Vol. 7, 1921 
PHYSIOLOGY: J. P. MINTON 
223 
as though we are justified in thinking of the ear as whole as a coupled 
vibratory system and referring to the maxima of sensitivity as its resonant 
frequencies. The resonant frequencies are not to be thought of as harmon- 
ics of the fundamental. 
Sensitivity of Abnormal Ears. — In the study of abnormal ears, where 
disease has affected certain portions of them and has produced partial 
deafness, curves of two types are plotted. The first type shows at the 
various frequencies how much current must pass through the receiver 
for the patient to just hear the tones compared with that required for 
a normal ear to hear. The second type shows the sensitivity of the ear 
at the various frequencies. Both methods of plotting the data are of 
value for studying the physical characteristics of the ear. 
In figures 2 and 3 are shown curves relative to the normal reference 
ear for two totally different types of deafness. The former curve is for 
a case of oto-sclerosis (so-called "Fixation of the Stapes"), a type of 
middle ear deafness and the latter curve is for a case of internal ear trouble 
(so-called "Nerve Deafness"). The curves are alike in no respects, what- 
soever. In the case of middle ear trouble there are marked depressions 
relative to the normal reference ear (figure 1) in the regions of 600 to 
1200, 1500 to 2000, 2000 to 2500 and 3000 to 3500 cycles. There have been 
taken for different patients with middle ear deafness several curves and all of 
them agree in the location of these depressions. Some of these depressions 
are relative and some of them are absolute as reference to figure 4 will 
show. This figure (4) gives the sensitivity at the various frequencies 
of the ear referred to in figure 2. The two curves shown in figures 2 and 4 
together give one accurate information on the physical characteristics of 
the defect. The stapes is not fixed but simply hindered and modified 
in its motion so as to produce less sensitivity than is possessed by a normal 
ear and also so as to give a sensitivity curve with three distinct resonant' 
frequencies all of which are at higher frequencies than the corresponding 
ones for the normal reference ear and, as is to be expected, the peaks at 
the lower frequencies are displaced toward higher frequencies more than 
those in the upper part of the scale. 
The curves for the case of the internal ear trouble shown in figures 3 
and 5 are of much value in suggesting how the internal ear system functions 
physically. The patient's hearing is essentially the same as a normal 
ear up to about 2600 cycles as shown by figures 3 and 5 ; shown better in 
the latter, however. Then, the depression (shown better in figure 3) 
from 2600 to 4500 cycles is very great. When one recalls that the vibra- 
tional energy of the receiver diaphragm is proportional to the square of 
the receiver current, he will then grasp the significance of these curves 
in showing the enormous increase in the vibrational energy necessary for 
the patient to just hear compared with a person possessing normal hearing. 
