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Re: Sauropod drinking



In article <35AC07C0.247FC09@erinet.com>, Jonathon Woolf
<jwoolf@erinet.com> writes
>C. Laibly wrote:
>
>>         I remember reading an article in my Princ. of Paleontology course
>> concerning a professor who tried testing the plausibiliy of this theory
>> (large sauropods breathing while bodily immersed in water). He breathed
>> through a hose that would supposedly have given him relative fresh
>> air and pressure amouns to deal with as that of a submersed sauropod.
>> He died from congestive heart failure in the process. Then again, a
>> plesiosaur could breathe. Hmmm. Something to think about...
>>
>
>What makes breathing in water difficult is the external pressure _differential_
>between the intake (nostrils) and the lungs. The nostrils are in air at normal
>atmospheric pressure of 14.7psi.  The lungs -- well, the pressure on them
>depends on how deep underwater they are, and how dense the water is.  As a
>general rule of thumb, the pressure increases one atmosphere for every ten
>meters of water.  A mere five feet of water, about 2.5psi of added pressure
>differential, is more than the average human's lungs can overcome.  Anything
>that wants to breathe with its nose at the surface and its lungs ten or twenty
>feet down had better have Brobdignagian lung muscles.

'snot the lung *muscles* that are the problem.  Lungs work by having a
really thin (=not very strong) membrane across which gases diffuse
readily.  The air on one side of the membrane (if you're snorkeling) is
at atmospheric pressure; the blood on the other side is at atmospheric
pressure, plus whatever blood pressure is required to drive the
pulmonary circulation, PLUS the external water pressure.  I really can't
see any way round that for any credible design of lung; you can't
snorkel more than a couple of feet or so down, without either collapsing
your lungs (if you're lucky) or breathing out most of your circulating
blood volume into what's meant to be air space, like the good professor
presumably did (I heard the same story in medical school).  And neither
could a sauropod.  

back to lurking...

-- 
Richard Keatinge 

homepage http://www.keatinge.demon.co.uk