260 HUMAN PHYSIOLOGY. 



The varieties of voice e. g. } bass, baritone, tenor, contralto, mezzo- 

 soprano, and soprana are due to the length of the vocal cords, 

 being longer when the voice has a low pitch, and shorter when it has 

 a high pitch. 



Speech is the faculty of expressing ideas by means of combina- 

 tions of sounds, in obedience to the dictates of the cerebrum. 



Articulate sounds may be divided into vowels and consonants. The 

 vowel sounds, a, e, i, o, u, are produced in the larynx by the vocal 

 cords. The consonant sounds are produced in the air-passages above 

 the larynx by an interruption of the current of air by the lips, tongue, 

 and teeth ; the consonants may be divided into : 



1. Mutes, b, d, k, p, t, c, g. 



2. Dentals, d, j, s, t, z. 



3. Nasals, m, n, ng. 



4. Labials, b, p, f, v, m. 



5. Gutturals, k, g, c, and g hard. 



6. Liquids, /_, m, n } r. 



