This section is from the book "A Text-Book Of Pharmacology, Therapeutics And Materia Medica", by T. Lauder Brunton. Also available from Amazon: A text-book of pharmacology, therapeutics and materia medica.
This method consists in applying the drug to the skin previously denuded of its epidermis or epithelial layer by blistering. The drug may be applied in the form of powder, solution, ointment, liniment, or plaster, but most frequently in the form of powder. The drug is more readily absorbed when applied in this manner than when applied over the epidermis. Cantharides may be used for the purpose of raising a blister, but a more convenient method is to fill a thimble with cotton-wool or lint soaked in the strongest liquor ammoniae, apply it to the spot and keep it on for five minutes. If the cuticle has not then risen in a blister apply a poultice until it rises. Cut off the cuticle, place the powder on the denuded surface, and cover it with a piece of oil-silk fixed in position by two pieces of strapping crossed over it. This method was chiefly employed for the local application of morphine. It has now been almost entirely superseded by the hypodermic method, but may still be occasionally employed in cases where it is advisable to combine the counter-irritant action of the blister with the local sedative effect of the morphine.