Giving blood

There is still no viable substitute for human blood in medical care, where it is used for transfusions for everything from bleeding disorders to trauma, surgeries, and organ transplant. In addition to an ongoing need, maintaining a sufficient blood supply is complicated by its limited shelf life. Unless it is frozen, donated blood must be used within a few weeks or it will spoil.

People can give whole blood every eight weeks, plasma every four weeks and platelets 24 times a year.

1. Given the history of blood donation as altruism, we can see how, in an era in which altruism is in short supply -- and even viewed with suspicion -- the blood supply might come up short.

1. Donating body to science

1. Increasing availability of therapeutic substances of human origin

1. Providing blood transfusions

1. Shedding blood