Figure 3d shows example promontory networks on mountains having these characteristics.įigure 4 shows wet-induced wrinkle networks from 28 fingers of 13 hands, and figure 5 indicates the channel-like depressions (in light blue) and divides (in black). 3c), wet wrinkles are predicted to have, like the illustration in figure 3b, disconnected channels that diverge away from one another downstream and divides (or borders between the channels) that form a tree with its root near the peak of the compression topography. If wet-induced wrinkles are drainage networks as we hypothesize, then, because the compression topography for fingertips is that of a promontory (fig. The leftmost network shows the aerial photo on its left. d Example drainage networks on convex mountain promontories (in Southern California) illustrating the signature features in b. Because a convex topography applies to grip, finger wrinkles are expected to have the signature morphology indicated in b. c Iso-pressure contours for fingers pressing down on glass, frame by frame, during a video.
The relevant topography for a finger grip is a convex promontory where the peak is the initial point of grip contact and later regions of contact are at a lower ‘elevation’. Example of channels (light blue color refers to online version only), divides (black), and iso-elevation contours for a concave basin ( a) and a convex promontory ( b). Predicted shape of wet-induced wrinkles if they have been selected for water drainage during grip. Wilder-Smith provides evidence that the finger-wrinkling mechanism may be due to digit pulp vasoconstriction: wet-induced wrinkles are accompanied by vasoconstriction, and wrinkles are induced by vasoconstrictive agents. showed that blocking the sympathetic response, either temporarily via lumbar epidural infusion or permanently via chemical or surgical cervical sympathectomy, terminated the wet-wrinkling response. However, it has long been known that cuts to sympathetic innervation to a finger abolish the wrinkling response to wetness, which has led to suggestions to use the wrinkling response as a simple test for sympathetic integrity in unresponsive patients. 1) if soaked in water for around 5 min, and this phenomenon is commonly attributed in lay opinion to local osmotic interactions.
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