{26} POSITION OF PATIENT AND OBSERVER.--The relative positions of the patient, observer, and the source of light are of very great importance, especially to the beginner, and a want of proper adjustment will often make it extremely difficult, if not impossible, to obtain the desired view of the larynx. The patient having been seated upon a chair, or better still upon a piano-stool, the source of light is placed upon a table at his right, at such a height that the centre of the flame is on a level with his eyes and a few inches behind. The observer then takes a seat directly in front of the patient, and, separating his knees, places his feet on either side of those of the patient, thus being able to grasp the patient's knees with his own should occasion require him to do so. This position is preferable to the one in which the knees of the observer are either on one side or the other of the patient's knees, because then the observer, in order to throw the light from the head mirror into the mouth of the patient, has to assume a constrained position which very soon becomes fatiguing. Under no circumstances should the patient be allowed to grasp the observer's knees, for then the latter is powerless to restrain the struggles of his patient, and cannot quickly leave his seat should vomiting occur. When the examination is made at the physician's office or wherever it is practicable, it is of advantage to have a head-rest, such as photographers use, for the patient's head. The positions having been taken, the observer places the head reflector upon his forehead a little above the left eye, and by rotating it upon its ball-and-socket joint reflects the light from the lamp- or gas-flame upon the patient's face so that the circle of light is bounded above by the tip of the nose and below by the tip of the chin. It is of great importance that the adjustment of the reflector should be made by means of its joint, and not by rotating or inclining the head, for it is necessary that the head should have an easy position which can quickly be resumed should it become necessary to move the head. It requires considerable practice to quickly reflect the light from the head mirror in any desired direction, and it is therefore well for the beginner to practise this by throwing the light upon a spot on the wall before he attempts to examine a patient, as he will thus save himself, as well as the patient, unnecessary annoyance. If a light concentrator be used which supports the reflector on the jointed arm, this of course is not necessary, but the practice with the head mirror will even then be found advantageous, because when a patient is to be examined in the sick room a light concentrator cannot usually be employed, and the physician has to fall back upon the head mirror for illuminating the laryngeal cavity.