sunday/weighing-the-end-of-life.html?hp> Our vet used the 50 percent rule — were half of our dogs' days happy? But you can't ask that about humans. Art & Design *<http://www.nytimes.com/pages/arts/design/index.html> Curator, Tear Down These Walls<http://www.nytimes.com/2013/02/03/arts/design/american-folk-vs-a