By Robert Klitzman, M.D
To help their soldiers on the front, Nazi physicians sawed off the limbs of concentration camp prisoners and then tried to reattach these body parts, but failed. Other prisoners were forced into the snow to measure how long it took for them to freeze to death.
In response, the Nuremberg Tribunal developed the first moral guidelines on how to conduct experiments.
Since then, science has grown enormously, improving our lives in areas from cancer to depression.
But experiments on humans have become not only more common, but more complicated and controversial, often raising profound moral dilemmas.