To determine if differences in coagulation were contributing factors to the bleeding and rebleeding results, prothrombin time (PT) and activated partial thromboplastin time (aPTT) were measured. PT is a measurement of the extrinsic coagulation pathway (activation of Factor VII by tissue factor) while aPTT is a measurement of the intrinsic pathway (activation of Factors XII, XI, IX and VIII). The products of both pathways activate Factor X, which initiates the common pathway leading to thrombin generation and fibrin clot formation. PT and aPTT were measured in the B6 and A/J mice and values were not different between the two mouse strains (Table 2). These results suggest that the coagulation pathway is not different in the two inbred strains.