A man runs into the vet's office carrying his dog, screaming for help.  The vet rushes him back to an examination room and has him put his dog down on the examination table.  The vet examines the still, limp body and after a few moments tells the man that his dog is dead.

The man, clearly agitated and not willing to accept this, demands a second opinion.  The vet goes into the back room and comes out with a cat and puts the cat down next to the dogs body.  The cat sniffs the body, walks from head to tail poking and sniffing the dog's body and finally looks at the vet and meows.  The vet looks at the man and says, "I'm sorry, but the cat thinks your dog is dead too."

The man, finally resigned to the fate of his dog, thanks the vet and asks how much he owes.  The vet answer, "$350."

"$350 to tell me my dog is dead?!" exclaims the man.

"Well," the vet replies, "I would have only charged you $50 for my initial diagnosis.  The additional $300 was for the cat scan."