Imagine for a moment that you personally rescued someone from death. Imagine the joy and gratitude of the family and imagine the good feeling you'd have for yourself for the rest of your life.

Sound good? Dr. Chi Van Dang from Johns Hopkins Hospital has a way of doing this, and you don't have to be a fireman or a life guard to gain this kind of satisfaction.

Dang suggests that you become a bone marrow donor. Fortunately, you can do this while you're still alive. And further, you won't miss what you've donated because your body will replace it in a couple of days.

Dang hopes you'll consider becoming a bone marrow donor because often a bone marrow transplant is the only hope that people with leukemia or other blood diseases have. Currently only about 70% of those who need it can get it, and the statistics are even less favorable for minorities.

Fortunately, becoming a donor is easier than you might think. "When most people think of transplantation," Dang says, "they think that it's cutting an organ out of someone and sewing it up in someone else. Bone marrow transplantation is different."

He goes on to explain that with a bone marrow donation, what they really do is insert a needle into one of your hip bones and withdraw about half a cup of liquid marrow. You have an anesthetic during the process so it's painless.

Doctors take the liquid that they've withdrawn and infuse it into the veins of the patient much the way they might with an ordinary blood transfusion. "The cells go through the patient's veins," says Dang, "and find their way back into the patient's bone marrow.

"If the transplant is a success, your bone marrow cells would, as Dang puts it, "set up house," and start growing new, healthy blood cells for the patient. When this happens, a patient who would otherwise have almost certainly died, can be restored to a full and active life.

The term "organ donation" may seem strange when it's applied to blood, but technically, blood is an organ just as much as a kidney or a liver. Blood has the distinction of being both the most active organ and the only one that migrates during an individual's life.

It's the most active because people make 200 times their weight in blood every year. And as for migrating, the cells that produce your blood have different locations at different times in your life.

According to Dang, when you were first conceived, the genetic pattern for your blood was contained in the yolk sac of the egg that produced you. As you developed in the womb, the cells that made your blood migrated to your liver.

The liver became the primary factory for producing the components of your blood, including your red cells, white cells, and platelets. But by the time you were born, an extraordinary transformation had taken place.

The cells that make blood had migrated from your liver to the hollow areas in your bones, particularly the long bones in your arms and legs. Finally, as you became an adult, almost all the cells that make blood became concentrated in your pelvic bones, ribs, and sternum.

Blood is an amazing organ. If you share it by becoming a bone marrow donor, you won't miss it, but you'll be giving life to someone who would otherwise lose theirs. To find out more about becoming a bone marrow donor, call the Marrow Foundation at: 1 800 Marrow2 and they'll send you their information packet.