The portion of the intestine that runs from the cecum to the rectum; in some mammals, it may be separated from the small intestine by an ileocecal valve. It is also known as the large intestine. The colon is usually divided into ascending, transverse, and descending portions. In the humans a fourth section, the sigmoid, is found. The colon is longer in herbivores and shorter in carnivores, and is about 4 to 6 ft (1 to 2 m) long in humans. Although no digestive enzymes are secreted in the colon, digestion is assisted by an alkaline fluid. Much digestion (for example, all breakdown of cellulose) occurs by bacteria, of which Escherichia coli is the most common. Most of the fluid added to the food during digestion is reabsorbed into the body in the colon. All digestive action, water absorption, and so on, is completed before the food materials pass out of the colon into the rectum.