Two signs of pathological auditory adaptation, temporary threshold shift and threshold tone decay, are considered to represent retrocochlear lesion.
Possible mechanisms of pathological auditory adaptation were discussed. It was suggested that the unmyelinate portion of the cochlear nerve might have a important part in its occurrence.
In Békésy findings small excursion was considered due to rapid adaptation and decreased difference limen of intensity, and tone decay was based on slow adaptation which was disturbance of impulse initiation at the beginning of the myelinated portion.

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Twenty families of which imformations were reliable were studied by means of historical, statistical and hiometry examinations.
The types of interitance in these families could be classified as follows: (i) simple dominant (twelve families), (ii) recessive in consanguineous marriage (five families), (iii) irregular dominant or recessive (three families).

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Cortical deafness is characterized by the inability to understand spoken words, in spite of persistence of hearing acuity.
The definition of the cortical deafness and pure word deafness was compared and found to be not always identical in a recent audiological point of view.
The possible mechanism of the cortical deafness was discussed.

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The definition and localisation of the cortical center for hearing were discussed and several cases of cortical deafness were reviewed from previous literatures.
It can be concluded that in human unilateral lesion does not cause any hearing loss and total deafness may occur only from bilateral damages of the auditory center.

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In order to find out the most suitable sound quality and sound volume for the hard-of-hearing people with nerve impairment, we investigated the relation of frequency pattern and sound level to articulation score and comfortableness.
The frequency pattern was one that compensated for a patient's individual hearing loss by “mirroring” his audicgram, and flat one.
The results were as follows.
1) The maximum syllable articulation scores were more than 60% for almost all subjects even if the hearing loss was at the range of 60-80dB.
2) The “mirroring” was especially succesful for the subjects with the maximum articulation scores at the range of 40-80% (in the flat frequency pattern).
3) For the subjects with hearing loss less than 40 dB, the most comfortable level was nearly equal to the sound level which gave the maximum articulation score. On the other hand, for the subjects with hearing loss more than 40dB, the sound level which gave the maximum articulation score was higher than the most comfortable level, occasionally it reached uncomfortable level (in the flat frequency pattern).
4) The difference between the most comfortable level, uncomfortable level in binaural listening and those in monaural listening was about 6 to 7 dB.

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Waardenburg-Klein syndrome consists of lateral displacement of the inner canthi of the eyes (dystopia canthorum), a broad nasal root and confluent eyebrows, heterochromia iridum, a white forelock and congenital deafness.
The clinical and genetic aspects of this syndrome were studied.
Investigation on this syndrome was aroused in 1968 when a five-year-old girl, who had all of the features except white forelock, complained of the congenital deafness.
Fourteen hundred and twenty eight pupils at ten schools for the deaf in Tokyo were screened for the features of this syndrome. Twelve probands and a complete pedigree were discovered. Recently a new additional case was discovered.
In the pedigree, proband had all of the features, mother had four features without heterochromia iridum and confluent eyebrows, and she showed unilateral deafness in left ear. Two siblings (brother and sister) had slightly dystopia canthorum and broad nasal root only.
Two out of fifteen cases had all of the features, another two cases had all of the features except white forelock, and another eleven cases showed three or four features of this syndrome.
In this series the interocular measurements of Japanese, twenty subjects of both sexes and of age from two to twenty years were used to provide normal standard. Interocular index recommended by Partington was also used on judging the presense of dystopia in Japanese.
Three cases had palpebral ptosis of both sides. One of them combined with epicanthus inversus, but showed no dystopia. Stiff ptosis may be an equivalent for dystopia.
Isochromic blue eyes were present in Japanese cases.
Relationship between the side of the heterochromia iridum and that of the deaf ear was discussed. Bilateral heterochromia tended to combine with total deafness. But no relationship was revealed in cases of unilateral heterochromia.
One case showed a remarkable disturbance of the vestibular function. But optokinetic pattern of nystagmus was normal.
X-ray findings of the temporal bone showed not only various degrees of cochlear apparatus, but also that of vestibular apparatus.
Combination of signs of this syndrome was divided into two groups; a group of deafness, eyelid deformity and heterochromia, and that of deafness, heterochromia and grey hair.
Incidence of this syndrome was 1.4 per cent of the congenital deafness in Tokyo. This value coincided with that of Waardenburg's finding in the Netherlands.
Chromosomal analysis in one case with this syndrome revealed normal karyotype.
Autosomal dominant transmission was present in one pedigree. But in another cases recessive transmission may be present in this series.

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The functional difference between cochlear and vestibular system, in special reference to the approaching method of functional test on the two system, was demonstrated.
Simplified schema of the cochlear and the vestibular system was presented and using this schema early and advanced acoustic tumor, congenital nystagmus were discussed.

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This is a report of eighteen hearing impaired children who have enrolled in the nursery program of Nippon Rowa Gakko at the age under two years old since July 1965. The youngest one was six months old. The parents of 11 children noticed their children's hearing impairment before their first birthday, never-the-less 5 of them consulted doctors and only 3 began training at the age.
Hearing aids were attempted to be worn on both ears as soon as possible. 7 children had adopted the aids within a month and the majority of children had adopted within 4 months. The most reactions using aids were the increase of amount and loudness of voice. Later many children had recognized the others calling them and several sounds, and many enjoyed music. Within 8 months most children began to understand the first word and within 12 months had started to say words.

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