Essence and emblem of life - feared, revered, mythologized, and used in magic and medicine from earliest times - human blood is now the center of a huge, secretive, and often dangerous worldwide commerce. It is a commerce whose impact upon humanity rivals that of any other business - millions of lives have been saved by blood and its various derivatives, and tens of thousands of lives have been lost. Douglas Starr tells how this came to be, in a sweeping history that ranges through the centuries.