As an idiopathic disease it is rare, consisting simply of a brittleness and an uneven and irregular formation of the hair-shaft, with a tendency to split up into filaments (_fragilitas crinium_); or there may be localized swelling and bursting of the hair-shaft, the nodes thus produced having a shining, semi-transparent appearance (_trichorrhexis nodosa_). This latter usually occurs upon the beard and moustache. #State the causes of atrophy of the hair.# The causes of the symptomatic variety are usually evident; the etiology of idiopathic atrophy is obscure, but by many is thought due to parasitism. [Illustration: Fig. 39. Trichorrhexis Nodosa. (_After Michelson._)] #What would be your prognosis and treatment in atrophy of the hair?# Symptomatic atrophy usually responds to proper measures, but always slowly; treatment is based upon the etiological factors. For the idiopathic disease little, as a rule, can be done; repeated shaving or cutting the hair has, in exceptional instances, been followed by favorable results. #Atrophia Unguis.# (_Synonyms:_ Atrophy of the Nails; Onychatrophia.) #Describe atrophy of the nails.# The nails are soft, thin and brittle, splitting easily, and are often opaque and lustreless, and may have a worm-eaten appearance. Several or more are usually affected. #State the causes of atrophy of the nails.# The condition may be congenital or acquired, usually the latter. It may result from trauma, or be produced by certain cutaneous diseases, notably eczema and psoriasis; or it may follow injuries or diseases of the nerves. Syphilis and chronic wasting constitutional diseases may also interfere with the normal growth of the nail-substance, producing varying degrees of atrophy. The fungi of tinea trichophytina and tinea favosa at times invade these structures and lead to more or less complete disintegration--_onychomycosis_. [Illustration: Fig. 40. Atrophy of the Nails.] #What is the treatment of atrophy of the nails?# Treatment will depend upon the cause. When it is due to eczema or psoriasis, appropriate constitutional and local remedies should be prescribed. If it is the result of syphilis, mercury and potassium iodide are to be advised. In onychomycosis--an exceedingly obstinate affection--the nails should be kept closely cut and pared, and a one- to five-grain solution of corrosive sublimate applied several times a day; a lotion of sodium hyposulphite, a drachm to the ounce, is also a valuable and safe application. #Atrophia Cutis.# (_Synonyms:_ Atrophoderma; Atrophy of the Skin.) #What do you understand by atrophy of the skin?# By atrophy of the skin is meant an idiopathic or symptomatic wasting or degeneration of its component elements. #State the several conditions met with.#