Bismuth subgallate, a hemostatic agent, acts on coagulation factor XII (Hageman factor), leading to the activation of the coagulation cascade and improving early formation of a fibrin clot[1][2].
[1]. Thorisdottir H, Ratnoff OD, Maniglia AJ. Activation of Hageman factor (factor XII) by bismuth subgallate, a hemostatic agent. J Lab Clin Med. 1988;112(4):481‐486. [2]. Puia SA, Renou SJ, Rey EA, Guglielmotti MB, Bozzini CE. Effect of bismuth subgallate (a hemostatic agent) on bone repair; a histologic, radiographic and histomorphometric study in rats. Int J Oral Maxillofac Surg. 2009;38(7):785‐789.