Most otologists believe that there is a standard, or normal bone conduction; that is to say, that any certain tuning fork should be heard when its stem is pressed against any part of the head for a length of time which, for clinical purposes, is constant enough to make it possible to fix a standard for any particular fork that, within reasonable limits, will not vary greatly in any number of normal persons. On this assumption, many tests of hearing by bone conduction have become established, several of which have been universally accepted and used for years in all routine examinations of the ear. It has never been definitely determined, however, whether hearing by bone conduction is, as taught by Bezold, simply the perception of those sound waves which, on their way to the labyrinth, have passed through the sound conduction apparatus; or whether, as argued by Wittmaack and