Grass consumed by an animal is crushed into pulp in the mouth. It is also moistened by saliva and moved to the rumen by peristalsis of the esophagus. In the rumen, crushed food is mixed with symbiotic microorganisms that break down cellulose and other organic compounds into simple sugars. These in turn are transformed into organic acids such as acetic acid and butyric acid and gases such as carbon dioxide and methane. Gases escape through the esophagus and the mouth, veilching while organic acids are absorbed into the blood and used by the cells of the organism as energy and structural materials. The rumen bacteria also bind in organic nitrogen and incorporate it into their own proteins. These bacteria also synthesize the complex vitamins. Apart from bacteria, the rumen is also inhabited by silicates, some of them break down cellulose while others feed on the rumen bacteria. The cut fermented by microorganisms is moved to the second chamber, the reticulum, where it is further grinded and formed into balls. These are regurgitated by anti-peristalsis into the mouth to be chewed again. Therally chewed and swallowed again, the digester is passed by peristalsis to the third chamber, the omisum, where water is absorbed and the digester condensed. From the omisum, the condensed digester passes to the ab omisum, the final chamber of the stomach. The ab omisum, which is the proper stomach, secretes enzymes to initiate the digestion of proteins released from plant cells and also proteins of bacteria and silicates found in the rumen. From the ab omisum, the food pulses to the duodenum and then to the small intestine, in which the digestion is completed and its products absorbed. Indigested food enters the large intestine, where water is absorbed and feces formed. These are later eliminated from the body through the rectum.