EESPIEATION 



323 





VOICE 



In connection with the respiratory mechanism of many 

 animals, an arrangement for the production of sound or voice 

 is developed. This is constructed on the principle of a wind 

 instrument, and it consists of (1) a bellows, (2) a windpipe, (3) 

 a vibrating reed, and (4) resonating chambers. In man and 

 other mammals the bellows are formed by the lungs and the 

 thorax. The trachea is the wind-pipe. The vocal cords in the 

 larynx are the vibrating reeds, and the resonating chambers 

 are the pharynx, nose, and mouth. 



A. Structure of the Larynx. The points of physiological im- 

 portance about the structure of 

 the larynx are the following : 



1. Cartilages (figs. 146, 147). 

 The ring-like cricoid (6V.) at the 

 top of the trachea is thickened 

 from below upwards at its pos- 

 terior part arid carries on its 

 upper border two pyramidal car- 

 tilages triangular in section 

 the arytenoids (dr.). These ar- 

 ticulate with the cricoid by their 

 inner angle. At the outer angle 

 the posterior and lateral crico- 

 arytenoid muscles are attached. 

 From their anterior angles the 

 vocal cords arise and run for- 

 ward to the thyroid. The thy- 

 roid cartilage (Th.) forms a large 

 shield which articulates by its 

 posterior and inferior process 



with the sides of the cricoid, so that it moves round a hori- 

 zontal axis. To the upper and anterior part, the epiglottis or 

 cartilaginous lid of the larynx is fixed. 



2. Ligaments. The articular ligaments require no special 

 attention. The true vocal cords are fibrous ligamentous 

 structures which run from the arytenoids forward to the 

 posterior aspect of the middle of the thyroid. They contain 



Ar. 



Or. 



FIG. 146. Side View of the Cartilages 

 of the Larynx. Cr., cricoid cartil- 

 age ; Ar. , right arytenoid cartilage ; 

 Th., thyroid cartilage. The dotted 

 line shows the change in the posi- 

 tion of the Thyroid by the action of 

 the Crico-thyroid Muscle, and the 

 stretching of the vocal cords which 

 results. 



