JE. W. Scripture — Nature of Vowels. 309 



Such relations between the cord vibrations and the month 

 vibrations are incompatible with the theoretical requirements 

 on the supposition of the harmonic nature of the cord vibra- 

 tion. The conclusion seems quite justifiable that the cords 

 emit a series of puffs, or explosions of air, instead of vibrating 

 regularly back and forth. 



These conclusions are apparently inconsistent with the treat- 

 ment of the vocal apparatus as a reed pipe ; various sugges- 

 tions for a modified treatment are gathered into the following 

 theory : 



The vocal bands, including the vocal muscles (thyroary- 

 tenoid) and their ligamentous edges, vibrate by compression 

 and not by movement in the axial direction of the larynx. 

 Even acoustic strings set in action by a blast of air vibrate 

 transversely to the current of air ;* in the vocal bands this would 

 result in a compression movement. The vibration of the vocal 

 bands may be like that of a cushion struck by a billiard ball 

 and not like that of a membrane. The possibility of such a 

 cushion-action seems to have been first suggested by Ewald.f 

 The suggestion is favored by the fact that the vocal bands are 

 not of a nature and shape to readily vibrate transversely. The 

 true shape is indicated in fig. 2 ; the usual diagrams in works 

 outside those specially pertaining to laryngology 

 give a quite erroneous idea of them. The vocal 2 - 



bands aa suggest a pair of cushions suitable for 

 compression, and not a pair of membranes. When 

 the bands are closed by the action of the carti- 

 lages, the air is retained behind them until the 

 pressure is great enough to force them open, the 

 pressure being regulated by the tension of the 

 vocal muscles constituting the bands. When 

 they have been forced apart to emit the puff of 

 air, they close again and remain closed until the 

 pressure is again sufficient for opening them. 

 The curious relation between the rise of pitch of the cord tone 

 and the increase in the force of the puff, as shown in the first 

 part of the /curve in ^g. 1, would naturally result from a grad- 

 ual tightening of the vocal muscles. In general, it may be 

 said, there will be a relation between period and amplitude in 

 a cord tone as long as the breathing pressure remains constant. 



Such a theory would be in accord with the most carefully 

 determined experimental results and there seem to be no seri- 

 ous objections to it from what is known of the action of 

 vibrating bodies. 



* Rayleigli, Phil. Mag., 1879, p. 161. 



f Heymann's Handbuch d. Laryngologie u. Rhinologie, 180, Wien 1898 



