"The three dogs" joke

(This joke is from a professor who refered to lawyers as the second
oldest profession:)
There once was a dog show to determine the world's smartest dog. Three
dogs were in the finals. One dog belonged to a doctor. One dog belonged
to an engineer. And, one dog belonged to a lawyer.
For the finals each dog was given a bag of bones to see what it could
make.
The doctor said, "Stethascope, go!" The dog built a human skeleton.
The judges were ready to award the trophy right then. But, they decided
to give the other dogs a try.
The engineer said, "Slide-rule, go!" (So, its an old joke.) The dog built
a suspension bridge.
The judges were beside themselves. Which dog would they pick?
The lawyer said. "Loop-hole, go!" The dog ate the bones, got a percentage
of all the tolls from the bridge and screwed the other two dogs.