826 SPECIAL MUSCULAR MECHANISMS. 



manoeuvres, as is also suggested by the fact that the ease with which falsetto 

 notes can be uttered is readily increased by practice. The change from the 

 chest to the falsetto voice is an abrupt one, and the combined range may be 

 very extensive, as in the case of persons who can carry on a duet, singing 

 alternately, for instance, in a tenor (chest) and a soprano (falsetto) voice. 



766. The ventricles of Morgagni are apparently of use in giving the 

 vocal cords sufficient room for their vibrations, and perhaps supply a secre- 

 tion by which the vocal cords are kept adequately moist. The purpose of 

 the false vocal cords is not exactly known. Some authors think that in the 

 falsetto voice they are brought down into contact with, and thus serve to 

 stop, the true vocal cords. 



At the age of puberty a rapid development of the larynx takes place, 

 leading to a change in the range of the voice. The peculiar harshness of 

 the voice when it is thus " breaking " seems to be due to a temporary con- 

 gested and swollen condition of the mucous membrane of the vocal cords 

 accompanying the active growth of the whole larynx. The change in the 

 mucous membrane may come on quite suddenly, the voice " breaking," for 

 instance, in the course of a night. 



SPEECH. 



Vowels. 



767. Every sound, every note (for all vocal sounds when considered 

 by themselves are musical sounds), caused by the vibrations of the vocal 

 cords, besides its loudness due to the force of the expiratory blast, and its 

 pitch due to the tension of the cords, has a quality of its own, due to the 

 number and relative prominence of the overtones which accompany the 

 fundamental tone. Some of these features which make up the quality are im- 

 posed on the note by the nature of the vocal cords, but still more arise from 

 various modifications which the relative intensities of the overtones undergo 

 through the resonance of the cavity of the mouth and throat. Whenever 

 we hear a note sounded by the larynx we are able to recognize in it features 

 which enable us to state that one or other of the " vowels " is being uttered. 

 Vowel sounds are in fact only extreme cases of quality, extreme prominence 

 of certain overtones brought about by the shape assumed by the buccal arid 

 pharyngeal passages and orifices, as the vibrations pass through them. Each 

 vowel has its appropriate and causative disposition of these parts. When i 

 (ee in feet) is sounded, the sounding-tube of the upper air-passages is made 

 as short as possible, the larynx is raised and the lips are retracted, the whole 

 cavity of the mouth taking on the form of a broad flask with a narrow neck. 

 During the giving out of e (a in fat) the shape of the mouth is similar, but 

 somewhat longer. For the production of a (as in father) the mouth is widely 

 open, so that the buccal cavity is of the shape of a funnel with the apex at 

 the pharynx. With o, the buccal cavity is again flask-shaped, with the 

 mouth more closed than in a, but the lips, instead of being retracted as in i 

 and e, are somewhat protruded, so that the sounding-tube is prolonged. The 

 greatest length of the tube is reached in u (oo), in which the larynx is 

 depressed and the lips protruded as much as possible. While the two latter 

 vowels are being uttered, the general form of the buccal cavity is that of a 

 flask with a short neck and a small opening, the orifice being smaller for u 

 than for o. 



768. Each of these various " vowel " forms of the mouth possesses a 

 note of its own, one toward which it acts as a resonance chamber. Thus, if 

 several tuning-forks of various pitch be held while sounding before a mouth 

 which has assumed the particular form necessary for sounding U, it will be 



