804 VOICE AND SPEECH [CH. LV1I. 



little alteration of the distance between the operator and the patient the point at 

 which the greatest amount of light is reflected by the mirror in other words, its 

 focal length is readily discovered. The small mirror fixed in the handle is then 

 warmed, either by holding it over the lamp, or by putting it into a vessel of warm 

 water; this is necessary to prevent the condensation of breath upon its surface. 

 The degree of heat is regulated by applying the back of the mirror to the hand or 

 cheek, when it should feel warm without being painful. 



After these preliminaries the patient is directed to put out his tongue, which is 

 held by the left hand gently but firmly against the lower teeth by means of a 

 handkerchief. The warm mirror is passed to the back of the mouth, until it rests 

 upon and slightly raises the base of the uvula, and at the same time the light is 

 directed upon it : an inverted image of the larynx and trachea will be seen in the 

 mirror. If the dorsum of the tongue is alone seen, the handle of the mirror must 

 be slightly lowered until the larynx comes into view ; care should be taken, how- 

 ever, not to move the mirror upon the uvula, as it excites retching. The observa- 

 tion should not be prolonged, but should rather be repeated at short intervals. 



The structures seen will vary somewhat according to the condition of the parts 

 as to inspiration, expiration, phonation, etc. ; they are (fig. 504) first, and apparently 

 at the posterior part, the base of the tongue, immediately below which is the arcuate 

 outline of the epiglottis, with its cushion or tubercle. Then are seen in the central 

 line the true vocal cords, white and shining in their normal condition. The cords 

 approximate (in the inverted image) posteriorly; between them is left a chink, 

 narrow whilst a high note is being sung, wide during a deep inspiration. On each 

 side of the true vocal cords, and on a higher level, are the pink, false vocal cords. 

 Still more externally than the false vocal cords is the aryteno-epiglottidean fold, in 

 which are situated upon each side three small elevations ; of these the most external 

 is the cartilage of Wrisberg, the intermediate is the cartilage of Santorini, whilst 

 the summit of the arytenoid cartilage is in front, and somewhat below the preceding, 

 being only seen during deep inspiration. The rings of the trachea, and even the 

 bifurcation of the trachea itself, if the patient be directed to draw a deep breath, 

 may be seen in the interval between the true vocal cords. 



Movements of the Vocal Cords. 



In Respiration. The position of the vocal cords in ordinary 

 tranquil breathing is so adapted by the muscles, that the opening 

 of the glottis is wide and triangular (fig. 504, B). The glottis 

 remains unaltered during ordinary quiet breathing, though in a 

 small proportion of people it becomes a little wider at each inspira- 

 tion, and a little narrower at each expiration. In the cadaveric 

 position the glottis has about half the width it has during ordi- 

 nary breathing; during life, therefore, except during vocalisation, 

 the abductors of the vocal cords (posterior crico-arytenoids) are in 

 constant action. (F. Semon.) On making a rapid and deep inspira- 

 tion the opening is widely dilated (fig. 504, c), and somewhat 

 lozenge-shaped. 



In Vocalisation. At the moment of the emission of a note, the 

 chink is narrowed, the margins of the arytenoid cartilages being 

 brought into contact, and the edges of the vocal cords approximated 

 and made parallel (fig. 504, A); at the same time their tension is 

 much increased. The higher the note produced, the tenser do the 

 cords become; and the range of a voice depends, in the main, on 

 the extent to which the degree of tension of the vocal cords can 



