"Science Lesson" joke
Tom Finn, the noted biologist, was stumped. He had spent months studying the little green frogs in the Keefo swamp. Despite all efforts at predator control, population was declining at an alarming rate. Finn finally went to the chemistry department at his college to see if anyone there might be able to help. Tom looked into the problem and came up with a solution. The little frogs had succumbed to a chemical change in the swamp's water and simply couldn't stay coupled long enough to reproduce. Tom brewed up a new adhesive, made from a dash of this, a toss of that and, most critically, one part sodium. "You mean...?" said Jim. "Yes," said Tom. "They need a mono-sodium glue to mate!"
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