|A vigorous 33-year-old professional, you have just been diagnosed with Parkinson's disease, a degenerative disease that is likely to cripple you within 15 years. You may lose the ability to walk, to button your shirt, to use the bathroom. Drugs can sometimes help, but there is no cure.
Your doctor tells you about an experimental treatment in which genetically modified cells from a pig are used to replace your dying brain cells. It's called xenotransplantation (from the Greek root "xeno," meaning "foreign"), and you are familiar with it because your wife is a physician. Your doctor suggests you try it, in part because she has nothing else to offer you.