222 Royal Society : — 



This theory, though now generally admitted for reeds, and un- 

 doubtedly evident in the liquid vein, the toothed-wheel of Savart, 

 the syrene of the Baron Cagnard Latour &c., has not to my know- 

 ledge, been yet applied to the glottis*. If we consider that the 

 lips of this aperture, taken separately, can give no kind of sound, 

 however we may try to make them speak, we must admit that the 

 sounds which they give forth by their mutual action, are only owing 

 to the explosions of the air produced by their strokes f. It is not 

 necessary in order to obtain the explosion of sound, that the glottis 

 should be perfectly closed each time after its opening ; it suffices 

 that it should oppose an obstacle to the air capable of developing its 

 elasticity. In this case the rushing of the air is heard accompanying 

 the sounds, and they take a veiled, and sometimes an extremely 

 muffled character ; an observation which we have already presented 

 to the reader's notice in speaking of the falsetto. 



Conjectures on the Formation of the different Registers. 



As the entire system of vibrations arises solely from the inferior 

 ligaments, it is evident that the cause of the different tones called 

 registers, must be sought for in the muscles which set these liga- 

 ments in motion ; and that the other parts of the larynx must be 

 considered only as apparatus for strengthening the sounds obtained, 

 and for modifying their quality. In our efforts to discover the more 

 intimate processes of the vocal organs which produce the sounds, 

 we shall recur at once to the observations already mentioned, to 

 some anatomical remarks which we are going to make, and to the sen- 

 sations which we feel in the organ itself whilst it is producing sounds. 



If we detach one of the halves of the thyroid cartilage, we shall 

 see a large muscular surface of oblique fibres, which fills all the 

 space between the arytenoid and thyroid cartilages. At its upper 

 end is to be seen the muscle corresponding to the superior vocal 

 ligaments, and which sometimes extends to the notch in the 

 thyroid. After detaching this generally frail muscle, all the fibres 

 constituting this muscular surface seem to start from two opposite 

 centres, viz. the anterior surface of the arytenoid, and the re-enter- 

 ing angle of the thyroid. These centres, occupying the extremities 

 of a diagonal line, send their fibres towards each other in parallel 

 lines. Those which start from the anterior face of the arytenoid 

 descend obliquely ; the most external ones go to the cricoid, whose 

 posterior half they cover at the side ; the most internal ones de- 

 scend to the vocal membrane J, which they cover entirely. The 

 fibres which terminate at the membrane become longer, as they be- 

 come more internal. Those which start from the re-entering angle 



* I find that Dr. Miiller hints at the possibility of the voice being thus formed, 

 but only to attack and reject the notion.— Haadbitch der Physiologie des Menschen, 



t Many controversies have arisen respecting the sounds sometimes emitted by 

 animals after the section of the superior and recuirent laryngeal nerves ; sounds 

 which have been perhaps occasioned by the struggling of the animal causing a 

 swelling of the neck and a mechanical contact of the vocal ligaments. However, 

 without doubt, after the section of these nerves, voice, as a voluntary act, can no 

 longer take place. 



X We thus designate that part of the membrane wliich goes from the bottom 

 of the vocal ligament, to the edge of the cricoid. 



