The interesting succession of colors which characterizes dermographism has been studied by Jankowsy, Lapinsky and others. It is well known that the lesions not only undergo alternations of pallor and redness, but that two or more zones of alternating pallor and redness may be observed simultaneously. A case of Raynaud's disease, presenting similar zones and undergoing similar alternations of color, suggested that these changes might be of fundamental importance and widespread occurrence. The following series of experiments was accordingly planned, with a view to ascertaining whether the zones of pallor and redness, or the occurrence of pallor followed by redness, were also characteristic of lesions produced by various other irritants.
The irritants used were mechanical, thermal, chemical and electric. Mechanical irritation or injury was provoked by stroking the skin with a blunt object, such as a toothpick; by scratching the skin with a needle; and by pinching a bit of