Chrysarobin, pyrogallol, tar, ammoniated mercury, [beta]-naphthol, and resorcin. #Are these several external remedies equally serviceable in all cases?# No. Their action differs slightly or greatly according to the case and individual. A change from one to another is often necessary. #In what forms and strength are these remedies to be applied?# _Chrysarobin_ is applied in several ways: as an ointment, twenty to sixty grains to the ounce, rubbed in once or twice daily; this is the most rapid but least cleanly and eligible method. As a pigment, or paint, as in the following:-- [Rx] Chrysarobini, ........................ [dram]j Acidi salicylici, .................... gr. xx Etheris, ............................. f[dram]j Ol. ricini, .......................... [minim]x Collodii, ............................ f[dram]vij. M. Or it may be used in liquor gutta-perchae (traumaticin), a drachm to the ounce. It may also be employed in chloroform, a drachm to the ounce; this is painted on, the chloroform evaporating, leaving a thin film of chrysarobin; over this is painted flexible collodion. If the patches are few and large, chrysarobin rubber-plaster may be used. Chrysarobin is usually rapid in its effect, but it has certain disadvantages; it may cause an inflammation of the surrounding skin, and, if used near the eyes, may give rise to conjunctivitis. As a rule, it should not be employed about the head. Moreover, it stains the linen permanently and the skin temporarily. _Pyrogallol_ is valuable, and is employed in the same manner and strength as chrysarobin. In collodion it should at first not be used of greater strength than three to four per cent., as in this form pyrogallol sometimes acts with unexpected energy. It is less rapid than chrysarobin, but it rarely inflames the surrounding integument. It stains the linen a light brown, however, and is not to be used over an extensive surface for fear of absorption and toxic effect. Oxidized pyrogallic acid, a somewhat milder drug in its effect, has been highly commended, and has the alleged advantage of being free from toxic action.