Ernst von Fleischl-Marxow, also Ernst Fleischl von Marxow, was an Austrian physiologist and physician who became known for his important investigations on the electrical activity of nerves and the brain. "He also invented various optical measuring instruments, such as the spectropolarimeter and the hematometer." Fleischl-Marxow is remembered for Sigmund Freud's prescribing cocaine to treat his morphine addiction, which resulted in Fleischl-Marxow's becoming addicted to cocaine as well as morphine.