5 8 2 TEXT-BOOK OF PHYSIOLOGY. 



to e", mi 4 , or from 192 to 640 vibrations per second; those of the 

 soprano from b, si 2 , to g", so! 4 ,'or 768 vibrations per second. The 

 range of the voice is thus seen to embrace from one and three-quarters 

 to two octaves. Some few individual singers have far exceeded this 

 range, but they are exceptional. 



Speech is the expression of ideas by means of articulate sounds. 

 These sounds may be divided into vowel and consonant sounds. 



The vowel sounds, a, e, i, o, u, are laryngeal sounds modified by 

 the superposition and reinforcement of certain overtones developed 

 in the mouth and pharynx by changes in their shapes. The number 

 of vibrations underlying the production of each vowel sound is a 

 matter of dispute. According to Konig, the sound of a is the result 

 of 940 vibrations; of e, 1880 vibrations; of i, 3760 vibrations; of o, 

 470 vibrations; of ou, 235 vibrations. 



Consonant sounds are produced by the more or less complete in- 

 terruption of the vowel sounds during their passage through the organs 

 of speech. These may be divided into: 



1. Labials, p, b, m. 



2. Labio-dentals, /, v. 



3. Linguo-dentals, s, z. 



4. Anterior linguo-palatals, /, d, /, n. 



5. Posterior linguo-palatals, k, g, h, y, r. 



The names of these different groups of consonants indicate the 

 region of the mouth in which they are produced and the means by 

 which the air blast is interrupted. 



THE NERVE MECHANISM OF THE LARYNX. 



The nerve mechanism by which the musculature of the larynx 

 is excited to action and coordinated so as to subserve both res- 

 piration and phonation involves the fibers contained in the superior 

 and inferior laryngeal nerves (both branches of the vagus) and their 

 related nerve-centers in the central nerve system. 



For respiratory purposes it is essential that the lumen of the 

 glottis shall be sufficiently large to permit the entrance and exit of air 

 without hindrance. Laryngoscopic examination of the larynx in the 

 human being shows that during quiet respiration the vocal bands are 

 widely separated and almost stationary, moving but slightly during 

 either inspiration or expiration. At this time, according to the in- 

 vestigations of Semon, the area of the glottis is approximately 

 160 sq. mm., somewhat less than the area of either the supraglottic 

 or infraglottic regions, which is about 200 sq. mm. This condition 

 of the glottis is maintained by the steady continuous contraction 

 of the posterior crico-arytenoid muscles, the abductors of the vocal 

 bands. 



