Confusion surrounding the concept of Langer's lines can be reduced by careful distinction among the operational definitions of the phenomenon, the empirical descriptions, and the theoretical explanations. An experimental analysis of the mechanical parameters of excisional wounds in pigskin shows that the marginal retraction, the elastic modulus at the wound midline, and the closing tension are higher for wounds oriented at right angles to tension lines--but the elastic modulus of the terminal segment of the force displacement curve is independent of orientation. The regional distribution of these values shows two patterns. The modulus parameters and the closing tension share a common distribution related to the steepness of regional force-displacement curves, while retraction has a qualitatively different distribution. On the basis of similarities in the behavior of retracting wound margins and in the distortion of punch holes which define tension lines, we hypothesize that the same mechanism may be responsible in both cases.