504 MOVEMENTS VOICE AND SPEECH. 



This action occurs in whispering and it can not properly be called vocal. It 

 is difficult to make any considerable variations in the pitch of a whisper, and 

 articulation in this way may be produced in inspiration as well as in expira- 

 tion, although the act in expiration is more natural and easy. The character 

 of a whisper may be readily distinguished from that of the faintest audible 

 sound involving vibration of the vocal chords. In aphonia from simple pa- 

 ralysis of the vocal muscles of the larynx, patients can articulate distinctly in 

 whispering ; but in cases of chronic bulbar paralysis (glosso-labio-laryngeal 

 paralysis), speech is entirely lost. 



The Phonograph. In 1877, a remarkable invention was made in this 

 country, by Mr. Thomas A. Edison, Avhich possesses considerable physiologi- 

 cal importance. Mr. Edison constructed a very simple instrument, called the 

 phonograph, which will repeat, with a certain degree of accuracy, the pecul- 

 iar characters of the human voice both in speaking and singing, as well as the 

 pitch and quality of musical instruments. This demonstrates conclusively 

 the fact that the qualities of vocal sounds depend upon the form of the sono- 

 rous vibrations. The following are the main features in the construction of 

 this instrument : It consists of a cylinder of iron provided with very fine, 

 shallow grooves in the form of an exceedingly close spiral. Upon the cylin- 

 der, a sheet of tin-foil is accurately fitted. Bearing upon the tin-foil, is a 

 steel-point connected with a vibrating plate of mica or of thin iron. The vi- 

 brating plate is connected with a mouth-piece which receives the vibrations of 

 the voice or of a musical instrument. The cylinder is turned with a crank, 

 and at the same time, the plate is thrown into vibration by speaking into 

 the mouth-piece. As the disk vibrates in consonance with the voice, the vi- 

 brations are marked by little indentations upon the tin-foil. When this has 

 been done, the cylinder is moved back to the starting point and is turned 

 again at the same rate as before. As the steel-point passes over the indenta- 

 tions in the tin-foil, the plate is thrown into vibration, and the sound of the 

 voice is actually repeated, although much diminished in intensity and dis- 

 tinctness. The improvements that have lately been made in the phonograph 

 do not involve any modifications in the principles of its construction. 



