**3.2.1 The importance of Virchow's** *real* **triad**

The morphological characterization of venous thrombi encapsulated in Virchow's publication is important in two respects:

First, an account of the aetiology of DVT must include a causal explanation for all three morphological features. That is the critical test of any aetiological hypothesis.

Second, Virchow's *real* triad constitutes a triple criterion for assessing experimental thrombi. Any coagulum or other structure produced in an experimental setting that does not display Lines of Zahn, dense fibrin and a white *Kopfteil* cannot be regarded as a thrombus, and the experimental model that generates such a structure cannot be considered a model for venous thrombogenesis (cf. Welch, 1887, 1899).
