=When middle-ear suppuration is present.= _In acute middle-ear suppuration_ the chief difficulty is to decide what operation to perform. As operation is only indicated if there is retention of pus, it is wiser to open the mastoid antrum; the exostosis, if superficial and pedunculated, can also be removed at the same time. If, however, the obstruction is due to multiple and deeply placed exostoses, this part of the operation should be deferred to a later date, that is, after the acute symptoms have subsided. _In chronic middle-ear suppuration_ the only operation to be recommended is the complete mastoid operation (see p. 392). =After-treatment.= The after-treatment is practically the same whatever operation has been performed. The first dressing need not be done until the third day. The gauze plugging is then withdrawn and the auditory canal is syringed out and dried. If only a single exostosis has been removed the wound surface is small, and it is usually sufficient to puff in some boracic powder and again insert a piece of gauze. This may be repeated every second day, healing usually taking place within two or three weeks. In the case of deeply situated multiple exostoses, especially if removed from the anterior wall, considerable swelling of the soft parts lining the auditory canal may occur as a result of the manipulations. In such cases, after syringing out any existing blood-clots, some cocaine and adrenalin solution should be instilled into the meatus. An aural speculum is then gradually worked into the auditory canal, which is gently mopped out with small pledgets of cotton-wool, and the deeper parts are carefully inspected. Sometimes the torn ends of the fibrous portion, instead of covering the bony walls, are found to project into the auditory canal and to cause considerable narrowing of its lumen. By careful manipulations with the probe or by stroking the edges with tiny pledgets of cotton-wool, these rough surfaces may be smoothed down. It is very important, in the early days of the after-treatment, to prevent any narrowing at the site of the operation. This is one of the chief causes of subsequent failure. The gauze should always be reinserted right down to the tympanic membrane, and if there is not much secretion it should be packed firmly against the posterior and outer portion of the canal in order to prevent subsequent stenosis from the tendency of the cartilage to prolapse forward owing to the soft parts having been separated from the bony canal at the time of the operation.