Pure carbolic acid forms long, colourless, prismatic needles, which melt at 35° C. into an oily liquid. It boils at 180° C., and greatly resembles creosote, for which it is very frequently substituted in commerce, but from which it differs in the following characters: It does not affect polarised light as creosote does; it forms a jelly-like mass with collodion, and is soluble in a solution of potash, whereas creosote is unaffected by collodion, and is insoluble in a solution of potash. It possesses a penetrating, characteristic odour; burning taste; is slightly soluble in water, but freely so in glycerine, ether, and alcohol; and gives no acid reaction to test paper. When undiluted, it attacks the skin, which it shrivels up. Creosote is obtained from wood-tar, which imparts to it its caustic properties. Carbolic acid acts as a corrosive and anæsthetic on the skin and mucous membranes, and as a narcotic on the brain. Its poisonous properties are exerted whether it be swallowed or merely applied to the skin, especially if a wound be present. _Effects on the Skin, &c._--Strong carbolic acid, when applied to the skin, corrugates, hardens, and destroys its sensibility, and is said to whiten it; though in one case, in which the crude acid had been taken with a suicidal intent, there was after death a dark brownish ring about half an inch wide surrounding the mouth; and in another, that of a child who, in climbing to a shelf, poured over its face and neck about half a saucerful of diluted acid, the colour of the skin touched by the acid was yellowish-white and yellowish-brown, dry and parchment-like. The action of the acid on the mucous membranes is similar to that on the skin, but the corrugation is more marked, and considerable softening and peeling may also take place. _Effects on the Nervous System._--Rapidly supervening stupor, total muscular relaxation, anæsthesia, and stertorous breathing are among the most prominent symptoms. Nearly all the sufferers die comatose. Carbolic acid appears to act principally on the central nervous ganglia at the base of the brain and on the spinal cord. The evidence is more in favour of its action on the brain than on the spinal cord, and not at all on the periphery of the nerves. The muscles contract vigorously after death, in response to galvanic stimulation applied either to the nerves or to the muscles themselves. _Effects on the Circulation._--The action of carbolic acid on the circulation has not yet been fully worked out, but it appears to be a cardiac depressant, the heart being arrested in diastole.