Anaesthetics are medicinal agents which diminish sensibility and relieve pain. They are generally in the form of vapors or gases, applied by inhalation, and possess the power of temporarily suspending the general sensibility, being commonly employed for the prevention of pain during surgical operations. They are divided into general and local anaesthetics.

General anaesthetics are agents capable of producing complete insensibility throughout the whole system. Included in this class are such agents as ether, chloroform, nitrous oxide gas, bromide of ethyl, bichloride of methylene, tetrachloride of carbon, bichloride of ethidene, bromoform, iodide of ethyl, tetrachloride of carbon, trichlorhydrin, etc., etc.

Local anaesthetics are agents whose action is limited to a certain part or organ, when topically applied, paralyzing the nerves of the part, and temporarily destroying the sensibility. Included in this class are such agents as absolute ether, rhigolene, aconite, pyrethrum, atropine, cocaine, etc., etc.