At times the addition to this formula of several drachms of alcohol and of five to ten minims of glycerin is of advantage. An external remedy, often valuable, is ichthyol. It is thus prescribed:-- [Rx] Ichthyol, ............................ [dram]ss-[dram]j Cerat. simp., ........................ [dram]iv. M. The various mercurial ointments, especially one of white precipitate, five to fifteen per cent. strength, are sometimes beneficial. A compound lotion, containing mercury, which frequently proves serviceable, is:-- [Rx] Hydrarg. chlorid. corros., ........... gr. ii-viij Zinci sulphatis, ..................... gr. x-xx Tinct. benzoini, ..................... f[dram]ij Aquae, ............ q.s. ad ........... f[Oz]iv. In extremely sluggish cases the following, used cautiously, is of value:-- [Rx] Ichthyol, Saponis viridis, Sulphur, praecip., Lanolin, ............. [=a][=a] ...... [dram]j. In such instances the application of a strong alcoholic resorcin lotion, ten to twenty-five per cent. strength, repeated several times daily till marked irritation and exfoliation occur (a matter usually of one to three days), will sometimes be followed by marked improvement. Acne of the back is treated with the same applications, but usually stronger; in this region applications of Vleminckx's solution and formaldehyde solution, weakened considerably, at first at least, prove of value. _Obstinate and indurated lesions_ may be incised, the contents pressed out, and the interior touched with carbolic acid by means of a pointed stick. The _x_-ray has proved a most valuable addition to our resources in the treatment of acne, and is especially serviceable in extensive and obstinate cases. An exposure should be made about twice weekly, at a distance of five to ten inches and for from three to ten minutes, and a tube of medium vacuum used. It must be used with great caution and never beyond the production of the mildest erythema. The hair, eyes, and lips should be protected. The _x_-ray treatment is best reserved for obstinate cases, and then used mildly, and rather as an adjuvant to the ordinary methods than as the sole measure. #What precaution is to be taken in advising a change from a sulphur to a mercurial preparation or the reverse?# Several days should be allowed to intervene, otherwise a disagreeable, although temporary, staining or darkening of the skin results--from the formation of the black sulphuret of mercury. #Acne Rosacea.# #Give a descriptive definition of acne rosacea.# Acne rosacea is a chronic, hyperaemic or inflammatory disease, limited to the face, especially to the nose and cheeks, characterized by redness, dilatation and enlargement of the bloodvessels, more or less acne and hypertrophy. #Describe the symptoms of acne rosacea.#