I was originally a biology in major in college. In Cell Bio, we had a lab that involved attempting to examine one of the circulatory subsystems of a limpet, but in vivo, so the idea was to chemically paralyze it and then dissect while it was still alive. I am certain to this day that I jacked it up somehow, because that poor limpet was absolutely not paralyzed and was squirming the entire time I was trying to cut it open. This will be seared into my memory for the rest of my life and I never took another biology class after that, only completing a minor instead.