UNTIL recent years, surgery was frequently accompanied with considerable discomfort and misery. Developments in the field of anesthesia have decreased these reactions appreciably. There still remains, however, the problem of postoperative pain. Parenteral administration of narcotic drugs, at present, is the principal method of solution of this problem. Side-reactions of these drugs, such as nausea, emesis, bowel distention, respiratory depression, suppression of the cough reflex, mental disorientation, vasomotor hypotension, and allergic manifestations, have led those investigators interested in this problem into the field of long-lasting local anesthetic agents. These investigations have proceeded along two main lines. The first attempts sought agents which, in themselves, produced prolonged anesthesia. Such drugs as absolute ethyl alcohol, benzyl alcohol, quinine salts, and compounds of the insoluble aminobenzoate series proved to have too great a local or systemic toxicity. The other method of prolonging local anesthetic action was the addition of a substance that would