Re: Tears
Phil Nicholls (pnich@globalone.net)
Sun, 16 Jul 1995 16:33:29 GMT
Elaine Morgan <Elaine@desco.demon.co.uk> wrote:
>On tears : No, the salinity if tears in modern humans is not as far as
>I know different from that of the apes. What is different is the
>innervation.
>Ape tears like those of land mammals in general are triggered off by
>the presence of irritants like dust or smoke, as ours often are.But
>hman tears are produced also, and much more prolifically by a quite
>different stimulus. In certain cases of damage to the trigeminal
>nerve, the patient is unable to produce tears in response to
>irritation, but can still weep copiously out of grief or sympathy.
Well, I knew all of that neuroanatomy would come in handy. Most
fibers of the trigeminal nerve are sensory fibers. The motor
component of the trigeminal nerve is involved only with the control of
facial muscles and to some extent the muscles of the lower jaw.
I have consulted two neuroanatomy texts. Neither of them reported any
affect of trigeminal nerve damage on the function of the lacrimal
gland. Let's assume that your statement is true. What does this
mean? It means that if you cut the sensory neurons you block the
stimulus. The nerves caring impulses TO the lacrimal glands is not
disrupted and and is therefore free to carry impulses from limbic
system nuclei to the lacrimal gland. The lacrimal gland, which in
humans secrets tears (contrary to Pat's undocumented claim, there are
NOT two types of tear glands in humans) is innervated by the lacrimal
nerve. The cells of origin for the lacrimal nerve is the
pterygopalatine ganglion, part of the parasympathetic nerveous system.
I sincerely doubt that there has been any kind of controlled
correlating the amount of tears secreted with the "emotional state" of
the animal. All of this aside, the concentration of salt in tears
clearly indicates that it cannot be an excretion.
Once more when "aquatic" features of human morphology are examined in
detail we find that the "evidence" presented by the AAH supporters
fails to hold up under any kind of close analysis.
>Elaine Morgan
-----------------------------------
Phil Nicholls "...it is infuriating to be quoted
pnich@globalone.net again and again by creationists --
whether from design or stupidity I
do not know -- as admitting that there
no transitional forms." S.J. Gould.
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