266 A MANUAL OF PHYSIOLOGY 



this can be distinctly felt by the hand. In head notes or falsetto 

 the resonance is chiefly in the upper cavities, the pharynx, mouth, 

 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, 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 consider- 

 able 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 appreciate as a definite 

 pitch. This difference of character corresponds to a differ- 

 ence of origin : the vowels are produced by the vibrations of 

 the vocal cords; the consonants are due to the rushing of the 

 expiratory blast through certain constricted portions of the 

 buccal chamber, where a kind of temporary glottis is estab- 

 lished by the approximation of its walls. One of these 

 ' positions of articulation ' is the orifice of the lips ; the 



