When the dog puts food in its mouth it breaks the food down mechanically and chemically by chewing it and the saliva from its mouth. The food goes down the esophagus and into the stomach. The stomach acid dissolves the food with a high amount of hydrochloric acid. After the stomach the food goes into the small intestines in the form of a liquid.From the small intestine, the unassimilated food passes through to the large intestine. The large intestine is the last stop before the waste is passed through rectum in the form of feces.