MUSCLES THAT GOVERN THE APERTURE OF THE GLOTTIS. 131 



Fig. 39.* Fig. 40.t 



GOVERN THE PITCH OF THE VOICE. 



^ \ Crico-thyroidei, 



Sterno-thyroidei , 



Thyro-arylenoidei, 

 Thyrohyoidei, 



i Depress the front of the thyroid cartilage on the cri. 



< coid, and stretch the vocal ligaments ; assisted by 

 f the arytenoideus and crico-arytenoidei postici. 



i Elevate the front of the thyroid cartilage, and draw 



< it towards the arytenoid, relaxing the vocal liga- 

 f ments. 



GOVERN THE APERTURE OF THE GLOTTIS. 



Crico-arytenoidei postici, 

 Arytenoideus, 

 Crico-arytenodei laterales. 



Close the glottis. 

 Open the glottis. 



The muscles that relax or stretch the vocal ligaments are con- 

 cerned in voice alone. Those that govern the aperture of the glottis 

 are also concerned in respiration, regulating the amount of air re- 

 ceived. They are also the seat of the spasmodic affections of the 

 larynx which so often occur in children. 



The vocal apparatus has been compared to various instruments, 

 such as stringed instruments, flutes, and reed instruments. It is not 

 justly compared to a stringed instrument, inasmuch as the cords are 

 too short to produce all the varied notes of which the human voice 

 IS capable, more especially the lower notes. Besides which they are 

 covered with mucous membrane, which would act effectually' as a 

 damper upon them. 



* Vertical section of the larynx to show its internal surface. 7. Superior vocal liaaments 

 8 Section of thyroid cartilage. 9. Ventricle of Galen. 10. Lowef vocaMiga nenT IL 

 Arytenoid cartilages. 12. Inside of cricoid cartilage. S^i ue n. ii. 



t Larynx from above. G.E.H. Thyroid cartilage. N. F. Arytenoid cartilages. T V T V 

 Yt'^^It'',^^^*^'"^*- N- X.Crico.arytenoideus lateralis. V. A./. Right thyro-arytenoideus 

 N. /. N. /. Crico-arytenoidei postici. B. B. Crico-arytenoid ligaments. ^e.iuiueus. 



