240 STUDIES IN ADVANCED PHYSIOLOGY. 



throat, the mouth, and in the production of some sounds 

 even the nose. By changing the relative dimensions of 

 these resonance cavities the quality of the individual sounds 

 of the voice may be much varied, just as the player on the 

 sliding trombone varies his notes by varying the relative 

 lengths of the resonance cavities in his instrument. The 

 pitch of the voice will be dependent upon the length and 

 tension of these vocal cords, just as the pitch of a piano 

 string is dependent upon its length and tension, while the 

 loudness 'will depend upon the strength with which the 

 vocal cords are made to vibrate. 



We have now to consider the anatomical arrangement 

 af the larynx by which the vibration of the cords and the 

 production of the voice is effected. 



THE ANATOMY OF THE LAETNX. 



The larynx is the expanded upper portion of the trachea. 

 It consists of three main cartilages, the general arrange- 

 ment of which is about as follows: At the base of the 

 larynx is the cricoid cartilage. This cartilage entirely sur- 

 rounds the base of the larynx like a ring surrounds a finger. 

 This cricoid cartilage actually resembles in its shape a sig- 

 net ring, the signet of which is, however, towards the back, 

 and the band of the ring forwards. This band may be felt 

 by pressing the finger hard against the base of the larynx 

 in front. Placed upon the band of this ring, that is, 

 towards the front of the trachea, is the thyroid cartilage. 

 This cartilage really consists of two cartilages which meet 

 in front., leaving a V-shaped slit. The two halves after 

 partially encircling the larynx do not meet behind, as the 

 signet of the cricoid cartilage separates them. This is the 

 largest of the cartilages and is the one we have in mind 

 when we speak of the "Adam's apple." The V-shaped slit 

 in this Adam's apple is readily felt with the finger. The 

 sides of the thyroid cartilage where they join the signet of 

 the cricoid behind are prolonged upwards into two horns, 

 indicated by C s, in Fig. 93. Similar horns, although not 



