The floating mass transducer produces a measurable reduction of the stapes displacement in the temporal bone model. The effect is more prominent at high frequencies.

Previous studies of perilymph proteins have emphasised the difficulty of obtaining samples free of blood or serum proteins. The present investigation has established a method of polyacrylamide gel electrophoresis, which enables contaminated specimens to be readily identified and therefore discarded. Analysis of uncontaminated samples has confirmed the presence of an elevated perilymph protein in cases of acoustic neurinomata. Perilymph proteins have been separated and identified and although no characteristic pattern of proteins associated with acoustic neurinomata has emerged, further work should be undertaken to establish the site of origin of perilymph proteins and the pattern of abnormalities to be expected in pathological processes.

The revival of endolymphatic sac surgery has led to many investigations in Meniere's disease, including lateral tomography of the periaqueductal pneumatization. We radiologically assessed a series of Meniere's patients and a control group, and found hypocellularity to be more common in Meniere's disease as the literature has stated. However, we found this finding bilaterally in patients with unilateral disease. Our assessment of this information in regard to the etiology and treatment of Meniere's disease is presented.

Letters to the Editor Accuracy of postal questionnaires Dear Sir, Having recently completed the data interpretation of a postal questionnaire of 'all' Otolaryngologists in the British Isles, we read with interest the recent correspondence on the subject of the accuracy of this means of gathering information. (November 1989, 1103), and of the validity of the numbers questioned and responding. Like the correspondents, we also had great difficulty in compiling an up-to-date, accurate mailing list of current Otolaryngologists across the country. The Department of Health was unable to provide a comprehensive listing, and other sources based on membership, (e.g. R.S.M.,B. A.O.L., Royal Colleges), are obviously not fully comprehensive. We have carefully examined the 1989 medical directory to produce the figure of 378 Consultants in England and Wales, 447 in the United Kingdom, and 491 in the British Isles. The total for England and Wales is close to Mr Watsons figure of 381 derived from Health Trends. (Perhaps the three Consultants we missed could make themselves known!) By enclosing a stamped addressed envelope with each questionnaire, (excluding Eire), we achieved a 76% response rate. Of course, a mailing list of this sort will become obsolete on a regular basis, as consultants retire and new appointed take up post. The 21% obsolescence rate in the I.L.O. list used by Messrs Fisher and Croft confirms this fact. Could we suggest that the correspondents and other interested parties contact us to compare mailing lists so that we can together produce one list which is as accurate as possible. This could be updated on a monthly or quarterly basis, using the consultant advertisements in the B.M.J. as a source of changes in post. An annual letter to each Regional Health Authority medical staffing department could be sent to confirm the changes. Once such an up-to-date mailing list is produced, this could be made available, possibly through the Journal for research use, as we feel that postal questionnaire is a useful means of gauging opinion and practice of the specialty on a national basis.

The revival of endolymphatic sac surgery has led to many investigations in Meniere's disease, including lateral tomography of the vestibular aqueduct. Contrary to recent literature, we found no difference in the presence and morphology of the vestibular aqueduct when assessed radiologically in a group of Meniere's patients and a control group. Our assessment of this information in regard to etiology and treatment of Meniere's disease is presented.