276 
PHYSICS: J. P. MINTON 
Proc. N. a. S. 
to a blurred noise of just audible intensity. When the tone was heard no 
noise sensation was present and when the noise was heard no tone was 
observed. So, it would seem that the same nerves were responding under 
both conditions and that a certain minimum amount of nerve energy was 
necessary for tone perception. It is quite improbable that such a varia- 
tion as this could be due to the mechanical condition of the internal-ear but 
it would appear most reasonable to consider it due to a condition of the 
auditory nerve system whose impairment, without doubt, was responsible 
for the deficiency in hearing. Even though there was such an impairment 
in hearing due to the condition of the nerves and their endings the patient 
was able to recognize all the pitches when the tones were sufficiently intense. 
b. In figure 2 is shown a group of six curves for the right and left ears 
of three partially deaf and dumb persons who had congenital deafness. 
Impaired hearing of this nature is caused, according to medical findings, 
by the incomplete or mal-development of the internal-ear system. These 
six curves are of much value from the theoretical viewpoint as will be seen 
later. 
Curves 1 and 2 are for the two ears of a young man 25 years of age. 
Curves 3 and 4 are for those of a young girl 18 years of age and Curves 5 
and 6 are for the two ears of a boy 10 years old. The first two curves are 
of the same general shape; both have their maximum depression at 3300 
d. v., but the degree of hearing for the two ears is quite different. Curves 
3 and 4 are also of the same general shape and the same is true of Curves 
5 and 6. All three of these patients recognized all the pitches, the tones 
sounded of the same pitch when listened to by the two ears (that is there 
was present no indication of diplacusis for these cases) and the pitch 
discriminating power was apparently normal. Therefore, the auditory 
nerve systems for these three patients responded in a normal manner in 
regard to pitch perception. The sound intensity, of course, needed to 
stimulate the nerves in order to produce the sensation of sound, was far 
more than required for normal hearing; this being due, no doubt, to the 
structural condition of the cochlea. 
Although these three persons were nominally deaf and dumb, all three 
of them recognized the difference between the fourteen fundamental 
vowel sounds when they were intoned in the patients ears. In the case 
of the girl the vowel sounds were repeated correctly by her. She was 
able to recognize and repeat, but with difficulty, spoken words and simple 
sentences. The results were not as satisfactory in the case of the boy. 
Nevertheless, he was able to repeat the vowel sounds with sufficient clear- 
ness to make it certain that he was able to distinguish the difference 
between these sounds. 
c. In figure 3 are given two curves for patients each of whom were con- 
sidered by the otologist totally deaf in one ear. The threshold curves 
