1879.] Dr. B. W. Richardson on the Audiometer. 



67 



pacity to hear is reached. If, for instance, the sonnd be very faintly 

 heard at 15°, and the induction coil be suddenly moved to 5°, the sound 

 at 5° may be quite inaudible ; but if the coil be slowly moved, unit 

 by unit, from 15° to 5°, the sound at 5° may be distinctly heard. 

 Mr. Maitland Tate, C.E., who noticed this point very markedly in his 

 own case, when I was submitting him to test, compared this to what is 

 observed by the sense of sight in making surveys. The eye will follow 

 a line to an extreme point with comparative readiness, but if it break 

 away from it, the object seems to have disappeared. 



Influence of Respiration on Hearing. 



The effect of filling the chest and holding the breath makes a differ- 

 ence in listeners. The capacity for hearing is for a few seconds 

 increased by holding the breath. Mr. Tate, who could hear with his 

 right ear only down to 8° under ordinary breathing, could hear down 

 to 5° when he held his breath. Another gentleman, who could hear 

 only down to 100° under ordinary breathing, could hear to 80° when 

 the breath was held with the chest full. Holding the breath with the 

 chest not full fails to produce the same result.. 



Influence of habitual Movements of the Body. 



As a rule, the hearing of persons who are right-handed is most refined 

 in the right ear, and as most persons are right-handed, it is found that 

 the right ear is the best ear. This rule is, however, attended with 

 many exceptions, since, for various reasons, some persons who use the 

 right hand exclusively, practise for some particular purpose the use of 

 the left ear, upon which that ear becomes more acute. Thus five physi- 

 cians, who were right-handed bat who had accustomed themselves to 

 use the stethoscope with the left ear, could hear to zero on that side, 

 but had lost from 4° to 5° on the right side. Four other persons who 

 were similarly circumstanced were able at once to account for the fact 

 by the habit they had acquired of listening to a public discourse or 

 sermon from the left side. Another point of interest attaching to this 

 observation is, that the practice of using one ear for special refinement 

 of the sense seems for the time slightly to impair the other ear, 

 although there is no physical evidence of such impairment. 



Influence of some Automatic Adjustment and of Memory, on Searing. 



Connected with the last-named fact is another, namely, that by this 

 instrument the deaf are found to fail in capacity of hearing not only 

 by reason of physical defect, but also by failure of memory of sounds. 

 Thus in a youth who had suffered serious defect of hearing for seven 

 years owing to partial destruction of the tympanum, and who in the 

 right ear could only detect sound at 107°, there was an inability to 



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