A system of practical medicine. By American authors. Vol. 3

by Unknown

¹⁶ Loc. cit.

THE LARYNGOSCOPE.—The laryngoscope as it is used at the present day, both by the specialist and the general practitioner of medicine, consists of a so-called laryngeal mirror and of an illuminating apparatus more or less complicated. The laryngeal mirror is a small circular glass mirror mounted in a metal frame varying in size from ¾ inch to 1½ inches in diameter, and attached to a wire stem at an angle of 120°. This stem, about 4 inches in length and about ¹/10 inch in thickness, should be soldered to the back of the mirror in such a manner that the rim of the frame forms the angle with the stem, and should not be below it, as this would increase the diameter of the instrument without increasing its reflecting surface. The stem is made to slide into a hollow handle of wood, ivory, or ebonite, and is clamped at any desired length by a set-screw. This arrangement is preferable to having the stem permanently fixed in the handle, inasmuch as the stem can be pushed entirely into it, thus economizing space and rendering the instrument more portable, and also allowing an adjustment of the length of the stem when in use. The handle should be 4 inches in length, and of the thickness of an ordinary lead-pencil (Fig. 1).

FIG. 1.

Laryngeal Mirror.

Mirrors of various shapes have been used, but it has been found that the circular form is the one most easily borne by the patient, and can be used in a greater number of cases than any other shape, at the same time giving the largest reflecting surface for its size. However, in cases where an hypertrophy of the tonsils is present an oval mirror can be introduced between the protruding glands more easily than a round one.

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.

A variety of devices for fastening the reflector on the head of the observer is in use, among which the head band, introduced by Cramer, will be found the most serviceable. It consists of a broad strap of some strong material which passes around the head and is fastened at the back by a buckle. To the part of the band or strap resting on the forehead is attached a padded plate, to which the reflector is fastened with its ball-and-socket joint (Fig. 2). The reflector usually either has a small hole in the centre or a small space in the centre is left unsilvered. This opening is intended to be brought before the pupil of one or the other eye of the observer in such a manner that the line of vision and that of light have exactly the same direction. Using the reflector in this way like the reflector of the ophthalmoscope, it is easier to obtain the image of the larynx well illuminated, but with the great disadvantage of monocular vision, which makes all objects appear on the same plane and prevents a correct interpretation of distances—a very important point in laryngoscopy. It will therefore be found more advantageous to place the reflector on the forehead, and from thence reflect the light into the patient's larynx. Both eyes may thus be employed in viewing the laryngeal image, and a correct idea of the relations of parts in regard to distance may be formed.