 The cell-based model of coagulation Hoffman et al., 1995; Kjalke et al., 1998; Monroe et al., 1996 Figure 1 provides the clearest explanation to date of how physiologic coagulation occurs in vivo. The advance of this model over prior descriptions of the coagulation reaction is that it incorporates the cellular surfaces upon which the specific coagulation factors accumulate and react, and thereby more accurately explains the phenotypes observed in individuals lacking, or deficient in, the various coagulation factors and platelet receptors. 