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From: mjranum@gouldsd.UUCP (Marcus J. Ranum)
Newsgroups: net.cycle,net.auto,net.politics
Subject: Re: Seat belts, Helmets and Freedom of Choice
Message-ID: <149@gouldsd.UUCP>
Date: Thu, 31-Jul-86 11:46:04 EDT
Article-I.D.: gouldsd.149
Posted: Thu Jul 31 11:46:04 1986
Date-Received: Sat, 2-Aug-86 01:35:31 EDT
References: <473@water.UUCP> <2975@pixar>
Organization: Gould Inc, ASDD, Landover, MD
Lines: 54
Xref: watmath net.cycle:1885 net.auto:12024 net.politics:17889
Summary: brain damage

> This is the second such claim I have seen, and I'd love to have
> someone explain it.  My understanding is that the human head can
> safely decellerate at about 80 gees, and that with a good helmet
> a 200 gee decelleration can be reduced to below 80 for the head.
> In other words, the only thing a helmet really can do is lessen
> the severity of a decelleration.  The relative accelleration of
> the brain vs the skul has got to be proportional to the accelleration
> being applied to the skull by the sidewalk, right?
> 
> 
> -- 
> 		--Craig
> 		...{ucbvax,sun}!pixar!good

	there are very delicate bundles of nerve fiber that connect the
forebrain to the rest of the brain. These are not the *only* connections
but they seem to be extremely important. when the brain receives a blow,
these  nerves can actually be cut by the impact. look at a picture of a
brain someday. there's a big fissure that runs up the front.
          _____
         /     \
        ( _     |   (rear)
      -> T_____/    (most brains are slightly larger, but I made this
			drawing by tracing around mine)

	This is the reason a lot of old boxers suffer co-ordination 
problems. high-divers and other people who regularly take jarring
impacts on the cranium also suffer from this form of slow brain damage.
it's like a lobotomy. remember, your optics are all running through 
there, and they are vital to co-ordination and orientation.

	When you hit a street with your head, your skull may survive just
fine, but the impact on your *BRAIN* is terrible. Nerve bundles can be
torn in several areas (other than just the forebrain)
	even running hard, I seem to recall, can jar your brain enough
to kill cells. remember that the brain is about the consistency of butter.
(warm butter) and think about the tidal forces it's going to undergo when
it decelerates quickly. at highway speeds every little bit is going to 
count a LOT. 
	if you hit straight on, it is actually less damaging than if you
bounce in such a way that your head skips. (like a stone)  That will make
a mini-milkshake out of your CPU, cause bleeding, and a nasty hangover.
The upshot of all this is that you skull and bones can survive a lot of
damage - damage that can in fact turn you into a vegetable. Severe
shell-shock and pressure have been known to produce personality changes,
memory disorders, and a drop of IQ as mesured with standard tests. While
your skull may just get scraped and re-modeled, you may disqualify yourself 
as a brain donor. Wear your helmet: every G counts.

Live Free.
mjr
-- 

*All opinions expressed aren't even mine, let alone those of Gould, Inc.*