586 PHYSIOLOGY 



of the tongue comes up against the front part of the soft palate, so 

 that the mouth cavity is divided into two, the anterior short narrow 

 cavity, and the posterior broader cavity between the soft palate and 

 the base of the tongue. We therefore have two notes produced, 

 one in each cavity. The change in shape of the mouth cavity is shown 

 in the figures. With U and A the cavity seems to be single ; with I 

 the development of a pharyngeal resonating cavity is well shown. 

 Diphthongs are produced by changing the form of the mouth cavity 

 from that of one vowel sound to another, thus AI (the English i) 

 ah-ee run together and abbreviated. 



Consonants are sounds produced by a sudden check being placed 

 in the course of the expiratory blast of air by closure of some part 

 of the pharynx or mouth. They are classified into labials, dentals, 

 or gutturals, according as the check takes place at the lips, between 

 teeth and tongue, or between back of tongue and soft palate. Each 

 of these again can be divided into soft and hard consonants as they 

 are accompanied or not with phonation. Thus when we pronounce 

 D the production of the laryngeal sound goes on during the check 

 of the sound produced at the teeth, whereas with T there is an absolute 

 interruption of phonation during the pronunciation of the consonant. 

 It is thus practically impossible to make any marked difference 

 between hard and soft consonants when whispering. 



In the production of nasal sounds such as NG the mechanism 

 is the same as for the production of B, D, G, except that the posterior 

 opening of the nares is not kept shut by the soft palate, so that part 

 of the sound comes continually through the nasal passages, when it 

 acquires a peculiar resonance. These sounds are on this account often 

 spoken of as ' resonants.' The aspirates are produced by the passage 

 of a simple blast of air through a narrow opening which may be at 

 the throat as in H, between tongue and teeth as in TH, or between 

 lips and teeth as in PH or F. 



The vibratives, such as R, are formed by placing the tip of the 

 tongue or the uvula, or the lips, in the path of the blast of air so that 

 they are set into vibration by the blast. In English the vibrative K 

 employed is entirely due to the tongue. 



The sibilants, which may be voiceless as in ' S ' or accompanied 

 with phonation as in * Z,' consist of continuous noises produced by 

 a narrowing of the path of the air between the tongue and the hard 

 palate. They are therefore similar in production to the aspirates. 

 In the production of the sound ' L ' the tongue is applied by its edge to 

 the alveolar process of the upper jaw. so that the air or voice escapes 

 by two small apertures in the region of the first molar and between 

 the inner side of the cheek and the teeth. The acoustic characters 

 of these various consonants are still but imperfectly studied. 



