The human hearing organ can undergo microscopical examination in its entirety only once, and this post mortem. To observe intermediate steps of a pathological process one has to turn to animal experimentation. In aural diseases which lead unavoidably to the end, the condition in which the ears are found corresponds to an irreversible stage. An intermediary state of ear pathology is seen only when the specimen originates from a patient who died because of an extra-aural illness; otherwise intermediary stages have to be reconstructed largely by conjecture or by forming an arbitrary sequence of findings as obtained from different individuals.
Residua after a bout of otitic infection are considered as stagnant, unchanging. Yet this state is challenged by every new infection.
To gain an approach to the problem on an experimental basis one has to know that a large percentage of the current laboratory animals show spontaneous, i. e., nonexperimental