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Re: My apologies, but... physiology revisited

Stan Friesen writes:

>It does, since the way the study is done assumes an *undemonstrated*
>equivalence between mammalian and avian respiratory systems. One simply
>cannot blithely lump birds and mammals together just because both are
>endothermic, some additional evidence is needed to make such a move

I have to agree with Stan on this one.  Mammalian and avian respiratory
systems are inherently and fundamentally different from each other, so to
easily combine the two into one study would be to make a grievous mistake.

The basic difference with the two respiratory systems how the air travels
through the lungs.  For birds, air is circulated in ONE DIRECTION ONLY (it
takes two breath cycles to move one breath of air through).  This is an
inherently more efficient mechanism (another flight modification???).  For
mammals, air travels along the same path into, and out of, the lungs
(resulting in a small percentage of air that is not expelled, but is brought
back into the lungs).  This mechanism is not as efficient.

This basic difference should force us to consider both groups separately in
any physiological study.

[ Please read Nick's recent message and take his advice or I'll start
  losing the faith again.  IMHO it seems more than a little arrogant
  for you to assume that Ruben et al. don't know the basic facts
  above.  Read Ruben's 1995 review paper and I'm reasonably confident
  you'll find he knows more about it than you do, Rob.  -- MR ]

Rob Meyerson
Orphan Vertebrate Paleontologist

"The most dangerous questions in the universe are, "Who am I?" and "What do I