A series of studies has been made at the Mayo Clinic on vascular reactions seen in chronically inflamed skin. The studies reported in this paper were concerned with mechanical cutaneous stimulation and with inhibition of white dermographism. Mechanical Stimuli to the Skin A white reaction, or pallor, may occur when a blunt point is stroked with light pressure across normal skin. Blood is displaced temporarily from the superficial vessels of the skin, but the stroked portion becomes paler than the surrounding skin within 10 to 15 seconds. This zone of paleness, limited strictly to the sites of mechanical stimulation, suggested to Lewis1and to Müller2that this change was caused by contraction of the vessels responsible for cutaneous color and not to the passive contraction of arterioles that supply zones of skin more than a square millimeter or so in extent. Lewis