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Re: A question on Bekesy.
Over the years our group has dissected many cochleae and I can assure you that the endolymph has a viscosity very similar to water.
On Fri, Mar 19, 2010 at 6:09 PM, reinifrosch@xxxxxxxxxx <reinifrosch@xxxxxxxxxx>
Yes, the TM is generally described as gelatinous. Nevertheless,
I now think that the mentioned sentence from page 475 of Bekesy's
book does not refer to the TM. I have read all of that book a few
years ago, but unfortunately have forgotten many details. Today I
found a sentence on page 467:
"If Reissner's membrane was removed and the material within the
cochlear duct was washed away, the elastic properties of the
tectorial membrane could be investigated [...]"
(Bekesy's Article 47, first published 1947 in JASA).
Bekesy apparently thought that the "material within the cochlear
duct" has a large viscosity. On his page 469, it says:
"The cochlear duct is bounded on the one side by the basilar membrane,
and on the other side its viscous contents are contained by the thin
(Article 39, first published in German in 1941; published in English
in JASA in 1948).
Bekesy mentions that gelatinous mass also on his page 443:
"When the gelatinous mass of the cochlear duct was removed from
the basilar membrane with a fine brush the traveling waves were observed
with a larger amplitude and less damping."
(Article 42, first published in German in 1942; published in English
in JASA in 1949; in that experiment, there was apparently no agar-
gelatin mixture, only dental cement).
So the problem is still unsolved. Are we sure today that the
"material in the cochlear duct" has a viscosity close to that
(I shall comment on Bekesy's BM stiffness measurements,
i.e., his Fig. 11-73, later.)
Datum: 19.03.2010 20:29
An: <reinifrosch@xxxxxxxxxx>, <AUDITORY@xxxxxxxxxxxxxxx>
Betreff: Re: A question on Békésy.
If I recall correctly from my studies with Dr. Tonndorf, that was how he described the TM. It stuck with me all
However, it is always possible that my memory may be a bit faulty on this.
Harriet B. Jacobster, Au.D., CCC-A, FAAA
Board Certified in Audiology
Dr. phil. nat.,
r. PSI and ETH Zurich,
Phone: 0041 56 441 77 72.
Mobile: 0041 79 754 30 32.
E-mail: reinifrosch@xxxxxxxxxx .
David C. Mountain, Ph.D.
Professor of Biomedical Engineering
44 Cummington St.
Boston, MA 02215
Phone: (617) 353-4343
FAX: (617) 353-6766
Office: ERB 413