Phlegmona diffusa is a more or less extensive inflammation of the cutaneous and subcutaneous tissues presenting symptoms partaking of the nature of both deep erysipelas and flat carbuncles, and usually attended with varying constitutional disturbance. Suppuration at several points takes place, and sloughing may ensue. Recovery usually finally results, but a fatal issue is possible. Treatment is based upon general principles. #Furunculus.# (_Synonyms:_ Furuncle; Boil.) #Define furunculus.# Furunculus, or boil, is an acute, deep-seated, inflammatory, circumscribed, rounded or more or less acuminated, firm, painful formation, usually terminating in central suppuration. #Describe the symptoms and course.# A boil begins as a small, rounded or imperfectly defined reddish spot, or as a small, superficial pustule; it increases in size, and when well advanced appears as a pea or cherry-sized, circumscribed, reddish elevation, with more or less surrounding hyperaemia and swelling; it is painful and tender, and ends, in the course of several days or a week, in the formation of a central slough or "_core_," which finally involves the central overlying skin (_pointing_). One or several may be present, gradually maturing and disappearing. Insignificant scarring may remain. In some cases sympathetic constitutional disturbance is noticed. #What is a blind boil?# A sluggish boil exhibiting little, if any, tendency to point or break. #What is furunculosis?# Furunculosis is that condition in which boils, singly or in crops, continue to appear, irregularly, for weeks or months. #State the etiology of furuncle.# A depraved state of the general health is often to be considered as a predisposing factor. Persistent furunculosis is not infrequent in diabetes mellitus. The immediate exciting cause is the entrance into the follicle of a microbe, the staphylococcus pyogenes aureus. It is not improbable, however, that boils may also be due to other pus-producing organisms. Workmen in paraffin oils or other petroleum products often present numerous furuncles and cutaneous abscesses. Conditions favoring a persistent miliaria have also a causative influence, especially observed in infants and young children. In these latter, especially among the poorer classes, sluggish boils or subcutaneous abscesses about the scalp in hot weather, are not at all infrequent. #What is the pathology of furuncle?# A boil is an inflammatory formation having its starting point in a sebaceous-gland, sweat-gland, or hair-follicle. The core, or central slough, is composed of pus and of the tissue of the gland in which it had its origin. #How would you distinguish a boil from a carbuncle?# A boil is comparatively small, rounded or acuminate, and has but one point of suppuration; a carbuncle is large, flattened, intensely painful, often with grave systemic disturbance, and has, moreover, several centres of suppuration.