224 PHYSIOLOGY CHAP. 



unreliable owing to the methods employed. Savart (1830) was 

 the first who obtained more exact results by his dented wheel, 

 which threw a sheet of cardboard into vibration. He found that 

 tones of 24,000 vibrations were still distinctly perceptible. Preyer 

 used Seebeck's syren for the same purpose, and found that 16,000 

 vibrations per sec. are audible as a very clear note, and that 

 24,000 vibrations are still perceptible, though feebly so. Pauchon 

 used a Cagnard de la Tour's steam syren for the same purpose. 

 With a steam pressure of 0'5 to 1-5 atmospheres he obtained a 

 limit of perception at 24,000 to 30,000 vibrations ; with a pressure 

 of 2*5 atmospheres the limit rose to 36,000, without even then 

 reaching the highest perceptible note. 



Preyer repeated these researches with Konig's sounding 

 cylinders. He found that e and g of the 8th and c of the 9th 

 octave are perceptible, but produce disagreeable sensations, and 

 concluded that the extreme limit of hearing is the e of the 9th 

 octave, which produces a brief and very weak sensation. 



The upper limit of audition, also, varies considerably for 

 different normal individuals. Zwaardemaker further noted that 

 it sinks with increasing age, although the figures he has given are 

 too low owing to the imperfections of his method. 



Edelmann held that in persons with optimum auditory 

 capacity the entire range of perceptible tones extends over 12 

 octaves (from 11 to 50,000 vibrations). 



But in music excessively high and low tones are both excluded. 

 The deepest note of a large organ consists of 16'5 vibrations (C of 

 sub-contra octave). The highest note of the piano consists of 

 3520-4244 vibrations (a 4 -c 5 ). The piccolo flute also comprises & 

 (4752 vibrations). But the notes usually employed in music lie 

 within the compass of about 8 octaves (from 40 to 4700 vibrations). 



To determine the capacity for perception of the highest notes, which 

 may vary greatly in ear-disease, otologists generally make use of Galton's 

 whistle, which can give a whole series of high notes, from (7 4 to the highest 

 tones that lie at the extreme limit of the auditory sensibility of the human 

 ear. The pitch of the tones produced by the instrument can be altered by 

 simply moving the two micrometer screws. 



In the most perfect form given by Edelmann to Galton's whistle it con- 

 sists of two metallic parts. One of these (A,B,D of Fig. 89) is joined to the 

 mouth A by a rubber tube, with an elastic ball or bellows, which provides 

 the air necessary for sounding the whistle. The second part (E,F,G) is the 

 whistle proper ; this consists of the tube E, by which the air enters, blown 

 through tube D placed opposite, at a distance that can be varied by the 

 micrometer screw B. The tube E communicates with the body of the 

 whistle F, which consists of a hollow cylinder, the floor of which can be dis- 

 placed by means of a second micrometer screw G. 



The pitch of the tone is in inverse ratio with the length of the hollow 

 cylinder, so that when the screw G is turned in one or other direction a 

 higher or lower tone results. An empirical graduation of the worm of the 

 screw makes it possible to count the number of vibrations in the tones 

 obtained by different positions of the screw. 



