MUSCLES OF THE LAKY^X. 493 



It has been conclusively shown, particularly by the ex- 

 periments of Longet, that the inferior vocal chords are alone 

 concerned in the production of the voice. This author, who 

 has made numerous experiments on phonation, has demon- 

 strated, by operations on dogs, that the epiglottis, the supe- 

 rior vocal chords, and the ventricles of the larynx, may be 

 injured, without producing any serious alteration jn the 

 voice ; but that phonation becomes impossible after serious 

 lesion of the inferior chords. 1 This being the fact, as far 

 as the mere production of the voice in the larynx is con- 

 cerned, we have only to study the mechanism of the action 

 of the inferior ligaments and the muscles by which their 

 tension and relations are modified. 



Muscles of the Larynx. Anatomists usually divide the 

 muscles of the larynx into extrinsic and intrinsic. The ex- 

 trinsic muscles are attached to the outer surface of the larynx 

 and to adjacent organs, such as the hyoid bone and the 

 sternum. They are concerned chiefly in its movements of 

 elevation or depression. The intrinsic muscles are attached 

 to the different parts of the larynx itself, and, by their action 

 upon the articulating cartilages, are capable of modifying 

 the condition of the vocal chords. The number of the in- 

 trinsic muscles is nine, four pairs and a single muscle. In 

 studying the situation and attachments of these muscles, it 

 will be useful at the same time to note their mode of action. 

 This has been experimentally demonstrated by Louget, who 

 has studied the isolated action of the different muscles by 

 galvanizing the nervous filament distributed to each one, 

 either in the living animal, or in animals recently killed. 

 In this way he has been able to show the mechanism of dila- 

 tation of the larynx during inspiration, and to indicate the 

 precise action by which the vocal chords are rendered tense 

 or are relaxed. 3 These experiments, by the positive charac- 



1 LOXGET, Traite de physiologic , Paris, 1869, tome ii., p. 728, et seq. 

 8 Op. cit., p. 727. 



