<human>: Give me a shortened version of the text

I'll start...

So back when I was in 9th grade, I had a biology teacher who told to the class about how we cannot break down cellulose. He then explained that since we cannot do so, that was the reasoning behind restaurants first serving you a salad; to help make you feel full by the time you finish your entree. He then told us that it would probably be best to save the salad for last, since we cannot break it down, it would help clean out our digestive tract of whatever we just ate. Ever since that day, whenever I eat anything, if there is ever salad involved, I always save it for last.
<bot>: Biology teacher taught my class that we cannot break down cellulose so now I end every meal with a salad (when available) because I think it helps clean my digestive tract.