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Re: pleurocoels

At 13:41 14/11/96 -0500, you wrote:
>To the best of my knowledge, an air-filled space within the body of a
>living animal would have to be connected to the external environment in
>order to stay open.  The air in a closed space would eventually be
>James M. Norton, Ph.D.

An exception is the swim bladders of fishes, which remain gas-filled
although closed to the outside because of a special gas-exchange mechanism
involving the circulatory system (as I recall) in the wall of the bladder;
fishes can "pump" gas into the bladder or resorb it through a rete
mirabile.  I am not saying this applies in any way to pleurocoels, except
to show that an internal gas-filled space can be maintained by active
metabolic mechanisms despite the resorption problem Dr Norton refers to.
Ronald I. Orenstein                           Phone: (905) 820-7886
International Wildlife Coalition              Fax/Modem: (905) 569-0116
1825 Shady Creek Court
Mississauga, Ontario, Canada L5L 3W2          Internet: ornstn@inforamp.net