The advantages of these tubes are, the small amount of irritation they provoke, and the ready exit furnished for the matter along their interior.
Issues are a contrivance for keeping up irritation of the surface. A piece of diachylon plaster the size of a half-crown, with a hole in the centre as large as a pea, is laid over the skin where the issue is to be formed. A bit of potassa fusa is laid in the hole and kept in sitû by a second plaster, for an hour or till the skin is destroyed under the hole. The plasters are then removed, the wound washed, and a fresh piece of the same size put on, having at its centre a slit ¼ inch long, under which a pea is slipped into the sore and covered over by another smaller piece of plaster. The discharge that soon sets up must be washed away twice daily, and the plaster and pea renewed from time to time as they become soiled.
Trusses for ruptures. These are various, in shape, strength of spring, &c.
Whatever variety of truss is employed, care should be taken that the pressure is made in the right direction, and that it is sufficient, but not too great for the strain it has to support.
In reducible hernia the pressure for inguinal rupture should be exerted on the inguinal canal and directly backwards (see fig. 109). For umbilical rupture, the pressure should be also backwards, and confined as much as possible to the aperture in the wall of the belly. In femoral rupture the pressure should be directed upwards as well as backwards into the femoral ring (see fig. 110). The pad in all should be large enough to well cover the passage through which the rupture passes. The ease and comfort of a truss much depend on the completeness with which it fulfils these conditions.
Fig. 109.—Inguinal truss.
Fig. 110.—Femoral truss.
The adequacy of a truss should always be tested by directing the patient to separate his legs, lean forward over the back of a chair, and cough or strain deeply. If the truss support the rupture during this exertion it fits satisfactorily.