Fibrinolysic cadaveric blood studied after a rapid death (strangulation asphyxia, traumatic and sudden death) contained no plasmin--an enzyme of fibrin destruction, and no plasminogen--its inactive precursor. In the absence of plasmin and plasminogen of interest is a high content of plasminogen activator. An increase in the content of the activator in the fibrinolysic blood exists along with a marked proactivator level. A relationshp between the concentration of the activator and the proactivator in this blood indirectly pointed to the intravascular (from the pre-existing blood proactivator of the living), and not the tissue origin of the activator. Activation of plasma proactivator is caused by the entrance of tissue lysokinases into the circulation.