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> During tests in pressurechamber seals got the bends when breathing > compressed air for quite a long time and after a quick ascend from a > greater depth. > Theoretical, even the whales would get the bends under the same > circumstances, although it could be associated with some difficulties to > get the whale in to the chamber (-: > From ANIMAL PHYSIOLOGY by Schmidt-Nielsen 1986: It is significant that a seal exhales at the beginning of a dive, rather than diving with filled lungs as a man usually does. Whether a whale also exhales is uncertain, but it has an exceptionally large and wide trachea. This may be an adaptation to enable the whale to ventilate its lungs rapidly when it surfaces to breathe. Equally or more important, the lungs are small relative to the large volume of the upper airways. As a whale dives, the increasing water pressure compresses the lungs and forces air into the large trachea, which is rigidly reinforced with circular bone rings. With no air in the lung, nitrogen cannot enter the blood, as it does in man. Another reason nitrogen does not enter the blood is that blood flow to the lungs is minimal during the dive; thus, even if the lung contains some air before the animal reaches the depth where the lung is collapsed, little nitrogen enters the blood. Hope this helps ! Bridget Elliott /\ /\ Department of Zoology / /\\ @@ //\ \ University of Port Elizabeth ///\ \\ (())) //\\ \ Box 1600 ////\\ ((***))//\\ \ Port Elizabeth // \ ((())/ \\ South Africa / \ 6000 fax : +27-41 - 504 2317 voice : +27-41 - 504 2424 e-mail:ZLBBLE@ZO*.UP*.AC*.ZA*
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