A Plasminogen Activator in Spontaneously Active Human Blood.∗ †

Summary 1. Fibrinolytically active blood, as obtained from the living and dead human organism, contains a plasminogen activator. The amount of this activator exceeds many times that needed for the complete activation of the plasminogen present in human blood. 2. The plasminogen activator in blood differs from the tissue activator, fibrinokinase, and is probably formed from a precursor contained in the blood.