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Re: A question on Békésy.

If your real interest is the basilar membrane stiffness gradient, then I would take Fig. 11-73 on face value. 

I doubt very much that the "gelatinous mass" is the tectorial membrane since, as you say, von Bekesy was very familiar with the TM and results from TM measurements are mentioned elsewhere in the book. 

The basilar membrane stiffness measurements that we measured in the gerbil are quite similar in slope to what von Bekesy found and we have some preliminary data for the dolphin basilar membrane that exhibit a similar slope.

On Fri, Mar 19, 2010 at 1:58 PM, reinifrosch@xxxxxxxxxx <reinifrosch@xxxxxxxxxx> wrote:
Thank you, Harriet and David -- but I have two different answers now !

Harriet: could you please give details on why you think that the "gelatinous
mass" is the TM? As you know, that verdict is hard to swallow; von Bekesy
knew the TM well.

David: fairly ingenious! Agar and gelatin are even mentioned twice on that
page 475. The helicotrema was closed with such a mixture, and after
conclusion of the measurements at the apex, the scala tympani was
closed again with agar and gelatin. With "cochlear lumen", Bekesy means
"cochlear channel", I believe. But I do not understand that page 475
completely. Can that gelatin get into the cochlear duct ?

It would be nice if we could now clear up this gelatinous problem.
I asked the List about it a few years ago already, I believe, but
did not get answers then.

The problem is important to me in connection with Bekesy's
Fig. 11-73 (BM stiffness).


----Ursprüngliche Nachricht----
Von: dcm@xxxxxx
Datum: 19.03.2010 17:00
An: <reinifrosch@xxxxxxxxxx>
Kopie: <AUDITORY@xxxxxxxxxxxxxxx>
Betreff: Re: A question on Békésy.

The viscosity of endolymph is similar to water.  The "gelatinous mass" is
probably the agar/gelatin mixture mention earlier on the same page.

On Fri, Mar 19, 2010 at 9:20 AM, reinifrosch@xxxxxxxxxx <
reinifrosch@xxxxxxxxxx> wrote:

> Dear colleagues,
> At the bottom of page 475 of his book "Experiments in Hearing",
> McGraw-Hill, New York, von Békésy (1960) has written:
> "[...] It was further established that the gelatinous mass in the
> cochlear duct increased the rigidity of the partition, especially
> near the helicotrema. [...]"
> What is that "gelatinous mass"? I seem to remember that
> the viscosity of endolymph is about equal to that of water.
> A wild guess: "gelatinous mass" = tectorial membrane (??)
> Your (on- or off-line) suggestions would be very welcome,
> of course, even if you are not absolutely sure !
> Reinhart.
> Reinhart Frosch,
> Dr. phil. nat.,
> r. PSI and ETH Zurich,
> Sommerhaldenstr. 5B,
> CH-5200 Brugg.
> 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

Boston University
44 Cummington St.
Boston, MA 02215

Email:   dcm@xxxxxx
Website: http://www.bu.edu/hrc/research/laboratories/auditory-biophysics/
Phone:   (617) 353-4343
FAX:     (617) 353-6766
Office:  ERB 413