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re: rearing up

At 02:02 PM 5/5/99 -0700, Bill Adlam wrote:
>Accessory hearts in the neck, if they existed, would be able to break
>down this pressure into manageable steps.  Peristalsis wouldn't work
>- the pressure gradient is much too great.  Valves could have kept
>the blood already in the head, so the sauropod could keep going until
>the blood around the brain ran out of oxygen.  However long that was.
> Unless it had an accessory lung, which is no more plausible than an
>accessory heart.

Actually it is far *less* plausible.  Depending on what is meant by the
term "accessory heart", there need be nothing particularly implausible
about it.  Arteries undergo active peristalsis as it is.  A combination of
a set of valves, and an enlarged arterial lining will naturally produce a
supplemental pumping locus.  This strikes me as being a very minor change,
so it looks quite plausible to me.

May the peace of God be with you.         sarima@ix.netcom.com