'Lucae is of the opinion that for diagnostic purposes it is not sufficient to determine whether the drum membrane and the malleus are mobile or whether they are able to carry out a great number of vibrations which the sound-conducting apparatus has to deal with in receiving sound. As the human eye is not able to follow the extraordinarily rapid vibrations of the drum membrane, the author has employed the otostroboscope method, which apparently retards the vibrations of the drum membrane so that they become visible. The otostroboscope consists of an ordinary reflector to which a rotating disc with ten holes is applied, permitting an intermittent observation of the vibrations of the drum membrane. The spaces between the openings must be so broad that they will completely cover the mirror opening in their rotation. In the anatomically normal drum membrane the most extensive vibrations take place in the upper and posterior quadrants, as well in the slow as in the rapid vibrations up to one thousand in a minute. In one case of definite sclerosis of the normal drum membrane, vibrations which had been invisible were made apparent with this instrument. In another patient with hereditary deafness no vibrations were visible with the instrument. In a case of diplacusis which can only be the result of labyrinthine affection, fifteen hundred vibrations were detected in the drum membrane in their various phases by this aid of the otostroboscope. It is not possible from the mobility of the hammer to state what may be the function of the other ossicles.

[Signed:] Denker.' (250)