CAT SCAN joke

A lady rushes into the veterinarian and screams, "I found my dog unconscious and I can't wake him - do something."
The vet lays the dog on the examination table and after a few simple tests he says, "I'm sorry, I don't feel a pulse, I'm afraid your dog is dead".
The lady can't accept this and says, "No, no, he can't be dead - do something else."
The vet goes into the other room, and comes back with a little cat. The cat jumps up on the table and starts sniffing the dog from head to toe. It sniffs and sniffs up and down the dog, then all of a sudden just stops and jumps off the table and leaves. "Well, that confirms it," the vet says, "your dog is dead."
The lady is very upset but finally settles down. "Okay, I guess you're right. How much do I owe you?" The vet says, "That will be $340."
The lady has a fit and asks, "Why is it so much? After all the vet didn't do anything for the dog."
"Well", the vet replied, "it's $40 for the office visit and $300 for the CAT SCAN!"