Tinnitus is a pathologic symptom. The quantitative study of it seems never to have been carried to a point of utility in diagnosis, or of fitting in with any quantitative theory of hearing. Tinnitus is described as being broadly of two kinds: the external, which originates in the middle ear and is due to mechanical causes resulting in actual sound such as the spasmodic contraction of the tensor muscles, and the internal tinnitus, which has associated with it no sound, but originates in the labyrinth as a result of some disturbance of the metabolic equilibrium of the nerves or their associated apparatus. I am under the impression that the presence of tinnitus of either kind generally indicates an active or progressive lesion, and that a cessation of it, perhaps as a result of treatment, is an indication that the progress of the degeneration or atrophy of tissue has been arrested.