I don't write on topics that require a lot of urgency. But in 'Stiff,' I wanted to change people's hearts about organ donation. Whenever I get a chance, I try to talk about that.

You won't see me writing about particle physics, or even planetary geology, or chemistry. I practically failed chemistry, and if I had to write a book in any of those areas, I don't think it would go well.

My books are not really books; theyre endless chains of distraction shoved inside a cover. Many of them begin at the search box of Pub Med, an Internet database of medical journal articles.

It would be especially comforting to believe that I have the answer to the question, What happens when we die? Does the light just go out and that's that-the million-year nap? Or will some part of my personality, my me-ness, persist? What will that feel like? What will I do all day? Is there a place to plug in my laptop?

It's this mood, these sentiments - the excitement of exploration and the surprises and delights of travel to foreign locales - that I hope to inspire with this book.

Yet if you don't understand the physiology of a biological system or process-like female sexual arousal-you can't possibly come up with a way to fix it when things go wrong. No one would have come up with a treatment for diabetes if physiologists hadn't figured out how metabolism, blood sugar, and insulin work.

Viagra does have a physiological effect, but it doesn't make women feel aroused. Nowadays, researchers are looking at drugs that affect the central nervous system rather than blood flow to the genitals.