Snake cages. Researcher with a caged Malaysian pit viper (Calloselasma rhodostoma) at a snake farm. The snakes are kept for their venom, which con- tains an anticoagulant drug. The drug, Ancrod, is being studied for use in treating stroke patients. It improves blood flow by reducing the amount of fibrinogen (a clotting protein) in blood plasma. Strokes occur when the blood supply to part of the brain is cut off by a blockage or bleeding in the brain. They can lead to brain damage and are often fatal. Ancrod may reduce the extent of brain damage and lower the mortality rate. Over 3000 snakes live at this facility, run by Knoll AG, a division of BASF Pharma, in Ludwigshafen, Germany.