The original quote, from E. B. White: “Humor can be dissected, as a frog can, but the thing dies in the process and the innards are discouraging to any but the pure scientific mind.”
Actually he is quoted by saying “Explaining a joke is like dissecting a frog. You understand it better but the …” (can’t get myself to write out such gory, morbid thoughts) “…in the process.”