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    Re: Sperm whale buoyancy.
    From: Fred Hebard
    Date: 2007 Mar 26, 16:17 -0400

    I was just thinking that the skull would resist the pressure more
    than the lungs, so there would be a pressure differential between the
    _interior_ of the skull and the lungs; but I'm no physicist nor
    physiologist!
    
    On Mar 25, 2007, at 7:23 PM, George Huxtable wrote:
    
    >
    > In reply to Fred Hebard's question, copied below, my answer is "No,
    > I doubt it". The point being that whatever the sea pressure is,
    > that is being applied to the lung-area of a sperm whale to collapse
    > it, that same sea-pressure, and a bit more, is being applied to
    > the head area, because it's a few feet lower down in the sea,
    > because of the creature's head-down orientation as it makes its
    > vertical dive. And surely, those pressures must transmit themselves
    > to the whale's interior, because it's constructed of such
    > flexible stuff. So I don't quite see how the remaining bubble of
    > air remains at that lower level, unless it's held there by some
    > muscular power creating a bit of extra pressure at the level of the
    > lungs.
    >
    > But there's a lot of speculation in that, and much ignorance, on my
    > part. I'm simply doing my best to apply physical principles to a
    > whale/water system. We need access to an expert on whale
    > physiology. I wonder where you find a helpful cetologist?
    >
    > We are discussing fine points here, and unlike the sperm whale, I
    > am well out of my depth.
    >
    > George.
    >
    > ================
    > |
    > | Wouldn't the pressure difference be provided by the sea in the form
    > | of the collapsed lungs?
    > |
    > |
    > | On Mar 25, 2007, at 1:24 PM, George Huxtable wrote:
    > |
    > | > That mechanism for avoiding the "bends" seems plausible, but
    > there's a
    > | > question occurs to me that isn't answered. As explained by Watson,
    > | > those air receptacles, being in the head, are many feet below
    > the lung
    > | > area, when the whale is diving, almost vertically, with its
    > head down.
    > | > So how does the whale ensure that the remaining bubble of air,
    > | > shrinking as it compresses, doesn't float upwards into the
    > lungs, but
    > | > instead stays down at the head-end? That must be achieved by
    > some sort
    > | > of muscular control of the chest cavity to provide the necessary
    > | > several-pounds-per-square-inch of pressure difference.
    >
    > contact George Huxtable at george---.u-net.com
    > or at +44 1865 820222 (from UK, 01865 820222)
    > or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
    >
    >
    > >
    
    
    
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