Abstract
FIFTY years have gone by since the term allergy was first used by Pirquet,1 whose original observations entitle him to be regarded as the father of that branch of medicine. During that half century much has happened. The term allergy, sometimes used in a broader sense to include altered reactions of any kind,2 is generally restricted to a group of immunologic reactions exhibited by certain individuals that differ in kind or in degree from those of the species as a whole. Interest in these phenomena has been increasing rapidly in the more "developed" parts of the world. As the more . . .