Seton, in Surgery, is an artificially produced sinus or channel, through which some substance—e.g. a skein of cotton or silk, or a long flat piece of india-rubber or gutta-percha—is passed so as to excite suppuration, and to keep the artificially formed openings patent. (The term is, however, very often employed to designate the inserted material.) Setons are established in the subcutaneous tissue of the body (1) as counter-irritants, or (2) to act as a drain on the system at large. For the purposes of counter-irritation setons are usually inserted in the neighbourhood of the affected parts; but when intended to act as a drain on the system at large—e.g. in threatened head-affections—the nape of the neck is the part always selected. The operation is very simple. A longitudinal fold of skin over the spines of the cervical vertebrae is raised by the fingers from the deeper structures, and is transfixed by the seton-needle rather obliquely, so that one of the openings shall be rather more dependent than the other. The needle must pass somewhat deeply through the subcutaneous tissue, as if it passed immediately beneath the skin the latter would probably slough over the whole track of the wound. The inserted material should be smeared with oil, and may be allowed to remain undisturbed for four or five days, till there is a free discharge of matter, after which a fresh portion should be drawn daily through the wound. The word seton is derived from the Latin seta, 'a hair,' because hairs were originally employed as the inserted material. Indeed at the present day it is the custom of many of the nomadic tribes of central Asia to insert a hair into the heels of their prisoners, which lames them to such an extent as to prevent their escape.
Sette Comuni. See VICENZA.