ERYTHEMA.
Definition.—Erythema as a generic name has been used to serve a complex or rather triple purpose. In itself the term simply denotes redness of the skin in which varying graduations of tint from yellowish red to violaceous red, darkish red, bluish red, or even blackish red are observed. In size it may not in volve a spot larger than a lentil, and again it may cover a limb or the greater portion of the trunk. It may assume a rounded, oval, or an irregular outline. As a significance of disease or disturb ance of the functions of the skin it im plies, on the one hand, only an hyperm mia or active inflammation. As these two forms are so likely to merge into each other, it is a difficult matter to determine just where the hypermmia ends and the inflammation begins. This is a patho logical rather than a clinical problem. Both of these forms have been usually placed in the class of inflammations, although recently Duhring, of Phila delphia, has placed the former in his class of hypermmia, referring to them as "disorders characterized by the presence of an abnormal quantity of blood in the vessels supplying the skin, without the presence of inflammation." In this class
is included erythema hyper2emium, or simplex, and in the class caused by actual inflammation is included ery thema exudativum, under which titles we will discuss them.
Simple Erythema.—In this form there is a discoloration of the skin, vary ing in tint, size, and shape, and due to an abnormal flux of blood to the tissues without the presence of inflammation.
SYMPTOMS.—The affection is tran sient, the coloring fading under pres sure, and is caused by numerous internal and external agencies. It is instanced by the abnormal flushings and blushings which are the expression of the varied feelings, such as anger, joy, and shame; it is also produced by disturbances of digestion due to indigestible foods, alco hol, drugs, or by various external in juries, as, for instance, the action of heat or cold, poisonous plants or drugs, or traumatism. The lesions produced vary from the slightest tint of red to a very dark color, and vary in shape from a round or oval to an irregular patch.