Effect of velocity gradient on the clotting time of blood and on the consistency of clots formed in vitro.

• Recent studies from this laboratory have shown that the clotting time of blood' and the morphology of blood clots' can be altered markedly by flow of blood during the period of clotting. The rheology of clots has been studied by Hartert, de Nicola, and Marchal et al. by means of thrombelastography, while Scott Blair and Copley and Scott Blair employed a gelometer. However, no observations have been published on the functional relationship between the consistency of the blood clot and the rates of shear at which such clot (or coagulum) is formed. In the present paper I will show (a) that there exists a quantitative relation between clotting time of blood and the velocity gradient, and (b) that the consistency of clots (or blood coagula, or artificial thrombi) is directly dependent on the velocity gradient at which such clots are cast. In addition, the manner in which rheological techniques may indicate the molecular and colloidal structure of clots will be discussed.