ITT 



THE DIGESTIVE ORGANS 



41 



The foocl after being submitted to a slight chewing passes 

 down the oesophagus and into a receptacle of great size called 

 the rumen or pautich. Here it undergoes a churning movement 

 and is acted on by the s%liva which is swallowed with it. In 

 the rumen cellulose is said to be digested through fermentative 

 processes to as much as sixty or seventy' per cent. This is due to 

 the action of bacteria present in the food, for the rumen possesses 

 no glands. Thus it corresponds functionally with the large 

 intestine in the horse as will be made clearer later. The reticulum, 

 which, from the ridges arranged in a honeycomb pattern on the 

 inside of its walls, is often called the honej^comb bag, is an 

 extension of the rumen. It acts as a reservoir of liquid which 



Fig. 25. Stomach of ruminant (from Flower and Lydekker). a oesophagus, 

 b rumen, c reticulum, d omasum, e abomasum, / duodenum. 



moistens the food before it is passed back into the mouth. The 

 reticulum is not essential for rumination since Flourens showed 

 that its excision did not inhibit the process. 



The oesophagus is continued along the side of the rumen and 

 reticulum in the form of a groove with lips or pillars which when 

 relaxed admit of its communicating wdth the rumen and reticulum. 

 During the churning movement which takes place in the nun en 

 the food becomes pressed against the lips of the groove. This 

 sets up a spasmodic contraction of the muscles of the abdomen 

 and diaphragm, as a result of which some of the food enters the 

 lower part of the oesophagus and is carried upwards bj- peristaltic 

 waves parsing- upwards along the muscles of that organ. In this 

 way the food is regurgitated to the mouth. The hquid part of 

 it is at once reswallowed, but the more solid part is masticated 

 afresh for a considerable period, during which time it is acted 

 on by the parotid saliva. It is then swallowed a second time 



