A mechanic was removing a cylinder head from the motor of a car when he spotted a well-known cardiologist in his shop, who was waiting for the service manager to take a look at his car.
The mechanic shouted across the garage, ‘Hey Doc, want to take a look at this?’ The cardiologist, a bit surprised, walked over to where the mechanic was working. The mechanic straightened up, wiped his hands on a rag, and asked, ‘So, Doc, look at this engine. I open its heart, take the valves out, repair any damage, and then put them back in; and when I finish, it works just like new. So how come I make a pretty small salary, and you get the really big bucks, when you and I are doing basically the same work?’
The cardiologist paused, smiled, and leaned over, then whispered to the mechanic, ‘Try doing it with the engine running!’