In an earlier paper on this subject,1we advanced a new method of production of wheals for the study of experimental urticaria. Previously, wheals had been produced only by the direct application of various agents to and into the skin. We, however, devised a method, based on an immunologic principle, by which wheals could be produced on the skin of almost any person through internal channels. It was shown that the injection of the serums of patients hypersensitive to certain food into the skin of a subject sensitized that site to the same food (Prausnitz and Küstner2), and that if the subject was fed the specific offending food, a wheal could be elicited at the passively sensitized site. One of us (M. W.) has taken advantage of this technic, employing it as a means of demonstrating the absorption of certain undigested proteins from the gastro-intestinal tract. This has