The lesions are usually limited to the extensor surfaces of the thighs and arms, especially the former. They appear as pin-head-sized, whitish or grayish elevations, consisting of accumulations of epithelial matter about the apertures of the hair follicles. Each elevation is pierced by a hair, or the hair may be twisted and imprisoned within the epithelial mass; or it may be broken off just at the point of emergence at the apex of the papule, in which event it may be seen as a dark, central speck. The skin is usually dry, rough and harsh, and in marked cases, to the hand passing over it, feels not unlike a nutmeg-grater. The disease varies in its development, in most cases being so slight as to escape attention. As a rule, it is free from itching. #What course does keratosis pilaris pursue?# It is sluggish and chronic. #Mention some of the etiological factors.# It is not an uncommon disease, and is seen usually in those who are unaccustomed to frequent bathing, being most frequently met with during the winter months. It is chiefly observed during early adult life. #Is there any difficulty in the diagnosis?# No. It is thought at times to bear some resemblance to goose-flesh (cutis anserina), the miliary papular syphiloderm in its desquamating stage, and lichen scrofulosus. In goose-flesh the elevations are evanescent and of an entirely different character; the papules of the syphiloderm are usually generalized, of a reddish color, tend to group, are more solid and deeply-seated, less scaly and are accompanied with other symptoms of syphilis; in lichen scrofulosus the papules are larger, incline to occur in groups, and appear usually upon the abdomen. #State the prognosis.# The disease yields readily to treatment. #Give the treatment of keratosis pilaris.# Frequent warm baths, with the use of a toilet soap or sapo viridis, will usually be found curative. Alkaline baths are also useful. In obstinate cases the ordinary mild ointments, glycerine, etc., are to be advised in conjunction with the baths. #Keratosis Follicularis.# #Describe keratosis follicularis.# Keratosis follicularis (_Darier's disease_, _ichthyosis follicularis_, _ichthyosis sebacea cornea_, _psorospermosis_) is a rare disease characterized by pin-head to pea-sized pointed, rounded, or irregularly-shaped grayish, brownish, red or even black, horny papules or elevations, arising from the sebaceous or hair-follicles. They are, for the most part, discrete, with a tendency here and there to form solid aggregations or areas. Many of them contain projecting cornified plugs which may be squeezed out, leaving pit-like depressions. The face, scalp, lower trunk, groins and flanks are the parts chiefly affected. The view advanced by Darier, that the malady was due to psorosperms, is now denied, the bodies thought to be such having been demonstrated to be due to cell transformation.