Re: Tears

Phil Nicholls (
Wed, 12 Jul 1995 23:30:19 GMT

Alex Duncan <> wrote:

>In article <3tniep$> Pat Dooley,
> writes:
>>How big is your computer? The area is fraught with difficulties because
>>other primates don't weep copiously, whereas humans actually have
>>two types of tears. Check out William Frey on the subject.

>I had the good fortune to speak to an opthomologist on friday night. As
>you might expect, I asked him about tears. According to him, tears have
>several functions, most of which I suspect we already know. I also asked
>him about the saline content of tears. He told me that the salinity of
>tears exactly matches the salinity of other bodily fluids and excretions.
> Apparently, this is especially important for the eyeballs, which would
>otherwise be subject to dessication due to exposure to air. Apparently
>this has a lot to do with osmotic action across membranes (which I don't
>understand well). If the salinity of tears was either greater than or
>less than that of the inter- and intracellular fluids of the eyeball,
>then the eyeball would be at risk of losing either fluid or saline. Loss
>of either of these substances would impede ocular function.

All of this argues against tears being an outlet for salt excretion.
If tears were a salt excretion they would have to be hypertonic
(saltier than the eyeball or body fluids). Actually I believe I read
someplace that human tears are usual slightly hypotonic.

Phil Nicholls "To ask a question you must first know most of the answer.
Semper Alouatta! - Robert Sheckley