FIBRINOLYTIC activity of the blood in vivo has been seen in the course of liver diseases1, in toxæmia of pregnancy2, in shock3, in violent death4, during surgical operations5,6, during the preparation of operations7 and in the course of resorption of thrombi6. The fibrinolytic enzyme may be activated in vitro by chloroform and by by-products of the metabolism of hæmolytic streptococci8,9.