In writing this paper, I have had several objects in view. The first object is to place the so-called "chronic mastitis" in its correct etiologic and pathologic position. Its morphologic appearances are identical with those of the physiologic active state at birth, at puberty and in certain phases of lactation (fig. 1). This active state becomes pathologic (fig. 2) when it is present at from about 30 to 45 years of age and induces diffuse pain, and when fibro-adenomas (usually of the same type as those which form at puberty) develop in its occupied areas (figs. 3 and 4). These two separate occurrences belong to the condition to which the term "chronic mastitis" is so universally applied.
A second object is to point out that the commonest type (fig. 6) of fibro-adenoma that occurs at puberty is a local exaggeration of the physiologic and active hyperplasias which are normal at