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In making patch tests with solutions or powders, the use of small pyrex cups has proved to be satisfactory.
The cups, made from 1 mm. pyrex, measure 15 mm. in diameter by 5 mm. deep. The ground rim should be fire glazed so as not to cut the skin. The cups are held in firm contact with the skin by means of elastic adhesive tape, which may be perforated to show the contents of the cup. A moderately firm 10 mm. ball of cotton is moistened with the test solution, or impregnated by being rolled in the powdered test material, and put in the pyrex cup.
The advantages of this method over the customary formation of a flat transparent "window" are as follows: 1. The test is confined to a small sharply defined area. 2. Any type of solvent indicated may be used. 3. The solvent is better retained in