We hear plenty about the widening income gap between the rich and the poor in America and about the expanding distance separating the haves and the have-nots. But when detailing the many things that the poor have not, we often overlook the most critical--their health. The poor die sooner. Blacks die sooner. And poor urban blacks die sooner than almost all other Americans. In nearly four decades as a doctor at hospitals serving some of the poorest...