282 



A MANUAL OF PHYSIOLOGY 



and nose. As to the mechanical conditions in the larynx, there is a 

 pretty general agreement that during the production of falsetto notes 

 the vocal cords are less closely approximated than in the sounding of 

 chest notes. The escape of air is consequently more rapid in the 

 head voice, and a falsetto note cannot be maintained so' long as a 

 note sung from the chest. But it is only the anterior part of the 

 rima glottidis that is wider in the falsetto voice ; the whole of the 

 glottis respiratoria, and even the posterior portion of the glottis 

 vocalis, are closed during the emission of falsetto notes. 



Oertel has stated, and the statement has been confirmed by others, 

 that the free edge of the vocal cord alone vibrates in the falsetto 

 voice, one or more nodes or motionless lines parallel to the edge 

 being formed by the contraction of the internal part of the thyro- 

 arytenoid muscle, which thus acts like a stop upon the cord. 



Approximation of the vocal cords may take place in certain 

 acts unconnected with the production of voice. Thus, a cough. 



HT/ 



FIG. 122. POSITION OF THE 

 GLOTTIS PRELIMINARY TO THE 

 UTTERANCE OF SOUND. 



rs, false vocal cord ; ri, true 

 vocal cord ; ar, arytenoid carti- 

 lage ; b, pad of the epiglottis. 



ti 



FIG. 123. POSITION OF OPEN GLOTTIS. 



/, tongue ; e, epiglottis ; ae, ary- 

 epiglottidean fold ; c, cartilage of 

 Wrisberg ; ar, arytenoid cartilage ; 

 o, glottis ; v, ventricle of Morgagni ; 

 ti, true vocal cord ; ts, false vocal cord. 



as has already been mentioned, is initiated by closure of the 

 glottis. During a strong muscular effort, too, the chink of. the 

 glottis is obliterated, and respiration and phonation both 

 arrested. The object of this is to fix the thorax, and so afford 

 points of support for the action of the muscles of the limbs and 

 abdomen. But considerable efforts can be made even by 

 persons with a tracheal fistula. 



Speech. Ordinary speech is articulated voice voice shaped 

 and fashioned by the resonance of the upper air-cavities, and 

 jointed together by the sounds or noises to which the varying 

 form of these cavities gives rise. Here we come upon the 

 fundamental distinction between vowels and consonants. Vowels 

 are musical sounds ; consonants are not musical sounds, but 

 noises that is to say, they are due to irregular vibrations, not 

 to regularly recurring waves, the frequency of which the ear can 



