GENERAL ARRANGEMENT OF THE PHONATING ORGANS 543 



jection of the arytenoids. The cuneiform cartilages are placed within 

 the aryteno-epiglottidean folds. 



The Function of the Epiglottis. — The larynx is protected against 

 the digestive tract by a leaf -like plate of yellow elastic cartilage which 

 is attached below by a stalk to the thyroid cartilage. In the adult 

 it usually assumes a nearly vertical position, while in children it is 

 placed more slantingly. It has a double purpose, namely, to prevent 

 the ingress of food into the respiratory passage and to aid in the modi- 

 fication of the currents of air during respiration and phonation. 



The closure of the pharyngolaryngeal opening, however, is not 

 effected solely by the epiglottis, because a rather efficient occlusion 

 of this orifice is also had when this structure is wanting or is imper- 

 fectly developed. Neither is it correct to assume that those muscle 

 fibers which arise upon the thyroid and are inserted upon the epiglottis 

 are sufficiently powerful to serve as sphincters.^ A third factor must 

 be taken into consideration, and that is the elevation and forward in- 

 clination of the entire larynx. This movement gives rise to an approxi- 

 mation with the hyoid bone so that the tongue, when drawn back- dur- 

 ing the act of swallowing, is in the best possible position to press the 

 epiglottis downward until it comes to lie across the laryngeal aperture. 

 At this very moment, the thyro-epiglottidean muscle fibers contract, 

 thereby tending to constrict this orifice. It is also held that the 

 epiglottis serves as a sort of sounding board against which the vibrat- 

 ing particles of air are forced. Thirdly, its partial closure upon the 

 forced expiratory blasts gives rise to the peculiar fragmented character 

 of the current of the air produced during the act of coughing. When 

 acting upon the inspiratory current of air, its partial closure gives rise 

 to such peculiar modifications as are noted during the act of hic- 

 coughing. The fact that the mucous lining of this structure is beset 

 with numerous taste-buds and glands does not possess a special 

 functional significance. 



The True and False Vocal Cords. — When looked at from above, the 

 wide expanse of the laryngeal cavity is seen to be limited by two 

 membranous bands, the vocal cords, which extend transversely across 

 its lumen in a direction from before backward. The space between 

 these bands is known as the glottis. The size and shape of the latter 

 vary with the respiratory movements and phonation. During in- 

 spiration it becomes large and during expiration small. When the vocal 

 cords are widely separated, its width measures about 13.5 mm. in 

 men and 11.5 mm. in women. During phonation it usually assumes 

 the shape of a mere slit, designated as the chink of the glottis, or rima 

 glottidis. 



The true vocal cords arise in front from the angle formed by the 

 alse of the thryoid cartilages, and, passing directly backward, are in- 

 serted upon the vocal processes of the arytenoid cartilages. They 



^ Meltzer, The Closure of Glottis During Deglutition, Zentralbl. fiir Physiol., 

 xxvi, 1912. 



