||The tympanic membrane is situated deeply within the head, at the medial end of the only skin‑lined canal in the body, the ear canal.
In order to examine the tympanic membrane it is necessary to illuminate adequately the entire recess.
This difficulty can be largely overcome if a sufficiently brilliant form of illumination is used and if the tortuous external auditory canal is straightened out to bring the tympanic membrane into view.
In the past, illumination has been traditionally provided by electric light reflected into the ear by a perforated head mirror.
This method provides coaxial illumination, which allows the examiner to look along the path of the beam of light, while freeing both of the examiner's hands to hold the aural speculum and instruments.
The tortuosity of the mobile outer cartilaginous external ear canal is straightened and the deeper bony canal and tympanic membrane are exposed by means of an aural speculum inserted into the outer external auditory canal.