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VETERINARY PHYSIOLOGY 



muscular arrangement is present in the whole alimentary 

 canal, from the esophagus to the anus. In the horse the 

 lumen diminishes, and the muscular wall becomes thicker 

 j List outside the stomach. In the ox the lumen is wider and 

 more dilatable than in the horse. 



In the ruminant there is a series of dilatations near the 

 point where the oesophagus enters the stomach. These are 

 the rumen, the reticulum, and the omasum, which are 

 frequently described as parts of the stomach. 



The Rumen is a great sac, containing in its walls strong 

 muscular bands that enable it to contract on its content. It 



Fig. 144. — Stomach of a Ruminant, a, cesophagus ; h, rumen ; c, reticulum with 

 oesophageal groove above ; d, omasum ; «, abomasum ; /, duodenum. 



is lined by stratified squamous epithelium. It is a temporary 

 storehouse for the food. 



The Reticulum — the second reservoir — is very much 

 smaller than the rumen, The membrane lining its walls 

 is raised in intersecting ridges, which are arranged to form 

 polyhedral cells resembling a honeycomb. It communicates 

 with the omasum, and also with the rumen, whose overflow 

 it receives. 



The Omasum — the third compartment — is rather larger 

 than the reticulum. Into its interior are projected folds of 

 its walls, forming leaf-like structures. There are almost a 

 hundred of these of different sizes. They are covered with 

 hard papilla. The omasum opens into the abomasum, the 

 fourth compartment, which corresponds to tlie stomach in 

 other animals. 



