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In the course of previous investigations, Dix, Hallpike, and Hood have concluded that the phenomenon of loudness recruitment is attributable to disordered function resulting from injury or disease of the hair cells of Corti's organ.In the present paper, an account is given of an experimental study of certain loudness changes caused by adaptation of the hair cell responses to pure tone stimulation.Two outstanding characteristics of the adapted state are defined: “on‐effect normality” and “relapse.” Both resemble very closely those described by Matthews in the case of adaptation occurring the muscle stretch receptors of the frog.Further studies in a number of human subjects show that both of these characteristics are exhibited regularly by the unadapted hair cell responses of individuals suffering from degenerative changes of the hair cells.These studies appear to establish a very close similarity between “on‐effect normality” occurring in the case of the adapted normal sense organ and the phenomenon of lou...

1. The loudness recruitment angle is defined. It is found to provide a useful quantitative index of the recruitment phenomenon.2. The results are described of a study of the angle based upon 200 cases of unilateral deafness due to Meniere's disease. The magnitude of the angle is found to vary linearly and within close limits, with the amount of the deafness.3. The recruitment angle shows some dependence upon the frequency characteristic of the deafness, being greater with low than with high frequency types of hearing loss.4. The results of a comparative study of two small selected groups of subjects, with and without severe symptoms, suggest that the recruitment angle tends to be increased during the active phases of the disease.5. The results are discussed in the light of recent work on the electromechanical behaviour of the cochlea, and an explanation is suggested of the neurological mechanism of the loudness recruitment phenomenon based upon the dual excitation theory of Hallowell Davis.

By means of a photocell, light source and interrupter, it has been found possible to produce phase-reversals in a musical tone of approximately sinusoidal waveform. When this tone is caused to fall on the human ear, phase-change beats are heard as has previously been described. When this tone is caused to fall on the ear of a decerebrate cat, and its auditory-tract responses are recorded by means of a cathode-ray oscillograph, a temporary and marked decrease in amplitude of the response occurs, corresponding to each phase-change. This decrease in amplitude corresponds to the phase-change beat which is heard by the human subject and is postulated on the resonance theory of hearing. When the cochlear (Wever-Bray) response of the cat is similarly recorded, the response exhibits no such fall in amplitude in correspondence with the phase-change, which is moreover reproduced with marked fidelity. The cochlear response must therefore originate in some non-resonant structure.

Schuknecht and his co-workers have shown that partial lesions of the cochlear nerve in cats may be associated with normal hearing at threshold for pure tones. Comparable findings are described in two human subjects.

Sensori-neural deafness — the nerve or perceptive deafness of the earlier text books of Otology — is due, with very few exceptions, to organic disorders which exert their effects, either separately or in combination, upon the sensory cells of Corti’s organ or upon the nerve cells or fibres of the peripheral cochlear neurones.

THE SUBJECT of this communication, a woman of 50 years, was first seen in April, 1948. She then gave a history of one month's duration of attacks of rotational vertigo preceded for some months by increasing deafness of the right ear accompanied, since the onset of vertigo, by a continuous humming tinnitus in the right ear. Examination of the ears, nose, and throat revealed nothing abnormal. Roentgenological examination of the paranasal sinuses showed mucosal thickening within the right antrum, which was washed out with negative results. Pure-tone audiometry, carried out in May, 1949, gave the result shown in Figure 1. Tuning-fork tests showed the deafness of the right ear to be of the perceptive type, the Weber test being referred to the left, with a false negative Rinne test on the right mastoid. There was no spontaneous or positional nystagmus, and the caloric tests gave the results shown in Figure

1. The results are described of a study of the spontaneous horizontal nystagmus found to be present in 75 subjects with unilateral acoustic neurofibromata.1. Es werden die Resultate einer Untersuchung auf spontanen Horizontal-Nystagmus beschrieben, der sich bei 75 Patienten niit cinseitigeni Akustikus-Neurofibroni fand.2. Aus Grunden der besseren Ubersichtlichkeit wurden alle Tumorcn dcs rechten Ncrven als solche dcs linken Ncrvcn angesehen, gleichzeitig wurde audi eine cntsprcdiende Scitenumkehr dcs Nystagmus und der andcrcn nenrologischi'n Syniptoinc vorgenommen. lis ergab sicli dadurcli cine Gesamtzahl von 75 Pa-tienten mit linksscitigeni Tumor.3. Der Nystagmus wurde entsprecbend der herkommlicben Bczeidinungswcisc nach Riehtung und Intensitat eingeteilt.4. Bei vielen Patienten war ein Nystagmus sowohl nacb recbts wic audi nach links vorbanden. Bei diesen wie audi bei anderen Patienten bestand ein eindeu-tiges Uberwiegen des Nystagmus nacb reebts.5. Eine elektronystagmograpbische Analyse des Spontan-Ny...

As is well known, raising of the threshold of hearing is caused by exposure to a continuous tone. The magnitude of this effect is a function of the frequency, duration and intensity of the tone. In general it is small, with intensities which do not exceed 90–100 db. above normal threshold in the middle frequency range.