter send me the book? I was born without a sense of smell. Or, at least, I have no memory of smell. The only doctor I have talked to about this suggested that my anosmia (that is what the condition is called) probably resulted from birth damage to the frontal lobe of my brain. Well, who knows?

Blodgett's book has a lot to say about the science of smell, and the trauma of losing that sense -- and the joy of recovery. I couldn't tell you what a smell smells like, never having smelled a smell. Sweet and sour, salty and bitter -- any thing to do with the tongue is OK. I can tell if a mug of coffee has sugar in it, but not if it has coffee in it. Could be hot water for all I know. Wine? I buy the cheapest stuff that hasn't gone to vinegar.

In her book A Natural History of the Senses, Diane Ackerman suggests "smumb" as an appropriate moniker for my condition. "There goes Chet. He's smumb."

Am I missing what Ackerman calls "all of the heady succulence of life"? Orange, lime, clove, musk, jasmine, bergamot, attar of roses, ambergris, civet, sandalwood. Maybe.

But, hey, don't feel sorry for me.

Apparently, our taste buds -- tiny onion-shaped receptors embedded in the tongue -- are multipurpose. Each bud can deliver multiple sensations to the brain. The buds are complex chemical processors capable of sorting out an assortment of molecular stimuli. For example, the salty pleasure I derive from anchovies begins with sodium chloride molecules, NaCl, approaching a taste cell. The atoms in the molecules disassociate, and sodium ions enter the cell through special channels on its surface. The accumulation of sodium ions in the cell enables calcium ions to enter, too. This prompts the release of chemical signals called neurotransmitters that trigger adjacent nerve cells. A message zips to the brain. Yum, I'll have more anchovies, please.

The sense of smell is rather different. The 100 million olfactory receptors in the nose are bare nerve endings; no fancy buds to do complex biochemistry. Smell is raw and primitive, a link to our premammalian past.

Mice, we are now told, have about 1200 genes for scent receptors, most of them in full working order. Humans, by contrast, have only about 1000 smell receptor genes, and the greater part of these have been put out of action by deleterious mutations. It seems that with our big brains and keen color vision modern humans don't rely as much on the nose as did our mammalian and premammalian ancestors.

So rather than smumb, I think of myself as more highly evolved.