A Falling Sphere Method for Studying Clotting in Systems of Purified Blood Components

Summary 1. To study the coagulation of the fibrinogen-thrombin system, a simple rapid method has been developed which measures the time required for the developing coagulum to stop the fall of a plastic bead in a glass tube containing the fibrinogen-thrombin mixture. 2. The “clotting time” thus obtained, increases somewhat with the age of the thrombin and fibrinogen solutions. 3. Kinetic studies of the coagulation process indicate that there is no change in viscosity for a considerable time after the mixing of thrombin and fibrinogen, but that this phase is followed by an abrupt increase in viscosity signifying coagulation of the system. 4. The rate of clotting varies with thrombin concentration in a roughly linear fashion.