As you crawl through the hot smelly tunnel, the dogs feces slowly seems to get thicker as the water gets reabsorbed through the large instestine wall. You keep moving through the tube until you get to a large wall of your own dogs poo. The walls get smoother and the feces is very compacted. You sit down and figure that this is the rectum. After about an hour however, you feel another wall of crap moving towards you from deeper in the large intestine. You realise you are pinned between them and soon you will be squished into a large log of the foul smelling substance. It wont be long and this will all come to an end.
