242 STUDIES IN ADVANCED PHYSIOLOGY . 



the mucous membrane lining the larynx is reflected over 

 these and so makes the vocal cords really membranes, free 

 only along their inner edge. The analogy of these mem- 

 branes might be found in a drum, the membrane of which 

 had been slit from one end to the other through its middle. 

 As the forward ends of the vocal cords are inserted in the 

 immovable thyroid cartilage, their length and tension must 

 be varied by the movements of the arytenoid cartilages be- 



Fig. 94. THE INSIDE OF THE VOICE-BOX, 



a, of arytenoid cartilage; cv, vocal cord; t, thyroid cartilage; s, cartilage of Santorini; 

 cap, articulation of arytenoid with the cricoid cartilage ; c, c, cricoid cartilage ; cth, space 

 between thyroid and cricoid cartilages. 



hind. It was pointed out that these cartilages connect with 

 the signet of the cricoid in a very movable joint, and there 

 now remains the description of the muscles by which the 

 desired movements are to be brought about. 



THE MANIPULATION OF THE LARYNX. 



1. The movements which bring the vocal cords into the 

 position found in quiet breathing. In quiet breathing, 

 when the passage of air through the larynx produces no vi- 

 brations, the vocal cords are relaxed and separated, and so 



