Effect of Certain Drugs on Acuity of Hearing 145 



It was stated in the beginning of this paper that our chief 

 problem was related to the effects of quinine on acuity of hear- 

 ing. Witmaak (5) has reviewed the literature on this drug and 

 the following notations are from this source : 



Roosa in 1873 reported the evidence of an injection of the 

 drum membrane in three colleagues after ten and fifteen grain 

 doses of the drug. Guder in 1880 experimented on twelve nor- 

 mal individuals and denies a hyperemia of the membrane. Wit- 

 maak did not find evidence of a congestion in experimental ani- 

 mals and come to the conclusion that quinine has a specific toxic 

 effect on the end organ and cochlear neurones. Ferreri in 1887 

 reported decrease in both air and bone transmitted sound in a 

 number of cases where large doeses were given (3-4 grams). 

 He found that the acuity of hearing was about as much depressed 

 by 2 grams, as when larger amounts were given. He found also 

 that the hearing returned to normal in about twenty-four hours. 

 It is unnecessary to devote much space to citing instances which 

 confirm the well-known symptoms of quinine intoxication. As 

 has been said we were more concerned in quantitative tests and 

 in particular the relation of the tinnitus to the decreased acuity 

 of hearing. Inadvertently, however, some interesting observa- 

 tions were made in relation to the toxic effects of a large dose 

 of the drug. 



The first step in our tests was the establishment of a curve 

 for minimum audibility as a function of pitch. This was obtained 

 in the following manner: Electrical currents of controllable and 

 measureable frequency and intensity were generated by means of 

 a vacuum tube oscillator and amplifier. The harmonic frequencies 

 were eliminated by the use of suitable electrical niters. The 

 thermophone was used as a sound source. This apparatus takes 

 advantage of the heating effect of the current in a thin platinum 

 strip and the consequent expansion of the adjacent air. The 

 sound intensity produced is calculable in terms of the electrical 

 energy input which can be easily measured. The thermophone 

 unit was mounted in a small telephone receiver case which was 

 held tightly to the observers ear under test. A frequency variator 

 of special design was used so that the observer could at will vary 

 the frequency over the range of nearly an octave. This variation 



■ Witmaak, Arch. Ges Physiol, 1903, xcv, 209. 



