A friend just directed me to an article by chemist Henry Schaefer. I've only read part of it, but here's a sampling:
I continued, "Let me tell you what my Sunday School teacher said yesterday." That raised their interest even more. "I was hoping the group at church would give me some support, moral, spiritual, or whatever for dealing with this large class, but I received none. In fact, the Sunday School teacher asked the class, in honor of me:
What was the difference between a dead dog lying in the middle of the street and a dead chemistry professor lying in the middle of the street?
The class was excited about this and I hadn't even gotten to the punch line. They roared with laughter. The very concept of a dead chemistry professor lying in the middle of the street was hilarious to them. I'm sure some of them began to think, "If this guy were to become a dead chemistry professor very close to the final exam, we probably wouldn't have to take the final exam. They'd probably give us all passing grades and this would be wonderful."
I told them my Sunday school teacher had said that the difference between the dead dog lying in the middle of the road and the dead chemistry professor lying in the middle of the road is that there are skid marks in front of the dead dog.
The class thought this was wonderful! Just as they settled down, I pressed the button and around came Lonny with the moles. It was a wonderful beginning to my career as a freshman chemistry lecturer.