With my supervision, they proceed to add ingredients to the bag, also known as stomach.
The tricky part was getting them to wait to add the warm water in the bag. Slowly. I finally had to take over and add the water myself. Then we waited as we watched the bag,stomach, fill up and go down the tube, small intestine. Interesting.
Yes, that's poop. Not real, but the experiment was to show them how the stomach digests the food. It was pretty interesting and the most important thing was that it kept the boys entertained. So much that they wanted to do it again. And again. And again.
Isn't it amazing that this cheap experiment would entertain kids so much? Kids are so easily amused.