MODEL RELEASED. Mechanical blood harvesting. Nurse adjusting a machine that is harvesting stem cells from the blood of a patient. Blood is being taken from one arm, passed through the apheresis machine and returned to the other arm. The machine uses a centrifuge to rapidly spin the blood. Components of different weight separate out, allowing needed parts to be harvested. The method allows greater collection of blood parts than by normal methods. The patient has Hodgkin's disease, a cancer of the lymph nodes. The treatments, such as radiotherapy, will destroy many white blood cells in the lymph nodes, requiring replacement by stem cells that develop into new blood cells.