The phenomenon of wheal formation (urticaria) of the skin is dependent on certain vascular phenomena, namely, dilation of the vessels and increased permeability of vessel walls, resulting in localized edema of the skin. As it has been observed that wheal formation is modified in a measureable degree in cardiac edema,1 it seemed advisable to study it in other conditions. It was hoped in this manner to obtain information as to the condition of the skin vessels, especially in relation to their permeability, in such abnormal conditions. Other methods have been used to determine vascular permeability:2 1. The distribution into the tissue of dyes injected into the blood stream. 2. Changes in the blood concentration under varying conditions. 3. The injection of fluids into the tissues and later withdrawing them and determining the changes that had taken place. 4. The determination of the blistering time of the skin.Because of its simplicity and rapidity of action, the wheal method was used in this investigation in a large number of infants and children, including normal children and those showing a variety of pathologic conditions.As it is well known, wheals are produced by a large number of unrelated substances, notably histamin, members of the morphin group and proteins, the latter at times being specific. Familiarity with the use of the morphin group in a previous work 1 led to the choosing of codein (whose action is identical with morphin) as the whealing agent. The quantity of the drug injected at any time was too small to produce symptoms or signs of systemic action.Description of the Codein Reaction.-Shortly after the intradermal injection of 0.15 c. c. of a 1 :1,000 codein solution, a flush appears, which
