Prof. S. Kawata worked out a way to judge the recruitment phenomenon by means of the retraction grade of the tympanic membrane resulting from the acoustic reflex of the tympanic muscle.
The author studied on the value (i. e. reliability, applicability and symplicity) of this method as a clinical examination by measuring the acoustic reflex of the tympanic muscle (the threshold of the reflective retraction of the tympanic membrane) on normal subject and patient with the impairment of hearing by means of the newly improved apparatus of precise measuring the retraction grade of the tympanic membrane.
1) The new apparatus is designed as precise myringogoniometer to measure the retraction grade of the tympanic membrane.
The stable, easy, correct and long measurement was made possible by preparing the fixing and adjusting apparatus of the myringogoniometer and the subject's head, and by increasing the degree of precision of it.
2) The threshold of the reflective retraction of the tympanic membrane on normal subject are as follows.
The reflective retraction of the tympanic membrane was observed by the stimulation of pure tones of 250, 500, 1000, 2000 and 4000 cps. except 8000 cps. in all subjects.
3) Relation between the judgement of recruitment phenomenon by means of Fowler's alternate binaural loudness balance test and the threshold of the reflective retraction of the tympanic membrane.
The examination results of 55 cases of the perceptive deafness (i. e. Meniere's disease, nerve deafness of unknown cause, acoustic trauma, head trauma, sudden deafness, acoustic tumor, cerebellar pontine angle tumor, etc.) are as follows.
(a) Recruitment (+)
In spite of the increment on the thershold of audibility, the threshold of the retracton of the tympanic membrane was normal or a shade of difference, and the level difference between the threshold of audibility was reduced clearly compared with the normal subject.
(b) Recruitment (-)
The threshold of the reflective retraction of the tympanic membrane increased with the increment of the threshold of audibility and the level difference between the threshold of audibility was normal. The reduction of the threshold difference as was observed in case of recruitment (+) was not shown, and there was the case in which the reflective retraction of tympanic membrane was not perceptible.(i. e. acoustic tumor and cerebellar pontine angle tumor etc.)
The expression of the relation between (a) and (b) with the mean value of the threshold difference classified by frequency are as follows.
From above experimental results, it is suggested that the concurred relation between the recruitment phenomenon and the threshold of the acoustic reflex of the tympanic muscle will be originated on the same pathological change of the innerear.
In case of judging the recruitment by this method, it was proved that it was a sure method when the limit of rejection on the threshold of the reflective retraction on the tympanic memb rane was set on the basis of the judgement.
4) The comparison between this method and Fowler's balance test in various points are shown in the following table.

View full abstract

Among 72 patients who were subjected to the laryngectomy in the department of otorhinolaryngology of Kyushu University, 67 cases used the artificial larynx. The statistical observation of the state of application and the frequency analytical studies of speaking by the artificial larynx were studied with the following results.
1) In the vocalisation of laryngectomized patients, 67 cases (93%) used the artificial larynx, and 5 cases (6.9%) the esophageal voice.
2) On the state of mutual understanding in the artificial larynx 25 cases among 67 suffered no inconvenience in everyday life, and 11 cases lacked in understanding.
3) On the term of becoming proficient in simple conversation by the artificial larynx, 44.8% was within 5 days, 31.3% 6 to 10 days and 76.1% within 10 days.
4) 33 cases in the artificial larynx used Tapia type, however, the materials of these constitu- tion were great variety and the vibrating membrane used rubber.
5) The direct relation between the method of operation and the proficiency of pronounciation by the artificial larynx was not observed. 6) In the examination of articulation score in pronounciation, articulation was good at the vowel and pronounciation (wa), and was worse at the “Ha” series, even in the man of experien ce, no improvement was shown.
7) On the comparative studies of artificial larynx with a normal voice by the frequency an alyser, the field of overtone reduced in the artificial larynx compared with the normal, and the formant which characterize the vowel made indistinct. This may be one of reasons that the voice of artificial larynx is not clear, has dry tone, and feel in a monotone.
8) The author examined the variation in the voice by changing the component parts of the artiftcial larynx. The examination revealed that the overtone in the high frequency range increas- ed if the mouth piece was short, and that the overtone in the low frequency range increased if the connecting tube was long.
It also revealed that the overtone increased when the tension of the rubber membrane was small and when the hole in the voice box was large. The variation in the overtone due to the width of the tracheal edge and to the material of the atrificial larynx was not perceivable.

View full abstract

The variation in the auditory acuity in the normal ear has been studied only by a small number of authors except on the rise in the audible threshold of a high pitched tone in old people. The auther has studied the effect produced by different physiological conditions on the hearing acuity of an individual.
The author made 76 young people, aged 17-21, play 9 kinds of games, tennis, judo, Japanese fencing, volleyball, basketball, 1500 meter race, Rugby, wrestling and 5000 meter race. Immediately before, immediately after, 30 minutes after, 1hour after and 2 hours after the exercises, the author made the pure tone audiometry and examined the variation in the auditory acuity in 152 ears.
The hearing loss after the exercises was most strongly observable in the sound of 4096 cps. The restoration of the hearing loss took 30 minutes with tennis, judo, Japanese fencing, and 1 hour with volleyball, basketball, 1500meter race, rugby, and 2 hours with wrestling, 5000meter race (in this case excepting a few ears).
C⁵ dip was observable in no ear with tennis, judo ; in 3 among 18 ears with Japanese fencing in 3 among 12 ears with volleyball; in 4 among 16 ears with basketball; in 4 among 20 ears with 1500 meter race; in 5 among 18 ears with Rugby ; in 10 among 24 ears with wrestling; in 12 am ong 20 ears with 5000meter race. The appearance of the dip became more frequent and its depth greater in proportion to the severeness of the exercises and the degree of the fatigues.
The author compared this temporary appearance of the c5 dip after physical exercises with that of auditory fatigue, and deduced the cause of this phenomenon as the result of circulatory disturbance.

View full abstract