Sick as a ...?

I'm slouching here in my apartment feeling "sick as a dog", wondering about the origins of this popular saying. So, I did what I always do first when I have questions that need answering: I turned to the all trusting, reliable World Wide Web! I started a quick Google search and instead of finding answers, found that I was not the only one wondering about this expression.

I read quite a few sites and can no longer remember which sites the following comments came from. One vague answer described that dogs have been attributed with negativity for a long time -- I mean, growing up, I used to think that calling another a dog was a big insult (not that I ever did or anything!) I also read that dogs eat about anything and often get sick from the filth they digest, hence "sick as a dog"! In any case, this expression was first recorded being used in the 1700.

Regardless, I am not quite sold on the idea. I don't think of dogs as despicable creatures, in fact I would like to have one, or two or three... Look at her? She's so cute (btw, I just decided she was female...too cute!!!)