Re: Biomechanics

[MKIRKALDY@aol.com]

(Comments from Rich Hengst, forwarded by permission.)

On 9/9/99, Toby White wrote:
>Paladino et al cite Hengst & Rigby (1994 Dinofest) for the estimate 
>that Apatosaurus had a lung volume of 1400 l with a dead space of 
>184 l.  Sounds like a reasonably serious physiological constraint to 
>me, but who knows how good these numbers are?  

And Matt Bonnan wrote:
> Hengst I know is developing more accurate models and ideas on 
> dinosaur breathing as we speak.  If he is reading this list, perhaps 
> he could add his two cents?

Rich Hengst now comments:

However, my original estimate of lung volume was based on the best
possible scenario for the animal I measured.  The tracheal volume I 
worked out is definitely LOW.  The tracheal diameter was arrived at 
using experimental methods but was assuming a mammalian 
FREQUENCY limit (It is higher than birds, crocs, and other reptiles).  
The original intent was to bracket the animal's limits in the manner 
most favorable to the animal.  Additional research has led me to
think that the breathing rate was slower and the dead space larger than 
I originally postulated.  Beware of the trap of discussing lungs 
without looking at ventilation first.  Until the volume is delivered, the 
lung cannot extract the oxygen.  Not having seen the thread, I am not 
certain what the croc lung volumes are, but I can tell you from direct 
measurement of alligators ranging from 28 cm to 1.4 m that the 
maximum breath is very, very, large.  Much larger than mammals 
deliver.  That is probably why mammals use a high frequency, but 
low volume breathing strategy.  (That, plus lung characteristics a la 
Steve Perry).
______

Mary
mkirkaldy@aol.com