/ON MUSICAL INSTRUMENTS. 313 



as if^g^ends from its origin at the upper part of the thyreoid cartilage, 

 fne glottis are extended its ligaments, contiguous to each other 

 before, where they are inserted into the thyreoid cartilage, but capable of 

 diverging considerably behind whenever the arytaenoid cartilages separate. 

 These ligaments, as they vary their tension, in consequence of the motions 

 of the arytaenoid cartilages, are susceptible of vibrations of various fre- 

 quency, and as they vibrate, produce a continuous sound. Properly speak- 

 ing, there are two ligaments on each side ; but it is not fully understood 

 how they operate ; probably one pair only performs the vibrations, and the 

 other* assists, by means of the little cavity interposed, in enabling the air to 

 act readily on them, and in communicating the vibrations again to the air. 

 (Plate XXVI. Fig. 357, 358.) 



The vowels and semivowels are continuous sounds, chiefly formed by 

 this apparatus in the glottis, and modified either in their origin or in their 

 progress by the various arrangements of the different parts of the mouth. 

 Of simple vowels sixteen or eighteen may be enumerated in different lan- 

 guages : in the French nasal vowels the sound is in part transmitted 

 through the nostrils, by means of the depression of the soft palate : the 

 perfect semivowels differ from the vowels only in the greater resistance 

 which the air undergoes in its passage through the mouth ; there are also 

 nasal and seminasal semivowels. The perfect consonants may be either 

 explosive, susurrant, or mute; the explosive consonants begin or end 

 with a sound formed in the larynx, the others are either whispers, or mere 

 noises, without any vocal sound. By attending to the various positions 

 of the organ, and by making experiments on the effects of pipes of dif- 

 ferent forms, it is possible to construct a machine which shall imitate very 

 accurately many of the sounds of the human voice ; and this has indeed 

 been actually performed by Kratzenstein * and by Kempelen.t (Plate 

 XXVI. Fig. 359.) 



Although the vibrating ligaments of the glottis may be anatomically 

 denominated membranes, yet their tension is probably confined to the 

 direction of their length, and their action is, therefore, the same with that 

 of a simple string or cord. But in the case of a tambourine and a drum, 

 the membrane is stretched in every direction, and the force of tension con- 

 sequently acts in a different manner. The principal character of such in- 

 struments is their loudness, derived from the magnitude of the surface which 

 strikes the air, and the short duration of the sound, on account of the great 

 resistance necessarily produced by the air's reaction. 



Musical instruments which produce sounds, by means of vibrations de- 

 pending on the elasticity of solid bodies, are less frequently employed than 

 others ; they have a peculiar character of tone, which is by no means un- 

 pleasant, but which renders them less fit to be mixed with other instru- 

 ments, since their secondary harmonics are in different proportions. Such 

 is the stacada, a series of cylinders of glass, or of metal, struck either im- 



t * Journal de Physique, xxi. 358. Acta Petr. 1780, iv. II. H. 16. 



f Ueber den Mechanismus der Menschlichen Sprache, Vienna, 1791. On this 

 subject consult Willis, Trans. Camb. Phil. Soc. iii. 231. Purkinje on the Physio- 

 logy of Speech, Cracow, 1836. 



