Take a good hard look at your toenails. are any of them flaky, yellow, and cracked? Then you, too, might be suffering from the heartbreak of onychomycosis.

No smirking please. Onychomycosis is an ugly fungal infection afflicting the toes of more than 35 million Americans. On occasion, it can be excruciatingly painful. More commonly, however, the disease turns toenails into unappetizing strips of calcified decay. Yech.

But what makes onychomycosis so infectiously intriguing is not its tendency to attack toenails while leaving fingernails untouched, nor its stubbornness in taking root in nail beds. No, what truly makes this parasite provocative is its profitability. In barely seven years, treating onychomycosis has grown into a business worth hundreds of millions of dollars annually for Novartis, one of the world's largest pharma firms. Millions of people have paid roughly $1,000 -- more than $100 per infected toe -- for pills made by Novartis that rid them of the evil fungus causing this unappealing condition. That's real money.

Remember, we're not talking baldness, depression, or erectile dysfunction here; we're talking toenails. "Toenail tech" is so utterly devoid of any charm or sex appeal that the ability to turn a toenail treatment into a fast-growth, high-margin business says something important about the nature of innovation.

Novartis's toenail triumph is particularly illuminating because its original innovation salvo seriously misfired. When the firm launched its first marketing campaign for its new drug Lamisil in 1997, it made a crucial analytical error that nearly condemned the medication to marginality. In the end, Lamisil's rebound and ultimate success required Novartis to ignore its most obvious selling point.