The most recently stated indications for opening the mastoid process are: 1. Purulent inflammation in the mastoid process appearing in the course of suppuration of the middle ear when persistent severe pain in the bone cannot be subdued by the application of the ice-bag, leeches, or by Wilds' incision. (Schwartz). 2. Painful inflammation in the mastoid process occurring in acute and chronic suppuration of the middle ear, in consequence of growths filling up the external meatus or the tympanic cavity. When attempts to remove the obstacle to the free escape of pus have failed, the operation is imperative. (Grüning). The operation is indicated even though the soft parts over the mastoid are not swollen or infiltrated. (Politzer). 3. When the posterior superior wall of the meatus is bulging, and when after incision the abscess is not emptied and the symptoms of retention of pus continue. (Toynbee, Duplay). 4. Persistent pain and tenderness in the mastoid process lasting for days or weeks, in which there is probably an osseous abscess not communicating with the tympanic cavity. (Politzer). 5. In every suppuration of the middle ear combined with inflammation of the mastoid process in which fever, vertigo and headache are developed during the course of the affection, which may indicate a dangerous complication. In such cases the indication for the operation is vital. (Politzer, Roosa, Buck.) As to the time when the operation should be performed, writers do not agree. While one proposes that the operation should be done as soon as there are symptoms of inflammation of the mastoid process, another defers it till the dangerous symptoms (fever, headache, vertigo, etc.,) set in. The latter proposal must not be followed, as in many cases it would be too late; on the other hand, many cases will recover without an operation. As far as it can be formulated, I would say that in a given case of acute purulent inflammation of the mastoid process I would first apply leeches, poultices, cathartics, antiflogistics. If the inflammation is not promptly subdued, I would make a Wilds' incision, including the periosteum, if the bone is found softened; or if a fistulous opening is found, this should be enlarged at once. If the bone is found healthy and not roughened, if there is no fever, vertigo, headache, etc., I would wait a few days; if the symptoms, pain, tenderness, etc., do not subside, I would then perforate the mastoid process.