Instead of presenting as described, it may occur as one or more pea- or finger-nail-sized, rounded and elevated, usually firm, discrete pustules, scattered over one part, or more commonly over various regions, such as the face, hands, feet and lower extremities. The pustules are such from the beginning, and when developed are usually of the size of a pea or finger-nail, elevated, semi-globular or rounded, with somewhat thick and tough walls, and of a whitish or yellowish color; at first there may be a slight inflammatory areola, but as the lesion matures this almost, if not entirely, disappears. The pustules show no disposition to umbilication, rupture or coalescence; drying in the course of several days or a week to yellowish or brownish crusts, which soon drop off, leaving no permanent trace. This variety was formerly thought to be a distinct disease, and was described under the name of _impetigo simplex_. As a rule there are no constitutional symptoms, but in the more severe cases the eruption may be preceded by febrile disturbance and malaise. Itching may or may not be present. #State the cause of the disease.# It is contagious, the contents of the lesions being inoculable and auto-inoculable. At times it seems to prevail in epidemic form. Pyogenic microorganisms are now regarded as causative. A relationship to vaccination has been alleged by some observers. It is more commonly observed in infants and young children. #From what diseases is impetigo contagiosa to be differentiated?# From eczema, pemphigus, and ecthyma. #How does impetigo contagiosa differ from these several diseases?# By the character of the lesions, their growth, their superficial nature, their course, the absence of an inflammatory base and areola, the thin, yellowish, wafer-like crusts, and usually a history of contagion. #State the prognosis.# The effect of treatment is usually prompt. The disease, indeed, tends to spontaneous disappearance in two to four weeks; in exceptional instances, more especially in those cases in which itching is present, the excoriations or scratch-marks become inoculated, and in this way it may persist several weeks. #What is the treatment of impetigo contagiosa?# Treatment consists in the destruction of the auto-inoculable properties of the contents of the lesions; this is effected by removing the crusts by means of warm water-and-soap washings, and subsequently rubbing in an ointment of ammoniated mercury, ten to twenty grains to the ounce. Some cases respond more rapidly to the use of a drying ointment, such as Lassar's paste, with ten to twenty grains of white precipitate or sulphur to the ounce. In itching cases, a saturated solution of boric acid, or a carbolic-acid lotion, one to two drachms to the pint, is to be employed for general application. #Impetigo Herpetiformis.# #Describe impetigo herpetiformis.#