458 



OF THE VOICE AND SPEECH. 



ligaments. This action will be further assisted by the Sterno-fhyroideus, 

 which tends to depress the Thyroid cartilage, by pulling from a fixed point 

 below ;* and the Thyro-hyoideus will be the antagonist of this, when it acts 



Part of Fig. 196 enlarged, to show the direction of the muscular forces, which act on the Arytenoid 

 cartilage. Q N v s, the right Arytenoid cartilage ; T v, ils vocal ligament ; B R s, bundle of ligaments unit- 

 ing it to Cricoid ; o p, projection of its axis of articulation ; h g-, direction of the action of the Thyro-ary- 

 tenoideus; N x, direction of Crico-arytenoideus lateralis ; N w, direction of Crico-arytenoideus posticus; 

 N Y, direction of Crytenoideus transversus. 



from a fixed point above, the Os Hyoides being secured by the opposing con- 

 traction of several other muscles. The respective actions of these muscles 

 will be best comprehended by the following Table. 



Govern the pitch of the notes. 



Depress the front of the Thyroid cartilage on the 

 Cricoid, and stretch the vocal ligaments; assisted 

 by the Arytenoideus and Crico-arytenoidei postici. 



Elevate the front of the Thyroid cartilage, and draw 

 it towards the Arytenoids, relaxing the vocal liga- 

 ments. 



>\ , 



% \ STERNO-THYROIDEI 



5. C THYHO-ARYTENOIDEI 

 ST \ THYHO-HYOIDEI 



> . . . . 



Govern the Aperture of the Glottis. 

 5. CRICO-ARYTENOIDEI POSTICI ................. Open the Glottis. 



CRTCO-ARYTEXOIDEI LATERALES 

 AHYTENOIDEUS 



Press together the inner edges of the Ary- 

 tenoid cartilages, and close the Glottis. 



605. The muscles which stretch or relax the Vocal ligaments, are entirely 

 concerned in the production of Voice ; those which govern the aperture of 

 the Glottis have important functions in connection with the Respiratory 

 actions in general, and stand as guards (so to speak) at the entrance to the 

 lungs. Their separate actions are easily made evident. We can close the 

 aperture of the Glottis, by an exertion of the will, either during inspiration or 

 expiration; and it is a kind of spasmodic movement of this sort, which is 



* This is not usually reckoned as one of the principal muscles concerned in regulating the 

 voice; but that it is so, any our ni;iy convince himself by placing his finger just above the 

 sternum, whilst he is sounding high notes; a strong feeling of muscular tension is then at 

 once perceived. 



