On the rates of coagulation and subsequent softening of bovine and human blood and of thrombin-fibrinogen

Hartert’s thrombelastograph is used to help in the diagnosis of abnormal conditions of blood clotting. Its practical usefulness lies in its capacity to distinguish borderline cases. It is felt that its efficiency for this purpose would be enhanced if the equations for the rate of increase of the complex modulus during coagulation and of its decrease during subsequent softening (fibrinolysis and/or retraction) were known. The parameters of these equations could then be used for diagnostic and prognostic purposes and the equations should also throw some light on the mechanism of fibrin polymerization and of softening. Experiments have been done on bovine blood (also using a somewhat similar but larger torsiometer) and on human blood as well as on fibrinogen-thrombin. The polymerization process, especially in the case of fibrinogen-thrombin, appears to consist of two well-defined stages, an equation proposed in a previous paper holding in the earlier stage and a still simpler equation in the later stage; but the very last stage of coagulation does not follow any known equation. The effects of additions of substances known to induce or inhibit fibrinolysis and retraction in human blood were confirmed; but considerable differences were found, in some cases, in the behavior of bovine blood. Some marked effects on rate and extent of coagulation produced by these substances do not appear to have been previously recorded.