LOCAL AURAL TREATMENT 291 trichloracetic acid or silver nitrate may be used for this purpose. The caustic must be applied under direct vision, and confined to the required area. Anaesthesia. Should local anaesthesia of the ear be required a watery solution of cocaine hydrochloride has but little effect. Anaesthesia of the tympanic membrane may be achieved by a 10 per cent solution of cocaine hydrochloride in aniline oil, but this carries a risk of aniline poisoning. Most surgeons inject a 0-5 per cent solution of procaine, containing a few drops of a solution of adrenaline hydrochloride 1 :1000, under the skin at Fig. 161. Instruments for aural examination and treatment. the upper and posterior part of the meatus. This is done under direct vision, and some practice is required before success is achieved. Instruments. Most instruments (Fig. 161) for use in the external ear are bent at an angle of rather more than 90°, with the object of bringing the hand below the line of vision when the instrument is in use. During routine examination of the ear a pair of angled forceps should be at hand to remove shreds of epithelium or flakes of wax. There should be probes, both for carrying wool for mopping, and to be used as an aid to diagnosis. A blunt wax curette should be available. Gentleness of touch is of paramount impor- tance in using instruments in the external meatus, especially in its inner half. Children will usually permit the removal of small pieces of wax by a moist wool-tipped probe to allow inspection of the drumhead, or the gentle mop- ping of discharge from the ear.