212 



PRACTICAL PHYSIOLOGY. 



[XXXVII. 



mach, acting on the suggestion of Kronecker. A steel tongue, vibrating a 

 hundred times per second, covers an oblong aperture placed at the lower part 

 of a gradually-narrowing brass tube, closed at the narrow end. To the 

 tongue is attached a stylette, which records the movements of the former. To 



the open end of the brass tube of the instrument is attached a brass ball or 

 resonator, and to the latter a caoutchouc tube. When air is sucked through 

 the apparatus, the reed (and with it the stylette) is set vibrating. It may be 

 kept vibrating by means of an aspirator placed in connection with a water- 

 tap. 



