Thomas, E. Donnall (1920-...), is an American physician who performed the first human bone-marrow transplant. Bone marrow is a soft, blood-forming tissue that fills the cavities of many bones. Thomas pioneered a technique by which patients with leukemia, a form of blood cancer, receive a healthy new supply of bone marrow after all their own marrow has been destroyed by powerful drugs or radiation. In 1990, Thomas shared the Nobel Prize in physiology or medicine with another transplant pioneer, American surgeon Joseph E. Murray.