86 



A COURSE ON ZOOLOGY. 



ments, much more relaxed, and the opening between 

 them is not nearly so narrow as that between the vocal 



cords. These are the 

 ligaments. 

 the upper 



FlG - 46 - 



superior 



Between 



and low^er ligaments 



on each side are the 



spaces or cavities 



called the ventricles 



of the larynx. 



Mutes are persons 

 deprived of the p'ower 

 of articulate speech 

 or of producing any 

 definite sound. This 

 infirmity may result 

 from paralysis of the 

 nerves which control 

 the movement of the 

 parts of the vocal ap- 

 paratus, but complete 



BACK VIEW OF THE LARYNX. 1, thyroid car- loss of speech is of 

 tilage ; 2, superior horn ; 3, inferior horn ; oopnrron oo ox 

 4, cricoid cartilage; 5, crico-thyroid liga- 

 ment; 6, arytenoid cartilage; 7, promi- Cepting in Cases of 

 nent external angle of the base into which idiocy or in those born 

 the crico-arytenoid muscles are inserted ; 



8, epiglottic cartilage; 9, thyro-epiglottic deaf. It then IS Caused 



ligament ; 10, posterior membrane of the by & com pl e t e 'absence 

 trachea. 



of the sense of hearing 



and the consequent impossibility of acquiring the princi- 

 ples of language. 



