During an operation on the mastoid, especially during a radical operation, it is a not uncommon occurrence for the operator to observe a piece of tissue which resembles nerve tissue. If this is near the path of the facial nerve the usual procedure is to ask the anesthetist to watch the face while some instrument is used to traumatize the tissue. If the tissue is the facial nerve, the trauma of pinching it will produce a twitching of the face provided the patient is under light anesthesia. Often there is a small nubbin of infected tissue near the region where the facial nerve is known to lie, and the operator removes this with considerable trepidation for fear that the facial nerve may be traumatized.
How much better it would be to apply a faradic current to all pieces of tissue about which one is in doubt and to explore with