Essentially chronic. The individual lesions usually run their course in several days or one or two weeks, but new lesions continue to appear from time to time, and the disease thus persists, with more or less variation, for months or years. In many cases there is, toward the age of twenty-five or thirty, a tendency to spontaneous disappearance of the disease. [Illustration: Acne.] #Is the eruption in acne usually abundant?# It varies in different cases and at different periods in the same case. In some instances, not more than five or ten papules and pustules are present at one time; in others they may be numerous. Not infrequently several lesions make their appearance, gradually run their course, and the face continues free for days or one or two weeks. #Does the eruption in acne disappear without leaving a trace?# In many instances no permanent trace remains, but in others slight or conspicuous scarring is left to mark the site of the lesions. #Are there any subjective symptoms in acne?# As a rule, not; but markedly inflammatory lesions are painful. #State the immediate or direct cause of an acne lesion.# Hypersecretion or retention of sebaceous matter. Recent investigations point to the possibility of a special bacillus being the exciting cause, in some instances at least. The pyogenic cocci are added factors in the pustular and furuncular cases. #Name the indirect or predisposing causes of acne.# Digestive disturbance, constipation, menstrual irregularities, chlorosis, general debility, lack of tone in the muscular fibres of the skin, scrofulosis; and medicinal substances such as the iodides and bromides internally, and tar externally. Working in a dusty or dirty atmosphere is often influential, resulting in a blocking-up of the gland ducts. Workmen in paraffin oils or other petroleum products often present a furuncle-like acne. The disease is more common in individuals of light complexion. #Is there any difficulty in the diagnosis of acne?# Not if it be remembered that acne eruption is limited to certain parts and is always follicular, and that the several stages, from the comedo to the matured lesion, are usually to be seen in the individual case. #In what respect does the pustular syphiloderm differ from acne?# By its general distribution, the longer duration of the individual lesions, the darker color, and the presence of concomitant symptoms of syphilis. #What is the pathology of acne?# Primarily, acne is a folliculitis, due to retention or decomposition of the sebaceous secretion or to the introduction of a micro-organism; subsequently, the tissue immediately surrounding becoming involved, with the possible destruction of the sebaceous follicle as a result. The degree of inflammatory action determines the character of the lesions. #State the prognosis of acne.#