. Diseases of the ear; a text-book for practitioners and students of medicine. stive investigationof any case it is scarcely necessary to multiply the arma-mentarium to this extent, since by means of the low forkalready mentioned, together with the modified Galton whistleand the series of five forks recommended by Hartmannf (), perfectly satisfactory work can be done. Each of the five forks in this set is tuned to the note C;the lowest fork making one hundred and twenty-eight vibra-tions per second, while the highest registers two thousandand forty-eight vibrations per second, each fork
. Diseases of the ear; a text-book for practitioners and students of medicine. stive investigationof any case it is scarcely necessary to multiply the arma-mentarium to this extent, since by means of the low forkalready mentioned, together with the modified Galton whistleand the series of five forks recommended by Hartmannf (), perfectly satisfactory work can be done. Each of the five forks in this set is tuned to the note C;the lowest fork making one hundred and twenty-eight vibra-tions per second, while the highest registers two thousandand forty-eight vibrations per second, each fork being tunedan octave higher than the one below it. This particular rangeis chosen as it includes those fundamental notes which maybe called essential to perfect audition—that is, the range ofnotes employed in ordinary conversation. In addition, the Fig. 63.—Blakes tun-ing fork. The rateof vibration indi-cated on the handle(512) refers to singlevibrations. * Archiv fur Ohrenheilk., vol. xxx, p. 283.\ Krank -»£i Ohres, Berlin, 1SS9, p. 32. 12 158 FUNCTIONAL Fig. 64.—Hartmanns series of tuning forks. Galton whistle will enable an investigation as to the powerof the patient to perceive those notes of the scale lying above the highest fork of the employed these instru-ments for some time, andhave seldom been misledin the deductions madefrom the results thus ob-tained. In making these quali-tative tests certain pre-cautionary measures arenecessary : for example,to avoid the productionof overtones in using thelarge tuning fork withthe clamps so placed asto produce the lowestobtainable rate of vibra-tion—that is, twenty-six vibrations per second. If care isnot taken, an overtone will be produced when the fork isstruck, and this may be perceived by the patient to the ex-clusion of the very low primary note of the fork. In everyinstance, therefore, the observer should make certain by hold-ing the vibrating fork for a moment before his own ear be-fore it is used to
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