PRODUCTION OF THE VOICE. 505 



of the female, and the contralto will sometimes imitate the 

 voice of the tenor in a surprisingly natural manner. These 

 facts have a somewhat important bearing upon certain dis- 

 puted points with regard to the mechanism of the different 

 vocal registers, which will be considered further on. 



Action of the Intrinsic Muscles of the Larynx in Pho- 

 nation. It is much more difficult to find an entirely satis- 

 factory explanation of the different tones produced by the 

 human larynx in the action of the intrinsic muscles than to 

 describe the changes in the tension and relations of the vocal 

 chords. These muscles are concealed from view, and the 

 only idea that we can have of their action is by reasoning 

 from a knowledge of their points of attachment, and by oper- 

 ations upon the dead larynx, either imitating the contrac- 

 tion of special muscles or galvanizing the nerves in animals 

 recently killed. In this way, as we have seen, some of the 

 muscular acts have been studied very satisfactorily ; but the 

 precise effect of the contraction of certain of the muscles, 

 particularly the thyro-arytenoids, is still a matter of dis- 

 cussion. 



In the production of low chest-tones, in which the vocal 

 chords are elongated and at the minimum of tension that 

 will allow of regular vibrations, the crico-thyroid muscles are 

 undoubtedly brought into action, and are assisted by the 

 arytenoid and the lateral crico-arytenoids, which combine to 

 fix the posterior attachments of the vibrating ligaments. It 

 will be remembered that the crico-thyroids, by approximat- 

 ing the cricoid and thyroid cartilages in front, have a ten- 

 dency to remove the arytenoid cartilages from the anterior 

 attachment of the chords. 



As the tones produced by the larynx become higher in 

 pitch, the posterior attachments of the chords are approxi- 

 mated more firmly, and at this time the lateral crico-aryte- 

 noids are probably brought into vigorous action. 



The function of the thyro-arytenoids is more complex ; 



