Though differing much in power, most of these acids act in a similar manner as escharotics. They rapidly destroy the cuticle, and then act with great energy on the parts beneath, decomposing them through chemical affinities for their constituents, and quickly producing extensive sloughs, if allowed to continue in contact with the flesh. in consequence of their liquid form, their action cannot be so easily limited as that of the solid escharotics; and the extent of their effects cannot be so well estimated. They are, therefore, comparatively little used; but, from the rapidity of their action, they are occasionally resorted to in urgent cases, especially when it is desirable to denude an extensive surface of the cuticle.

In violent stomachic affections, in which life is in imminent danger, one of these acids may be applied to the epigastrium, so as to separate the epidermis. Great caution is necessary not to allow their action to proceed too far, and, as soon as the desired effect is produced, to neutralize the remaining acid, by washing the surface over with a weak solution of one of the alkaline carbonates. The denuded surface may then be dressed with either simple cerate or resin cerate, according as it may be desirable to promote healing, or to sustain inflammation. in consequence of the powerful chemical action of the acids on organic, and on many mineral substances, it is somewhat difficult to apply them neatly. A sort of brush, however, for the purpose may be made by wrapping old linen around the end of a stick, securing it with a string, and ravelling the projecting border. Recently glass brushes have been introduced into use, and are admirably adapted to the purpose of apply ing liquid caustics. They may be made very small, so as to confine the application to a point, or in various degrees larger, so as to spread it more rapidly over broad surfaces.