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CLINICAL EXAMINATION                             283

downwards and backwards. In a considerable proportion of cases these
manipulations permit of an inspection of the drumhead without the use of a
speculum, unless vibrissae interfere with the view or the outer end of the
meatus is slit-like. The speculum should have a wide mouth and an oval or
circular end, and there should be three or four different sizes to suit all ages.
The auricle is held up by the middle and ring fingers as the speculum, held by
the thumb and index finger, is gently inserted into the meatus {Fig. 155).
Obstructing vibrissae may be passed by a rotary movement of the speculum,
but the instrument must not be inserted far enough to come in contact with
the bony meatus as this part of the canal is exceedingly sensitive.

The electric auriscope, or otoscope, is more frequently employed in general
practice. There are many patterns on the market. It is wise to select one which
gives a good light directed through the tip of the speculum and not falling on
one of the walls. There should be four or five specula of different sizes, and
especially one small enough for use in infants. Some auriscopes have closed
h eadswhile others have open heads to allow the passage of wool mops or wax
curettes, but the latter are generally used by specialists. Many have a fixed
focus, and this may mean that the definition of the tympanic membrane is not
always satisfactory. Others have an adjustable focus. Magnification is usually
x 2, but it is possible to acquire one with a magnification of x 3, or even x 6
although this is too great for general use. Some patterns have an attachment
for a rubber bulb, thus adapting the instrument for use as a pneumatic
speculum {Fig. 156), but frequently the rubber tube or the cement in the eye-
piece becomes loose in time, and the advantage is lost.

On looking into the meatus, the skin of the posterior inferior meatal canal
will probably meet the eye first. The tip of the speculum must be pointed
upwards and inwards to display the membrane. In health, the drumhead
presents a highly polished grey surface (Plate X, 1) of which the posterior and
upper part is distinctly nearer the eye than the anterior and inferior. The
colour alone is not sufficient for recognition of the membrane; the handle of
the malleus must also be seen. At the upper end of the handle the short process
is noted as a small projection, and running backwards and downwards from
this the handle of the malleus appears as a whitish-yellow streak ending at a
point (the umbo) below the centre of the membrane.

For purposes of description the membrane is divided into four quadrants by
imaginary lines, one drawn horizontally through the umbo while the other
bisects this line at right angles (Fig. 157). Extending downwards and forwards
from the umbo the cone-shaped light reflex is seen. This is fairly constant in
position as the anterior inferior quadrant of the membrane is the only part
that is approximately at right angles to the meatus, and therefore in a position
to reflect the light from the mirror. The reflex may be absent owing to loss of
gloss, or it may be altered in position by changes in the curvature of the
drumhead. In front of and behind the short process two folds are seen on the
membrane. These are called the anterior and the posterior malleolar folds.
They are only very slightly marked in the normal drumhead, but become
exaggerated in cases of indrawing (Plate X, 2). Above the short process the
membrana flaccida, or ShrapnelFs membrane, fills the gap in the tympanic
ring known as the notch of Rivinus. As its name implies, this part of the
drumhead is less taut than the part inferior to the malleolar folds, called the
membrana tensa.