For use in the study a paraffin reading-lamp or a gas standard is equally suitable. The latter is rendered more effective by the adoption of an Argand burner or a Welsbach mantle. The oxy-hydrogen limelight is the most perfect of artificial illuminants, but it is bulky and expensive. The most convenient light is that given by a 32 or 50 candle-power electric light in a frosted globe, and with the filament waved. The Nernst electric burner gives increased brilliancy.
The electric light has the further advantage that it is unnecessary to maintain it constantly vertical. When enclosed in a bull’s-eye, the lamp can be rotated so as to direct the pencil of light-rays either upwards or downwards, as well as from side to side.
| Fig. 281. Laryngoscope Lamp. | Fig. 282. Clar’s Electric Light. |
Whichever light is employed the rays can be concentrated and rendered more powerful by enclosing it in a dark chimney with a bull’s-eye condenser. The light must also be provided with some arrangement by which it can be raised and lowered (Fig. 281). For operating the Clar light is useful (Fig. 282).
In all these methods the light is reflected, but the direct rays of the electric light can be used in a small lamp fixed on the forehead, and fed from an accumulator or direct from the street current through a suitable resistance. It is better than reflected light in operations on the nose and throat, and the portable accumulator and frontal photophore (Fig. 283) are convenient for use in the patient’s own home.
Fig. 283. Frontal Search-light.
The lamp should be placed on a stand or table so that the light is on a level with the patient’s ear, and 3 or 4 inches distant from it. In Continental schools it is customary to place the light on the patient’s right hand. In this country the lamp is usually placed close to the patient’s left ear, i.e. on the observer’s right hand. As practitioners will often be called to see patients who are confined to a bed which can only be approached from one side, it is desirable that they should accustom themselves to work equally well with the light on either side, and the frontal mirror over either eye.