208 Mr. Bishop's Experimental Researches on the Human Voice. 



Haighton *, Cruikshanks, Scarpa, Arneman, Magendie, and 

 others have been attended with curious results. The description 

 given of them by the latter however is opposed by Rudolphi, 

 Andersch, Soemmerring, Meckel, Bellengeri and others. 



The truth is, that the superior and recurrent nerves anasto- 

 mose in giving filaments to some of those muscles which di- 

 late, as well as to those which close the glottis. 



The action of these muscles may be briefly recapitulated as 

 follows : 



The crico-ai-ytenoidei postici open the glottis. 

 All the other muscles close it. 



The at-ytencideus obliquus and ai-yt. transversus close the 

 arytenoid cartilages posteriorly. 



The crico-ai-ytenoidei lateralis and the thyro-arytenoidei 

 close them anteriorly. 



The thyro-arytenoidei close the centre of the glottis, and 

 with the crico-thyroidei, regulate its tension, position, and vi- 

 brating length. 



The views here taken of the actions of these muscles differ 

 from those entertained respecting them by anatomical authors 

 in general. 



Not having found any two anatomists strictl}' agreeing on 

 the subject, I have been induced to make numerous dissec- 

 tions to ascertain their functions in producing voice. 



The annexed figures were drawn by Mr. Henry Dayman, 

 from these dissections. 



The actions assigned to the thyro-arytenoidei admit of 

 most discussion. 



That these muscles relax the vocal ligaments, and at the 

 same time close the glottis, may at first sight appear exceed- 

 ingly doubtful ; but all my attempts to close the glottis by the 

 approximation of the arytenoid cartilages and the tension of 

 the thyroidei muscles were unsuccessful, nor could any sound 

 be produced until the thyroidei were brought into action, ex- 

 cept by forcing such a volume of air through the glottis as it 

 is almost impossible can take place during life f . 



In confirmation of this view, it is observed by M. Magendie, 



* Mera. of the Med. Soc. London. 



+ The quantity of air expelled to produce voice of ordinary intensitj' 

 is about twenty-five cubic inches in the adult male, with a voice pitched in 

 the tenor G. To produce its grave octave of the same intensity will re- 

 quire 50 cubic inches. In ten seconds therefore the lungs will be almost ex- 

 hausted in producing the upper G, and in five seconds for the grave octave ; 

 allowing 200 cubic inches to be expelled, which is the average quantity of 

 air the lungs are estimated'to contain after a full inspiration. 



The quantity of air expelled from the lungs will consequently vary with 

 every note in the scale relatively with the key and the intensity of tone. 



