Other valuable applications are: lotions of carbolic acid, of liquor carbonis detergens, of boric acid; alkaline baths, mild sulphur ointment and carbolized oxide-of-zinc ointment, and dusting-powders of starch, zinc oxide, talc and boric acid. A two- to ten-per-cent. ichthyol lotion or ointment is sometimes of advantage; thiol employed in the same manner has also been commended. #Psoriasis.# #Give a definition of psoriasis.# Psoriasis is a chronic, inflammatory disease, characterized by dry, reddish, variously-sized, rounded, sharply-defined, more or less infiltrated, scaly patches. [Illustration: Psoriasis.] #At what age does psoriasis usually first make its appearance?# Most commonly between the ages of fifteen and thirty. It is rarely seen before the tenth year, and a first attack is uncommon after the age of forty. #Has psoriasis any special parts of predilection?# The extensor surfaces of the limbs, especially the elbows and knees, are favorite localities, and even when the eruption is more or less general, these regions are usually most conspicuously involved. The face often escapes, and the palms and soles, likewise the nails, are rarely involved. In exceptional instances, the eruption is limited almost exclusively to the scalp. #Are there any constitutional or subjective symptoms in psoriasis?# There is no systemic disturbance; but a variable amount of itching may be present, although, as a rule, it is not a troublesome symptom. #Describe the clinical appearances of a typical, well developed case.# Twenty or a hundred or more lesions, varying in size from a pin-head to a silver dollar, are usually present. They are sharply defined against the sound skin, are reddish, slightly elevated and infiltrated, and more or less abundantly covered with whitish, grayish or mother-of-pearl colored scales. The patches are usually scattered over the general surface, but are frequently more numerous on the extensor surfaces of the arms and legs, especially about the elbows and knees. Several closely-lying lesions may coalesce and a large, irregular patch be formed; some of the patches, also, may be more or less circinate, the central portion having, in a measure or completely, disappeared. #Give the development and history of a single lesion.# Every single patch of psoriasis begins as a pin-point or pin-head-sized, hyperaemic, scaly, slightly-elevated lesion; it increases gradually, and in the course of several days or weeks usually reaches the size of a dime or larger, and then may remain stationary; or involution begins to take place, usually by a disappearance, partially or completely, of the central portion, and finally of the whole patch. #Describe the so-called clinical varieties of psoriasis.#