This laryngeal mirror, however, would be of little or no value as an instrument of diagnosis if used by itself, for in order to see the cavity of the larynx it must be illuminated, lying as it does far below the level of the back of the tongue; and this cannot be done satisfactorily by merely allowing ordinary daylight to fall into the oral cavity. It becomes, therefore, necessary to use a stronger light to illuminate the larynx, and for this purpose either direct or reflected artificial or sunlight may be used. Direct illumination, by allowing a strong artificial light or sunlight to fall into the patient's mouth, although it is used by several of the eminent laryngologists of Europe, is both inconvenient and unsatisfactory, because the observer must either place his head in the path of the light in order to be able to see the surface of the laryngeal mirror, as in the case when sunlight is used, or he must place the lamp, candle, or other source of light between himself and the patient, which materially interferes with the freedom of his motions. For these reasons reflected light is now almost universally employed in laryngoscopy. Reflected light may be obtained by throwing the light of a lamp, candle, gas-jet, or light from any other source into the mouth of the patient by means of a round concave reflector. This concave mirror--which, when made of glass, should be silvered and not backed with amalgam--is from 3 to 4 inches in diameter, and should have a focus of from 12 to 14 inches. The metal frame in which it is mounted is attached by means of a ball-and-socket joint to some contrivance by which it can be supported on the observer's head or be attached to the source of illumination if a stationary artificial light, such as a gas-lamp, is used at the physician's office.