Inquiring minds want to know

So at what point do you take a cat to the vet? Dumb Cat is really not himself. He is sneezing and snuffling and curled up looking very bedraggled in the basement. I mean, if he has a cold I know how he feels because if I could curl up in a nice dark place I would, but I've never seen him like this. But can a vet really do anything for a cat with a cold? I have to assume that it is kind of like taking a child to the pediatrician for a runny nose, right? Is there a way to tell if a cat is running a fever?

Who knew I would get so worked up about the heath of Dumb Cat...