Liver-transplant operations are almost routine these days. Finding suitable donors remains the hard part. Each year thousands of patients suffering from cirrhosis, hepatitis and other severe liver ailments die while on waiting lists. Artificial livers aren’t likely to fill the gap, either. The liver is almost as complex as the brain: it handles some 400 physiological functions, from detoxifying the blood to turning food into the nutrients and chemicals our cells need to function and survive.