laughing when you aren't supposed to makes you laugh way harder

Today I visited my sister at her classroom at VVMS to do a few read-aloud sessions with her classes. I was asked to read from a book called "Blood River" - a story about some Pilgrims just arriving in the New World. The first class went well. I read five pages and enjoyed it very much. The second class (the one I just finished) didn't go so well. I actually got the giggles and had to stop reading because I was laughing so hard.

It all started when the Pilgrims I was reading about started getting sick and dying from disease. I read something about them getting "bloody diarrhea" when Jodi stopped me and asked me to write the word "diarrhea" on the white board since no one knew how to spell it. So I wrote it. Then erased it. From that point on I tried to keep a straight face but could not for the life of me not laugh! When I started to read about the meal-worms in the barley and the diseased river water I lost it. I burst out laughing and sputtered every time I tried to continue. The more terrible and serious the story grew, the funnier it was to me. One boy in the second row suggested I think about something sad... a dead puppy. I immediately thought of what I usually think of to stop laughing (eating spoonfuls of dead cats) but even that didn't work. Alas, I finally waved my white flag and handed the story over to be completed by the controlled teacher.